DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Response to Amendment
The present amendment, filed on or after 3/24/2026, has been entered. The Applicant has amended claims 1, 3, 5, 9-10, 12, 14, and 18. Claims 1-18 are pending in the application.
Claim Objections
Claims 1, 3, 5, 9-10, 12, 14, 18 are objected, because the following limitations/phrases should be aligned to the prior limitations/phrases to avoid 112 issues due to indefiniteness:
Claim 1: “at least one yttrium oxide layer” on line 8 should be changed to “at least one layer of yttrium oxide”, and “a bulk side of the 4H-SiC wafer” on line 11 should be changes to “a bulk side of a 4H-SiC wafer”.
Claim 3: “the yttrium oxide layer” on line 2 should be changed to “the at least one layer of yttrium oxide”, and “the 4H-SiC epilayer” on line 3 should be changed to “the at least one n-type 4H-SiC epilayer”
Claim 5: “the yttrium oxide layer” on line 3 should be changed to “the at least one layer of yttrium oxide”.
Claim 9: “the 4H-SiC epilayer” on line 2 should be changed to “the at least one n-type 4H-SiC epilayer”, and “the yttrium oxide layer” on line 3 should be changed to “the at least one layer of yttrium oxide”.
Claim 10: “the yttrium oxide layer” on line 5 should be changed to “the at least one layer of yttrium oxide”, “the 4H-SiC epilayer” on line 2 should be changed to “the at least one n-type 4H-SiC epilayer”, and “a bulk side of the 4H-SiC wafer” on line 10 should be changes to “a bulk side of a 4H-SiC wafer”.
Claim 12: “the yttrium oxide layer” on lines 3 should be changed to “the at least one layer of yttrium oxide”, and “the 4H-SiC epilayer” on line 2-3 should be changed to “the at least one n-type 4H-SiC epilayer”.
Claim 14: “the 4H-SiC epilayer” on line 4 should be changed to “the at least one n-type 4H-SiC epilayer”, and “the yttrium oxide layer” on line 4 should be changed to “the at least one layer of yttrium oxide”.
Claim 18: “the 4H-SiC epilayer” on line 2 should be changed to “the at least one n-type 4H-SiC epilayer”, and “the yttrium oxide layer” on line 3 should be changed to “the at least one layer of yttrium oxide”.
Appropriate corrections are required.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-5, 8-14, and 17-18 are rejected under 35 U.S.C. 103 as being unpatentable over Jia (Jia et al, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 997, 2021, 165166, ISSN 0168-9002, doi.org/10.1016/j.nima.2021.165166) in views of Quah (Hock Jin Quah et al., 2010, Electrochem. Solid-State Lett. 13 H396, DOI 10.1149/1.3481926), Zhang (Zhang and Xiao, J. Appl. Phys. 83, 3842–3848 (1998), doi.org/10.1063/1.366615), and Mandal (Mandal et al., Advances in High-Resolution Radiation Detection Using 4H-SiC Epitaxial Layer Devices. Micromachines 2020, 11, 254. doi.org/10.3390/mi11030254).
Regarding claim 1, Jia teaches a betavoltaic cell for power generation (SiC radiation detector; Fig. 1; Abstract) in harsh environment applications (4H-SiC substrate is a material that is suitable for extreme environments (page 1, col. 2, para. 1)) comprising:
at least one metal-oxide-semiconductor (Fig. 1b: the SiC detector is a metal-oxide-semiconductor device) comprising:
at least one layer of oxide (SiO2 layer, Fig. 1b; page 2, col. 1, para. 2) deposited on at least one n-type 4H--SiC epilayer (u-SiC epitaxial, Fig. 1b; page 2, col. 1, para. 2);
at least one first nickel contact (Ni/Au, Fig. 1; page 2, col. 1, para. 2), deposited on the at least one oxide layer (SiO2 layer, Fig. 1b), configured to act as a gate contact (the limitation "configured to act as a gate" directs to intended use of the "at least one first nickel contact". A recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the limitation (see MPEP § 2114, subsection II). In the instant case, the device structure is identical to the one in the current application); and
at least one second contact (Ti/Al/Ti, Fig. 1b; page 2, col. 1, para. 2) formed on the at least one n-type 4H-SiC epilayer (u-SiC epitaxial, Fig. 1b) as a back contact (Ti/Al/Ti contact is on the back side of the device) on a bulk side of the 4H-SiC wafer (n-doped 4H-SiC substrate Si-face with off-cut of 4° shown as n-SiC substrate in Fig. 1b; page 2, col. 1, para. 2: the Si-face represents the top surface of the wafer, and the bottom surface is the bulk side).
Jia, however, does not teach that
a vertical heteroepitaxial metal-oxide-semiconductor (MOS) stack configured for self-biased radiation response at zero applied bias;
the oxide layer is at least on layer of yttrium oxide layer pulse laser deposited; and
the second contact is a second nickel contact formed on a bulk side of the 4H-SiC wafer.
Quah, on the other hand, teaches a gate oxide layer formed from yttrium oxide, instead of silicon dioxide, on an n-doped 4H-SiC (page 1, col. 1, para. 1), which is advantageous due to the relatively high k-value of yttrium oxide (k=14-18 compared to k=3.9 for silicon dioxide; page 1, col. 1, para. 1). Quah discloses that high-k gate oxides on SiC substrates have been thoroughly investigated to enable the exploitation of the SiC breakdown field (page 1, col. 1, para. 1). Quah further teaches that yttrium oxide layer deposited by pulsed laser deposition would provide a very high breakdown voltage of about 6.5 MVcm-1 at 10-6 Acm-2, which is higher than other high-k gate oxides (page 3, col. 2, para. 2).
Therefore, also knowing that the use of SiO2 in 4H-SiC technologies is not an ideal choice due
to the poor quality of the SiO2/4H-SiC interface, as evidenced by Siddiqui (Abstract, Siddiqui et al., High-k dielectrics for 4H-silicon carbide: present status and future perspectives, J. Mater. Chem. C, 2021, 9, 5055), a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to replace the silicon dioxide layer in the betavoltaic cell of Jia with a pulse laser deposited yttrium oxide layer, as taught by Quah, to obtain an oxide layer with a high k-value (reduces leakage current) and a high breakdown voltage.
Thus, the combination of Jia and Quah leads to a betavoltaic cell further comprising
at least one layer of yttrium oxide pulse laser deposited on at least one n-type 4H-SiC epilayer.
The combination of Jia and Quah, however, does not teach that
a vertical heteroepitaxial metal-oxide-semiconductor (MOS) stack configured for self-biased radiation response at zero applied bias;
the second contact is a second nickel contact formed on a bulk side of the 4H-SiC wafer.
Zhang, on the other hand, teaches methods for pulse laser deposition of yttrium oxide layers epitaxially (page 5, col. 2) with leads to good electrical characteristics for the semiconductor-yttrium oxide interface (pages 7-8). Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to deposit the yttrium oxide layer in the betavoltaic cell of Jia in view of Quah epitaxially, which leads to a better crystal structure (smoother yttrium oxide layer, Zhang, page 8) with less interface defects (Zhang, page 7), and thereby a reduced leakage current. Thus, the combination of Jia, Quah, and Zhang leads to a betavoltaic cell further comprising
a vertical heteroepitaxial metal-oxide-semiconductor (MOS) stack configured for self-biased radiation response at zero applied bias (the limitation "configured for self-biased radiation response at zero applied bias" directs to intended use of "a vertical heteroepitaxial metal-oxide-semiconductor (MOS) stack ". A recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the limitation (see MPEP § 2114, subsection II). In the instant case, the device structure is identical to the one in the current application, and therefore can be configured for self-biased radiation response at zero applied bias.).
The combination of Jia, Quah, and Zhang, however, does not teach that
the second contact is a second nickel contact formed on a bulk side of the 4H-SiC wafer.
Mandal, on the other hand, teaches radiation detection with 4H-SiC epitaxial layer devices (Fig. 1) for harsh environment application (Abstract), wherein
the second contact is a second nickel contact formed on a bulk side of the 4H-SiC wafer (Fig. 1: Ni contact at the backside (bottom) of the n-type Ni/4H-SiC Schottky barrier device).
A person of ordinary skill in the art before the effective filing date of the claimed invention would already know that using nickel as a contact material on the n-doped 4H-SiC is a known method for forming ohmic contacts on 4H-SiC, as also evidenced by Mandal (page 4, para. 1). Selection of a known material based on its suitability for its intended use supported a prima facie obviousness determination in Sinclair & Carroll Co. v. Interchemical Corp., 325 U.S. 327, 65 USPQ 297 (1945) "Reading a list and selecting a known compound to meet known requirements is no more ingenious than selecting the last piece to put in the last opening in a jig-saw puzzle." 325 U.S. at 335, 65 USPQ at 301. See also In re Leshin, 227 F.2d 197, 125 USPQ 416 (CCPA 1960) (selection of a known plastic to make a container of a type made of plastics prior to the invention was held to be obvious). Furthermore, it should also be noted that substituting nickel as disclosed by Mandal for Ti/Al/Ti as disclosed by Jia in views of Quah and Zhang as ohmic contact is a simple substitution of one known element for another to obtain predictable results (see MPEP2143). Thus, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify the second contact of Jia in views of Quah and Zhang such that the second contact is a second nickel contact, as disclosed by Mandal.
Regarding claim 2, Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1, wherein
Jia further teaches that the betavoltaic cell (SiC radiation detector; Fig. 1) is mounted on a printed circuit board (Fig. 1a; page 2, col. 1, last paragraph).
Regarding claim 3, Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1, wherein
the combination of Jia, Quah, Zhang, and Mandal teaches that the betavoltaic cell is heteroepitaxial (see claim 1 rejection above).
Jia, Quah, Zhang, and Mandal do not disclose that the yttrium oxide layer comprises a (222) Y-2O3 plane epitaxially aligned on the 4H-SiC epilayer.
However, considering that the top surface of the 4H-SiC is Si-face (0001) (Jia, page 2, col. 1, para. 2), the lattice constant of yttrium oxide is a=1.0604 nm (cubic crystal structure), and the lattice constants of 4H-SiC are a=0.307nm and c=1.053nm (hexagonal crystal structure), a person of ordinary skill in the art before the effective filing date of the claimed invention would understand that the (222) Y2O3 plane would lead to an in-plane atomic distance of 1.0604nm*sin45 = 0.75nm with a triangular shape that can closely match the triangular atomic arrangements in the hexagonal (0001) plane of 4H-SiC, because the ratio of 0.75nm/ 3.07nm = 2.44 (within 3% of 2.5=5/2) (other alternative triangular matches can also be found due to hexagonal arrangement of atoms in the 4H-SiC). Therefore, the (222) plane of Y2O3 matches the 4H-SiC Si-face both structurally and in terms of periodicity, and the epitaxially grown Y2O3 is naturally formed as a (222) plane. Thus, the specific arrangement of 4H-SiC layers in the betavoltaic cell of Jia, Quah, Zhang, and Mandal leads to an heteroepitaxial cell wherein the yttrium oxide layer comprises a (222) Y-2O3 plane epitaxially aligned on the 4H-SiC epilayer.
Regarding claim 4, Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1, wherein
Jia further teaches that the betavoltaic cell has reduced dark current (Fig. 3: dark current curves with silicon dioxide layer; page 3, col. 1, para. 3) as compared to a Schottky barrier diode (Fig. 3: the curve without silicon dioxide layer) fabricated on at least one 4H-SiC epilayer (Fig. 1a).
Regarding claim 5, while Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1,
the combination of Jia, Quah, Zhang, and Mandal does not explicitly disclose that the betavoltaic cell has less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer due to passivation of a 4H-SiC epilayer surface by the yttrium oxide layer.
However, Jia teaches that the interface between the electrodes and the SiC affects the device performance, and the oxide layer is a passivation layer (page 2, Col. 1, para. 1) as an insulator between the metal electrodes and SiC and significantly improves the device performance (page 2, Col. 1, para. 1) compared to a Schottky barrier device (the device without an oxide layer). Quah, further teaches that the oxide layer decreases the interface trap density which increases the dielectric breakdown field (Quah, Conclusion). it is known in the field of SiC-based radiation detectors that the surface recombination velocity depends on the point defects and surface recombination due to surface traps in 4H-SiC, as evidenced by Ichikawa (page 2, col. 1, para. 1; Ichikawa et al, 2018, ECS J. Solid State Sci. Technol. 7 Q127, DOI 10.1149/2.0031808jss) and high-quality oxide layers is applicable to suppress surface recombination (Ichikawa; page 2, col. 1, para. 1) for decreasing the surface recombination. Considering that Quah teaches that yttrium dioxide can be such an oxide layer and can decrease the oxide-semiconductor trap densities significantly according to conditions of a post annealing process (Quah; pages 2-3, Results and Discussion section), a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to use the yttrium oxide layer in the betavoltaic cell of Jia, Quah, Zhang, and Mandal in a way disclosed by Quah, to reduce to oxide semiconductor interface trap density and obtain a betavoltaic cell that has less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer due to passivation of a 4H-SiC epilayer surface by the yttrium oxide layer which would provide the benefit of increased carrier lifetimes and detection efficiency.
Regarding claim 8, Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1, wherein
Jia further teaches that the betavoltaic cell (SiC radiation detector; Fig. 1) further comprises a 4H-SiC buffer layer (u-SiC buffer; Fig. 1b; page 2, col. 1, para. 2).
Regarding claim 9, Jia in views of Quah, Zhang and Mandal teaches the betavoltaic cell of claim 1, wherein
Jia further teaches that the betavoltaic cell (SiC radiation detector; Fig. 1) further comprises a depletion layer edge (page 2, col. 2, last paragraph: a depletion layer is formed, and therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would know that there would be a depletion layer edge) within the n-type 4H-SiC epilayer (u-SiC epitaxial, Fig. 1b; page 2, col. 1, para. 2) at an interface with the yttrium oxide layer (SiO2layer after replaced by an Y2O3 layer (see claim 1 rejection above), Fig. 1b, page 2, col. 2, para. 1: “there was no carrier accumulation in the dielectric layer”, and therefore, the depletion layer is within the n-type 4H-SiC epilayer at an interface with the yttrium oxide layer).
Regarding claim 10, Jia teaches a method for making a betavoltaic cell for power generation (SiC radiation detector; Fig. 1; page 2, Section 2.1 Detector Fabrication) in harsh environment applications (4H-SiC substrate is a material that is suitable for extreme environments (page 1, col. 2, para. 1)) comprising:
forming at least one vertical metal-oxide-semiconductor (Fig. 1b: the SiC detector is a metal-oxide-semiconductor device) via:
growing at least one layer of oxide (SiO2 layer, Fig. 1b; page 2, Section 2.1 Detector Fabrication), on at least one n-type 4H-SiC epilayer (u-SiC epitaxial, Fig. 1b; page 2, Section 2.1 Detector Fabrication);
depositing at least first one nickel contact (Ni/Au, Fig. 1; page 2, Section 2.1 Detector Fabrication) on the at least one oxide layer (SiO2 layer, Fig. 1b) configured to act as a gate contact (Fig. 1b-c: the first contact acts as a gate contact as the device structure is identical to the one in the current application); and
depositing at least one second contact (Ti/Al/Ti, Fig. 1b; page 2, Section 2.1 Detector Fabrication) on the at least one n-type 4H-SiC epilayer (u-SiC epitaxial, Fig. 1b) to form a back contact (Ti/Al/Ti contact is on the back side of the device) on a bulk side of the 4H-SiC wafer (n-doped 4H-SiC substrate Si-face with off-cut of 4° shown as n-SiC substrate in Fig. 1b; page 2, col. 1, para. 2: the Si-face represents the top surface of the wafer, and the bottom surface is the bulk side).
Jia, however, does not teach that
the oxide layer is an at least on layer of yttrium oxide deposited via pulse laser deposition; wherein the yttrium oxide layer is epitaxially grown on the n-type 4H-SiC epilayer; and
the second contact is a second nickel contact.
Quah, on the other hand, teaches a method for forming a gate oxide layer formed from yttrium oxide, instead of silicon dioxide, on an n-doped 4H-SiC (page 1, col. 1, para. 1), which is advantageous due to the relatively high k-value of yttrium oxide (k=14-18 compared to k=3.9 for silicon dioxide; page 1, col. 1, para. 1). Quah discloses that high-k gate oxides on SiC substrates have been thoroughly investigated to enable the exploitation of the SiC breakdown field (page 1, col. 1, para. 1). Quah further teaches that yttrium oxide layer deposited by pulsed laser deposition would provide a very high breakdown voltage of about 6.5 MVcm-1 at 10-6 Acm-2, which is higher than other high-k gate oxides (page 3, col. 2, para. 2).
Therefore, also knowing that the use of SiO2 in 4H-SiC technologies is not an ideal choice due
to the poor quality of the SiO2/4H-SiC interface, as evidenced by Siddiqui (Abstract, Siddiqui et al., High-k dielectrics for 4H-silicon carbide: present status and future perspectives, J. Mater. Chem. C, 2021, 9, 5055), a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to modify the method of Jia to replace the silicon oxide layer with an yttrium oxide layer by growing at least one layer of yttrium oxide, via pulsed laser deposition, on at least one n-type 4H-SiC epilayer, as taught by Quah, to obtain a gate oxide layer with a high k-value (reduces leakage current) and a high breakdown voltage.
Thus, the combination of Jia and Quah leads to a method comprising
growing at least one layer of yttrium oxide, via pulse laser deposition, on at least one n-type 4H-SiC epilayer.
The combination of Jia and Quah, however, does not teach that
the yttrium oxide layer is epitaxially grown on the n-type 4H-SiC epilayer; and
the second contact is a second nickel contact.
Zhang, on the other hand, teaches methods for pulse laser deposition of yttrium oxide layers epitaxially (page 5, col. 2) with leads to good electrical characteristics for the semiconductor-yttrium oxide interface (pages 7-8). Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to deposit the yttrium oxide layer method of Jia in view of Quah epitaxially, which leads to a better crystal structure (smoother yttrium oxide layer, Zhang, page 8) with less interface defects (Zhang, page 7), and thereby a reduced leakage current. Thus, the combination of Jia, Quah, and Zhang leads to a method further comprising that
the yttrium oxide layer is epitaxially grown on the n-type 4H-SiC epilayer.
The combination of Jia, Quah, and Zhang, however, does not teach that
the second contact is a second nickel contact.
Mandal, on the other hand, teaches radiation detection with 4H-SiC epitaxial layer devices (Fig. 1) for harsh environment application (Abstract), wherein
the second contact is a second nickel contact formed on a bulk side of the 4H-SiC wafer (Fig. 1: Ni contact at the backside (bottom) of the n-type Ni/4H-SiC Schottky barrier device).
A person of ordinary skill in the art before the effective filing date of the claimed invention would already know that using nickel as a contact material on the n-doped 4H-SiC is a known method for forming ohmic contacts on 4H-SiC, as also evidenced by Mandal (page 4, para. 1). Selection of a known material based on its suitability for its intended use supported a prima facie obviousness determination in Sinclair & Carroll Co. v. Interchemical Corp., 325 U.S. 327, 65 USPQ 297 (1945) "Reading a list and selecting a known compound to meet known requirements is no more ingenious than selecting the last piece to put in the last opening in a jig-saw puzzle." 325 U.S. at 335, 65 USPQ at 301. See also In re Leshin, 227 F.2d 197, 125 USPQ 416 (CCPA 1960) (selection of a known plastic to make a container of a type made of plastics prior to the invention was held to be obvious). Furthermore, it should also be noted that substituting nickel as disclosed by Mandal for Ti/Al/Ti as disclosed by Jia in views of Quah and Zhang as ohmic contact is a simple substitution of one known element for another to obtain predictable results (see MPEP2143). Thus, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Ji in views of Quah and Zhang such that the second contact is formed from nickel, as disclosed by Mandal, instead of Ti/Al/Ti by
depositing at least one second nickel contact on the at least one n-type 4H-SiC epilayer to form a back contact on a bulk side of the 4H-SiC wafer.
Regarding claim 11, Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10, wherein
Jia further teaches that the method comprises
mounting the betavoltaic cell (SiC radiation detector; Fig. 1) on a printed circuit board (Fig. 1b; page 2, col. 1, last paragraph).
Regarding claim 12, Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10, wherein
the combination of Jia, Quah, Zhang, and Mandel further teaches that the method (see claim 10 rejection above)) comprises configuring the betavoltaic cell to be heteroepitaxial (n-type SiC and yttrium oxide layers are epitaxial, see claim 10 rejection above), by epitaxially growing the yttrium oxide layer on the n-type 4H-SiC epilayer.
Regarding claim 13, Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10,
Jia, Quah, and Mandel do not disclose that the method further comprises configuring the betavoltaic cell to have reduced dark current (Fig. 3: dark current curves with silicon dioxide layer; page 3, col. 1, para. 3) as compared to a Schottky barrier diode (Fig. 3: the curve without silicon dioxide layer) fabricated on at least one 4H-SiC epilayer (Fig. 1a).
Regarding claim 14, while Jia in views of Quah, Zhang and Mandal teaches the method for making a betavoltaic cell of claim 10,
the combination of Jia, Quah, Zhang, and Mandal does not explicitly disclose that the method further comprises configuring the betavoltaic cell to have less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer by passivating a surface of the 4H-SiC epilayer with the yttrium oxide layer.
However, Jia teaches that the interface between the electrodes and the SiC affects the device performance, and the oxide layer is a passivation layer (page 2, Col. 1, para. 1) as an insulator between the metal electrodes and SiC and significantly improves the device performance (page 2, Col. 1, para. 1) compared to a Schottky barrier device (the device without an oxide layer). Quah, further teaches that the oxide layer decreases the interface trap density which increases the dielectric breakdown field (Quah, Conclusion). it is known in the field of SiC-based radiation detectors that the surface recombination velocity depends on the point defects and surface recombination due to surface traps in 4H-SiC, as evidenced by Ichikawa (page 2, col. 1, para. 1; Ichikawa et al, 2018, ECS J. Solid State Sci. Technol. 7 Q127, DOI 10.1149/2.0031808jss) and high-quality oxide layers is applicable to suppress surface recombination (Ichikawa; page 2, col. 1, para. 1) for decreasing the surface recombination. Considering that Quah teaches that yttrium dioxide can be such an oxide layer and can decrease the oxide-semiconductor trap densities significantly according to conditions of a post annealing process (Quah; pages 2-3, Results and Discussion section), a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to modify the yttrium oxide layer in the method of Jia, Quah, Zhang, and Mandal in a way disclosed by Quah, to reduce to oxide semiconductor interface trap density by configuring the betavoltaic cell to have less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer by passivating a surface of the 4H-SiC epilayer with the yttrium oxide layer, which would provide the benefit of increased carrier lifetimes and detection efficiency.
Regarding claim 17, Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10, wherein
Jia further teaches that the method comprises configuring the betavoltaic cell (SiC radiation detector; Fig. 1) to include a 4H-SiC buffer layer (u-SiC buffer, Fig. 1b; page 2, Section 2.1 Detector Fabrication).
Regarding claim 18, Jia in views of Quah, Zhang and Mandal teaches the method for making a betavoltaic cell of claim 10, wherein
Jia further teaches that the method comprises configuring the betavoltaic cell to include a depletion layer edge (page 2, col. 2, last paragraph: a depletion layer is formed, and therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would know that there would be a depletion layer edge) within the n-type 4H-SiC epilayer (u-SiC epitaxial, Fig. 1b; page 2, col. 1, para. 2) at an interface with the yttrium oxide layer (SiO2layer after replaced by an Y2O3 layer (see claim 1 rejection above), Fig. 1b, page 2, col. 2, para. 1: “there was no carrier accumulation in the dielectric layer”, and therefore, the depletion layer is within the n-type 4H-SiC epilayer at an interface with the yttrium oxide layer)
Claims 6 and 15 are rejected under 35 U.S.C. 103 as being unpatentable over Jia in views of Quah, Zhang, and Mandal as applied to claims 1-5, 8-14, and 17-18 above, and further in view of Thomas (Thomas et al., Appl. Phys. Lett. 108, 013505 (2016), doi.org/10.1063/1.4939203).
Regarding claim 6, while Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1,
Jia, Quah, Zhang, and Mandal do not teach that the betavoltaic cell has at least a maximum power density output of 11 nW/cm3.
Thomas, on the other hand, teaches that the betavoltaic power sources find potential utilization in systems, which require power in the range of 0.01–100 µW, and are space constrained (less than 1 cm3) (page 2, col. 1, para. 1), which makes at least a maximum power density of 10nW/cm3 (0.01 µW/1 cm3 = 10nW/cm3).
Therefore, the range of maximum power density output provided by the prior art overlaps with the range of maximum power density output provided in the claimed invention, and a prima facie case of obviousness exists (see MPEP 2144.05(I)), as the range of maximum power density output can be optimized by design and routine experimentation to adapt the betavoltaic cell to specific practical applications (see MPEP 2144.05(II)). Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to configure the betavoltaic cell of Jia, Quah, Zhang, and Mandal in such a way that the betavoltaic cell has at least a maximum power density output of 11 nW/cm3, which would increase the potential applications of the betavoltaic cell.
Regarding claim 15, while Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10,
Jia, Quah, Zhang and Mandel do not disclose that the method further comprises configuring the betavoltaic cell to have at least a maximum power density output of 11 nW/cm3.
Thomas, on the other hand, teaches that the betavoltaic power sources find potential utilization in systems, which require power in the range of 0.01–100 µW, and are space constrained (less than 1 cm3) (page 2, col. 1, para. 1), which makes at least a maximum power density of 10nW/cm3 (0.01 µW/1 cm3 = 10nW/cm3).
Therefore, the range of maximum power density output provided by the prior art overlaps with the range of maximum power density output provided in the claimed invention, and a prima facie case of obviousness exists (see MPEP 2144.05(I)), as the range of maximum power density output can be optimized by design and routine experimentation to adapt the betavoltaic cell to specific practical applications (see MPEP 2144.05(II)). Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to modify the method of Jia, Quah, Zhang, and Mandal to configure the betavoltaic cell to have at least a maximum power density output of 11 nW/cm3, which would increase the potential applications of the betavoltaic cell.
Claims 7 and 16 are rejected under 35 U.S.C. 103 as being unpatentable over Jia in views of Quah, Zhang, and Mandal as applied to claims 1-5, 8-14, and 17-18 above, and further in view of Chandrashekar (Chandrashekar et al, Appl. Phys. Lett. 88, 033506 (2006), doi.org/10.1063/1.2166699).
Regarding claim 7, while Jia in views of Quah, Zhang, and Mandal teaches the betavoltaic cell of claim 1,
Jia, Quah, Zhang, and Mandal do not disclose that the betavoltaic cell has at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter.
Chandrashekar, on the other hand, teaches a 4H-SiC betavoltaic cell (Abstract) wherein the betavoltaic cell has at least a fill factor of 51% (Fig. 2 and Table I) when exposed to a 1mCi 63Ni beta particle emitter (page 3, col. 1, para. 1).
Chandrashekar further discloses that numerical modeling of the betavoltaic cell shows that the betavoltaic cell is capable of providing a fill factor of 68% for the same exposure (Table I). Furthermore, a person of ordinary skill in the art before the effective filing date of the claimed invention would know that the device geometry and size would further affect the fill factor. In addition, the incorporation of the oxide layer in the betavoltaic cell of Jia, Quah, and Mandal would further provide the benefit of reducing the surface recombination at the SiC-oxide interface, as evidenced by Ichikawa (page 2, col. 1, para. 1; Ichikawa et al, 2018, ECS J. Solid State Sci. Technol. 7 Q127, DOI 10.1149/2.0031808jss), which would increase the fill factor. Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would realize that the betavoltaic cell of Jia, Quah, Zhang, and Mandel would be able to provide a fill factor of at least 66% when exposed to a 2.5 mCi 63Ni beta particle emitter, and would be motivated to the design the betavoltaic cell such that the betavoltaic cell has at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter.
Regarding claim 16, while Jia in views of Quah, Zhang, and Mandal teaches the method for making a betavoltaic cell of claim 10,
Jia, Quah, Zhang, and Mandel do not disclose that the method further comprises configuring the betavoltaic cell has at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter.
Chandrashekar, on the other hand, teaches a 4H-SiC betavoltaic cell (Abstract) wherein the betavoltaic cell has at least a fill factor of 51% (Fig. 2 and Table I) when exposed to a 1mCi 63Ni beta particle emitter (page 3, col. 1, para. 1).
Chandrashekar further discloses that numerical modeling of the betavoltaic cell shows that the betavoltaic cell is capable of providing a fill factor of 68% for the same exposure (Table I). Furthermore, a person of ordinary skill in the art before the effective filing date of the claimed invention would know that the device geometry and size would further affect the fill factor. In addition, the incorporation of the oxide layer in the betavoltaic cell of Jia, Quah, and Mandal would further provide the benefit of reducing the surface recombination at the SiC-oxide interface, as evidenced by Ichikawa (page 2, col. 1, para. 1; Ichikawa et al, 2018, ECS J. Solid State Sci. Technol. 7 Q127, DOI 10.1149/2.0031808jss), which would increase the fill factor. Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would realize that the betavoltaic cell of Jia in views of Quah, Zhang, and Mandel would be able to provide a fill factor of at least 66% when exposed to a 2.5 mCi 63Ni beta particle emitter, and would be motivated to modify the method of Jia in views of Quah, and Mandel to configure the betavoltaic cell to have at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter.
Response to Arguments
It has been acknowledged that the applicant amended claims 1, 3, 5, 9-10, 12, 14, and 18 per response dated on 3/24/2026. Applicant's arguments with respect to claims have been fully considered.
Applicant argues in substance:
As an initial matter, the Office Action does not identify any actual disclosure in Jia that the top metal contact is ''configured to act as a gate contact." Instead, the rejection states that Jia's first contact acts as a gate contact because the device structure is ''identical to the one in the current application." That is not a teaching from Jia. It is an inference drawn from Applicant's own disclosure. A rejection under § 103 cannot be sustained by using the present application as a template and then retrofitting isolated teachings from the references to match that template. The present specification describes a specific vertical MOS betavoltaic structure in which the nickel gate contact cooperates with the pulsed-laser-deposited yttrium oxide and the n-type 4H-SiC epilayer to achieve the disclosed self-biased response, reduced leakage, and improved carrier transport. The cited art does not show that Jia's front contact is disclosed or suggested as the claimed gate contact in that architecture.
The Examiner agrees with the Applicant on that Jia does not explicitly discloses that the top metal contact “is configured to act as a gate contact”. However, the Examiner respectfully disagrees with the Applicant on that the limitation that the top metal contact “is configured to act as a gate contact” has a patentable weight. The Examiner notes that this limitation is a functional limitation covered under MPEP 2114 (II). Accordingly, a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim limitation. As pointed out in the non-final office action, the device disclosed in Jia is identical to the betavoltaic cell of the current application, and the top metal contact can be configured to act as a gate contact.
In their remarks, the Applicant states that “the nickel gate contact cooperates with the pulsed-laser-deposited yttrium oxide and the n-type 4H-SiC epilayer to achieve the disclosed self-biased response, reduced leakage, and improved carrier transport. The cited art does not show that Jia's front contact is disclosed or suggested as the claimed gate contact in that architecture.” Jia also shows that the bias voltage V-g applied at the top contact (Fig. 1c) affects the dark current (Fig. 3) and energy resolution (page 2, col. 1, para. 1) of the detector, and in a similar fashion, the top metal contact of Jia cooperates with the oxide layer and the n-type 4H-SiC epilayer to improve the detector performance (energy resolution and dark current), and therefore can also be configured as a gate contact in a similar architecture. Therefore, the Examiner suggests amending claim 1 with limitations that disclose structural differences caused by configuring the top metal gate contact to act as a gate.
The Office Action's reliance on Quah also does not cure this deficiency. Quah is directed to electrical properties of pulsed-laser-deposited Y2O3 gate oxide on 4H-SiC and emphasizes high dielectric constant and breakdown voltage. Applicant does not dispute that Quah discusses Y2O3 as a gate oxide material. However, the rejection does not explain why a person of ordinary skill would have taken Quah's MOS gate-oxide teaching and inserted it into Jia's cited device to arrive at the specific harsh-environment betavoltaic MOS cell now claimed. The present application is not directed merely to replacing one dielectric with another. Rather, the specification explains that the pulsed-laser-deposited yttrium oxide layer, together with the nickel gate contact and the 4H-SiC epilayer, yields a device exhibiting improved hole transport, lower leakage, and strong self-biased radiation response. The Office Action provides no evidence that those device-level results would have been expected from the proposed substitution.
The Examiner respectfully disagrees with the Applicant on that “the rejection does not explain why a person of ordinary skill would have taken Quah's MOS gate-oxide teaching and inserted it into Jia's cited device to arrive at the specific harsh-environment betavoltaic MOS cell now claimed”. The rejection of claim 1 on page 4 of the non-final office action states the advantages of pulsed laser deposited yttrium oxide as reduced leakage current and higher breakdown voltage as a gate oxide, which are explicitly disclosed by Quah. Notably, Quah also suggests that pulsed laser deposited yttrium oxide is a better alternative to silicon dioxide for a gate oxide due to its higher permissible electric field, large bandgap, and high thermal stability (page 1, col. 1, para. 1). Issues about silicon dioxide on 4H-silicon carbide epilayers and search for alternatives to silicon dioxide as a gate oxide were already reported by Siddiqui (Siddiqui et al., High-k dielectrics for 4H-silicon carbide: present status and future perspectives, J. Mater. Chem. C, 2021, 9, 5055) before the effective filing date of the claimed invention. Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to replace silicon dioxide with pulsed laser deposited yttrium oxide to obtain benefits of yttrium oxide over silicon dioxide. These specific points made by Quah and Siddiqui are now also included in the current office action for clarification
The Applicant also states that “The present application is not directed merely to replacing one dielectric with another”, and “the specification explains that the pulsed-laser-deposited yttrium oxide layer, together with the nickel gate contact and the 4H-SiC epilayer, yields a device exhibiting improved hole transport, lower leakage, and strong self-biased radiation response. The Office Action provides no evidence that those device-level results would have been expected from the proposed substitution.”. The non-final office action did not suggest yttrium oxide as a simple replacement for silicon dioxide. As noted above, yttrium oxide has been considered as an alternative to silicon oxide, and Quah specifically lists advantages of yttrium oxide over silicon dioxide, including higher permissible electric fields, higher breakdown voltage, and low leakage current, which provide obvious motivation to replace the silicon dioxide of Jia with yttrium oxide.
The reliance on Mandal for the ''second nickel contact'' is likewise insufficient. Mandal concerns a Schottky barrier radiation detector and does not disclose the combined MOS betavoltaic structure proposed by the Office Action. The rejection characterizes the substitution of nickel for Jia's Ti/Al/Ti back contact as a ''simple substitution," but contact selection in 4H-SiC devices is architecture- and interface-dependent. The Office Action does not explain why a person of ordinary skill would have modified Jia's already operative back-contact arrangement with Mandal's backside nickel contact in the specifically modified Jia/Quah structure, or why the resulting device would have been expected to retain the claimed MOS betavoltaic operation. Conclusory reliance on ''simple substitution'' is not enough under KSR.
The Examiner respectfully disagrees with the Applicant. In both the current application and Mandal, the aim of the second contact is to make an ohmic contact on the n-type 4H-SiC substrate. As noted in the non-final office action, nickel is an alternative metal for making ohmic contact on n-type 4H-SiC, and such a substitution does not provide an inventive concept as long as the specification contains no disclosure of either the critical nature of specific material nickel for the back contact or any unexpected results arising if nickel is not used (see MPEP2143).
The rejection therefore fails for at least two independent reasons. First, the cited combination does not teach or suggest the complete claimed MOS architecture, including the first nickel contact ''configured to act as a gate contact." Second, the Office Action does not provide an adequate, non-hindsight rationale showing why a person of ordinary skill would have combined Jia, Quah, and Mandal in the particular manner required by Claims 1 and 10 with a reasonable expectation of success. Claims 1 and 10 are accordingly patentable over the cited combination.
The Examiner respectfully disagrees with the Applicant due to reasons detailed in points a-c above. Therefore, the rejections made on claims 1 and 10 in the non-final office action based on Jia, Quah, and Mandal remain valid. However, the amendments made to the claims 1 and 10 regarding the betavoltaic cell being heteroepitaxial and forming the back contact on a bulk side of a 4H-SiC wafer led to rejection of claims 1 and 10 by including Zhang along with Jia, Quah, and Mandel.
The Office Action expressly acknowledges that Jia, Quah, and Mandal do not disclose that ''the betavoltaic cell is heteroepitaxial'' or that the method includes ''configuring the betavoltaic cell to be heteroepitaxial." The rejection then relies on the proposition that pulsed laser deposition can be used to deposit epitaxial yttrium oxide layers, citing Zhang, and concludes that a person of ordinary skill would have been motivated to make the yttrium oxide layer epitaxial. That reasoning is insufficient.
The claimed limitation is not that pulsed laser deposition is capable of producing epitaxial yttrium oxide somewhere or under some conditions. The claim requires that the betavoltaic cell itself ''is heteroepitaxial," and the parallel method claim requires configuring the betavoltaic cell to be heteroepitaxial. The present specification demonstrates this with specific disclosure of epitaxial Y203 on 4H-SiC and corresponding X-ray diffraction evidence. By contrast, neither Jia nor Quah nor Mandal teaches an actual heteroepitaxial Y203/4H-SiC betavoltaic device. The Office Action thus moves from a generic proposition about what pulsed laser deposition can sometimes achieve to the conclusion that the claimed heteroepitaxial betavoltaic cell would have been obvious. That leap is precisely the kind of hindsight-driven reasoning that § 103 does not permit.
The Examiner respectfully disagrees. A person of ordinary skill in the art before the effective filing date would be motivated to deposit an yttrium oxide layer on 4H-silicon carbide with minimal surface defects and maximal smoothness. The cited prior art, Zhang, teaches that the parameters of the pulsed laser deposition can be adjusted to deposit the yttrium oxide layer in an epitaxial form, which improves electrical and structural properties of the semiconductor-yttrium oxide interface (page 7). Therefore, by knowing that the yttrium oxide layer can be deposited epitaxially by pulsed laser deposition, a person of ordinary skill in the art before the effective filing date of the claimed invention would be motivated to deposit the yttrium oxide layer epitaxially to improve the electrical characteristics of the interface between the n-type 4H-SiC epilayer and yttrium oxide layer.
Moreover, the rejection as stated is over Jia in view of Quah and Mandal, yet the Office Action must resort to an additional reference merely to suggest that PLD can be used to form epitaxial yttrium oxide layers generally. Even with that extra citation, there is still no teaching or reasoned explanation why a person of ordinary skill would have selected and achieved the specific heteroepitaxial Y203/4H-SiC structure required by Claims 3 and 12 in Jia's cited device. Claims 3 and 12 are therefore independently patentable.
The Examiner respectfully disagrees with the Applicant. The reasons given in the points a-c, and e above lead to combination of the teachings of the mentioned prior art, and thereby to a betavoltaic cell structure which is heteroepitaxial.
Claims 5 and 14 require that the betavoltaic cell ''has less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer," and that the method includes configuring the betavoltaic cell to have that comparative characteristic. The Office Action acknowledges that Jia, Quah, and Mandal do not disclose this limitation. The rejection attempts to bridge the gap by citing general teachings that oxide quality and lower interface-trap density can suppress surface recombination. That is not enough.
A reduced oxide-semiconductor trap density is not synonymous with the specific claimed comparative result of ''less surface recombination velocity as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer." The claims recite an actual device-performance relationship relative to a specific comparator. The present specification attributes this advantage to passivation of the 4H-SiC surface by the yttrium oxide layer in the claimed Ni/Y203/4H-SiC MOS structure. The cited art does not disclose that comparative result for the proposed combination, and the Office Action offers no evidence that such a result would necessarily or predictably follow from the cited references. At most, the rejection suggests that reduced trap density might be beneficial. That does not establish obviousness of the claimed comparative performance limitation.
For the foregoing reasons, Applicant respectfully submits that the Office Action has not established a prima facie case of obviousness with respect to Applicant's claims. Applicant respectfully requests withdrawal of the rejection under 35 U.S.C. § 103.
The Examiner respectfully disagrees. As indicated in the non-final office action, the surface recombination velocity depends on surface recombination due to surface traps in 4H-SiC (evidenced by Ichikawa, page 2, col. 1, para. 1; Ichikawa et al, 2018, ECS J. Solid State Sci. Technol. 7 Q127, DOI 10.1149/2.0031808jss). Therefore, the reduced trap density at the 4H-SiC and yttrium oxide interface, as disclosed by Quah (pages 2-3, Results and Discussion section), will lead to reduced surface recombination velocity as claimed.
To further clarify the limitations of claim 5 and 14, the Applicant amended these claims by including a limitation regarding that the surface of the 4H-SiC epilayer is passivated by the yttrium oxide layer. This clarification further supports the prior art as used in the non-final office action, because both Jia and Quah disclose that the oxide layer passivates the interface with 4H-SiC (Jia, page 2, Col. 1, para. 1; and Quah, Results and Discussion, and Conclusion sections). Therefore, the office action clearly establishes evidence that the consequence of the teachings of the prior art is reduced surface recombination velocity by passivation of the 4H-SiC surface. Unless the Applicant provides evidence for another mechanism for reduced surface recombination velocity, claims 4 and 15 remain rejected by current prior art.
Claims 4 and 13 stand rejected under 35 U.S.C. § 103 as allegedly obvious over Jia in view of Quah and Mandal, and further in view of Choi. Claim 4 depends from Claim 1 and requires that ''the betavoltaic cell has reduced dark current as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer." Claim 13 depends from Claim 10 and recites the parallel method limitation. Applicant respectfully traverses this rejection.
The Office Action expressly recognizes that Jia, Quah, and Mandal do not disclose the claimed comparative dark-current limitation. Choi is then cited for an Al203 spacer between Ni and 4H-SiC, and the rejection concludes that the proposed device would have reduced dark current and that such reduction would be inherent. Neither proposition is supported.
First, Choi does not disclose the claimed Ni/Y203/4H-SiC MOS betavoltaic structure. Choi concerns an Al203 spacer and barrier modulation in a different device context. The fact that Choi discusses an oxide spacer affecting current flow does not teach the particular limitation of Claims 4 and 13, namely, reduced dark current ''as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer." The claims require a comparative result against a specific SBD comparator. The cited art does not disclose that result for the Office Action's proposed combination.
Second, the rejection's reliance on inherency is improper. Inherency in the obviousness context requires that the missing feature necessarily and inevitably flow from the prior art combination. The Office Action does not show that every device formed from Jia, Quah, Mandal, and Choi would necessarily exhibit reduced dark current relative to the claimed Schottky-barrier comparator. To the contrary, dark current in these devices depends on oxide composition, interface quality, thickness, contact configuration, and processing conditions. The present specification reports a specific comparative reduction in leakage current density for the disclosed Ni/Y203/4H-SiC MOS structure. That measured result cannot be dismissed as inherently present in the cited art without evidentiary support.
Third, the Office Action's rationale again depends on hindsight. The rejection assumes that because Applicant's disclosed device exhibits reduced dark current relative to an SBD, a person of ordinary skill would have modified the references to ''construct'' a device having that same comparative result. That reasoning begins with Applicant's disclosure and works backward. Section 103 requires the opposite. The prior art itself must provide a reasoned basis to expect the claimed result. It does not do so here.
Claim 13 rises or falls with Claim 4 in this rejection. Because the cited combination does not teach or render obvious configuring the claimed betavoltaic cell to have reduced dark current as compared to a Schottky barrier diode fabricated on at least one 4H-SiC epilayer, both Claims 4 and 13 are patentable. For these reasons, Applicant respectfully requests withdrawal of the rejection of Claims 4 and 13 under 35 U.S.C. § 103.
The Examiner respectfully disagrees with the Applicant. Choi does not need to have an exact combination of materials to teach that the dark current is reduced by the inclusion of an oxide layer. The physical principles (including an energy barrier at the metal/4H-SIC interface; Fig. 4, page 5, col. 1) provided by Choi provides clear evidence. On the other hand, the Examiner also realized that Jia actually teaches that the inclusion of an oxide layer between the at least one n-type 4H-SiC epilayer and Ni contact decreases the dark current in comparison to a Schottky diode device (see Fig. 3 of Jia). Therefore, in the current office action the teachings of Jia are provided as direct comparative evidence.
Claims 6 and 15 stand rejected under 35 U.S.C. § 103 as allegedly obvious over Jia in view of Quah and Mandal, and further in view of Thomas. Claim 6 depends from Claim 1 and requires that ''the betavoltaic cell has at least a maximum power density output of 11 nW/cm3." Claim 15 depends from Claim 10 and recites the parallel method limitation. Applicant respectfully traverses this rejection.
The rejection rests on the assertion that Thomas teaches betavoltaic power sources requiring power in the range of 0.01-100 microWatts and being space constrained to less than 1 cm3, which the Office Action states ''makes at least a maximum power density of 10 nW/cm3." That is not an actual disclosure of the claimed parameter. It is an Office Action-derived calculation based on two unrelated, generalized statements about potential system requirements. Thomas does not disclose a measured maximum power density output for the claimed Ni/Y203/4H-SiC MOS betavoltaic cell, or for the Office Action's proposed Jia/Quah/Mandal combination.
Because Thomas does not disclose an actual power-density range for the claimed structure, there is no genuine overlap between a prior-art range and the claimed threshold of ''at least a maximum power density output of 11 nW/cm3." The Office Action's premise of range overlap is therefore misplaced. Nor does the rejection identify any teaching that maximum power density in the proposed combination was a recognized result-effective variable that could simply be optimized by routine experimentation to reach the claimed threshold.
The present specification describes the claimed maximum power density output in the context of the disclosed Ni/Y203/4H-SiC MOS betavoltaic cell, with the particular advantages produced by the yttrium oxide layer, the nickel contacts, and the 4H-SiC epitaxial structure. The cited art does not show that the proposed combination would have been expected to produce the claimed value, much less that a person of ordinary skill would have been motivated to configure the device to achieve that threshold based on Thomas's generalized discussion of desired power and system volume.
The Examiner respectfully disagrees with the arguments of the Applicant. The Office Action-derived calculation sets forth of the range of power density levels for potential utilization of betavoltaic power sources in typical systems which again typically require powers in the range of 0.01–100 µW (see Thomas, page 2, para. 1). Given the space constraints of power sources being 1cm3 or less, this leads to are quired output power density range from 10nW/cm3 to 100 µW/cm3 for betavoltaic power sources. Therefore, to be able to operate typical systems, a betavoltaic power source needs to provide a power density of at least 10nW/cm3. This value sets a standard which has to be achieved through design optimization by a person of ordinary skill in the art before the effective filing date of the claimed invention. Therefore, the rejection based on additional evidence provided by Thomas is valid, unless the Applicant provides information that the betavoltaic cell design disclosed by the prior art does not allow such an optimization, and claims 6 and 15 remain rejected in the current application.
Claims 7 and 16 stand rejected under 35 U.S.C. § 103 as allegedly obvious over Jia in view of Quah and Mandal, and further in view of Chandrashekar. Claim 7 depends from Claim 1 and requires that ''the betavoltaic cell has at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter." Claim 16 depends from Claim 10 and recites the parallel method limitation. Applicant respectfully traverses this rejection.
The Office Action acknowledges that Jia, Quah, and Mandal do not disclose the claimed fill factor under the claimed exposure condition. Chandrashekar is cited for a measured fill factor of 51% when exposed to a 1 mCi 63Ni beta emitter, together with a modeled value of 68% for the same exposure. The rejection then reasons that a person of ordinary skill would have realized that the modified Jia/Quah/Mandal device would be able to provide a fill factor of at least 66% when exposed to a 2.5 mCi 63Ni beta particle emitter. This conclusion is unsupported.
The claimed limitation is not merely ''a high fill factor." It is a specific numerical threshold under a specific source condition: ''at least a fill factor of 66% when exposed to a 2.5 mCi 63Ni beta particle emitter." Chandrashekar does not disclose that condition. A measured value under 1 mCi exposure, and a modeled value for that same 1 mCi exposure, do not teach or suggest the claimed performance at 2.5 mCi. The Office Action provides no evidence that fill factor scales predictably with source activity in the manner assumed, particularly for a materially different device architecture using the Office Action's proposed combination.
The additional assertion that oxide incorporation would reduce surface recombination and thereby increase fill factor also does not bridge this gap. At most, that reasoning suggests that an oxide layer may be beneficial. It does not establish that the claimed 66% threshold under the claimed 2.5 mCi 63Ni condition would have been expected for the proposed Jia/Quah/Mandal device. The rejection therefore relies on a chain of extrapolation rather than on actual teachings from the prior art.
The present specification, by contrast, reports the claimed fill factor for the disclosed Ni/Y203/4H-SiC MOS betavoltaic cell and explains that this was achieved even under partial illumination conditions. That underscores that the claimed value is a concrete performance characteristic of the disclosed device, not a routine or predictable consequence of simply combining the cited references.
The Examiner respectfully disagrees with the arguments of the Applicant. As detailed in the non-final office action, the prior art, Chandrashekar, already teaches that fill factors similar to the claimed fill factor are achievable in theory and practice with 4H-SiC-based betavoltaic cells. Therefore, a person of ordinary skill in the art before the effective filing date of the claimed invention would already expect to achieve a similar level of fill factor from the betavoltaic call of Jia in views of Quah, Zhang, and Mandel. Because the Applicants did not provide any specific structural or methodological limitation specific to the current application that the prior art fails to teach and that prevents achieving the claimed fill factors, the rejection based on evidence provided by Chandrashekar is valid, and claim 7 and 16 remain rejected in the current application.
For the purpose of compact prosecution, the Examiner notes that the rejections based on prior art in the current office action can be overcome by providing structural, methodological, and material limitations that support several arguments made by the Applicant above. For example, structural, methodological, and material limitations regarding the back contact, the epitaxial yttrium oxide layer, depletion region and self-bias condition, passivation of the surface of the at least one 4H-SiC epilayer, the reduction of the surface recombination velocity, and achieving claimed power output density and fill factor would be able to distinguish the disclosed betavoltaic cell from the prior art.
The Examiner is available for an interview at Applicant’s convenience if the Applicant would like to discuss the application.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/ILKER NMN OZDEN/Examiner, Art Unit 2812 /William B Partridge/Supervisory Patent Examiner, Art Unit 2812
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