Detailed Office Action
Examiner’s Comment – 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 .
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 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.
Request for Continued Examination
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 19 January 2026 has been entered.
Response to Arguments
Applicant’s arguments with respect to claims 1 and 3 have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument.
Claim Rejections - 35 USC § 103
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 of this title, 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 set forth in Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), that are applied 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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 1 and 3
Claims 1 and 3 are rejected under 35 U.S.C. 103 as being unpatentable over Burberry et al. (2007/0159574; “Burberry”) in view of Emrose et al. (Multilayer broadband switchable absorbers based on phase-change materials, 4 October 2023, San Diego, California, United States, Proceedings Volume 12647, Active Photonic Platforms (APP) 2023; 126470M; “Emrose”), further in view of in view of Lawandi et al. (Switchable distributed Bragg reflector using GST phase change material. Opt Lett. 2022 Apr 15;47(8):1937-1940; “Lawandi”), further in view of Goossens (Filter width affects the transmittance of patterned all-dielectric Fabry-Perot filters. Opt Lett. 2021 Dec 1;46(23):5926-5929; “Goossens”), further in view of Kim et al. (Simple method to extract extinction coefficients of films with the resolution of 10-5 using just transmission data and application to intermolecular charge-transfer absorption in an exciplex-forming organic film. Opt Express. 2020 Apr 13;28(8):11892-11898; “Kim”), and further in view of Rios et al. (Color Depth Modulation and Resolution in Phase-Change Material Nanodisplays. Adv. Mater., 28: 4720-4726; “Rios”).
Regarding independent claim 1, Burberry discloses in figure 8, and related figures and text, embodiments of displays having two optical materials (‘display materials’) separated by a transparent common electrode while sandwiched between plane of transparent row electrodes and a lower plane of column electrodes. See below, Burberry – Figure 8 and Burberry - Selected Text.
Burberry - Figure 8
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Burberry – Selected Text
Abstract. The present invention relates to a display comprising, in order, a support, a first patterned conductor, a first level of electrically modulated imaging material, a coextensive common electrode conductor, a second level of electrically modulated imaging material, and a second patterned conductor and a method of imaging the display.
[0021] FIG. 8 illustrates one embodiment of a common electrode structure.
[0026] The present invention relates to a support, a first conductor patterned into columns, a first layer of electrically modulated imaging material, a common electrode coextensive across multiple columns, a second layer of electrically modulated imaging material, and a second electrode patterned into rows. The invention includes an element and a method for making the element. The device may include a color contrast or pigmented layer and a field spreading layer or layers may be incorporated on either side of the electrically modulated imaging material--common electrode--electrically modulated imaging material stack, adjacent to the first and second electrodes, as well as other functional layers or may be incorporated in a contrasting absorber layer. Specific means of energizing the electrodes to reset and select image data are also included. A preferred embodiment of the present invention integrates two stacked displays in the most efficient way. Particular uses are intended in flexible chiral nematic liquid crystal displays, as well as other field driven displays, such as electrophorectic displays. The invention also reduces the number of drive channels needed, compared with alternative methods, thus reducing system cost and, in some embodiments, can provide spot color.
[0040] At least one two conductive layers are present in display devices. A first conductor is formed over substrate. The first conductor can be a transparent, electrically conductive layer of tin oxide or indium tin oxide (ITO), with ITO being the preferred material. Alternatively, first conductor can be an opaque electrical conductor formed of metal such as copper, aluminum or nickel. If first conductor is an opaque metal, the metal can be a metal oxide to create a light absorbing first conductor. This conductive layer may comprise other metal oxides such as indium oxide, titanium dioxide, cadmium oxide, gallium indium oxide, niobium pentoxide and tin dioxide. See, Int. Publ. No. WO 99/36261 by Polaroid Corporation. In addition to the primary oxide such as ITO, the at least one conductive layer can also comprise a secondary metal oxide such as an oxide of cerium, titanium, zirconium, hafnium and/or tantalum. See, U.S. Pat. No. 5,667,853 to Fukuyoshi et al. (Toppan Printing Co.) Other transparent conductive oxides include, but are not limited to ZnO.sub.2, Zn.sub.2SnO.sub.4, Cd.sub.2SnO.sub.4, Zn.sub.2In.sub.2O.sub.5, MgIn.sub.2O.sub.4, Ga.sub.2O.sub.3--In.sub.2O.sub.3, or TaO.sub.3.
[0044] The transparent common electrode is coextensive with multiple row and column electrode. It is common in the sense that multiple independently addressable pixels share the coextensive electrode. Contact to the common electrode can be made, for example, at a single point at an outer edge of the display area and the resulting electrical signal on the common electrode is shared between multiple rows and columns in the device. The common electrode material, or combinations of materials, can be selected from any of the same substances used for the transparent electrode as previously enumerated but may be considerably thinner, and therefore more transparent, because its effective area is much larger than the row or column electrodes.
[0046] The liquid crystal (LC) is used as an optical switch. The supports are usually manufactured with transparent, conductive electrodes, in which electrical "driving" signals are coupled. The driving signals induce an electric field which can cause a phase change or state change in the liquid crystal material, the liquid crystal exhibiting different light reflecting characteristics according to its phase and/or state.
Further regarding claim 1, Burberry does not explicitly disclose phase change materials.
However, Emrose discloses in Emrose – Poster and Emrose – Selected Text, and related figures and text, embodiments of multilayer structures comprising two phase change materials (GST) that can be, “switched between its amorphous and crystalline phases with a drastic change in its optical properties. The phase transition can be induced reversibly and rapidly by applying external electrical pulses, optical pulses or thermal annealing. Emrose – Poster (“Power is consumed only during the phase transition process.”).
Emrose - Poster
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Emrose – Selected Text
ABSTRACT We introduce multilayer structures with the phase-change material germanium-antimony-tellurium (GST) for use as broadband switchable absorbers in the infrared wavelength range. We use a memetic optimization algorithm coupled with the transfer-matrix method to optimize both the material composition and the layer thicknesses of the multilayer structures. We show that in the optimized structures near perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. Our results could pave the way to a new class of broadband switchable absorbers and thermal sources in the infrared wavelength range.
1. INTRODUCTION
Controlling the precise spectral absorption, reflection, and transmission properties within optical structures gained substantial attention in photonics in recent times. Achieving perfect absorption across a broad wavelength range holds particular significance for applications such as thin-film thermal emitters,1 color displays,2 photovoltaics,3 plasmonic waveguides,4 smart windows,5 and more. In technological domains, infrared light absorbers play a pivotal role, spanning biochemical sensors,6 medical devices,7 solar energy harvesting,8 thermal management,9–11 and infrared imaging.12 The mid-infrared spectral range, encompassing wavelengths where materials at temperatures of around 300-700°C exhibit peak thermal emission,13 holds particular significance. Near-complete light absorption within this range is vital for optimizing optical device performance. To address this, researchers have turned to materials with tunable absorption properties, especially phase-change materials (PCMs). Unlike volatile tuning methods involving transparent conducting oxides or phase transition materials, PCMs offer non-volatile tunability. These materials can switch between their amorphous and crystalline phases through thermal annealing, electrical pulses, or optical heating methods on nanosecond timescales,14 all due to their distinctive metavalent bonding mechanism.15
In this study, we present a novel approach involving multilayer structures incorporating the phase-change material GST for use as versatile broadband switchable absorbers in the infrared wavelength range. Employing a memetic optimization algorithm along with the transfer-matrix method, we fine-tune both material composition and layer thicknesses in aperiodic multilayer structures. These structures, composed of infinite slabs above a semiinfinite substrate, offer absorption profiles akin to more complex three-dimensional structures, but with simplified fabrication. By optimizing the absorption difference between GST in its crystalline and amorphous phases, we demonstrate the ability to switch near-perfect absorption to very low absorption across a wide wavelength range. Our simultaneous optimization of material composition and layer thickness results in improved performance with fewer layers. Additionally, we analyze the angular dependence of absorption for GST in both phases and clarify the physical basis of broadband switchability through electric field profile comparisons. These findings hold potential for a new generation of broadband switchable absorbers and thermal sources in the infrared domain.
2. RESULTS
Our objective is to optimize the composition and layer thicknesses of these multilayer structures to achieve nearly perfect absorption that can be switched to very low absorption across a broad spectrum by inducing GST’s transition between its crystalline and amorphous phases. To achieve this, we employ a memetic optimization algorithm in combination with the transfer-matrix method to design and fine-tune the multilayer structures. Our exploration spans various materials, including GST, dielectrics, metals, and semiconductors, all aimed at maximizing the absorption contrast between GST’s different phases within the desired wavelength range. Our results distinctly highlight the success of the optimized structures in achieving the desired broadband switchability. We concentrate primarily on a five-layer configuration within two near-infrared wavelength ranges: 1 to 1.6 μm and 2.1 to 4.1 μm. The first range showcases an optimized structure that achieves an impressive 93.6% average absorption in the crystalline phase and a significantly lower 25.8% average absorption in the amorphous phase. The second optimized design, targeting the 2.1 to 4.1 μm range, demonstrates even more remarkable performance, boasting an average absorption of 98.0% and 0.8% in the crystalline and amorphous phases, respectively. Importantly, the improved performance beyond 2 μm is attributed to the transition of amorphous GST to a lossless medium. Our investigation further delves into electric field profiles, providing additional confirmation of the absorbers’ broadband switchability and insights into their underlying physical mechanism. Moreover, we explore incident angle dependency, demonstrating that these broadband switchable absorbers maintain their superior performance across a wide range of angles of incidence, underscoring their versatility and practical viability. This research not only advances absorber design through harnessing phase-change material properties but also holds significant promise for enhancing light detection efficiency and introducing a new class of broadband switchable absorbers and thermal sources within the infrared spectrum. Further exploration can build upon our work by investigating alternative optimization approaches and expanding applications into different spectral regions.
Consequently, it would have been obvious to one of ordinary skill in the art to modify Burberry to disclose phase change materials because the resultant configuration would enable predictably switchable and wavelength tailorable broadband absorbers. Emrose – Selected Text.
Further regarding claim 1, Burberry in view of Emrose does not explicitly disclose a filter structure comprising alternate high and low refractive index materials.
However, Lawandi discloses in figures 1 and 2 modulation structure of n multi-layer phase change unit arrays. Lawandi, figures 1 and 2, and related figures and text, including abstract (“We demonstrate the design, fabrication, and measurement of a switchable distributed Bragg reflector (DBR) that can be thermally switched from a close-to-zero reflective OFF state to a more than 70% reflection in its ON state. This is accomplished using a multilayer thin film stack using germanium (Ge) and the phase change material (PCM) Ge2Sb2Te5 (GST). The refractive indexes of Ge and GST in the amorphous state are closely matched, resulting in a nearly zero interface reflection. With appropriate antireflection coatings at the cavity ends, the overall reflection can be designed to be close to zero. When the GST is switched to the crystalline state, the refractive index contrast between the Ge and GST layers will increase dramatically contributing to the DBR reflection. Using this unique feature, we were able to design and experimentally demonstrate more than 70% reflection in the ON state and close”).
Lawandi - Figures 1 and 2
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Lawandi – Selected Text
Abstract. We demonstrate the design, fabrication, and measurement of a switchable distributed Bragg reflector (DBR) that can be thermally switched from a close-to-zero reflective OFF state to a more than 70% reflection in its ON state. This is accomplished using a multilayer thin film stack using germanium (Ge) and the phase change material (PCM) Ge2Sb2Te5 (GST). The refractive indexes of Ge and GST in the amorphous state are closely matched, resulting in a nearly zero interface reflection. With appropriate antireflection coatings at the cavity ends, the overall reflection can be designed to be close to zero. When the GST is switched to the crystalline state, the refractive index contrast between the Ge and GST layers will increase dramatically contributing to the DBR reflection. Using this unique feature, we were able to design and experimentally demonstrate more than 70% reflection in the ON state and close.
Theory. The reflectivity in a DBR structure is achieved by coherently combining the interface reflection between multiple high/low refractive index interfaces …
Conclusions. The antireflection design also includes a GST layer to tune from a low reflective state to a high reflective state.
Consequently, it would have been obvious to one of ordinary skill in the art to modify Burberry in view of Emrose’s embodiments, in light of Lawandi’s disclosure of alternating indices of refraction multilayers, to disclose: a pixel grayscale modulation structure based on phase change materials, is characterized by comprising n multi-layer phase change unit arrays in each sub-pixel, an upper all-dielectric filter structure, an all-dielectric intermediate cavity, a lower all-dielectric filter structure and a crossbar control structure; each multi-layer phase change unit array comprises at least two phase change material layers separated by transparent electrodes, a phase change state of each phase change material layer can be independently controlled by applying a voltage, so as to achieve a multi-gray level control; the upper all-dielectric filter structure is composed of alternately high and low refractive index materials, which is used to enhance a structural transmittance and reduce a light transmission of a non-target wavelength; the all-dielectric intermediate cavity is composed of all-dielectric materials with a high refractive index, and is used to improve transmission characteristics of the filter structure and reduce a stray light; the lower all-dielectric filter structure is used to further enhance an overall transmittance and reduce the light transmission of the non-target wavelength; the crossbar control structure comprises a horizontal electrode layer composed of a plurality of horizontal electrodes arranged along X-axis direction and a vertical electrode layer composed of a plurality of vertical electrodes arranged along Y-axis direction,, and the plurality of horizontal electrodes and the plurality of vertical electrodes form a cross point array, and each cross point in the middle has a light modulated pixel unit; Burberry – Figure 8 and Burberry – Selected Text; Emrose – Poster and Emrose – Selected Text; Lawandi - Figures 1 and 2 and Lawandi - Selected Text; because the resultant configuration would enable predictably switchable and wavelength tailorable broadband absorbers; Emrose – Selected Text; that predictably vary reflection states; Lawandi, Conclusions; while predictably controlling pixel-crosstalk. Goossens, figure 1 and abstract (“Patterned thin-film Fabry–Pérot filters are used to develop compact spectral cameras. Recent articles report on crosstalk in such devices, raising concerns regarding spectral and spatial resolution. It has been suggested that light entering a filter might spill over to neighboring filters but this has not yet been analyzed in detail. The proposed mechanism in this Letter is that the Fabry–Pérot filters act as coupled waveguides that can propagate crosstalk above the pixel array. The results show that the crosstalk can be asymmetric, enabling elimination by rearranging the filters on the sensor.”).
Goossens - Figure 1
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Further regarding claim 1, Burberry in view of Emrose, further in view of Lawandi, and further in view of Goossens’ embodiments do not explicitly disclose a structure of the upper all-dielectric filter structure and the lower all-dielectric filter structure is H (LH) x, where H is a film layer of high refractive index and low extinction coefficient, L is a film layer of low refractive index and low extinction coefficient, X is a number of periods of the film layer group, X is≥1, and an optical thickness of each film layer is one quarter of a target light wavelength; the all-dielectric intermediate cavity is composed of an all-dielectric material with a high refractive index and a thickness is one half of an optical thickness of the transmitted light to effectively improve transmission characteristics of the filter structure; and the pixel grayscale modulation structure is suitable for various display devices, including electronic paper, projection devices, augmented reality/virtual reality devices, vehicle displays, and mobile device displays.
However, Kim discloses in figures 1-4, and related text, that one of ordinary skill in the art would understand how to determine ‘the exact thickness, refractive index, and small extinction coefficient of films in the sub-bandgap wavelength region,’ Kim, Exact film thickness, ‘When the difference in extinction coefficients at the interface of the films is negligible compared to the difference in the refractive indices at the interface.’ Kim, 3.2. Transmissivity. Kim, figures 1-4, and related text, for example, Kim – Selected Text.
Kim – Selected Text
3.2. Transmissivity
When the difference in extinction coefficients at the interface of the films is negligible compared to the difference in the refractive indices at the interface, Tfilm and Rfilm can be expressed as follows, considering thin-film interference:
3.3. Exact film thickness
Thin-film interference can be used to obtain the exact thickness, refractive index, and small extinction coefficient of films in the sub-bandgap wavelength region. First, the refractive index of the film can be obtained based on the absorbance at the absorbance points where the destructive interference of transmitted waves takes place and the extinction coefficients are zero. Second, the exact film thickness can be calculated from the wavelength at the absorbance points where destructive interference occurs. The refractive index can also be obtained from the exact film thickness. Finally, the film’s extinction coefficient can be determined based on the exact thickness and refractive index of the film
3.4. Refractive index
The refractive index at wavelengths of the destructive interference can be obtained using Eq. (11), based on the exact film thickness in the sub-bandgap wavelength region. n is a continuous function of wavelength,
We determined the wavelengths at which constructive interference of the transmitted waves occurs as the local minima for the oscillating absorbance
Middle interference takes place when the phase difference between the transmitted waves is an odd multiple of wavelength/2.
3.5. Extinction coefficient
Given the exact thicknesses and refractive indices of the films at the wavelengths of destructive, constructive, and middle interference, the extinction coefficient can be calculated from the absorbance.
Consequently, it would have been obvious to one of ordinary skill in the art to modify Burberry in view of Emrose, further in view of Lawandi, further in view of Goossens’ embodiments, in light of Kim’s disclosure of the predictable relationship between film thickness, refractive indices and extinction coefficients, to disclose: a pixel grayscale modulation structure based on phase change materials, comprising n multi-layer phase change unit arrays in each sub-pixel, an upper all-dielectric filter structure, an all-dielectric intermediate cavity, a lower all-dielectric filter structure and a crossbar control structure; each multi-layer phase change unit array comprises at least two phase change material layers separated by transparent electrodes, a phase change state of each phase change material layer can be independently controlled by applying a voltage, so as to achieve a multi-gray level control; the upper all-dielectric filter structure is composed of alternately high and low refractive index materials, which is used to enhance a structural transmittance and reduce a light transmission of a non-target wavelength; the all-dielectric intermediate cavity is composed of all-dielectric materials with a high refractive index, and is used to improve transmission characteristics of the filter structure and reduce a stray light; the lower all-dielectric filter structure is used to further enhance an overall transmittance and reduce the light transmission of the non-target wavelength; the crossbar control structure comprises a horizontal electrode layer composed of a plurality of horizontal electrodes arranged along X-axis direction and a vertical electrode layer composed of a plurality of vertical electrodes arranged along Y-axis direction, and the plurality of horizontal electrodes and the plurality of vertical electrodes form a cross point array, and each cross point in the middle has a light modulated pixel unit; a structure of the upper all-dielectric filter structure and the lower all-dielectric filter structure is H (LH) x, where H is a film layer of high refractive index and low extinction coefficient, L is a film layer of low refractive index and low extinction coefficient, X is a number of periods of the film layer group, X is≥1, and an optical thickness of each film layer is one quarter of a target light wavelength; the all-dielectric intermediate cavity is composed of an all-dielectric material with a high refractive index and a thickness is one half of an optical thickness of the transmitted light to effectively improve transmission characteristics of the filter structure; and the pixel grayscale modulation structure is suitable for various display devices, including electronic paper, projection devices, augmented reality/virtual reality devices, vehicle displays, and mobile device displays; Burberry – Figure 8 and Burberry – Selected Text; Emrose – Poster and Emrose – Selected Text; Lawandi - Figures 1 and 2 and Lawandi - Selected Text; Kim, figures 1-4, and related text, for example, Kim – Selected Text; because the resultant configuration would enable predictably switchable and wavelength tailorable broadband absorbers; Emrose – Selected Text; that predictably vary reflection states; Lawandi, Conclusions; while predictably controlling pixel-crosstalk. Goossens, figure 1 and abstract; and while predictably enabling ‘better depth modulation capability (i.e., grayscale)’ to achieve ‘continuous “grayscale” images, which in turn adds a new degree of functionality to the newly emerging field of PCM displays.’ Rios, figures 1-5, and related text, for example, Rios – Selected Text.
Rios – Selected Text
Ge 2 Sb 2 Te 5 (GST) as the active bistable component. [ 17] PCMs promise great potential given that state-of-the-art alloys are capable of switching in picoseconds timescales between two optically and electrically differentiable states in response to appropriate heat stimuli (crystallization) or melt-quenching processes (amorphization). [ 18–20] More interestingly, they present room temperature non-volatile behavior by stably retaining either state for years. [ 21–23] All these properties together mean that two highly differentiable optical states, allowed by the modulation in both the real and the imaginary refractive index under phase switching, are achievable within the same thin film; which in turn can be harnessed to switch colors. [ 17,24,25] The approach presented by Hosseini et al. [ 17] relies on the strong Fabry–Perot-type interference undertaken within a stack of layers featuring a highly absorptive medium, [ 6] GST in this case. By using such material, colors were obtained with just a few layers thus presenting low-dimensionality (70 to 300 nm for the whole stack), which in turns allows for flexible substrates to be employed. Furthermore, GST can be locally and reversibly switched at nanometric scales, enabling resolution beyond any other display previously reported. In this work, we demonstrate that Ag 3 In 4 Sb 76 Te 17 (AIST), a growth dominated phase-change alloy, [ 26] can be employed for similar color modulation, but with better depth modulation capability (i.e., grayscale). We further demonstrate the limits of this technique in terms of resolution and switching energy. Lastly, we present a comparison between the performance of AIST and GST in terms of color modulation, resolution, and energy efficiency in devices constituted by uniform films.
We use optical cavities consisting of two transparent conducting layers of indium-tin oxide (ITO) sandwiching a thin film of PCM, either AIST or GST, on top of a mirror; as sketched in Figure 1 a . ITO was selected among other optically transparent materials due to its remarkable electrical conductance, [ 27] which is useful for electrical switching as demonstrated later in this paper. In our devices, the top ITO layer has no effect on the color being reflected and it is used only to protect the PCM from oxidation; it is fixed to be 10 nm thick. On the other hand, the bottom ITO layer plays a crucial role as it is the medium inside the optical cavity between two ultra-thin absorptive layers. Therefore, the reflected color, i.e., the resonance condition of the cavity depends mainly on the thickness of this layer.
To engineer our devices such that the thickness of each layer is optimized for any specific color, we utilize the theory of thin film optics to numerically calculate the total reflectance of an assembly of thin films using the algorithm detailed in ref. [ 1 ] . Using the continuity condition of the tangential electric ( E ) and magnetic ( H ) fi elds at each boundary and the directionality of the incident radiation, one can obtain the transmission through the bottom interface towards the substrate (given by the amplitudes Esubs, Hsubs) and the total reflection towards air (from the incident amplitudes on the upper interface given by E air , H air ) from the transfer matrix, i.e., the product of the matrices carrying the contribution of the local interference in each intermediate thin film layer….
We use the transfer matrix in Equation ( 1) to study the differences and similarities in color generation and modulation between devices containing both GST and AIST. In order to have a more comprehensive understanding on how the colors on the devices are really perceived by the human eye, we calculated from the reflectance spectrum obtained in Equation ( 2) , all the achievable colors using the XYZ tristimulus [ 28] values as a function of PCM and ITO thicknesses for both the amorphous and the crystalline phases. Subsequently, we plotted the XY color gamut on a chromaticity diagram as shown in Figure 4 . Here, we varied the ITO thickness from 0 to 300 nm (one mark per 5 nm), which covers a vast range of colors in both phase states of the PCMs. From these results, we observe very similar color gamut in amorphous phase for both AIST and GST. The performance of both materials is quite similar due to the similarity of their complex refractive indices, which is dominated by the SbTe optical properties (see Figure S1, Supporting Information). [ 29,30] This can also be inferred by comparing the experimental spectra for AIST in Figure 1 a with previously reported experiments for GST in ref. [ 17 ] . However, when both materials are switched to the crystalline state, AIST presents a similar but broader color gamut than GST only if the PCM layer is 6 nm or thicker. For thicknesses of 2 nm, the slight difference in the refractive index between the two materials plays a significant role in influencing the interference conditions; as it is seen for this case only, GST allows for a better color modulation. This could be a considerable advantage for GST, as thinner films lead to greater color contrast upon switching. Furthermore, we calculated the wavelength at peak maximum spectra as a function three parameters—phase state, ITO and PCM thickness—as presented in Figure S2 (Supporting Information) for AIST and GST. Reflectance peaks centered in any color in the visible spectrum are achievable for both materials by changing only the ITO spacer dimensions. Moreover, the same device (i.e., same ITO spacer thickness) leads to similar color when using either phase-change alloy notwithstanding the different nature of their crystallization processes. The effect of the thickness of the PCMs only results in a slight red-shift in the spectrum as it gets thicker in both cases. However, the blue-shift resulting from the high-to-low real refractive index and low-to-high extinction coefficient change, when switching from amorphous to crystalline state, is definitely more pronounced and the reason why the color switching is possible. Considering the shift between spectra in amorphous and crystalline (for ITO thicknesses in the range 100–160 nm), AIST presents, on an average, a modest peak shift of 6 nm larger than for GST.
…
In conclusion, we demonstrate that the growth dominated AIST can be used as an active material to obtain off-line color modulation with voltages as low as 2 V and resolutions down to 300 nm in scanning mode and less than 50 nm in pixel-by-pixel mode employing multilayer optical cavities. Furthermore, we presented the very first demonstration of non-binary color rendering on a single device (pixel) by exploiting the dependency of the degree crystallization on applied voltage. Using this, we achieved continuous “grayscale” images, which in turn adds a new degree of functionality to the newly emerging field of PCM displays. [ 17,24] We then demonstrate that Ge 2 Sb 2 Te 5 and Ag 3 In 4 Sb 76 Te 17 present very similar properties and performance. Finally, resolution limits below 50 nm are achievable in both materials, in the pixel by pixel approach, with differences in the nucleation formation due to the different crystallization dynamics of both materials. These results, together with previously reported capabilities such as reversible switching on cross-bar devices and the feasibility of nano-displays on flexible substrates, pave the way toward a new generation of bistable, ultra high-resolution and flexible display technologies in parallel with other potential applications in nanophotonics and optoelectronics.
Regarding dependent claim 3, it would have been obvious to one of ordinary skill in the art to modify Burberry in view of Emrose, further in view of Lawandi, further in view of Goossens, further in view of Kim, and further in view of Rios, as applied in the rejection of claim 1, to disclose: an arrangement of the crossbar control structure can be a square arrangement, a strip arrangement, a hexagon or a honeycomb arrangement. Burberry – Figure 8 and Burberry – Selected Text; Emrose – Poster and Emrose – Selected Text; Lawandi - Figures 1 and 2 and Lawandi - Selected Text; Goossens, figure 1 and related text; Kim, figures 1-4, and related text, for example, Kim – Selected Text; Rios, figures 1-5, and related text, for example, Rios – Selected Text; because the resultant configurations would enable predictably switchable and wavelength tailorable broadband absorbers; Emrose – Selected Text; that predictably vary reflection states; Lawandi, Conclusions; while predictably controlling pixel-crosstalk. Goossens, figure 1 and abstract; and while predictably enabling ‘better depth modulation capability (i.e., grayscale)’ to achieve ‘continuous “grayscale” images, which in turn adds a new degree of functionality to the newly emerging field of PCM displays.’ Rios, figures 1-5, and related text, for example, Rios – Selected Text.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to PETER RADKOWSKI whose telephone number is (571)270-1613. The examiner can normally be reached on M-Th 9-5. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Thomas Hollweg, can be reached on (571) 270-1739. The fax phone number for the organization where this application or proceeding is assigned is (571) 273-8300.
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/PETER RADKOWSKI/Primary Examiner, Art Unit 2874