Entropy stabilizing material with high optical quality factor and preparation method thereof

Abstract

The invention belongs to the technical field of functional thin film materials, and particularly relates to an entropy stabilizing material with a high optical quality factor and a preparation method of the entropy stabilizing material. In order to solve the problem that in the prior art, a high-symmetry crystal system is difficult to form due to strong orbital hybridization of a material in a middle-infrared band, so that low refractive index contrast ratio and low extinction coefficient of a phase change material are difficult to consider at the same time, the invention provides a light element and heavy element synergistic high-entropy doping strategy, and light elements Si and Ge and a heavy element Te are jointly introduced into a Sb2Se3 system, so that the phase change material has high refractive index contrast ratio and low extinction coefficient. And the high-entropy phase change material Si < x > Ge < y > Sb < 1-x-y > Se < 1-y > Tez is successfully prepared. The material is converted into a high-symmetry cubic structure from a low-symmetry orthogonal structure under high configuration entropy driving, p-track alignment is achieved, the optical quality factor of the material is greatly improved compared with that of traditional Ge2Sb2Te5, the material bottleneck of near-infrared and middle-infrared band all-optical memory computing image processors is broken through, and the application prospect is wide. And a key material basis is provided for practical application of the system in an intelligent visual system.

Description

Technical Field

[0001] This invention belongs to the field of functional thin film materials technology, specifically relating to an entropy-stabilized material with a high optical quality factor and its preparation method. Background Technology

[0002] All-optical in-memory computing image processors (AIMs) achieve efficient optical information computation through their homogeneous computing-memory architecture, representing a core technology for next-generation intelligent vision. However, existing solutions are limited to the visible and near-infrared bands, and the fabrication of mid-infrared AIMs presents significant challenges. The fundamental limitation stems from the difficulty in forming highly symmetric cubic crystal systems with strongly orbital hybrid elements, resulting in low refractive index contrast Δn in chalcogenide phase transition materials with low extinction coefficients (k). Therefore, developing high-refractive-index, low-extinction-coefficient chalcogenide phase transition materials in the mid-infrared band has become crucial to overcoming this technological bottleneck.

[0003] In past research, all-optical memory computing image processors based on liquid crystals and two-dimensional photosensitive materials have achieved success in the visible and near-infrared bands, realizing non-von Neumann architecture all-optical computing with a recognition accuracy exceeding 95%. However, extending the operating band of all-optical memory computing image processors to the mid-infrared region still faces challenges in material selection. The technical difficulties mainly focus on the following two aspects: 1) Traditional Ge2Sb2Se4Te1 materials, by doping with a small amount of Ag, have only achieved a FOM of 7.48 in the infrared band. The optical properties of materials extended to the mid-infrared band may be drastically different, and the increased Ag doping content may lead to additional absorption in the mid-infrared region, thereby increasing optical loss. 2) Existing Sb2Se3 anion (Te) or cation (Bi) doping schemes can improve the optical dielectric constant of Sb2Se3 by forming "hypervalent bonds," but this requires that the content of the dopant element (Te or Bi) must be extremely high (>70%). This high content of heavy element doping will significantly reduce the band gap of the material, resulting in a sharp increase in light absorption (i.e., an excessively high extinction coefficient k value), which cannot meet the application requirements of achieving a large Δn / k in the mid-infrared band.

[0004] In view of this, the inventors aim to design an entropy-stable material with a high optical quality factor and a method for preparing it. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in conventional technologies and to provide an entropy-stable material with a high optical quality factor and its preparation method.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0007] This invention provides an entropy-stable phase transition material with a high optical quality factor (FoM, Δn / k). This entropy-stable material is formed by introducing the light elements Si, Ge, and the heavy element Te into a strongly orbital hybridized Sb₂Se₃. x Ge y Sb 1-x-y Se 1-y Te z Thin film, where x = 0.1–0.4, y = 0.2–0.6, z = 0.2–0.6.

[0008] Furthermore, the entropy-stabilized material is an amorphous phase below 250°C and transforms into a crystalline cubic phase above 300°C, with space group Fm. The refractive index contrast Δn between the amorphous and cubic phases is 1.98, and the extinction coefficients k of both phases are less than 0.01.

[0009] Furthermore, the film thickness is 50–300 nm.

[0010] This invention also provides a method for preparing an entropy-stable phase transition material, which is prepared by magnetron co-sputtering using a pure Si target, a GeTe target, and an Sb₂Se₃ target. The method specifically includes the following steps:

[0011] 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target, and semiconductor materials are used as substrates;

[0012] 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the vacuum level inside the chamber reaches the required level, and then introduce argon gas into the sputtering chamber until the gas pressure inside the sputtering chamber reaches the ignition gas pressure required for sputtering.

[0013] 3) By controlling the sputtering power of pure Si targets, GeTe targets and Sb2Se3 targets, the thin films deposited on the substrate are entropy-stable phase change materials with high optical quality factors.

[0014] Furthermore, in step 1), a single-crystal silicon wafer, quartz glass, or zinc sulfide is used as the substrate. Before the substrate is placed in the vacuum chamber, it is ultrasonically cleaned with acetone, anhydrous ethanol, and distilled water in sequence and then dried.

[0015] Further, in step 2), the required vacuum level is 3.8×10-4 to 4.2×10-4 Pa. After the vacuum chamber reaches the required vacuum level, the two targets are pre-sputtered for 5 to 15 minutes under an argon flow rate of 55 to 65 sccm to remove the oxide layer and adsorbed impurities on the target surface.

[0016] Furthermore, in step 3), the RF sputtering power of the pure Si target is 60-100W, the RF sputtering power of the GeTe target is 20-60W, and the RF sputtering power of the Sb2Se3 target is 60-100W.

[0017] Further, in step 3), the sputtering conditions are as follows: target-substrate distance is 23 mm, substrate temperature is 20-30 °C, working pressure is 0.1 Pa, argon flow rate is 55-65 sccm, and sputtering time is 5-30 min.

[0018] The beneficial effects of this invention are:

[0019] This invention, through a combination of experimental fabrication, optical simulation, and theoretical calculation, reveals the physical origins of high optical quality factor and entropy stability, and designs a Si alloy that simultaneously possesses a high optical quality factor (FOM=318.9) and entropy stability. x Ge y Sb 1-x-y Se 1-y Te z Thin film materials fundamentally solve the problem of low refractive index contrast Δn in traditional chalcogenide phase transition materials in the mid-infrared band due to the difficulty in forming a highly symmetric cubic crystal system in the strongly orbital hybrid element system. This provides a material design basis for the development of next-generation high-stability all-optical memory computing image processors.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z XRD patterns;

[0023] Figure 2 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z STEM-EDS image of a thin film cross-section;

[0024] Figure 3 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z High-resolution transmission electron microscopy image;

[0025] Figure 4 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z Optical constants diagram;

[0026] Figure 5 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z PDOS diagram;

[0027] Figure 6 Si prepared in Example 1 x Ge y Sb 1-x-y Se 1-y Te z The local electronic function graph. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] An entropy-stable phase transition material with a high optical quality factor, wherein the entropy-stable material is Si in Sb₂Se₃ with strong orbital hybridization introduced by light (Si, Ge) and heavy (Te) elements. x Ge y Sb 1-x-y Se 1-y Te z Thin films, where x = 0.1–0.4, y = 0.2–0.6, z = 0.2–0.6, and the film thickness is 50–300 nm.

[0030] The above-mentioned method for preparing entropy-stable phase transition materials involves magnetron co-sputtering with pure Si, GeTe, and Sb₂Se₃ targets, and includes the following steps:

[0031] 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target, and semiconductor materials are used as substrates;

[0032] 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the required vacuum level is reached. Then, introduce argon gas into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure for sputtering. The required vacuum level is 3.8×10-4 to 4.2×10-4 Pa. After the vacuum chamber reaches the required vacuum level, pre-sputter the two targets for 5 to 15 minutes under the condition of argon gas flow rate of 55 to 65 sccm to remove the oxide layer and adsorbed impurities on the target surface.

[0033] 3) Control the sputtering power of pure Si target, GeTe target and Sb2Se3 target. The RF sputtering power of pure Si target is 60-100W, the RF sputtering power of GeTe target is 20-60W, and the RF sputtering power of Sb2Se3 target is 60-100W.

[0034] The sputtering conditions were as follows: target-substrate distance of 23 mm, substrate temperature of 20–30 °C, working pressure of 0.1 Pa, argon flow rate of 55–65 sccm, and sputtering time of 5–30 min. The thin film deposited on the substrate is an entropy-stable phase change material with a high optical quality factor.

[0035] The technical solution of this invention does not use expensive and complex experimental equipment. Instead, it predicts the optical constants of materials through extensive optical simulations and experimentally synthesizes Si with different properties. x Ge y Sb 1-x-y Se 1-y Te z Thin film. The innovative concept of this invention is embodied in the following:

[0036] From an optical property perspective, the inventors experimentally prepared Si. x Ge y Sb 1-x-y Se 1-y Te z Through simulation of the optical constants of its transmission spectrum, the inventors discovered that Si... x Ge y Sb 1-x-y Se 1-y Te z The thin film possesses the best optical quality factor. Subsequently, in order to analyze Si... x Ge y Sb 1-x-y Se 1-y Te zThe reason why the thin film has a high optical quality factor is that the inventors used AC-STEM to show that the phase structure of Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 is the cubic crystal system with high symmetry. The inventors found that this high symmetry is due to the increased configurational entropy (ΔS) caused by the doping of Si, Ge, and Te. The cubic phase Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 adopts the rock salt type (NaCl type) crystal structure, in which Si, Ge, and Sb are randomly distributed on the cation sublattice, while Se and Te are randomly distributed on the anion sublattice. The ΔS of the cation and anion sublattices are 1.01R and 0.69R respectively. In contrast, the ΔS of Sb2Se3 is zero because each atom occupies a unique crystallographic position without random occupancy. According to ΔG = ΔH - TΔS, ΔS is negatively correlated with the Gibbs free energy ΔG. The co-doping of Si, Ge, and Te increases ΔS and simultaneously reduces ΔG, thus stabilizing the cubic phase Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 . This discovery breaks through the strict dependence of traditional PCMs with high symmetry crystal systems on heavy elements.

[0037] To verify the inventors' conjecture, the inventors experimentally prepared Si x [[ID=3�]]Ge y Sb 1-x- y Se 1-y Te z thin films with different x, y, z contents, and simulated the optical constants of their transmission spectra through the Drude-Lorentz model. The inventors found that when 0.15 < x < 0.25, 0.25 < y < 0.35, 0.45 < z < 0.55, the Si x Ge y Sb 1-x-y Se 1-y Te z thin film has a high optical quality factor.

[0038] In terms of electronic structure, the inventors constructed an electronic structure model of Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 and found in the PDOS diagram that Si 0.2 Ge0.3 Sb 0.5 Se 0.5 Te 0.5 Both the valence band and the conduction band near the Fermi level are dominated by Sb-5p. In the charge density map, Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 The density of electronic states near the Fermi level is significantly enhanced compared to undoped Sb2Se3. Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 exhibits a homogenized charge distribution. In the ELF map, Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 has an ELF value close to 0.5, which represents an approximate free electron gas. Therefore, the ELF results, charge density, and PDOS together prove that Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 has enhanced electron delocalization, which increases the electronic polarizability and thus enhances Δn. <000025(...)The present invention selects light (Si, Ge) and heavy (Te) elements to introduce into the stable cubic phase of Sb2Se3, Si x Ge y Sb 1-x-y Se 1- y Te z [[ID=(...)]]thin films (0.15 < x < 0.25, 0.25 < y < 0.35, 0.45 < z < 0.55) to solve the problem in the prior art that it is difficult to form a high-symmetry crystal system due to strong orbital hybridization of materials in the mid-infrared band, resulting in the difficulty of balancing the high refractive index contrast (Δn) and low extinction coefficient (k) of phase change materials.

[0040] The specific embodiments of the present invention are as follows:

[0041] Example 1

[0042] An entropy-stable phase change material with a high optical quality factor, which is a stable cubic phase of Sb2Se(...) introduced with light (Si, Ge) and heavy (Te) elements, Si x Ge y Sb 1-x-y Se 1-y Te z It should be noted that there seems to be an incomplete tag in the original text at line 49 which is "<000025(...)". This might be a formatting or input error. The translation is done as accurately as possible based on the available text.Thin film. Where x=0.2, y=0.3, z=0.5, and the film thickness is 200nm.

[0043] The above-mentioned method for preparing entropy-stable phase transition materials involves magnetron co-sputtering with pure Si, GeTe, and Sb₂Se₃ targets, and includes the following steps:

[0044] 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target. Single crystal silicon wafers, quartz glass and zinc sulfide are used as substrates. Before the substrates are placed in the vacuum chamber, they are ultrasonically cleaned with acetone, anhydrous ethanol and distilled water in sequence and then dried.

[0045] 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the required vacuum level is reached. Then, introduce argon gas into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure for sputtering. The required vacuum level is 4.0×10-4 Pa. After the vacuum chamber reaches the required vacuum level, pre-sputter the two targets for 10 minutes under the condition of argon gas flow rate of 60 sccm to remove the oxide layer and adsorbed impurities on the target surface.

[0046] 3) Control the sputtering power of the pure Si target, GeTe target, and Sb₂Se₃ target. The RF sputtering power of the pure Si target is 60W, the RF sputtering power of the GeTe target is 40W, and the RF sputtering power of the Sb₂Se₃ target is 60W. The sputtering conditions are: target-substrate distance of 23mm, substrate temperature of 25℃, working pressure of 0.1Pa, argon flow rate of 60sccm, and sputtering time of 20min.

[0047] 4) The amorphous deposited thin film was annealed at 350℃ in a high-purity argon atmosphere (99.9%) for 20 min, and then transformed into a crystalline cubic phase thin film.

[0048] Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 The phase structure was determined by XRD spectroscopy. Figure 1 ), Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 The elemental distribution was tested by STEM-ED (Science, Technology, Engineering, and Manufacturing). Figure 2 ), Figure 3 These are the test results from a high-resolution transmission electron microscope. Figures 1-3 The test results together prove that the prepared thin film is a cubic phase. Figure 4 It can be seen that Si in the mid-infrared band 0.2 Ge 0.3 Sb0.5 Se 0.5 Te 0.5 This achieved Δn = 1.98, k < 0.01. (From...) Figures 5-6 It can be seen that Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 The ELF value is close to 0.5, representing an approximate free electron gas, which enhances electron delocalization, increases electronic polarizability, and thus enhances Δn. Therefore, Si 0.2 Ge 0.3 Sb 0.5 Se 0.5 Te 0.5 The thin film achieves compatibility between high refractive index contrast and entropy stability in the mid-infrared band.

[0049] Example 2

[0050] An entropy-stable phase transition material with a high optical quality factor, comprising a stable cubic Si phase introduced into Sb₂Se₃ by light (Si, Ge) and heavy (Te) elements. x Ge y Sb 1-x-y Se 1-y Te z Thin film. Where x=0.3, y=0.2, z=0.2, and the film thickness is 200nm.

[0051] The above-mentioned method for preparing entropy-stable phase transition materials involves magnetron co-sputtering with pure Si, GeTe, and Sb₂Se₃ targets, and includes the following steps:

[0052] 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target. Single crystal silicon wafers, quartz glass and zinc sulfide are used as substrates. Before the substrates are placed in the vacuum chamber, they are ultrasonically cleaned with acetone, anhydrous ethanol and distilled water in sequence and then dried.

[0053] 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the required vacuum level is reached. Then, introduce argon gas into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure for sputtering. The required vacuum level is 4.0×10-4 Pa. After the vacuum chamber reaches the required vacuum level, pre-sputter the two targets for 10 minutes under the condition of argon gas flow rate of 60 sccm to remove the oxide layer and adsorbed impurities on the target surface.

[0054] 3) Control the sputtering power of the pure Si target, GeTe target, and Sb₂Se₃ target. The RF sputtering power of the pure Si target is 60W, the RF sputtering power of the GeTe target is 20W, and the RF sputtering power of the Sb₂Se₃ target is 60W. The sputtering conditions are: target-substrate distance of 23mm, substrate temperature of 25℃, working pressure of 0.1Pa, argon flow rate of 60sccm, and sputtering time of 20min.

[0055] 4) The amorphous deposited thin film was annealed at 380℃ in a high-purity argon atmosphere (99.9%) for 20 min, and then transformed into a crystalline cubic phase thin film.

[0056] Example 3

[0057] An entropy-stable phase transition material with a high optical quality factor, comprising a stable cubic Si phase introduced into Sb₂Se₃ by light (Si, Ge) and heavy (Te) elements. x Ge y Sb 1-x-y Se 1-y Te z Thin film. Where x=0.1, y=0.4, z=0.6, and the film thickness is 200nm.

[0058] The above-mentioned method for preparing entropy-stable phase transition materials involves magnetron co-sputtering with pure Si, GeTe, and Sb₂Se₃ targets, and includes the following steps:

[0059] 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target. Single crystal silicon wafers, quartz glass and zinc sulfide are used as substrates. Before the substrates are placed in the vacuum chamber, they are ultrasonically cleaned with acetone, anhydrous ethanol and distilled water in sequence and then dried.

[0060] 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the required vacuum level is reached. Then, introduce argon gas into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure for sputtering. The required vacuum level is 4.0×10-4 Pa. After the vacuum chamber reaches the required vacuum level, pre-sputter the two targets for 10 minutes under the condition of argon gas flow rate of 60 sccm to remove the oxide layer and adsorbed impurities on the target surface.

[0061] 3) Control the sputtering power of the pure Si target, GeTe target, and Sb₂Se₃ target. The RF sputtering power of the pure Si target is 60W, the RF sputtering power of the GeTe target is 50W, and the RF sputtering power of the Sb₂Se₃ target is 60W. The sputtering conditions are: target-substrate distance of 23mm, substrate temperature of 25℃, working pressure of 0.1Pa, argon flow rate of 60sccm, and sputtering time of 20min.

[0062] 4) The amorphous deposited thin film was annealed at 400℃ in a high-purity argon atmosphere (99.9%) for 20 min, and then transformed into a crystalline cubic phase thin film.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An entropy-stable phase transition material with a high optical quality factor, characterized in that, This entropy-stabilized material is formed by introducing the light elements Si and Ge and the heavy element Te into strongly orbital hybridized Sb₂Se₃. x Ge y Sb 1-x-y Se 1-y Te z Thin film, where x = 0.1–0.4, y = 0.2–0.6, z = 0.2–0.

6.

2. The entropy-stable phase transition material according to claim 1, characterized in that, The entropy-stable material is an amorphous phase below 250°C and transforms into a crystalline cubic phase above 300°C, space group Fm. The refractive index contrast Δn between the amorphous and cubic phases is 1.98, and the extinction coefficients k of both phases are less than 0.

01.

3. The entropy-stable phase transition material according to claim 1, characterized in that, The film thickness is 50–300 nm.

4. The method for preparing the entropy-stable phase change material according to any one of claims 1-3, characterized in that, The material was fabricated using magnetron co-sputtering with a pure Si target, a GeTe target, and a Sb₂Se₃ target, and specifically included the following steps. 1) In the magnetron sputtering coating system, pure Si targets, GeTe targets and Sb2Se3 targets are installed in the magnetron RF sputtering target, and semiconductor materials are used as substrates; 2) Evacuate the sputtering chamber of the magnetron sputtering coating system until the vacuum level inside the chamber reaches the required level, and then introduce argon gas into the sputtering chamber until the gas pressure inside the sputtering chamber reaches the ignition gas pressure required for sputtering. 3) By controlling the sputtering power of pure Si targets, GeTe targets and Sb2Se3 targets, the thin films deposited on the substrate are entropy-stable phase change materials with high optical quality factors.

5. The preparation method according to claim 4, characterized in that, In step 1), a single-crystal silicon wafer, quartz glass, or zinc sulfide is used as the substrate. Before the substrate is placed in the vacuum chamber, it is ultrasonically cleaned with acetone, anhydrous ethanol, and distilled water in sequence and then dried.

6. The preparation method according to claim 4, characterized in that, In step 2), the required vacuum level is 3.8×10-4 to 4.2×10-4 Pa. After the vacuum chamber reaches the required vacuum level, the two targets are pre-sputtered for 5 to 15 minutes under the condition of argon flow rate of 55 to 65 sccm to remove the oxide layer and adsorbed impurities on the target surface.

7. The preparation method according to claim 4, characterized in that, In step 3), the RF sputtering power of the pure Si target is 60-100W, the RF sputtering power of the GeTe target is 20-60W, and the RF sputtering power of the Sb2Se3 target is 60-100W.

8. The preparation method according to claim 4, characterized in that, In step 3), the sputtering conditions are as follows: target-substrate distance is 23 mm, substrate temperature is 20-30 °C, working pressure is 0.1 Pa, argon flow rate is 55-65 sccm, and sputtering time is 5-30 min.

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