A method for preparing a chalcogenide superlattice phase change material thin film by self-assembly

Abstract

The application relates to a method for preparing a chalcogenide superlattice phase change material film by self-assembly, which comprises the following steps: preparing an alloy target by taking a chalcogenide compound as a parent material; preparing an elemental target by selecting a suitable transition metal as a doping element; depositing and preparing a phase change material film on a substrate in a double-target co-sputtering mode by placing the alloy target and the elemental target in an argon atmosphere; respectively characterizing the crystal structure and the micro-morphology of the phase change material film by adopting X-ray diffraction and a scanning electron microscope; preparing a nanometer-thickness flake from the phase change material film by adopting a focused ion beam processing technology; observing the microstructure in a spherical aberration correction transmission electron microscope, optimizing deposition parameters, and cyclically and iteratively optimizing the above steps until a chalcogenide superlattice phase change material film is obtained. The application greatly reduces the process complexity of the superlattice phase change material and significantly improves the preparation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic information storage material preparation technology, and more specifically, relates to a method for preparing chalcogenide superlattice phase change material thin films by self-assembly. Background Technology

[0002] With the rapid development of emerging technologies such as the Internet of Things and artificial intelligence, global data storage has experienced explosive growth. In traditional computing architectures, the inherent separation of memory and processor leads to severe speed and power consumption bottlenecks in data storage, and storage performance is gradually failing to meet the ever-increasing data storage demands of the information age.

[0003] Phase-change memory (PCM) is considered a strong contender for the next generation of new memory due to its many advantages, such as compatibility with standard CMOS processes, non-volatile data, and high-speed storage.

[0004] PCM devices utilize the reversible structural transformation between a high-resistivity amorphous state and a low-resistivity crystalline state induced by an external field to achieve "0" and "1" data storage. PCM devices typically employ alloy-type phase change materials, such as the Ge2Sb2Te5 pseudo-binary phase change alloy composed of GeTe and Sb2Te3. This alloy is characterized by its simple fabrication process and good amorphous thermal stability, making it a very mature phase change material. However, PCM devices based on Ge2Sb2Te5 suffer from high power consumption and a large resistance drift coefficient, hindering their efficient application.

[0005] In recent years, researchers have discovered that PCM devices fabricated based on ordered stacking superlattice phase change materials (SCTs) have advantages such as low operating power consumption and small resistance drift coefficient. For example, PCM devices fabricated from alternating stacks of GeTe and Sb₂Te₃ superlattice materials have only half the operating power consumption of PCM devices fabricated from Ge₂Sb₂Te₅, and their cycle life is also improved. Therefore, superlattice phase change materials are key to improving PCM performance in the future. However, the fabrication of superlattice phase change materials is subject to strict limitations on the phase change sublayer materials. Generally, a high lattice matching degree is required between the two different sublayer materials. For example, in GeTe / Sb₂Te₃ superlattice phase change materials, the lattice parameter difference between GeTe and Sb₂Te₃ is less than 3%, ensuring that one sublayer can be epitaxially grown along the same crystal orientation between two sublayers. Traditional methods for fabricating superlattice phase change materials involve artificially alternating deposition of different sublayers in magnetron sputtering or atomic layer deposition systems to achieve ordered stacking growth. This deposition process requires precise control of composition and thickness, resulting in low fabrication efficiency. Optimizing the preparation process of superlattice phase change materials and improving their production efficiency will help accelerate the industrialization of PCM devices.

[0006] The applicant discovered that certain transition metal elements can be doped into alloy-type phase change materials. During high-temperature crystallization, these dopants spontaneously and orderly occupy the cation lattice sites in the layered crystal structure. In this way, a superlattice-like structure can be self-assembled within the alloy material without relying on artificial alternating deposition. Therefore, by further controlling the crystal orientation of the phase change material, based on the spontaneous formation of a superlattice-like structure by dopants in the parent material, it is hoped that superlattice phase change materials can be prepared through atomic self-assembly, achieving the same effect as traditional artificially alternating superlattice phase change materials. Summary of the Invention

[0007] The main objective of this invention is to propose a method for preparing chalcogenide superlattice phase change material thin films using self-assembly, thereby solving at least one of the technical problems in the prior art, such as the complexity of the alternating stacking process for preparing superlattice phase change materials and the low production efficiency.

[0008] To achieve the above objectives, this invention proposes a method for preparing chalcogenide superlattice phase change material thin films using self-assembly, comprising the following steps:

[0009] Step 1: Select chalcogenide compounds with texturing properties as the matrix material to prepare alloy targets;

[0010] Step 2: Select dopant elements from transition metal elements to prepare elemental target materials;

[0011] Step 3: Place the alloy target and the elemental target in an argon atmosphere and deposit a phase change material thin film on a silicon substrate using a dual-target co-sputtering method;

[0012] Step 4: The crystal structure and microstructure of the phase change material film are characterized by X-ray diffraction and scanning electron microscopy, respectively, and the phase change material film is screened accordingly.

[0013] Step 5: The selected phase change material thin film is processed into a nanometer-thick phase change material sheet using focused ion beam processing technology;

[0014] Step 6: Place the phase change material sheet in a spherical aberration-corrected transmission electron microscope for observation to obtain information on the internal grain structure of the phase change material sheet with a thickness of nanometers;

[0015] Step 7: Optimize the deposition parameters for depositing and preparing the phase change material thin film on the silicon substrate in step 3 based on the internal grain structure information of the phase change material thin film;

[0016] Step 8: Repeat steps 3 to 7 iteratively until the phase change material film deposited on the silicon substrate in step 3 is an atomically scaled periodically stacked chalcogenide superlattice phase change material film; wherein,

[0017] The face-centered cubic

[111] orientation or hexagonal

[0001] orientation of the chalcogenide compound with texture characteristics is parallel to the normal direction of the silicon substrate.

[0018] Furthermore, in step 1, Ge2Sb2Te5 or Sb2Te3 with texturing properties are selected as the matrix material to prepare the alloy target.

[0019] It should be noted that an alloy target is a sputtering coating material formed by uniformly mixing two or more elements (metal and metal, or metal and non-metal) through a metallurgical process. It can be classified into binary alloys (such as Al-Cu, Ti-Ni), ternary alloys (such as Al-Si-Cu), and multi-element alloys. This invention selects chalcogenide compounds with texturing properties as the matrix material for preparing the alloy target. This makes it easier to prepare thin films with the same orientation as the textured target during subsequent sputtering deposition, resulting in better phase transition uniformity of the film. Simultaneously, it also improves the in-plane uniformity of the prepared film and accelerates crystallization.

[0020] Furthermore, the thickness of the parent material is 20nm-500nm; preferably, it is 20nm-100nm; more preferably, it is 20nm-50nm; even more preferably, it is 20nm.

[0021] Furthermore, in step 2, the doping element is selected from indium or tin.

[0022] It should be noted that the dopant elements selected from the aforementioned transition metal elements should possess characteristics such as having an ionic radius comparable to that of the cations in the parent material and an atomic number close to that of the parent material. For example, when the parent material is Ge2Sb2Te5 with textured properties, because the electronegativity of Te (2.1) is higher than that of Ge (1.8) and Sb (1.9), electrons will be slightly biased towards Te atoms, causing Ge and Sb atoms to exhibit weak positive charge due to the loss of some electron density; since the oxidation state of Sb in Ge2Sb2Te5 is +3, taking Sb³⁺ as an example, the radius of Sb³⁺ is 76 pm, and the atomic number of Sb is 51. The dopant elements selected using the aforementioned principles are indium (In), with an indium³⁺ radius of 80 pm and an atomic number of 49; and tin (Sn), with Sn… 4 ⁺ Radius 69 pm, atomic number 50.

[0023] Furthermore, in step 3, the alloy target is sputtered using a pulsed DC power supply, and the single-element target is sputtered using a radio frequency power supply.

[0024] It should be noted that when depositing phase change material thin films on a silicon substrate using dual-target co-sputtering, the alloy target is sputtered using a fixed-pulse DC power supply, while the elemental target is sputtered using an RF power supply. By adjusting the power of the fixed-pulse DC power supply and the RF power supply, the content of indium or tin dopants in the phase change material thin film can be controlled; by changing the deposition time, the thickness of the phase change material thin film can be controlled; and by adjusting the annealing temperature and annealing time of the silicon substrate, the crystal structure and crystal orientation of the phase change material thin film can be controlled, thereby obtaining a phase change material thin film with excellent texture characteristics.

[0025] Further, in step 3, the atomic percentage of the dopant elements in the phase change material film is 1 at%-20 at%. Preferably, the atomic percentage of the dopant elements in the phase change material film is 15 at%.

[0026] Furthermore, step 3 also includes adjusting the annealing temperature and annealing time of the silicon substrate, wherein the annealing temperature of the silicon substrate is in the range of 150-300℃ and the annealing time is in the range of 5min-60min.

[0027] Furthermore, in step 3, the thickness of the phase change material film is 1nm-30nm.

[0028] Further, in step 4, X-ray diffraction (XRD) is used to characterize the peak intensity and full width at half maximum (FWHM) of the face-centered cubic phase

[111] peak or the distribution, peak intensity, and FWHM of the hexagonal phase

[0001] peak of the phase change material film after silicon substrate annealing.

[0029] It should be noted that in XRD spectra, peak intensity can be obtained by directly reading the maximum intensity value of the target diffraction peak (usually in CPS units) or calculating the integral intensity (peak area) of the peak. In XRD spectra, the width at half the peak height of the target diffraction peak is taken as the full width at half maximum (FWHM). Peak distribution can be characterized by the positional distribution of peaks in XRD spectra or by pole figure analysis. If the face-centered cubic phase

[111] peak has high intensity, narrow FWHM, and strong orientation in the pole figure, it indicates that the film has high crystallinity, uniform grain size, and ordered orientation, which usually corresponds to better phase transition reversibility; if the hexagonal phase

[0001] peak has a diffuse distribution and wide FWHM, it may mean that the grains are small and the orientation is disordered, and the preparation process such as annealing needs to be optimized.

[0030] Furthermore, in step 4, the size and distribution of the face-centered cubic

[111] or hexagonal

[0001] oriented grains of the phase change material film after silicon substrate annealing are characterized by scanning electron microscopy backscatter diffraction (SEM-EBSD).

[0031] It should be noted that, firstly, the annealed phase change material thin film sample on the silicon substrate undergoes surface pretreatment to remove any possible oxide layer, contaminants, and surface damage layers, ensuring a smooth and clean surface in the test area. Then, the pretreated sample is fixed on the sample stage of a scanning electron microscope and moved into the sample chamber, where a high vacuum environment is evacuated as required by the instrument. Next, the operating parameters of the scanning electron microscope (such as accelerating voltage and beam current) and the position and angle of the backscattered diffraction detector are adjusted to focus the electron beam onto the area to be characterized on the thin film surface. The backscattered electron diffraction signal generated by the interaction between the electron beam and the grains in the thin film is collected by the detector. Then, the collected diffraction data is processed using the matching crystallographic analysis software. By identifying the diffraction patterns corresponding to the face-centered cubic

[111] or hexagonal

[0001] oriented grains, their spatial position and crystallographic orientation are determined. Then, based on the grain contour information, the size of a single grain (such as equivalent diameter, major axis length, etc.) is calculated, and the number, size distribution range and spatial distribution uniformity of these specific oriented grains in the thin film test area are statistically analyzed. Finally, the size and distribution of face-centered cubic

[111] or hexagonal

[0001] oriented grains in the phase change material thin film after silicon substrate annealing are characterized.

[0032] Furthermore, in step 5, the selected phase change material film is processed into a phase change material sheet with a thickness of 20nm-200nm using a focused ion beam processing technology.

[0033] It should be noted that using focused ion beam (FIB) processing to prepare the selected phase change material thin films into phase change material sheets with a thickness of 20 nm to 200 nm can meet the electron penetration requirements for subsequent aberration-corrected transmission electron microscopy characterization.

[0034] Furthermore, in step 6, an aberration-corrected transmission electron microscope is used to observe the crystal orientation and periodic distribution of dopant elements in the grains inside the phase change material sheet.

[0035] It should be noted that, firstly, the nano-thickness phase change material sheet prepared by focused ion beam processing is transferred to the sample holder of an aberration-corrected transmission electron microscope, ensuring the sheet is stable in a vacuum environment without significant drift. Then, the sample is precisely focused in the aberration-corrected transmission electron microscope by adjusting the optical path system, including the condenser and objective lenses. A suitable accelerating voltage (typically 200-300 kV) is selected to balance imaging resolution and sample damage. The aberration corrector is activated to compensate for objective spherical aberration, achieving sub-angstrom spatial resolution. Subsequently, the microscope is switched to scanning transmission electron microscopy (STEM) mode and combined with high-angle annular dark-field (HAADF) imaging technology. The atomic arrangement structure of the grains inside the sheet is observed through atomic number contrast differences, while electron diffraction (ED) or selected area electron diffraction is used. Electron diffraction (SAED) technology records diffraction patterns, and the crystallographic orientation relationship of face-centered cubic phase

[111] orientation or hexagonal phase

[0001] orientation grains is determined by analyzing the position and intensity distribution of diffraction spots. In addition, energy dispersive X-ray spectroscopy (EDS) is activated to enable the electron beam to perform high-resolution line scanning or surface scanning inside the grains. By collecting characteristic X-ray signals of different elements and performing energy analysis, combined with the spatial position information of scanning transmission electron microscopy (STEM) imaging, the distribution spectrum of doped elements is drawn, thereby identifying and characterizing whether the doped elements have a periodic arrangement and specific distribution period and pattern inside the grains. Finally, high-resolution observation and analysis of the crystal orientation and periodic distribution of doped elements inside the phase change material thin sheet is achieved.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention provides a method for preparing chalcogenide superlattice phase change material thin films using self-assembly. The method involves preparing an alloy target material with textured properties (Ge2Sb2Te5 or Sb2Te3) as the parent material and a single-element target material with doping elements selected from indium or tin. The phase change material thin film is deposited on a silicon substrate by dual-target co-sputtering.

[0038] By adjusting the power of the fixed-pulse DC power supply and the power of the RF power supply used in dual-target co-sputtering, the content of indium or tin dopants in the phase change material thin film can be controlled; the thickness of the phase change material thin film can be controlled by changing the deposition time; and the crystal structure and crystal orientation of the phase change material thin film can be controlled by adjusting the annealing temperature and annealing time of the silicon substrate, thereby obtaining a phase change material thin film with excellent texture characteristics. Therefore, this invention does not require frequent changes to the type of deposition target or the process parameters used during deposition (e.g., deposition power, gas flow rate, time, temperature, etc.). By characterizing the phase change material thin film and phase change material flakes, and iterating the deposition parameters in step 3 for depositing the phase change material thin film on the silicon substrate, the phase change material thin film deposited on the silicon substrate can be a periodically stacked chalcogenide superlattice phase change material thin film at the atomic scale. This invention greatly reduces the process complexity of superlattice phase change materials and significantly improves the preparation efficiency. Attached Figure Description

[0039] Figure 1 This is an electron backscattering diffraction image of an ultrathin Ge2Sb2Te5 thin film (20nm) according to one embodiment of the present invention;

[0040] Figure 2 The image shows an XRD pattern of an In-doped Ge2Sb2Te5 thin film annealed at 400°C with a concentration of 15 at% in one embodiment of the present invention.

[0041] Figure 3 In one embodiment of the present invention, an In-doped Ge2Sb2Te5 film with a concentration of 15 at% was prepared into a nano-thickness sheet.

[0042] Figure 4 This is a high-angle annular dark field image (HAADF) of an In-doped Ge2Sb2Te5 thin film with a concentration of 15 at% after process optimization in one embodiment of the present invention, and the corresponding In element distribution map. Detailed Implementation

[0043] The various aspects of the present invention will be further described in detail below.

[0044] Unless otherwise defined or stated, all technical and scientific terms used herein have the same meaning as are familiar to a user skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention.

[0045] See appendix Figure 1 To be continued Figure 4 This invention proposes a method for preparing chalcogenide superlattice phase change material thin films using self-assembly, comprising the following steps:

[0046] Step 1: Select a pseudo-binary Ge2Sb2Te5 alloy as the parent material to prepare the alloy target; wherein the atomic numbers of Ge, Sb and Te are 32, 50 and 51, respectively;

[0047] The thermodynamically stable structure of Ge2Sb2Te5 is a hexagonal phase structure, with the lowest surface energy at the

[0001] plane. When the thickness of the Ge2Sb2Te5 film is at the nanometer scale, the film exhibits significant texturing characteristics, showing that the

[0001] plane is parallel to the silicon substrate. Figure 1 As shown;

[0048] Step 2: Select indium (In), a target transition metal element with a radius comparable to and an atomic number close to that of the Sb³⁺ cation in the parent material, as the dopant element to fabricate a single-element target; wherein, the atomic number of In is 49.

[0049] Step 3: Place the Ge2Sb2Te5 alloy target prepared in Step 1 and the In elemental target prepared in Step 2 in an argon atmosphere, and deposit an In-doped Ge2Sb2Te5 phase change material thin film on a silicon substrate by dual-target co-sputtering.

[0050] The sputtering of the Ge2Sb2Te5 alloy target uses a pulsed DC power supply with a power range of 10W-30W; the In elemental target uses an RF power supply with a power range of 2W-50W; during the deposition process, under a certain pulsed DC power supply power, the In doping content in the phase change material film can be controlled by changing the RF power supply power, thereby making the In doping content range from 1-20 at%; and by changing the deposition time of the phase change material film, the thickness of the phase change material film can be controlled from 1nm to 30nm; in addition, by setting the annealing temperature of the silicon substrate between 200℃ and 450℃ and the annealing time between 2min and 5min, the phase change material film can be annealed and crystallized into a hexagonal phase structure with significant

[0001] orientation texture characteristics.

[0051] Step 4: The crystal structure and texture characteristics of the In-doped Ge2Sb2Te5 phase change material thin film prepared in Step 3 are characterized by X-ray diffraction and scanning electron microscopy, and the phase change material thin film is screened accordingly.

[0052] Figure 2 XRD images of In-doped Ge2Sb2Te5 phase change material films annealed at 300℃ and 350℃ with a concentration of 15 at%. As the annealing temperature increases, the intensity of the XRD diffraction peaks increases, indicating that the crystallinity of the phase change material film increases.

[0053] Step 5: Using standard focused ion beam processing technology, the 15 at% In-doped Ge2Sb2Te5 phase change material film obtained in Step 4 (after initial screening) is fabricated into a nanometer-thick phase change material sheet, such as... Figure 3 As shown;

[0054] Step 6: Place the nano-thickness phase change material sheet prepared in Step 5 into a spherical aberration-corrected transmission electron microscope for microstructure observation to obtain the structural information of the internal grains of the nano-thickness phase change material sheet. The structural information of the internal grains includes information such as crystal orientation and atomic arrangement rules.

[0055] Step 7: Based on the structural information of the internal grains of the thin film obtained in Step 6, obtain the influence of dopant content, thin film thickness, and annealing parameters on the crystal structure, texture characteristics, and atomic arrangement of the phase change material thin film, and further optimize the deposition parameters for the deposition preparation of the phase change material thin film in Step 3; for example: if the content of the target transition metal element In as the dopant element is too low, the distribution periodicity of In element along the

[0001] orientation is not obvious or the doping is uneven, and the doping concentration of In needs to be appropriately increased in Step 3; if the content of the target transition metal element In as the dopant element is too high, In element will form amorphous clusters, and the doping concentration of In needs to be appropriately reduced in Step 3; the above-mentioned increase or decrease of the content of the target transition metal element In in the phase change material thin film can be achieved by adjusting the RF power supply power in Step 3, etc.; in addition, the thickness of the phase change material thin film can be controlled by changing the deposition time of the phase change material thin film in Step 3; the adjustment of annealing temperature and annealing time can make the phase change material thin film crystallize into a hexagonal phase structure with significant

[0001] orientation texture characteristics;

[0056] Step 8: Repeat steps 3 to 7 until the phase change material film deposited on the silicon substrate in step 3 is an atomically scaled periodically stacked chalcogenide superlattice phase change material film.

[0057] Figure 4 The high-angle annular dark field image (HAADF) and corresponding In element distribution of the optimized 15 at% In-doped Ge2Sb2Te5 phase change material film show that the In element distribution along the

[0001] orientation exhibits obvious periodic distribution characteristics. Therefore, the self-assembly method achieves the same effect as the superlattice phase change material prepared by the traditional artificial alternating deposition method.

[0058] In summary, this invention discloses a method for preparing chalcogenide superlattice phase change material thin films using self-assembly. Using chalcogenide phase change materials as the parent material and transition metal elements as dopants, the crystal orientation and structure of the film are controlled by altering the dopant concentration, temperature, and film thickness, thereby constructing atomically scaled periodically stacked chalcogenide superlattice phase change material thin films. This invention can achieve the same effect as superlattice phase change materials prepared by traditional alternating deposition methods, while reducing the complexity of the superlattice phase change material preparation process and improving preparation efficiency.

[0059] Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Furthermore, this device and / or practice the method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0060] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for users of ordinary skills in this field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0061] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing description of this invention, users skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing chalcogenide superlattice phase change material thin films by self-assembly, characterized in that, Includes the following steps: Step 1: Select chalcogenide compounds with texturing properties as the matrix material to prepare alloy targets; Step 2: Select dopant elements from transition metal elements to prepare elemental target materials; Step 3: Place the alloy target and the elemental target in an argon atmosphere and deposit a phase change material thin film on a silicon substrate using a dual-target co-sputtering method; Step 4: The crystal structure and microstructure of the phase change material film are characterized by X-ray diffraction and scanning electron microscopy, respectively, and the phase change material film is screened accordingly. Step 5: The selected phase change material thin film is processed into a nanometer-thick phase change material sheet using focused ion beam processing technology; Step 6: Place the phase change material sheet in a spherical aberration-corrected transmission electron microscope for observation to obtain information on the internal grain structure of the phase change material sheet with a thickness of nanometers; Step 7: Optimize the deposition parameters for depositing and preparing the phase change material thin film on the silicon substrate in step 3 based on the internal grain structure information of the phase change material thin film; Step 8: Repeat steps 3 to 7 iteratively until the phase change material film deposited on the silicon substrate in step 3 is an atomically scaled periodically stacked chalcogenide superlattice phase change material film; wherein, The face-centered cubic [111] orientation or hexagonal [0001] orientation of the chalcogenide compound with texture characteristics is parallel to the normal direction of the silicon substrate.

2. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 1, characterized in that, In step 1, Ge2Sb2Te5 with textured properties is selected as the matrix material to prepare the alloy target.

3. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 1, characterized in that, In step 2, the doping element is selected from indium.

4. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 1, characterized in that, In step 3, the alloy target is sputtered using a pulsed DC power supply, while the single-element target is sputtered using a radio frequency power supply.

5. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 4, characterized in that, In step 3, the atomic percentage of the dopant elements in the phase change material film is 1 at% to 20 at%.

6. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 5, characterized in that, Step 3 also includes adjusting the annealing temperature and annealing time of the silicon substrate. The annealing temperature of the silicon substrate is in the range of 200-450℃, and the annealing time is in the range of 2min-5min.

7. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 6, characterized in that, In step 3, the thickness of the phase change material film is 1 nm-30 nm.

8. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 1, characterized in that, In step 4, X-ray diffraction (XRD) is used to characterize the peak intensity and full width at half maximum (FWHM) of the face-centered cubic phase [111] peak or the peak intensity and FWHM of the hexagonal phase [0001] peak of the phase change material film after silicon substrate annealing.

9. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 8, characterized in that, In step 4, the size and distribution of the face-centered cubic [111] or hexagonal [0001] oriented grains of the phase change material film after silicon substrate annealing are characterized by scanning electron microscopy backscatter diffraction (SEM-EBSD).

10. The method for preparing chalcogenide superlattice phase change material thin films by self-assembly according to claim 1, characterized in that, In step 6, a spherical aberration-corrected transmission electron microscope is used to observe the crystal orientation and periodic distribution of dopants in the grains inside the phase change material sheet.

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