Layered transition metal telluride single crystal material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of layered single crystal materials, and particularly discloses a layered transition metal telluride single crystal material as well as a preparation method and application thereof. The preparation method comprises the following steps: weighing tantalum powder, tellurium powder, nickel powder and palladium powder as raw materials, adding the raw materials into a mortar, adding iodine granules, and grinding until the raw materials are uniformly mixed; and putting the ground powder into a quartz tube, sealing in vacuum, calcining, cooling to a preset temperature, preserving heat, and cooling to obtain the layered transition metal telluride single crystal material. Precise doping of Pd to the Ta2Ni3Te5 single crystal is realized by adopting a chemical vapor transport (CVT) method, on one hand, the single crystal prepared by the CVT method is high in purity, good in crystallinity and complete in layered structure, and meets the high-quality requirement of a device on a base material; on the other hand, controllable adjustment of conductive core parameters is realized through Pd doping, and a flexible scheme is provided for matching performance requirements of different devices; and the conversion of the typical layered transition metal chalcogenide Ta2Ni3Te5 from basic research to actual device application is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of layered single crystal materials, in particular to a layered transition metal telluride single crystal material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous evolution of microelectronic devices towards high integration, low power consumption and high speed response, developing new functional materials with excellent electrical conductivity and structural stability has become a core issue in the field of condensed matter physics and materials science. Two-dimensional layered transition metal chalcogenides (TMDs) have shown great application prospects in photodetectors, flexible electronics, field effect transistors and other devices due to their unique electronic structure, high specific surface area and controllable physical and chemical properties. Ta2Ni3Te5, as a typical layered transition metal telluride, has special interlayer interaction and electron transport channel in its crystal structure, and is considered as a potential candidate material for the next generation of high-performance electronic devices. The wide application of photodetectors in remote sensing, somatosensory interaction, optical fiber communication and other fields has great practical significance for the development of photodetectors with room temperature operation, lightness, flexibility and wide spectral response. The visible and near-infrared wavelength regions are quite mature, and the application of photodetectors based on narrow-band semiconductors in the mid-infrared wavelength region is limited by the requirement of low-temperature operation. The room temperature operation of mid-infrared photodetectors with wide spectral response and high sensitivity still faces important technical challenges. The wide-band photodetector based on Ta2Ni3Te5 single crystal material can greatly improve the output performance of wide-band photodetectors and break through the long-term technical bottleneck of photodetectors by utilizing the inherent properties of two-dimensional topological materials.

[0003] However, the electrical conductivity of pure-phase Ta2Ni3Te5 single crystal is still limited by the problems of insufficient intrinsic carrier mobility, strong interlayer scattering and defect scattering in the electron transport process, which makes it difficult to meet the stringent requirements of high-end devices for charge transport rate, response sensitivity and energy conversion efficiency. To improve the output performance of wide-band photodetectors, the optimization of three basic physical properties, namely light absorption characteristics, carrier transport characteristics, photoelectric conversion and stability, is essential. Therefore, precise regulation of the electrical conductivity of Ta2Ni3Te5 single crystal material is the key to breaking through the application bottleneck. SUMMARY

[0004] Therefore, the present application aims to provide a layered transition metal telluride single crystal material and a preparation method and application thereof to solve the problem of insufficient carrier mobility of pure-phase Ta2Ni3Te5 single crystal and difficulty in meeting the requirements of high-end electronic devices.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: The application provides a preparation method of a layered transition metal telluride single crystal material. S1. Tantalum powder, tellurium powder, nickel powder and palladium powder are weighed as raw materials, and are added into a mortar, and are ground to be uniformly mixed after iodine particles are added; S2. The ground powder is placed into a quartz tube for vacuum sealing, calcination, temperature maintaining after being reduced to a predetermined temperature, and cooling to obtain the layered transition metal telluride single crystal material.

[0006] The application realizes accurate doping of Pd on Ta2Ni3Te5 single crystals by adopting a chemical vapor transport (CVT) method, on one hand, the single crystal prepared by the CVT method has high purity, good crystallinity and complete layered structure, and meets the high quality requirement of a device on a base material; on the other hand, the Pd doping realizes controllable adjustment of a conductive core parameter, provides a flexible scheme for matching the performance requirement of different devices, promotes the conversion of the typical layered transition metal chalcogenide Ta2Ni3Te5 from basic research to practical device application, and has important reference significance for performance adjustment and industrialization exploration of related functional materials.

[0007] As a further improvement of the above-mentioned scheme of the application, in step S1, the molar ratio of the tantalum powder, the tellurium powder, the nickel powder and the palladium powder is 2:5:3-3x:3x, 0

[0008] As a further improvement of the above-mentioned scheme of the application, in step S1, the mass ratio of the iodine particles to the raw materials is 0.06-0.12:1, and the grinding time is 10-20 min.

[0009] As a further improvement of the above-mentioned scheme of the application, in step S2, the vacuum sealing method is that the quartz tube is pumped to vacuum, and the quartz tube is heat sealed by using a hydrogen-oxygen flame sealing technology.

[0010] As a further improvement of the above-mentioned scheme of the application, in step S2, after the vacuum sealing, the following step is further included: the quartz tube is placed into an ultrasonic cleaning machine for ultrasonic treatment for 1-3 min.

[0011] As a further improvement of the above-mentioned scheme of the application, in step S2, the calcination method is that the quartz tube is calcined at 150-200 DEG C for 1-2 h, then the quartz tube is immediately placed into a double-temperature-zone tube furnace, one end of the quartz tube in which is placed in a high-temperature zone and the other end is placed in a low-temperature zone, the high-temperature zone is raised to 900-950 DEG C, the low-temperature zone is raised to 800-850 DEG C, temperature maintaining is performed for 50-70 h, and the temperature difference between the high-temperature zone and the low-temperature zone is kept to be 100 DEG C during the temperature maintaining; then the high-temperature zone is reduced to 800-850 DEG C, the low-temperature zone is raised to 900-950 DEG C, and temperature maintaining is performed for 100-120 h.

[0012] As a further improvement to the above-mentioned solution of the present invention, in step S2, the heat preservation after cooling to the predetermined temperature involves cooling the high temperature zone and the low temperature zone to 600-650℃ at a rate of 5-10℃ / h and preserving the temperature for 24-36h.

[0013] The present invention also provides a layered transition metal telluride single crystal material, which is prepared by the preparation method described above.

[0014] This invention also provides an application of layered transition metal telluride single crystal materials prepared by the preparation method described above in photodetectors, field-effect transistors, flexible electronic devices, thermoelectric conversion devices, topological electronic devices, and low-temperature electronic devices.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention employs chemical vapor transport (CVT) to achieve precise Pd doping of Ta₂Ni₃Te₅ single crystals. On one hand, the single crystals prepared by CVT exhibit high purity, good crystallinity, and a complete layered structure, meeting the high-quality requirements of device substrate materials. On the other hand, Pd doping enables controllable adjustment of the core conductivity parameters, providing a flexible solution to match the performance requirements of different devices. This invention promotes the transformation of Ta₂Ni₃Te₅, a typical layered transition metal chalcogenide, from basic research to practical device applications, and has important reference significance for the performance regulation and industrialization exploration of related functional materials.

[0016] This invention leverages the advantages of high purity and easy controllability of the CVT method. By precisely controlling the Pd doping concentration by varying the amount of Pd source, the changing trends of carrier mobility and resistivity are analyzed in conjunction with electrical performance tests. The results show that with increasing Pd doping concentration, the carrier mobility of Ta2Ni3Te5 single crystal exhibits a significant increasing trend. This is attributed to the introduction of Pd atoms optimizing the electronic transport path of the crystal and suppressing defect scattering. Simultaneously, the resistivity increases with increasing doping concentration, presumably related to the changes in internal carrier concentration and enhanced interface scattering induced by doping.

[0017] This invention not only clarifies the regulation mechanism of Pd doping concentration on the conductivity of Ta2Ni3Te5 single crystal, but also provides a feasible method for the precise regulation of the conductivity of layered tellurides, which has important reference value for promoting their application in high-performance devices such as high-frequency field-effect transistors and flexible electronics. Attached Figure Description

[0018] Figure 1 These are physical images of the single crystals obtained in Examples 1-4 and the comparative examples of the present invention. Figure 2 The XRD patterns of single crystals obtained in Examples 1-4 and the comparative examples of this invention are shown below. Figure 3These are schematic diagrams of the single crystal structures obtained in Examples 1-4 and the comparative examples of the present invention; Figure 4 These are SEM images of the single crystals obtained in Examples 1-4 of this invention. Figure 5 The Raman spectra of the single crystals prepared in Examples 1-4 and the comparative examples of this invention are shown below. Figure 6 The resistivity of the single crystals prepared in Examples 1-4 and the comparative examples of this invention is shown as a function of temperature. Figure 7 The graphs show the activation energy and room temperature conductivity of the single crystals prepared in Examples 1-4 and the comparative examples of the present invention as a function of Pd doping concentration. Figure 8 The graphs show the carrier concentration and mobility of the single crystals prepared in Examples 1-4 and the comparative examples of the present invention as a function of Pd doping concentration. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] Example 1 This embodiment proposes a layered transition metal telluride single crystal material, the preparation method of which includes the following steps: S1. Weigh tantalum powder, tellurium powder, nickel powder, and palladium powder according to the molar ratio Ta:Te:Ni:Pd=2:5:2.85:0.15 (x=5%) as raw materials; weigh iodine particles as transport agent, with the mass ratio of iodine particles to raw materials being 0.08:1; place the raw materials and transport agent into a mortar, use anhydrous ethanol as a dispersant, and grind thoroughly to ensure that the dopant particles are uniformly dispersed on the surface of the main raw materials; S2. Place the ground mixed powder into a quartz tube, then evacuate the quartz tube to a vacuum of less than 0.1 Pa, and use oxyhydrogen flame sealing technology to heat seal the quartz tube to ensure the reliability of the seal and prevent external impurities from entering and affecting crystal growth; then place the sealed quartz tube into an ultrasonic cleaner for ultrasonic treatment for 150 seconds. S3. The mixed powder is calcined at 200℃ for 1 hour to form a weakly bonded coating structure between the dopant, transport agent, and raw material, preventing the dopant from separating from the main raw material due to differences in volatilization rates during high-temperature growth and reducing doping segregation. Then, the quartz tube is immediately placed in a dual-temperature zone tube furnace, with one end containing the raw material in the high-temperature zone (source zone) and the other end in the low-temperature zone (growth zone). The temperature of the high-temperature zone is set to 900℃, and the temperature of the low-temperature zone is set to 800℃, with a heating time of 10 hours. The temperature difference between the high-temperature and low-temperature zones is then maintained at 100℃ (temperature gradient of 5℃ / cm) for 50 hours. Then, within 1 hour, the high-temperature zone is lowered to 800℃, and the low-temperature zone is raised to 900℃ and held for 100 hours. After single crystal growth is complete, the temperatures of both the high-temperature and low-temperature zones are lowered to 600-650℃ at a rate of 5-10℃ / h and held for 24 hours. The furnace is then cooled to obtain a layered transition metal telluride single crystal material, Ta2(Ni). 0.95 Pd 0.05 3Te5, carefully break the quartz tube, separate the crystal with tweezers, avoiding damage to the surface, dissolve the residual transfer agent on the crystal surface with ethanol, and carefully wipe it with degreased cotton.

[0022] Example 2 The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, tantalum powder, tellurium powder, nickel powder, and palladium powder are weighed according to a molar ratio of Ta:Te:Ni:Pd=2:5:2.79:0.21 (x=7%). This embodiment ultimately yields a layered transition metal telluride single crystal material Ta2(Ni 0.93 Pd 0.07 )3Te5.

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, tantalum powder, tellurium powder, nickel powder, and palladium powder are weighed according to a molar ratio of Ta:Te:Ni:Pd=2:5:2.58:0.42 (x=14%). This embodiment ultimately yields a layered transition metal telluride single crystal material Ta2(Ni 0.86 Pd 0.14 )3Te5.

[0024] Example 4 The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, tantalum powder, tellurium powder, nickel powder, and palladium powder are weighed according to a molar ratio of Ta:Te:Ni:Pd=2:5:2.43:0.57 (x=19%); this embodiment ultimately obtains a layered transition metal telluride single crystal material Ta2(Ni 0.81 Pd 0.19 )3Te5.

[0025] Comparative Example The difference between this comparative example and Example 1 is that in step S1 of this comparative example, tantalum powder, tellurium powder, and nickel powder are weighed according to the molar ratio of Ta:Te:Ni=2:5:3 (x=0%); this comparative example finally obtains layered transition metal telluride single crystal material Ta2Ni3Te5.

[0026] Figure 1 Ta2(Ni) 1-x Pd x )3Te5 single crystal physical image, Figure 1 (a) is a physical image of a Ta2Ni3Te5 single crystal prepared in comparison. Figure 1 (b) Ta2(Ni) prepared in Example 1 0.95 Pd 0.05 )3Te5 single crystal physical image, Figure 1 (c) Ta2(Ni) prepared in Example 2 0.93 Pd 0.07 )3Te5 single crystal physical image, Figure 1 (d) is Ta2(Ni) prepared in Example 3. 0.86 Pd 0.14 )3Te5 single crystal physical image, Figure 1 (e) is Ta2(Ni) prepared in Example 4. 0.81 Pd 0.19 )3Te5 single crystal physical image. From Figure 1 It can be seen that the single crystal samples are all strip-shaped or needle-shaped, which is a macroscopic manifestation of the special crystal structure of quasi-one-dimensional materials.

[0027] X-ray diffraction (XRD, PANalytical X'pert, Cu-Kα1, λ = 0.15406 nm) was used to analyze the Ta2(Ni) prepared in Examples 1-4 and the comparative examples. 1-x Pd x X-ray diffraction was performed on a 3Te5 single crystal to obtain the following results: Figure 2 The single-crystal XRD pattern shown is from Figure 2 It can be seen that the doped samples in Examples 1-4 are all single crystals with a natural growth surface of (100).

[0028] like Figure 3 The Ta2(Ni) prepared in Examples 1-4 shown 1-x Pd x Schematic diagrams of the crystal structures of Ta2Ni3Te5 and the comparative example of Ta2Ni3Te5; Ta2Ni3Te5 has an orthorhombic crystal structure with space group pnma, with atomic chains extending along the b-axis and stacked by van der Waals forces. Ni atoms are filled in the tetrahedral structure layer of Ta2Ni3Te5, and Pd replaces the Ni atom sites during doping.

[0029] The Ta2(Ni) prepared in Examples 1-4 were observed using scanning electron microscopy (SEM). 1-x Pd x The macroscopic morphology and microstructure of 3Te5 single crystal were obtained as follows: Figure 4 The SEM morphology shown is as follows, Figure 4 (a) Ta2(Ni) prepared in Example 1 0.95 Pd 0.05 )3Te5 single crystal physical image, Figure 4 (b) Ta2(Ni) prepared in Example 2 0.93 Pd 0.07 )3Te5 single crystal physical image, Figure 4 (c) Ta2(Ni) prepared in Example 3 0.86 Pd 0.14 )3Te5 single crystal physical image, Figure 4 (d) is Ta2(Ni) prepared in Example 4. 0.81 Pd 0.19 )3Te5 single crystal physical image. Figure 4 This reflects that the crystal surface is smooth and flat, with no obvious defects.

[0030] The concentrations of Examples 1-4 and the comparative example were measured using an EDS device. The results are shown in Table 1. The actual doping concentrations of the comparative example and Examples 1-4 were x=0, x=5%, x=7%, x=14%, and x=19%, respectively.

[0031] Table 1

[0032] Micro-Raman Spectroscopy was introduced to analyze the Ta2(Ni) prepared in Examples 1-4 and the comparative examples. 1-x Pd x Phonon vibrational modes of 3Te5 single crystals were characterized, and data were collected at room temperature and with different Pd doping concentrations (x values) in Ta2(Ni)4. 1-x Pd x Raman spectra of 3Te5 single crystals, such as Figure 5 As shown, the introduction of Pd atoms will change the bond length and bond energy of the chemical bonds in the layer due to the difference in atomic radius (Pd atomic radius is larger than Ni), which will lead to a red shift of the characteristic Raman peak. The red shift trend of Pd doping amount x=14% and x=19% is more obvious than that of Pd doping amount x=5% and x=7%.

[0033] In terms of electrical transport performance testing, the Ta2(Ni) prepared in Examples 1-4 and the comparative examples were tested using a physical property measurement system (PPMS-9T, 1.8K≤T≤400K, 0≤H≤9T). 1-x Pdx Temperature-dependent resistivity and Hall effect measurements were performed on 3Te5 single crystals. (1) p-T The curve can reflect the change of resistivity with temperature. Analysis of the electron transport mechanism yields results as follows: Figure 6 As shown. From Figure 6 The results show that the resistivity curve with temperature generally shifts upward as the doping concentration x increases, indicating that doping significantly increases the intrinsic resistivity of the system. At the same time, with the increase of doping amount, the resistivity behavior in the low temperature region (T≤100K) gradually deviates from the continuous decreasing behavior of the pure phase (x=0%), showing the characteristics of resistivity plateauing, reflecting the modulation effect of doping on the transport behavior of the system.

[0034] (2) such as Figure 7 The figure shows Ta2(Ni) with different x values. 1-x Pd x The activation energy and room temperature conductivity curves for 3Te5 are shown. The activation energy is derived from the Arrhenius equation. p(T) = p 0 exp(E a / k B T) Obtained through fitting. From Figure 7 The results show that, with increasing doping concentration... x The increase in activation energy E a The trend is characterized by an initial significant decrease followed by a slow increase. It can be argued that at low doping levels, impurity atoms introduce shallow energy levels within the band gap, lowering the energy barrier for thermal excitation of charge carriers. However, excessively high impurity concentrations lead to the overlap of impurity energy levels, forming narrow impurity bands. Charge carrier excitation also requires crossing the energy barrier between the impurity band and the conduction band, causing Ea to vary with doping concentration. x The room temperature conductivity σ shows a continuous decreasing trend, which should be attributed to the impurity compensation effect, i.e., donor-acceptor recombination, which reduces the effective carrier concentration. n Reduced.

[0035] (3) Combine Hall measurement to calculate carrier concentration and mobility, explore the regulation law of Pd doping on carrier transport, and use the seven-wire method to fabricate electrode leads for Ta2(Ni 1-x Pd x Electrical transport measurements on 3Te5 single crystal samples can simultaneously yield detailed temperature-dependent longitudinal resistivity. p xx Hall resistivity p xy Information: The measurement of Hall resistivity requires measuring the Hall signals under both forward and reverse fields, subtracting the transverse resistance, and then obtaining the intrinsic Hall resistivity. p xy = (p xy(B) - p xy (-B)) / 2 The Hall coefficient is calculated using the following formula: R H = p xy B Calculate the Hall coefficient R H Then, according to the formula: n = 1 / R H e Calculate the carrier concentration n Hall mobility p According to the formula: p = R H / p xx The result is as follows Figure 8 As shown.

[0036] from Figure 8 The results show that at 300K, the carrier concentration of this system... n The doping concentration decreases monotonically with increasing doping concentration; while the carrier mobility increases with increasing doping concentration. x The increase in doping can lead to a significant recombination of carriers provided by impurities with existing carriers of the opposite type, resulting in a decrease in the actual carrier concentration. Conversely, doping can improve mobility by modulating the band structure of the crystal, reducing carrier transport resistance, or by altering the density of states distribution of the material, thus reducing energy dispersion. A more concentrated density of states distribution reduces the resistance to transitions between different energy states and decreases energy disturbances during carrier movement, thereby improving mobility.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a layered transition metal telluride single crystal material, characterized in that, It includes the following steps: S1. Weigh tantalum powder, tellurium powder, nickel powder, and palladium powder as raw materials, add them to a mortar, add iodine granules, and grind until they are evenly mixed; S2. Place the ground powder into a quartz tube, seal it under vacuum, calcine it, lower it to a predetermined temperature, hold it at that temperature, and then cool it to obtain a layered transition metal telluride single crystal material.

2. The method for preparing layered transition metal telluride single crystal material according to claim 1, characterized in that, In step S1, the molar ratio of tantalum powder, tellurium powder, nickel powder, and palladium powder is 2:5:3-3x:3x, 0 <x≤0.2。 3. The method for preparing layered transition metal telluride single crystal material according to claim 1, characterized in that, In step S1, the mass ratio of iodine granules to the raw material is 0.06~0.12:1; the grinding time is 10~20 min.

4. The method for preparing layered transition metal telluride single crystal material according to claim 1, characterized in that, In step S2, the vacuum sealing method is as follows: the quartz tube is evacuated to a vacuum and then heat-sealed using an oxyhydrogen flame sealing technique.

5. The method for preparing layered transition metal telluride single crystal material according to claim 1, characterized in that, In step S2, after vacuum sealing, the following steps are also included: placing the quartz tube into an ultrasonic cleaner for ultrasonic treatment for 1-3 minutes.

6. The method for preparing layered transition metal telluride single crystal material according to claim 1, characterized in that, In step S2, the calcination method is as follows: after calcining the quartz tube at 150~200℃ for 1~2 hours, the quartz tube is immediately placed in a dual-temperature zone tube furnace, with one end of the raw material placed in the high-temperature zone and the other end placed in the low-temperature zone. The high-temperature zone is heated to 900~950℃ and the low-temperature zone is heated to 800~850℃, and the temperature is maintained for 50~70 hours, while the temperature difference between the high-temperature zone and the low-temperature zone is maintained at 100℃. Then, the high temperature is lowered to 800~850℃ and the low-temperature zone is heated to 900~950℃, and the temperature is maintained for 100~120 hours.

7. The method for preparing layered transition metal telluride single crystal material according to claim 6, characterized in that, In step S2, the heat preservation after cooling to the predetermined temperature involves cooling the high-temperature zone and the low-temperature zone to 600-650℃ at a rate of 5-10℃ / h and preserving the temperature for 24-36 hours.

8. A layered transition metal telluride single crystal material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. The application of a layered transition metal telluride single crystal material prepared by the preparation method according to any one of claims 1-7 in photodetectors, field-effect transistors, flexible electronic devices, thermoelectric conversion devices, topological electronic devices and low-temperature electronic devices.

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