CN114457426B - Ti-doped monolayer molybdenum disulfide single crystal and its preparation method and application - Google Patents

Abstract

The invention discloses a Ti-doped single-layer molybdenum disulfide single crystal and its preparation method and application. The preparation method includes the following steps: preparing a quartz tube with two ends open, and the two ends of the quartz tube are respectively raw material ends and a base end, place a base in the base end of the quartz tube, place raw material and transport agent in the raw material end of the quartz tube, evacuate the quartz tube, seal the quartz tube, so that the The inner pressure of the quartz tube is 10 ^-6 ~ 10 ^-3 Pa, the raw material end and the base end of the quartz tube are heated simultaneously for 0.5 ~ 1h, cooled to room temperature 20 ~ 25°C, and a Ti-doped monolayer bismuth is obtained on the substrate. Molybdenum sulfide single crystal. The preparation method of the present invention can realize the in-plane substitution and doping of the transition element Ti on the single _- layer MoS2 single _- crystal under the premise of ensuring the crystal quality of the single _- layer MoS2 single crystal, and realize the substantial enhancement of the photoluminescence intensity of the MoS2.

Description

Ti-doped monolayer molybdenum disulfide single crystal and its preparation method and application

technical field

The invention belongs to the technical field of molybdenum disulfide single crystal, and specifically relates to a Ti-doped single-layer molybdenum disulfide single crystal and a preparation method and application thereof.

Background technique

Two-dimensional chalcogenide materials have great application potential in flexible transistors, optoelectronic sensors, and information storage. However, two-dimensional materials have more intrinsic defect states, which trap a large number of carriers, resulting in weaker luminous efficiency. By selecting appropriate dopant atoms, their luminescent properties can be improved without changing their intrinsic bandgap.

However, there are not many doping methods currently available, and the high crystal quality of single-layer _MoS2 single crystal cannot be maintained after doping, and the crystallinity is poor, easy to be polluted, and greatly affected by external interference.

Contents of the invention

For the deficiencies in the prior art, the object of the present invention is to provide a method for preparing a Ti-doped single-layer molybdenum disulfide single crystal, which can realize the high crystallization quality of the single-layer _MoS2 single crystal The in-plane doping of single-layer MoS ₂ with Ti element can realize the enhancement of photoluminescence of MoS ₂ , which solves the technical problem of Ti-doped two-dimensional single-layer MoS ₂ , and the obtained Ti-doped single-layer molybdenum disulfide single crystal The photoluminescent efficiency is greatly improved, which provides support for the realization of high-performance photodetectors.

The purpose of the present invention is achieved through the following technical solutions.

A method for preparing a Ti-doped monolayer molybdenum disulfide single crystal, comprising the following steps:

1) Prepare a quartz tube with open ends, the two ends of the quartz tube are respectively the raw material end and the base end, a base is placed in the base end of the quartz tube, and a base is placed in the raw material end of the quartz tube. Raw material and transport agent, vacuumize the quartz tube, seal the quartz tube so that the inner pressure of the quartz tube is 10 ^-6 ~ 10 ^-3 Pa, wherein the raw material is 1.5 ~ 2.5 parts by mass MoO ₃ , 0.36-0.42 parts by mass of S powder and 0.2-1.0 parts by mass of TiO ₂ , the transport agent is elemental iodine;

In the step 1), the substrate is mica or graphite.

In the step 1), the length of the quartz tube is 15-40 cm, and the inner diameter is 10-20 mm.

In the step 1), in parts by mass, the ratio of the raw material to the transport agent is (2-6):(3-8).

2) Heating the raw material end and the base end of the quartz tube simultaneously for 0.5-1h, cooling to room temperature 20-25°C, and obtaining a Ti-doped single-layer molybdenum disulfide single crystal on the substrate, wherein the heating temperature of the raw material end is 750-900°C, and the heating temperature of the base end is 400-700°C.

In the step 2), the heating rate to 750-900°C is 25-50°C/min, and the heating rate to 400-700°C is 25-50°C/min.

In the step 2), the temperature gradient between the raw material end and the base end is 3-30° C./cm.

The Ti-doped monolayer molybdenum disulfide single crystal obtained by the above preparation method.

The application of the above preparation method in simultaneously realizing the enhancement of photoluminescence of monolayer molybdenum disulfide and the preparation of monolayer molybdenum disulfide single crystal.

The preparation method of the present invention can realize the in-plane substitution and doping of the transition element Ti on the single-layer _MoS2 single crystal under the premise of ensuring the crystal quality of the single-layer _MoS2 single crystal, and realize the substantial enhancement of the photoluminescence intensity of the _MoS2 .

Description of drawings

Figure 1 is an optical photograph of a Ti-doped single-layer molybdenum disulfide single crystal, where a is the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1, and b is the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 2 Single crystal, c is the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 3;

Fig. 2 is the optical photograph of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Comparative Example 1 and 2, wherein, a is the Ti-doped single-layer molybdenum disulfide single crystal obtained in Comparative Example 1, and b is the Ti-doped single-layer molybdenum disulfide single crystal obtained in Comparative Example 2. Heterogeneous monolayer molybdenum disulfide single crystal;

Fig. 3 is the photoluminescence of the Ti-doped monolayer molybdenum disulfide single crystal obtained in Example 1 and the molybdenum disulfide single crystal obtained in Comparative Example 3;

Fig. 4 is the photoluminescence of the obtained Ti-doped monolayer molybdenum disulfide single crystal obtained in Comparative Example 1 and the obtained molybdenum disulfide single crystal obtained in Comparative Example 3;

Fig. 5 is the photoluminescence of the obtained Ti-doped monolayer molybdenum disulfide single crystal obtained in Comparative Example 2 and the obtained molybdenum disulfide single crystal obtained in Comparative Example 3;

Fig. 6 is the Raman Mapping and PL Mapping figure of Ti-doped monolayer molybdenum disulfide single crystal obtained in Example 1, wherein, a is Raman Mapping, b is PL Mapping;

Fig. 7 is the AFM image of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1, wherein, a is the AFM image, and b is the height measurement map of the Ti-doped single-layer molybdenum disulfide single crystal of the underlined part in a. ;

Fig. 8 is the XPS data figure of Mo element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in embodiment 1;

Fig. 9 is the XPS data diagram of the S element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 10 is the XPS data diagram of the Ti element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 11 is the low magnification TEM figure of the obtained Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 12 is the TEM-EDS elementalmapping diagram of the Mo element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 13 is the TEM-EDS elementalmapping diagram of the S element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 14 is the TEM-EDS elementalmapping diagram of the Ti element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

Fig. 15 is the EDS energy spectrum diagram and the element content of each element in the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1;

FIG. 16 is a STEM image of a Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1. FIG.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

MoO ₃ : purity ≥ 99.9%, Beijing Hulk;

S powder: purity ≥ 99.999%, sigma;

I ₂ : purity ≥ 99.999%, Alfa Aesar;

TiO ₂ : purity ≥99.99%, Beijing Hulk;

OLYMPUS-bx53m-microscope;

WITec confocal Raman and atomic force microscope system (Raman-AFM);

The quartz tube is heated using a tube furnace.

The quartz tubes used in the following examples and comparative examples have a length of 15 cm and an inner diameter of 11 mm.

Examples 1-3

A method for preparing a Ti-doped monolayer molybdenum disulfide single crystal, comprising the following steps:

1) Prepare a quartz tube with open ends, the two ends of the quartz tube are respectively the raw material end and the base end, a base is placed in the base end of the quartz tube, and raw materials and transport agents are placed in the raw material end of the quartz tube, Vacuum the quartz tube with a vacuum sealing device, and seal the quartz tube with a flame gun, so that the internal pressure of the quartz tube is 3.5*10 ^-4 Pa, to ensure that no other elements except Ti are introduced, and the raw material is MoO _3. S powder and TiO ₂ , the transport agent is elemental iodine;

2) Heat the raw material end and the base end of the quartz tube simultaneously for 0.5h, then cool naturally with the furnace to room temperature 20-25°C, and obtain a Ti-doped single-layer molybdenum disulfide single crystal on the substrate, wherein the heating temperature of the raw material end is T1 ℃, the heating temperature at the base end is T2°C, the heating rate to T1°C is t1°C/min, the heating rate to T2°C is t2°C/min, and the temperature gradient between the raw material end and the base end is x°C/min cm.

Table 1

Comparative example 1～2

A method for preparing a Ti-doped monolayer molybdenum disulfide single crystal, comprising the following steps:

1) Prepare a quartz tube with open ends. The two ends of the quartz tube are the raw material end and the base end respectively. A mica is placed in the base end of the quartz tube as the base, and the raw material and transportation are placed in the raw material end of the quartz tube. Use a vacuum sealing device to evacuate the quartz tube, and use a flame gun to seal the quartz tube so that the internal pressure of the quartz tube is 3.5*10 ^-4 Pa to ensure that no other elements except Ti will be introduced. Among them, the raw material MoO ₃ , S powder and TiO ₂ , and the transport agent is elemental iodine;

2) Heat the raw material end and the base end of the quartz tube simultaneously for 0.5h, then cool naturally to room temperature 20-25°C with the furnace, and obtain a Ti-doped single-layer molybdenum disulfide single crystal on the substrate, wherein the heating temperature of the raw material end is 850 °C, the heating temperature at the base end is 600 °C, the heating rate to 850 °C is 42.5 °C/min, the heating rate to 600 °C is 30 °C/min, and the temperature gradient between the raw material end and the base end is 16 °C/min cm.

Table 2

Comparative example 3

A method for preparing molybdenum disulfide single crystal, comprising the following steps:

1) Prepare a quartz tube with open ends. The two ends of the quartz tube are the raw material end and the base end respectively. A mica is placed in the base end of the quartz tube as the base, and the raw material and transportation are placed in the raw material end of the quartz tube. Use a vacuum sealing device to evacuate the quartz tube, and use a flame gun to seal the quartz tube so that the internal pressure of the quartz tube is 3.5*10 ^-4 Pa, wherein the raw materials are 2.7 mg of MoO ₃ and 0.4 mg of S Powder, the transport agent is 3mg of elemental iodine;

2) Heat the raw material end and the base end of the quartz tube simultaneously for 0.5h, then cool naturally with the furnace to room temperature 20-25°C, and obtain molybdenum disulfide single crystal on the substrate, wherein, the heating temperature of the raw material end is 850°C, and the heating temperature of the base end The temperature is 600°C, the heating rate to 8501°C is 42.5°C/min, the heating rate to 6002°C is 30°C/min, and the temperature gradient between the raw material end and the base end is 16°C/cm.

A, b, and c in Fig. 1 are light micrographs of Ti-doped single-layer molybdenum disulfide single crystals grown on different substrates in Examples 1 to 3 of the present invention, indicating that the Ti-doped single-layer molybdenum disulfide single crystals obtained by the preparation method of the present invention Layered molybdenum disulfide single crystal can be suitable for growth on a variety of substrates, and the growth temperature range is wide, and it can still maintain the triangular shape of single-layer MoS ₂ after doping.

In Fig. 2, a and b are the optical photographs of Ti-doped single-layer molybdenum disulfide single crystal grown under the doping amounts of Comparative Example 1 and Comparative Example 2, respectively. Compared with Example 1, Comparative Example 1 has a smaller doping amount than Example 1, and the growth morphology hardly changes; Comparative Example 2 has a larger doping amount than Example 1, and the growth morphology is obviously deformed , and the central nucleation is serious, and the ideal single-layer MoS ₂ single crystal cannot be obtained.

Fig. 3 is the photoluminescence of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 and the molybdenum disulfide single crystal obtained in Comparative Example 3, showing that the Ti-doped single-layer MoS2 single crystal is compared with the undoped single-layer MoS2 _single crystal. The photoluminescence is greatly enhanced. The inset is the comparison of the luminescence peak position after normalizing the luminescence intensity, indicating that the peak position is blue-shifted after doping with Ti element.

Figure 4 is the photoluminescence of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Comparative Example 1 and the molybdenum disulfide single crystal obtained in Comparative Example ₃ . The luminous performance enhancement effect is not obvious.

Figure 5 is the photoluminescence of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Comparative Example 2 and the molybdenum disulfide single crystal obtained in Comparative Example ₃ . The effect of enhancing the luminescence performance is not obvious, because excessive doping introduces a large number of defects, which affects its crystallinity.

Fig. 6 is the Raman Mapping and PL Mapping diagram of _the isolated triangular morphology sample of Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention, which shows that the doped MoS still has the uniformity of crystalline quality and Uniformity of luminous performance.

Figure a in Figure 7 is an AFM image of a Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention, and Figure b corresponds to the height change curve at the line in Figure 1, showing that a Ti-doped single crystal was grown. The thickness of the single-layer molybdenum disulfide single crystal is about 0.8nm, which is consistent with the thickness of the single-layer MoS ₂ , indicating that the MoS ₂ obtained by the preparation method of the present invention is a single-layer material.

Figures 8 to 10 are the XPS data diagrams of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention. Through the analysis of the data, it shows that Ti atoms have successfully entered the _MoS2 lattice and formed Ti-S bonds .

11 to 14 are TEM-EDS elemental mapping diagrams of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention, which more intuitively illustrate the uniform distribution of doping elements in the MoS ₂ crystal.

Figure 15 is the TEM-EDS energy spectrum of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention and the proportion of each element. The characteristic peak of Ti-K can be seen, and the doping amount of Ti element About 1.2%.

Figure 16 is the STEM image of the Ti-doped single-layer molybdenum disulfide single crystal obtained in Example 1 of the present invention, from which it can be judged that the Ti element has replaced the original Mo position in the _MoS2 lattice, thereby obtaining a transition Element-doped monolayer MoS _single crystals.

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (8)

1. a preparation method of Ti-doped single-layer molybdenum disulfide single crystal, is characterized in that, comprises the following steps: 1) Prepare a quartz tube with open ends. The two ends of the quartz tube are the raw material end and the base end respectively. A base is placed in the base end of the quartz tube, and a base is placed in the raw material end of the quartz tube. Raw material and transport agent, vacuumize the quartz tube, seal the quartz tube, so that the inner pressure of the quartz tube is 10 ^-6 ~ 10 ^-3 Pa, wherein, the raw material is 2.3 ~ 2.5 parts by mass MoO ₃ , 0.36-0.42 parts by mass of S powder and 0.35 parts by mass of TiO ₂ , the transport agent is elemental iodine; 2) Heating the raw material end and the base end of the quartz tube at the same time for 0.5~1h, cooling to room temperature 20~25°C, and obtaining a Ti-doped single-layer molybdenum disulfide single crystal on the substrate, wherein the heating temperature of the raw material end is is 750-900°C, and the heating temperature of the base end is 400-700°C. 2. The preparation method according to claim 1, characterized in that, in the step 1), the substrate is mica or graphite. 3. The preparation method according to claim 1, characterized in that, in the step 1), the length of the quartz tube is 15-40 cm, and the inner diameter is 10-20 mm. 4. The preparation method according to claim 1, characterized in that, in the step 1), in terms of parts by mass, the ratio of the raw material to the transport agent is (2~6): (3-8 ). 5. The preparation method according to claim 1, characterized in that, in the step 2), the heating rate to 750-900°C is 25-50°C/min, and the heating rate to 400-700°C 25~50°C/min. 6. The preparation method according to claim 1, characterized in that, in the step 2), the temperature gradient between the raw material end and the base end is 3-30°C/cm. 7. The Ti-doped monolayer molybdenum disulfide single crystal obtained by the preparation method described in any one of claims 1 to 6. 8. The application of the preparation method according to any one of claims 1 to 6 in simultaneously realizing the enhancement of photoluminescence of monolayer molybdenum disulfide and the preparation of monolayer molybdenum disulfide single crystal.

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