Spontaneous nucleation growth method for thallium bromide single-crystal

Abstract

The invention provides a method for growing thallium bromide monocrystal by spontaneous nucleation, comprising the following steps of: 1) filling a thallium bromide material into a cylindrical ampoule with diameter of 8 to 15mm, vacuumizing, sealing, and processing one end of the ampoule into a cone with the cone angle between 15 and 45 degrees; 2) placing the ampoule into a vertical tube furnace with the conical end towards the bottom of the furnace, heating the vertical tube furnace to enable the temperature of the thallium bromide material in the conical tip not to be lower than the melting point of thallium bromide, raising the temperature from the conical tip upward to the inside of a top area of the thallium bromide material with the temperature gradient between 1.0 and 1.5 DEG C / mm, and then, insulating; 3) reducing the temperature of the tube furnace to between 450 and 460 DEG C at the speed between 1 and 5 DEG C / h; and 4) cooling the ampoule to room temperature along with the furnace. Because a heater and the ampoule are not required to be moved, the invention saves the complicated mechanical transmission device, simplifies the technology and reduces cost. The ampoule and the heater are both fixed, the temperature field is stable, heat inside the crystal and molten mass is uniformly distributed, a convex growth interface can be easily acquired, and the thallium bromide with good integrity and considerable size can be grown.

Description

technical field [0001] The invention belongs to the technical field of single crystal growth, and in particular relates to a growth method of thallium bromide single crystal. Background technique [0002] High-energy X-ray and gamma-ray detection is one of the core technologies in the field of space science and technology. Semiconductor materials such as Ge and Si commonly used in classical detectors must work at low temperature (about 70K), which adds many difficulties and costs to the use in space. Although semiconductor materials such as CdZnTe and CdTe developed in recent years have excellent characteristics at around -30°C, their hole transport ability is limited in the frequency range above hard X-rays, making it difficult to meet the detection requirements of high-energy X-rays and γ-rays. . Thallium bromide material has higher atomic number (Tl: 81, Br: 35), higher density (7.5g / cm 3 ), large band gap (2.68ev) and large electron-hole mobility, so it is a promising...

AI Technical Summary

Problems solved by technology

However, according to M.S.Kouznetsov et al. in the literature "Development of the technology for growing TlBr detector crystals.Nuclear Instruments and Methods in Physics Research A, 531 (2004) 174-180" research shows that when growing a single crystal with the Bridgman method, The temperature in the upper part of the furnace area is still about 100-150 °C higher than the temperature in the lower part. In this way, there is still a large temperature gradient along the length of the crystal, and there is a large stress between the crystal and the crucible. The disappearance of this stress needs to pass through lattice sliding. shift or form defects to eliminate

Due to the high plasticity of thallium bromide, it will form a lattice deformation, which will eventually affect the quality of the crystal

In addition, when growing crystals by these two methods, precise mechanical transmission devices are required, and the equipment is expensive

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