硼硫协同掺杂金刚石的高压合成与电学性能研究

FeNiMnCo-C体系中,在压力6.5 GPa、温度1280—1300℃的极端物理条件下,采用温度梯度法成功合成了硼(B)、硫(S)协同掺杂金刚石大单晶.通过傅里叶红外光谱测试对高温高压所制备金刚石中的杂质进行了表征.借助霍尔效应对典型金刚石样品的电输运性能进行了测试,测试结果表明:硼硫协同掺杂有利于提高p型金刚石的电导率,而且硼硫在合成体系中的添加比例可以决定金刚石的p, n特性.此外,第一性原理计算结果表明,合成体系中不同比例的硼硫协同掺杂对金刚石的p, n特性以及电导率有着直接的影响,计算结果与实验测试结果相吻合.

Synthesis of diamond co-doped with B and S under high pressure and high temperature and electrical properties of the synthesized diamond

As is well known, diamond is extensively used in many fields, because of its excellent properties, such as its hardness, high thermal conductivity, high electron and hole mobility, high breakdown field strength and large band gap (5.4 eV). However, its application in semiconductor area needs to be further understood, because it is irreplaceable by conventional semiconductor materials, especially in the extreme working conditions. Furthermore, the preparation of n-type diamond semiconductors is still an unsolved problem. The reason is that an effective donor element has not yet been found. Recently, both the theoretical and experimental studies show that it is difficult to obtain n-type diamond semiconductor with excellent properties by doping single element in the synthetic system. In this paper, diamond single crystals co-doped with B and S are successfully synthesized in FeNiMnCo-C system at a pressure of 6.5 GPa and temperature ranging from 1280 ℃ to 1300 ℃, by using temperature gradient method. The impurity defects in the synthesized diamond single crystals are characterized by Fourier infrared absorption spectra and the results indicate that the corresponding characteristic absorption peaks of B and S are located at 1298 cm^-1 and 847 cm^-1, respectively. Furthermore, the absorption attributed to B-S group is not detected. The N concentration of the synthesized diamond crystals decreases to 195 ppm, resulting from the incorporation of B and S impurities into the diamond lattices. Additionally, the electrical properties of the typical diamond single crystals are measured in virtue of Hall effects at room temperature. The measurement results display that the electrical conductivity of the diamond doped with B is obviously enhanced, resulting from the involvement of the S when B addition amount is fixed in the synthesis system. Hall mobility of the corresponding diamond crystals increases from 12.5 cm^-2·V^-1·s^-1 to 760.87 cm^-2·V^-1·s^-1. And then, the relative proportion of S and B will determine the p/n properties of the obtained diamond. In order to further study the electrical properties of diamond, first-principles calculations are adopted and the theoretical calculation results show that the impurity elements involved in the obtained diamond can affect the band structures of the synthetic diamond crystals, which is consistent with the experimental result.