Luo Jinping, Zhou Chenyang, Li Qihang, Liu Lijun
School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Materials (Basel). 2022 Jun 6;15(11):4026. doi: 10.3390/ma15114026.
Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to investigate the formation energies, total formation free energies and formation entropies of the point defects in a germanium crystal. As far as we know, this is the first time that the total formation free energies of point defects in a germanium crystal have been reported in the literature. We found that the formation energies increased slightly with temperature. The formation free energies decreased significantly with an increase in temperature due to the increase in entropy. The estimated total formation free energies at the melting temperature are ~1.3 eV for self-interstitial and ~0.75 eV for vacancy, corresponding to a formation entropy of ~15 for both types of point defects.
点缺陷对于确定锗晶体的质量至关重要。定量了解点缺陷的热力学形成特性对于后续控制晶体生长过程中的缺陷形成是必要的。在此，采用分子动力学模拟来研究锗晶体中点缺陷的形成能、总形成自由能和形成熵。据我们所知，这是首次在文献中报道锗晶体中点缺陷的总形成自由能。我们发现，形成能随温度略有增加。由于熵的增加，形成自由能随温度升高而显著降低。在熔点温度下，自间隙原子的估计总形成自由能约为1.3电子伏特，空位的约为0.75电子伏特，两种类型的点缺陷的形成熵均约为15。
