高压下锗化镁的金属化相变研究

发布时间：2018-03-06 07:17

本文选题：锗化镁　切入点：金属化相变　出处：《物理学报》2017年16期 　论文类型：期刊论文

【摘要】：锗化镁是一种窄带半导体,压力作用可以使锗化镁导带底与价带顶的能隙变小.本文基于第一性原理计算了锗化镁在高压下的能带结构以及反萤石相(常压稳定相)和反氯铅矿相(高压相)的焓值,发现在7.5 GPa时反萤石结构锗化镁导带底与价带顶的能隙闭合,预示着半导体相转变为金属相,计算结果还预测在11.0 GPa时锗化镁发生从反萤石结构到反氯铅矿结构的相变.实验研究方面,本文采用长条形压砧在连续加压条件下测量了锗化镁高压下的电阻变化,采用金刚石对顶压砧测量了锗化镁的高压原位拉曼光谱,发现在8.7 GPa锗化镁的电阻出现不连续变化,9.8 GPa以上锗化镁的拉曼振动峰消失.由于金属相的自由电子浓度高会阻碍激发光进入样品,进而引起拉曼振动峰消失,因此我们推测锗化镁在9.8 GPa转变为金属相.
[Abstract]:Magnesium germanate is a narrow band semiconductor, The energy gap between the bottom of the conduction band and the top of the valence band can be reduced by pressure. Based on the first principle, the energy band structure of magnesium germanide at high pressure and the enthalpy values of antifluorite phase (stable phase at atmospheric pressure) and antichlorite phase (high pressure phase) have been calculated. It is found that the energy gap between the bottom of the conduction band and the top of the valence band is closed at 7.5 GPa, indicating the transition of the semiconductor phase to the metallic phase. The calculated results also predict the phase transition of magnesium germanate from antifluorite structure to antichlorite structure at 11.0 GPa. In terms of experimental study, the resistance changes of magnesium germanium germanide at high pressure have been measured under continuous pressure by means of long strip anvil. High pressure in situ Raman spectra of magnesium germanate were measured by diamond anvil. It is found that the Raman vibrational peak of magnesium germanium germanide disappears over 9.8 GPa due to the discontinuous change of resistance at 8.7 GPa. The high concentration of free electron in the metal phase will prevent the excited light from entering the sample, which will lead to the disappearance of the Raman vibration peak. Therefore, we speculate that magnesium germanate will be transformed into metallic phase at 9. 8 GPa.
【作者单位】：西南交通大学物理科学与技术学院材料先进技术教育部重点实验室;西北工业大学材料学院;
【基金】：国家自然科学基金(批准号:11004163) 中央高校基本科研业务费专项资金(批准号:2682014ZT31,2682016CX065)资助的课题~~
【分类号】：O521.23

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