Raman Scattering Investigation of Tetramethylsilane under High Pressure
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摘要: 选用四甲基硅烷作为富氢电子材料，利用拉曼光谱，分析其在室温高压(68.9~142.2 GPa)下的振动模式和结构特性。结果表明：随着压力的增大，四甲基硅烷仅保留常压下的3个振动模式，且均被压力锁定；从72.2 GPa开始，出现了新的振动模式，且均随着压力的增大而发生软化，预示着四甲基硅烷可能即将半金属化。Abstract: The vibrational and structural properties of tetramethylsilane were investigated using the Raman scattering measurements under pressures ranging from 68.9 to 142.2 GPa and at room temperature.The results revealed that 3 vibrational modes of tetramethylsilane under 68.9 GPa remain locked in a certain position and are quite stable upon compression to 142.2 GPa.Moreover, new vibrational modes appear with the pressure going up to 72.2 GPa and all exhibit softening with further compression, suggesting that tetramethylsilane will become semi-metallic under such high pressures.
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Key words:
- high pressure /
- tetramethylsilane /
- Raman spectroscopy /
- vibrational mode /
- semi-metallic
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图 1 常压和68.9 GPa压力下TMS的拉曼光谱(插图显示TMS的分子结构)
Figure 1. Raman spectra of TMS under ambient pressure and 68.9 GPa (The insert shows the molecular structure of TMS)
图 3 TMS拉曼振动模式的频移与压力的关系(实心符号表示原有模式，空心符号表示新模式，100.6 GPa处的竖直虚线表示相界，插图显示显微镜观测的样品腔形态)
Figure 3. Raman shifts vs. pressure for the observed modes of TMS (The solid and hollow symbols represent original and new modes respectively, and the vertical dashed line under 100.6 GPa indicates the proposed phase boundary.The insets show the stressed samples via a microscope)
表 1 常压和高压下观测的TMS拉曼振动模式的类别和峰位
Table 1. Raman shifts and assignments of the observed vibrational modes of TMS under ambient and high pressures
Vibrational mode Vibrational type Raman shift/(cm-1) 0.1 MPa 68.9 GPa 72.2 GPa 84.4 GPa 100.6 GPa 122.1 GPa ν1 E(C─Si─C skeletal deformation) 201 ν2 F2(C─Si─C skeletal deformation) 244 ν3 A1(C─Si skeletal stretch) 595 848 853 865 872 869 ν4 F2(C─Si skeletal stretch) 697 ν5 E(CH3 rocking), F2(CH3 rocking) 869 968 976 971 970 983 ν6 A1(CH3 symmetrical deformation), F2(CH3 symmetrical deformation) 1 265 ν7 E(CH3 nonsymmetrical deformation), F2(CH3 nonsymmetrical deformation) 1 420 ν8 E(CH3 symmetrical stretch), F2(CH3 symmetrical stretch) 2 903 3 214 3 218 3 236 3 259 3 296 ν9 E(CH3 nonsymmetrical stretch), F2(CH3 nonsymmetrical stretch) 2 963 ν10 3 649 3 465 ν11 3 924 3 827 3 801 3 634 ν12 3 922 3 903 
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