Aspects of point defects in coherent terahertz-wave spectroscopy

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• 作者：Jun-ichi Nishizawa ; Tetsuo Sasaki ; Yutaka Oyama ; Tadao Tanabe
• 关键词：Point defects ; Coherent THz spectroscopy ; Stoichiometry ; GaSe
• 刊名：Physica B
• 出版年：2007
• 出版时间：15 December 2007
• 年：2007
• 卷：401-402
• 期：Complete
• 页码：677-681
• 全文大小：406 K

文摘

The ε-type monocrystalline GaSe crystals were successfully grown by liquid phase epitaxy at constant and low (530–590 °C) growth temperatures under different Se vapor pressures (P_Se0–7.75 Torr). From coherent terahertz (THz)-wave spectroscopy, the absorption spectra have different resonant frequencies and absorption coefficients due to the stoichiometry-dependent point defects, which depend on the applied P_Se. It is shown that the resonance in GaSe under P_Se0 Torr shifts toward lower THz frequencies compared with those under high P_Se, maybe due to the degraded intermolecular interactions caused by the introduction of selenium vacancy-related defects. The absorption coefficients (1–5 THz) decreased according to the increase of Se vapor pressure, thus the transparency of GaSe under higher P_Se is improved by 25 % compared with that of Bridgeman-grown crystals. It is revolutional method, in which value of Q could be as high as 3 million, for the molecular structure and defects in organic molecule also could be already analyzed.