Shimizu Yasuo, Uematsu Masashi, Itoh Kohei M
Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
Phys Rev Lett. 2007 Mar 2;98(9):095901. doi: 10.1103/PhysRevLett.98.095901.
We have determined silicon self-diffusivity at temperatures 735-875 degrees C based on the Raman shift of longitudinal optical phonon frequencies of diffusion annealed 28Si/30Si isotope superlattices. The activation enthalpy of 3.6 eV is obtained in such low temperature diffusion annealing. This value is significantly smaller than the previously reported 4.95 eV of the self-interstitial mechanism dominating the high temperature region T>>855 degrees C and is in good agreement with the theoretical prediction for the vacancy-mediated diffusion. We present a model, containing both the self-interstitial and the vacancy terms, that quantitatively describes the experimentally obtained self-diffusivity between 735 and 1388 degrees C, with the clear crossover of the two diffusion mechanisms occurring around 900 degrees C.
我们基于扩散退火的28Si/30Si同位素超晶格纵向光学声子频率的拉曼位移，测定了735 - 875摄氏度温度范围内的硅自扩散系数。在这种低温扩散退火中获得了3.6电子伏特的激活焓。该值明显小于先前报道的在T >> 855摄氏度高温区域占主导的自间隙机制的4.95电子伏特，并且与空位介导扩散的理论预测高度吻合。我们提出了一个同时包含自间隙项和空位项的模型，该模型定量描述了在735至1388摄氏度之间实验测得的自扩散系数，两种扩散机制在约900摄氏度处明显交叉。
