矽原子在銥(100)切面上的動態行為與交互作用

Abstract

本實驗利用場離子顯微鏡觀察吸附矽原子在銥(100)切面上的動態行為及交互作用。利用單顆吸附矽原子在不同溫度下的熱擴散運動，並配合Arrhenius plot求得擴散活化能E_d=0.91±0.02 eV。雙顆吸附矽原子在加熱到400 K以上時，彼此間的距離較低溫時的大，也間接證明在此溫度下，原子有足夠的能量去排列成有序結構。觀察雙顆吸附矽原子在銥(100)切面上的動態分布，顯示出矽原子在銥(100)切面上會位於不同佔位上(例如：四重對稱站位、橋位和上位)，也表示矽原子彼此間的交互作用力大於矽原子與基底間的交互作用。雙顆吸附矽原子會在相距三個銥基底的晶格常數下處在最低的交互作用能0.086 eV。原子間的交互作用會受到基底的二維自由電子氣影響，產生Fridel oscillation的現象，藉由理論公式與實驗數據擬合，可以得到銥(100)切面上的費米波向量應該為1.35 Å。當加熱到431 K時，蒸鍍在銥(100)切面下的矽原子會發生上行運動。This study is about the dynamics and interaction of silicon adatoms on Ir(100) by field ion microscopy (FIM). The activation energy of a single silicon adatom diffusion on Ir(100) which is calculated with the diffusion motion at different temperature and the Arrhenius plot is 0.91±0.02 eV. The distance of the two silicon adatoms heated above 400 K is larger than at low temperature. That is the silicon atoms would have enough energy to arrange the order structure at 400 K. The distribution of two silicon adatoms on Ir(100) shows the silicon adatoms on the different sites (ex. 4-fold site, bridge site and top site). That is the interaction energy between the two silicon adatoms is larger than the interaction energy between silicon adatom and iridium. The lowest interaction energy of two silicon adatoms is -0.086 eV as they are between 3 iridium lattice constants. 2-dimetion free electron gas of iridium surface results in Fridel oscillation. We calculated the Fermi wave vector of Ir(100) surface was 1.35 Å by fitting formula. The silicon adatoms on Ir(100) would be step up motion above 431K.