摘要
用基于第一性原理的密度泛函理论研究了W(100)c(2×2)再构表面的表面弛豫以及扫描隧道显微镜(STM)图像和衬底偏压的关系.计算所得到的表面原子沿[110]方向的畸变位移δ为0.027nm,畸变能△E为80.6meV·atom-1,表面原子的弛豫分别为-7.6%(△d12/d0)和+0.8%(△d23/d0),功函数Φ为4.55eV.STM图像模拟表明,由于表面原子沿[110]方向的位移,会导致出现平行于[110]方向的亮暗带状条纹.STM图像中突起所对应的并不是表面或次表面的钨原子,而是zig-zag型W原子链中线位置;而STM暗区对应于原子位置畸变形成的相邻zig-zag型W原子链中间区域.当衬底负偏压时,STM针尖典型起伏高度大约在0.008-0.013nm之间;而当衬底正偏压时,针尖起伏高度在0.019-0.024nm之间变化.
Scanning tunneling microscope （STM） images and surface relaxations of a reconstructed W（100） c（2×2） surface have been investigated by density functional theory calculations. The distorted displacement （8） of a tungsten atom along [110] was 0.027 nm. The distortion energy was 80.6 meV·atom^-1 and the relaxations of the W（100） c（2×2） surface was calculated to be -7.6% for △d12/d0 and ＋0.8% for △d23/d0. The surface work function （Ф） was 4.55 eV. Calculated STM images of the W（100） c（2×2） surface displayed the following unusual features： protrusions in the STM image along the [110] axis are in the middle of a zig-zag chain of tungsten atoms while the dark regions in STM images correspond to valleys between neighboring zig-zag chains. These are due to surface reconstruction. Typical corrugations of a STM scan have been calculated to be between 0.008-0.013 nm for negative bias voltages while the corrugation varies from 0.019-0.024 nm for positive bias voltages.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2008年第12期2185-2190,共6页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(10204018)资助项目
