W(100)c(2 2)表面的STM图像

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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. The surface relaxation of the W (100) c (2 × 2) reconstructed surface and the relationship between the scanning tunneling microscope (STM) image and the substrate bias were studied by using the first-principles-based density functional theory. The calculated The distorted displacement δ of the surface atoms along the [110] direction is 0.027 nm, the distortion energy ΔE is 80.6 meV · atom-1, and the surface atomic relaxation is -7.6% (Δd12 / d0) and + 0.8% (Δd23 / d0), and the work function Φ is 4.55eV.STM image simulations show that bright-dark bands appear parallel to the [110] direction due to the displacement of the surface atoms along the [110] direction But not the surface or subsurface tungsten atoms, but the zig-zag W atom chain center line position; and STM dark zone corresponding to the atomic position distortion of the adjacent zig-zag W atom chain intermediate region when the substrate negative bias The typical tip height of the STM tip is about 0.008-0.013 nm when pressed, while the tip height varies between 0.019-0.024 nm when the substrate is positively biased.
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