局域功函数图像及其在Cu(111)-Au/Pd表面的应用

Local work function measurement on Cu(111)-Au and Cu(111)-Pd surfaces

用扫描隧道显微镜 (STM)对Cu(111) Au和Cu(111) Pd表面的局域功函数进行了研究 .通过测量隧道电流对针尖样品间距的响应 ,得到了与STM形貌图一一对应的表面局域功函数图像 .实验发现 ,Au Pd覆盖层和Cu衬底间的功函数有明显的不同 .Pd薄膜的功函数甚至超过了其体本征值 ,且功函数在台阶处变小 .用偶极子的形成解释了台阶处功函数的降低 .这一工作表明 ,用测量局域功函数的方法容易区分表面上不同的元素 ,并具有纳米尺度的空间分辨率 .

In this paper, we report the local work function measurements on the Cu(111)-An, and Cu(111)-Pd surfaces with scanning tunneling microscopy (STM). We successfully observed the local work function difference between the Au/Pd overlayer and the Cu substrate, the decreased work function at the step edges. We also found that the work function of the I'd film is larger than that of the bulk Pd (111). The lower work function at step edges can be explained by the dipole moment formation. It is demonstrated that the local work function measurement by STM is a powerful way to identify different elements with nanometer resolution.