Construction of the apparatus for the local photoelectron spectroscopy

利用扫描隧道显微镜（STM）观察到了金属薄膜的局域紫外光电子谱。测量了光电子电流沿着和垂直于样品表面的变化以及光电子电流的偏压依赖性。利用STM针尖探测局域光电子流，针尖除针尖顶端外涂有绝缘层。光电子由Ar离子（11.8eV）的紫外光激发。对Co和Ni金属膜进行了测量。对Co和Ni薄膜在紫外光照射下的光电子发射进行了测量。在紫外光照射过程中的图像依赖于反馈电流，其中包括隧道电流和光电子电流。观察到的光电子图像示出了在沿表面沿着20 nm和沿表面法线沿着15 nm的区域内发生局部光电发射。我们还测量了电流的函数的尖端样品的距离和STM偏置电压。电流随针尖-样品距离的平方幂律变化，表明针尖处光电子电流的变化可以用针尖处探测区的探测立体角随针尖-样品距离的变化来解释。这一事实表明，光电子电流是不均匀分布的，但光电子发射的辐射附近的尖端样品结的区域。

The local ultraviolet (UV) photoemission has been observed by using STM for the local characterization of the metal films. The change in the photoelectron current along and normal to the sample surface has been measured as well as the bias dependence of photoelectron current. The local photoelectron current is detected by STM tip which is coated with insulator except for the area of tip apex. The photoelectrons are excited by UV light of Ar ion (11.8 eV). The measurements are made for Co and Ni metal films. The measurement of photoelectron emission has been made for the Co and Ni films during irradiation of UV light. The images during UV irradiation are dependent on the feedback current which includes tunneling current and photoelectron current. The observed photoelectron image shows the occurrence of local photoemission within the region of 20 nm along the surface and 15 nm along the normal to the surface. We have also measured the current as functions of the tip-sample distance and STM bias voltage. The current changes approximately as the squared power laws with the tip-sample distance, indicating that the change in the photoelectron current at tip can be explained in terms of the change in the detection solid angle of detection area at STM tip with lithe change in the tip-sample distance. This fact suggests that the photoelectron current is not uniformly distributed, but photoelectrons emit radially from the area near the tip-sample junction.