Construction of the apparatus for the local photoelectron spectroscopy

利用STM对金属薄膜进行了局部紫外（UV）光发射表征。测量了光电子电流沿和垂直于样品表面的变化，以及光电子电流的偏置依赖性。利用STM尖端除尖端尖端部分外涂有绝缘体的尖端检测局部光电子电流。光电子是由Ar离子（11.8 eV）的紫外光激发的。对Co和Ni金属薄膜进行了测量。对Co和Ni薄膜在紫外光照射下的光电子发射进行了测量。紫外辐射过程中的图像依赖于反馈电流，反馈电流包括隧道电流和光电子电流。观察到的光电子图像显示，在沿表面20 nm和沿表面法向15 nm的区域内发生了局部光电发射。我们还测量了电流作为尖端样品距离和STM偏置电压的函数。电流随针尖-样品距离近似成平方幂律变化，表明针尖处光电子电流的变化可以用STM针尖处检测区域的检测立体角随针尖-样品距离的变化而变化来解释。这一事实表明，光电子电流不是均匀分布的，而是从尖端-样品结附近的区域径向发射的。

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.