Development of Field Emission Type Ultra-High Vacuum Gauge

场发射型超高真空计的研制

基本信息

批准号：
02555009
负责人：
NISHIKAWA Osamu
金额：
$ 6.85万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02555009/
关键词：
Tip Apex Field Emission Field Emission Microsocpe (FEM)Surface Ultra-High Vacuum Imaging Faraday Cage Vacuum Gauge

项目摘要

Field emission is the electron tunneling through the potential barrier lowered by the high electric field - 0.5V/A. The tunneling rate for the electrons confined in the surface varies sensitively with the adsorption of gas atoms and molecules. In this study the high field required for the field emission was realized by employing a hemispherical apex of a sharp tip of a field emission microscope (FIM) and by applying a high negative voltage. The vacuum was measured by observing the reduction rate of field emission current with time.The study aimed the following items : (1) Improvement of the existing vacuum system up to the vacuum of 10^<-11> - 10^<-13> Torr, (2) Clarification of the relation between the reduction rate of emission current and vacuum, (3) Examination of various metals as tip materials, (4) Evaluation of the advantageous point of multiple tips, (5) Development of a new highly efficient and reliable system to measure emission currents.The results of above items are as follows : (1) The vacuum better than 10^<-11> Torr could not be obtained possibly due to the insufficient surface refinish of the vacuum chamber, (2) It was found that the reduction rate of emission current is fairly well proportional to vacuum, (3) The study indicates that a W tip is more sensitive than an Ir tip for vacuum measurement because the W surface is more active than the Ir surface, (4) No multiple tip was examined because the study of item (5) must be preceded, (5) In order to measure the emission current efficiently and precisely, a 2-dimensional imaging Faraday cage was developed. Since the screen of the imaging cage projects the image of the currents emitted from every apex of the multiple tip, it allows us to examine all the tips directly at a single glance.

场发射是电子隧道穿过高电场（0.5V/A）降低的势垒。限制在表面的电子的隧道速率随着气体原子和分子的吸附而敏感地变化。在这项研究中，场发射所需的高场是通过使用场发射显微镜（FIM）尖头的半球形顶点并施加高负电压来实现的。通过观察场发射电流随时间的减少率来测量真空度。研究目的如下： (1) 改进现有真空系统，达到真空度 10^<-11> - 10^<-13> Torr，（2）阐明发射电流的降低率与真空之间的关系，（3）作为尖端材料的各种金属的研究，（4）评估多个尖端的优点，（5）开发新的高度高效可靠的系统测量发射电流。以上项目的结果如下：（1）可能由于真空室表面整修不充分而无法获得优于10^<-11> Torr的真空，（2）发现发射电流的降低率与真空度成正比，(3) 研究表明，对于真空测量，W 尖端比 Ir 尖端更灵敏，因为 W 表面比 Ir 表面更活跃，(4) 无倍数提示被检查，因为项目的研究(5)必须先行，(5)为了高效、精确地测量发射电流，开发了二维成像法拉第笼。由于成像笼的屏幕投射从多个尖端的每个顶点发出的电流图像，因此我们可以一眼直接检查所有尖端。