Development of Field Emission Type Ultra-High Vacuum Gauge

场发射是指在- 0.5V/A的高电场作用下，电子穿隧穿过势垒。限制在表面的电子隧穿速率随气体原子和分子的吸附而敏感地变化。在本研究中，采用场发射显微镜（FIM）尖端的半球形顶点和施加高负电压来实现场发射所需的高场。通过观察场发射电流随时间的衰减率来测量真空度。本研究的目的是：(1)改进现有的真空系统，使其达到10^<-11> ~ 10^<-13>托尔的真空度；(2)阐明发射电流降低率与真空度的关系；(3)检验各种金属作为尖端材料；(4)评价多个尖端的优势；(5)开发一种新的高效可靠的发射电流测量系统。以上各项结果如下：(1)真空比10 ^ < -11 >托可能由于无法获得足够的表面整修表面真空室,(2)发现减少的速度发射电流正比于真空相当好,(3)研究表明,W的小费比真空测量的红外提示更敏感,因为W表面比红外表面更加活跃,(4)没有检查多个提示,因为必须先于研究项目(5),(5)为了高效、精确地测量发射电流，研制了二维成像法拉第笼。由于成像笼的屏幕投射了从多个尖端的每个顶点发出的电流的图像，它允许我们一眼就能直接检查所有的尖端。

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.