Development of Field Emission Type Ultra-High Vacuum Gauge

点击翻译按钮获取中文摘要

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.