Why UHV for Surface Analysis? 压强 Remove adsorbed gases 真空度 Torr from the sample. 102 Eliminate adsorption of Low Vacuum contaminants on the sample. 101 ■ Prevent arcing and high Medium Vacuum 104 voltage breakdown. High Vacuum Increase the mean free path 108 for electrons,ions and Ultra-High Vacuum photons. 1011 中国斜学我术大学 University of Science and Technology of China Why UHV for Surface Analysis?  Remove adsorbed gases from the sample.  Eliminate adsorption of contaminants on the sample.  Prevent arcing and high voltage breakdown.  Increase the mean free path for electrons, ions and photons. 真空度 10 10 10 10 10 2 -1 -4 -8 -11 Low Vacuum Medium Vacuum High Vacuum Ultra-High Vacuum 压强 Torr