Oxygen Environmental Scanning Electron Microscopy On Oxide Materials

In order to reduce and compensate charge phenomena at the surface of non-conductive oxide materials under the electron irradiation, oxygen environmental scanning electron microscopy (SEM) is offered in this thesis. Introduce oxygen environment in general SEM (sample chamber in high vacuum of 2×10-3( 4×10-2 Pa), and directly observe and analyze materials (no conductive films), simultaneously, keep original electron optical and detecting system unchanged.In this work the devices of feeding and controlling oxygen are set up. Absorbable current is measured with a PA meter in order to estimate charge phenomena of non-conductive oxide materials (for example Al2O3,Cu/SiO2,YS-ZrO2 etc) and charge compensation in oxygen environmental SEM. Heating specimen and changing imaging parameter are performed to reduce charge phenomena. For Al2O3 and Cu/SiO2, a strong charge reduction is observed in oxygen environment of 10-3～10-2 Pa; Charge phenomena of YS-ZrO2 are reduced through heating to 230℃. The mechanisms of charge and charge compensation are discussed: We suggest electron stimulated desorption (ESD) at the surface and inner defects induced by the electron beam bombardment are main reasons of charge. The charge related to ESD can be compensated by oxygen environment, oxygen environment works mainly through making up oxygen vacancy and repairing energy band distortion in time. Heating the sample and reducing defect concentration can reduce the charge related to inner defects.Oxygen environmental scanning electron microscopy is a new and practical method for directly observing and analyzing non-conductive oxide materials.