Investigation of electrical contacts on a nanometer scale using a Nano-manipulator in Scanning Electron Microscope

The indentation using tin oxide film which was deposited on tin substrate was executed by a tungsten probe whose curvature was about 5 micro meter in radius with a nano-manipulator in Scanning Electron Microscope. We measured contact resistance and the load force simultaneously, found cracks of tin oxide layer and tin penetration into the cracks and investigated in detail the correlation between indented surface morphology and electrical resistance characteristics with respect to load force by changing indentation depth. In case of 100 nm oxide film, abrupt electrical resistance decrease was observed by applying load force about 1.0×10^-3N. The increase of tin penetration area on indented surface correlated with the abrupt electrical resistance decrease. This directly indicated that tin penetration into the cracks and tin appearances on the oxide surface were crucial phenomena for reliable electrical contact. Nano-manipulator used in this study was a powerful instrument for basic research of electrical contacts and realization of the miniaturized and lower load force connector.