The Friction Behavior and Surface Topography of YBa_2Cu_3O_7 Film in Ambient Environment

YBa 2Cu 3O 7 film and polysilicon film were prepared over the oxide layer of about 100 nm thick on Si substrate. The friction behavior of the films sliding against a sapphire ball or a steel ball in ambient environment was investigated with a ball on flat tribometer. The surface topography of the original film surfaces and worn film surfaces was examined by means of atomic force microscopy (AFM). As the results, the friction coefficient of YBa 2Cu 3O 7 film is lower than that of polysilicon film when sliding against a sapphire ball. It is almost the same for the two films when sliding against a steel ball. The initial friction of YBa 2Cu 3O 7 film in sliding against both sapphire ball and steel ball is much stable. However, the initial friction of polysilicon film in sliding against a sapphire ball fluctuates greatly during a cycle period. AFM observation of the original film surfaces and worn film surfaces indicates that super conducting protrusions exist on the original YBa 2Cu 3O 7 film surface. The protrusions are liable to remove during the friction process, thus the worn surface of YBa 2Cu 3O 7 film becomes much smooth.