Mechanical Properties of Metal Oxide Films

Abstract

A brief review is given of mechanical property measurements on oxide films. This review is followed by a detailed discussion of the mechanical and fracture properties of anodic aluminum oxide films as observed in the author's laboratory. Extensive measurement of Young's modulus, E c ,and fracture strain, ε f , for separated films 3000Aå thick is reported as a function of environmental water vapor pressure. The fracture of these unsupported films is shown to occur by a brittle mechanism. Mechanical properties of adhering aluminum oxide films are given as a function of their thickness. These oxides were observed to fracture either at slip steps, or at right angles to the tensile axis in a regularly spaced fashion. A theory of adhering oxide fracture is discussed which accounts well for the observations. An equation which describes the spacing d of regular oxide fracture cracks as a function of substrate strain ε is given in the form ln ( ε / ε 0 ) = k √ t ( 1 / d − l / d 0 ) , where ( ε o , d o ) are the initial conditions for regular fracture, t is the oxide thickness, and k is a constant.