Linear Coefficient of Thermal Expansion of Porous Anodic Alumina Thin Films from Atomic Force Microscopy

In this article, a precise and convenient technique based on the atomic force microscope (AFM) is developed to measure the linear coefficient of thermal expansion of a porous anodic alumina thin film. A stage was used to heat the sample from room temperature up to 450 K. Thermal effects on AFM probes and different operation modes at elevated temperatures were also studied, and a silicon AFM probe in the tapping mode was chosen for the subsequent measurements due to its temperature insensitivity. The topography of the porous anodic alumina sample was obtained, and the pore sizes and the surface roughness were analyzed. The thermal expansion of the sample was measured within the temperature range of 293 to 443 K. The results show that the linear coefficient of thermal expansion of the porous anodic alumina thin film is approximately two times larger than that of bulk alumina.