We present the theory and experimental results for the inductive contactless measurement of the product of thickness and conductivity for cylindrical metallic thin film samples. The method is based on the detection of the change in the frequency of a sinusoidal oscillator, with an L-C tank circuit, when the samples are introduced into the coil of the tank. We derive the equivalent circuit for the cylindrical samples: a parallel combination of an inductance, a resistance and a capacitance. We obtain expressions for the change in the oscillator frequency in terms of these parameters, and we express them in terms of the physical characteristics of the samples (thickness, radius and conductivity). We present experimental results for silver films, evaporated in high vacuum, with thickness D in the range 0.1-2 μm. The inductive measurements are correlated with direct thickness measurements obtained by optical interferometry and by using a Sloan ångstrometer. The product of thickness and conductivity was also obtained from four-terminal d.c. measurements. All measurements were carried out inside the evaporation chamber under high vacuum.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry