Silicon Thin Film Powder Samples for Electron Spin Resonance Investigation: Role of Substrate and Preparation Procedure

Different methods to prepare powder samples of amorphous and microcrystalline thin film silicon material deposited on glass and metal substrates for application in electron spin resonance (ESR) experiments are compared. The powder is needed to provide sufficient sample mass for ESR experiments which otherwise suffer from low signal-to-noise ratio for thin film silicon material deposited on glass with thickness of typically 1 µm and spin densities of less than 10 16 cm -3 , all in view of the geometrical constraints of ESR cavities. As temporary substrates, Al and Mo foils and glass covered with ZnO are used and we compare the influences of the different substrates, the removal procedure and the exposure time to the etchant or ambient on the ESR properties of the silicon films. We describe reliable sample preparation and annealing procedures under which all three temporary substrates yield very similar ESR properties for the different silicon materials.