Metallic to semiconducting transition and hydrophobicity properties of indium films

Abstract

Indium films of thicknesses: 38–450 nm were deposited by thermal evaporation on Si substrates by varying the angle of deposition from 0° to 75° and their structural, surface morphology, electrical and wettability properties were characterized. XRD studies confirm the tetragonal structure of all In samples. Films of thickness >100 nm exhibit metallic electrical properties whereas films of lower thicknesses (<100 nm) are semiconducting. XPS studies revealed similar electronic structure of low and high thickness films and that the surface oxidation is found to be greater in high thickness samples. The differences in the electrical transport properties are not due to surface oxidation but due to low dimensionality effects. The water contact angle (WCA) studies showed that In films are strongly hydrophobic and hydrophobicity enhances with an increase in thickness and with the angle of deposition; the enhancement in WCA correlates with an increase in surface roughness. The maximum WCA values of 125° and 131° are found in samples with maximum thickness (450 nm) and film prepared at highest angle of deposition (75°) respectively. It is concluded that the electrical and hydrophobic properties of In films can be significantly tailored by variation in their thickness and angle of deposition.