Effects of thickness on the wettability and electrical properties of Sn thin films

Abstract

Sn films of four thicknesses, 50, 200, 500, and 1000 nm, were deposited on Si (111) substrates by a thermal evaporation technique, and the effects of thickness on the structural, surface morphology, electrical, and wettability properties were investigated. X-ray diffraction studies revealed the coexistence of predominantly β-Sn (metallic phase) and small concentration of α-Sn (semiconducting phase) in all samples except the 1000 nm thickness sample which is entirely β-Sn. The crystallite size and surface roughness enhance with thickness, and the 1000 nm film shows secondary nucleation growth which lowers the average crystallite size and the surface roughness of the sample. The 50 nm film shows semiconducting electrical properties while all other samples are metallic. The wettability studies found that Sn films are hydrophobic with a maximum water contact angle of 128° for the 1000 nm sample. It is concluded that the thickness critically determines the phase formation, surface topography, electrical properties, and hydrophobic properties of Sn films.