Preparação e caracterização elétrica de filmes amorfos de dióxido de titânio

Abstract

Titanium dioxide is a stable, polymorphic semiconductor material that can appear in three known crystalline phases, anatase, rutile and bruquita. Temperature is a factor that affects the crystallization of phases. At low processing temperatures, titanium dioxide may present in an amorphous phase, which has no long-range order. This amorphous phase, however, is not widely studied, but may its properties may be of interest to industries. With the objective of developing functional surfaces of amorphous titanium dioxide, such as self-cleaning surfaces, for use in solar cells, for thermal detection, in photocatalysts for organic removal, among others, was investigating, in this work, the characteristics of thin films deposited by pulsed plasma magnetron sputtering. Three different deposition procedures were used. There was the formation of amorphous thin films with only a short-range order. Only two films obtained presented hydrophilic characteristics, and their contact angles ranged from 33.2 to 37.7 °. Films with the hydrophobic characteristics of contact angles ranging from 49.5 to 84.1 °. Concernig to the optical properties, the films presented reduction of transmittance and reduction of the optical band gap with the increase of deposition time. The films formed had uniformly distributed grains, and grain size and roughness increased with longer deposition times. It was also observed that the resistivity of the films reduced with increasing temperature, characterizing the films as NTC thermistors. Characteristic parameters of the thermistors were calculated, obtaining values of α between 0.54 to 0.98 % to the resistivity by Kelvin, and values of β between 480 and 874 K.