Preparação e caracterização de nanofilmes de nb2o5 com tempos variáveis de deposição via plasma magnetron sputtering

Abstract

This thesis investigated the properties of niobium oxide (Nb2O5) thin films produced with variable deposition times using the plasma magnetron sputtering (PMS) technique. Brazil holds approximately 98% of the world's pyrochlore reserves, the primary niobium ore, establishing itself as the largest holder of this resource. Given this abundance, exploring new applications for its oxides has become increasingly relevant, particularly in areas such as electronic devices and thermal sensors. Niobium nanometallic films were deposited onto titanium metallic substrates obtained via plasma processing on glass slides. The Nb films were subsequently oxidized at 450 °C for 120 minutes under ambient atmosphere. The resulting Nb2O5 films exhibited a low- crystallinity monoclinic nature. Longer deposition times led to an increase in agglomerate sizes, consistent with Thornton’s morphological zone model. The film thickness reached a maximum of 100 nm for samples with longer niobium deposition times. The investigation of optical properties revealed high film transparency, with an average transmittance ranging from 60% to 95% in the 500–800 nm wavelength range. Contact angle measurements showed an increase with longer niobium deposition times. From an electrical perspective, the films exhibited typical n-type semiconductor behavior, with electrical resistivity decreasing exponentially with increasing temperature. The Ti5Nb0.5 and Ti5Nb1 films, with activation energy values of 0.12 eV, demonstrated properties consistent with negative temperature coefficient (NTC) materials. These films exhibited α coefficients of approximately 1.6 %/K and a β parameter close to 1392 K, making them suitable for thermal sensor applications at low temperatures and bolometers. Low-crystallinity Nb2O5 films obtained with relatively short deposition times demonstrated promising technological potential for the fabrication of advanced devices, such as efficient NTC-type thermal sensors, hydrophobic materials, and optically transparent components.