APLICAÇÃO DE MOLÉCULAS AUTO-ORGANIZÁVEIS (SAM) EM FILMES FINOS DE SnO2

Abstract

Thin films of tin dioxide (SnO2) with the addition of doping are widely used because its various applications, so develop a search on this subject is of great value technology, since many different forms of doping, formulation and preparation, can be made and modified, intended to improve this material according to their physical and chemical properties. This paper used for niobium oxide (Nb2O5) as doping, an important factor in the formulation, since Brazil has the largest reserves of natural element, found in various forms of ore. The preparation of thin films is a process that requires great care and high quality control. However, care is not sufficient to avoid the appearance of defects in his deposition, and subsequent calcination, as broken, deterioration, poor adhesion to the substrate, which are considered problems, undermining the efficiency of the material and its applicability. The addition of self assembled monolayers (SAM) on thin films of SnO2 aimed to reduce or correct this type of defect. Different techniques were used experimentally, as: X-ray diffraction, fotochronoamperometric, eletrochemical impedance spectroscopy, electrochemistry, measures of potential open circuit, optical microscopy optical, scanning electron microscopy and Infrared. The results of the measures to density of current and electrochemical impedance of samples of thin films of SnO2 containing SAM showed positive results, confirming that the SAM not only improved the structure of films about the electrochemical properties and photovoltaic, but also corrected the defects caused existing surface the techniques for the generation thin film. The efficiency of photosensitive films studied increased in the following sequence: SnO2 + SAM < SnO2:Nb2O5(0.1) + SAM SnO2:Nb2O5(0.3) + SAM. The electrochemical impedance spectroscopy, showed that the addition of SAM to thin films studied in this work is diminishing Rtc, minimizing the resistance. The film of SnO2 containing 0.3 Nb2O5 + SAM presents a resistance around 1000 Wcm-1 less than the film containing 0.1 Nb2O5. The thin films containing SAM showed that when immersed in the electrolyte solution, extending the capacitance of double layer electrical probably due to accumulation of cargo between the surface of films. The scanning electron microscopy showed that the nucleation of SAM has a higher incidence of disruptions in the regions (of higher energy) in the form of needles and often mixed, needles and mushrooms, as observed for the film: SnO2: Nb2O5 (0.3 ) + SAM.