Crescimento de materiais semicondutores cristalinos de iodeto de mercúrio para aplicações como detectores de radiação

Abstract

Semiconductor materials have several applications in the construction of electronic devices, such as diodes, transistors, capacitors and photoconductors. Several of these devices are currently used in medical and biological applications. Among these interdisciplinary applications, the potential use in the construction of ionizing radiation detectors is emphasized, whether in dosimetry or radiodiagnosis. The HgI2 (Mercuric Iodide) is an inorganic halide material, semiconductor and photoconductor, which presents high efficiency in the absorption of photons of high energy and collection of carriers of electric charges. It is listed as a good candidate in the construction of radiation detecting devices by the direct detection method at room temperature. However, the different methods of obtaining these materials, as well as the variation of the synthesis parameters can influence or modify the structural, optical and electrical properties of these materials. Thus, in this work an alternative assembly of the Spray technique will be analyzed and crystalline HgI2 semiconductor materials will be grown, directed to the use as radiation sensor, accompanied by the study of the structural and electrical properties of this material, as a function of the variation of the synthesis parameters. For this purpose, the material was grown in the form of films by method CVD (Chemical vapor deposition) and Spray technique using N, N-Dimethylformamide as a solvent of the HgI2 powder. The influence of the concentration of HgI2 solution (from 100 g / l to 250 g / l) and the deposition temperature (from 60ºC to 100ºC) on the final properties of the films was investigated. The technique demands low cost of equipment and may eventually become viable solution for the construction of such devices on a large scale. The structural characterizations were performed by Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Energy Dispersion Spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). The electrical characterizations were performed in the devices produced from the deposited films, by the measurement of electric transport as a function of the electric field. From the obtained results studies, the best conditions of production of these materials were found, directed to the use as radiation detectors. Briefly, the present work presents original results, constituting a new combination of materials and techniques, ranging from the synthesis and deposition of films, including the assembly of the deposition system used, to results of structural and electrical characterization of the films.