Caracterização de efeitos fotoinduzidos em amostras vítreas e MoS2

Abstract

This work presents the study of morphological and electronic properties in vitreous samples and two-dimensional material under photoinduced effects. Techniques such as Raman spectroscopy, photoluminescence, and atomic force microscopy (AFM) were used to characterize the effects and alterations in the samples. AFM was employed to study the thermoplastic and thermoelastic expansion induced by laser radiation in arsenic trisulfide (As2S3) based chalcogenide glasses and erbium (Er3+) doped zinc tellurite glasses (80TeZn). In the As2S3, we investigated the geometry and dynamics of laser-induced permanent deformation on the surface. The results show a clear distinction between metastable and transient dynamics, with permanent photoexpansion being slower than transient, which exhibits a dynamic response similar to thermoelastic expansion. Comparison with theoretical results may point to a non-thermal origin of the permanent photoexpansion. In the zinc tellurite glasses, we studied the transient deformations through AFM, in real-time, and the influence of Er3+ ion concentration in the glass. The ability of this technique to detect nanoscale surface deformations and the good agreement between theoretical and experimental results demonstrate the potential of this technique for studying the amplitude and dynamics of thermal effects in solid materials. In another study, we measured the effects of laser-induced excitation on the monolayer and bilayer of molybdenum disulfide (MoS2) through Raman spectroscopy and its photoluminescent properties. Exposing MoS2 to laser intensity over a period of time, we observed changes in the Raman spectra, suggesting photocarrier effects, that is, charge generation without the application of an electric field. These alterations reflect changes in the optoelectronic characteristics of the material, resulting in an increase in photoluminescence and the intensity of trion peaks. Adjusting the properties of MoS2 by subjecting it to structural manipulation constitutes an important strategy to enhance its performance and, consequently, promote its direct application in the electronics industry.