Preparação e caracterização de filmes finos de MOS2 para termoeletricidade

Abstract

The objective of this work is to present the results of the synthesis and characterization of two-dimensional molybdenum disulfide (MoS2) layers, obtained through the Physical Vapor Deposition (PVD) technique on silicon dioxide (SiO2) substrates, aiming to evaluate their potential in thermoelectric applications. MoS2 is a two-dimensional material with promising electronic and thermal properties, making it a strong candidate for use in energy conversion devices. Three distinct experimental approaches were adopted to assess the effects of different synthesis conditions on the quality of the obtained material. In the first experiment, thin MoS2 layers were synthesized from commercial MoS2 powder under a sulfur-rich S2 atmosphere using a PVD furnace. In the second, an H2O atmosphere was added along with S2 to evaluate the effects of this modification on the layer growth. In the third, silver doping was performed in a tubular furnace to investigate its effects on the structural and vibrational properties of the material. The samples were characterized by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), used to evaluate the morphology and distribution of the formed layers. X-ray Diffraction (XRD) was applied for qualitative identification of the crystalline structure, while Raman Spectroscopy was employed for a detailed analysis of the vibrational properties of MoS2, with emphasis on the 𝐸1 2𝑔 and 𝐴1𝑔 modes. The results showed that the presence of H2O during deposition favored the formation of films with lower structural disorder and higher crystallinity, as evidenced by the enhancement of characteristic peaks in the XRD and Raman analyses. Silver doping also influenced the vibrational properties, suggesting changes in the material’s electronic structure. These findings contribute to the application of MoS2 in electronic and thermoelectric devices, demonstrating that controlled modifications in the synthesis conditions can significantly improve its structural quality and functionality.