Synthesis and characterization of copper sulfides and formation of heterostructures with tin dioxide

Author(s)

João Victor Morais Lima

• Document type: Master's Dissertation
• Press: Bauru. 2021-06-06.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências. Bauru
• Defense date: 2021-05-25
• Advisor: Luis Vicente de Andrade Scalvi

Abstract

Deposition and characterization of thin films of tin dioxide (SnO2) and copper sulfides (Cu2-xS) was one of the main points of this work, along with the formation of the Cu2S/SnO2 heterostructure, which constitutes a p-n junction of semiconductors. Thin films of SnO2 with a tetragonal rutile structure were obtained using the sol-gel dip-coating technique. The films showed high surface roughness, due to the addition of the surfactant Triton X-100. This increase in surface area can bring improvements to the material for applications in gas sensors and photocatalysis. The Poole-Frenkel effect was evidenced in the samples of SnO2 from electrical measurements at different temperatures. Thin films of Cu2-xS were obtained through resistive evaporation of precursor powders synthesized from two distinct and relatively simple chemical routes, whose basic difference is the copper precursor. Time and temperature parameters were studied to obtain different phases of copper sulfide, from which it was possible to obtain non-stoichiometric powders, in addition to the CuS and Cu2S compositions. The thin films deposited have good adhesion to the substrate, good surface homogeneity and low electrical resistivity (1 × 10-2 Ω.cm). The p-n junction formed from the Cu2S/SnO2 heterostructure, under forward bias, presented electrical conduction only for negative potentials, a highly reproductive result, although different from the expected. A model has been proposed to explain this behavior, assuming that it is conducted by minority carriers. This electrical transport by minority carries corroborates with the results obtained in the X-ray diffraction experiments, which show the formation of semicrystalline films and with a high defects concentration. (AU)

• FAPESP's process: 18/26039-4 - Investigation of the semiconductor oxide SnO2, in the form of thin films, and combination with Cu2-xS forming multilayered heterostructures
• Grantee: João Victor Morais Lima
• Support Opportunities: Scholarships in Brazil - Master