Síntese e caracterização de sulfetos de cobre e formação de heteroestruturas com dióxido de estanho
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Data
2021-05-25
Autores
Lima, João Victor Morais
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Universidade Estadual Paulista (Unesp)
Resumo
A deposição e caracterização de filmes finos de dióxido de estanho (SnO2) e sulfetos de cobre (Cu2-xS) foi um dos pontos centrais deste trabalho, além da formação da heteroestrutura Cu2S/SnO2, que constitui uma junção p-n de semicondutores. Filmes finos de SnO2 de estrutura tetragonal rutilo foram obtidos através da técnica sol-gel dip-coating. Os filmes apresentaram alta rugosidade superficial, devido a adição do surfactante Triton X-100. Este aumento de área superficial pode trazer melhoras para o material para aplicações em sensores de gás e fotocatálise. Efeito Poole-Frenkel foi evidenciado nas amostras de SnO2 a partir de medidas elétricas em diferentes temperaturas. Filmes finos de Cu2-xS foram obtidos através de evaporação resistiva de pós precursores sintetizados a partir de duas rotas químicas distintas e relativamente simples, cuja diferença básica é o precursor do cobre. Parâmetros de tempo e temperatura foram estudados para a obtenção de diferentes fases do sulfeto de cobre, a partir das quais foi possível obter pós não estequiométricos, além das composições CuS e Cu2S. Os filmes finos depositados apresentam boa aderência ao substrato, boa homogeneidade superficial e uma baixa resistividade elétrica (1 × 10-2 Ω.cm). A junção p-n constituída a partir da heteroestrutura Cu2S/SnO2, quando polarizada diretamente, apresentou condução elétrica somente para potenciais negativos, um resultado altamente reprodutivo, ainda que diferente do esperado. Um modelo foi proposto para a explicação deste comportamento, assumindo uma condução por portadores minoritários. Este transporte elétrico por portadores minoritários corrobora com os resultados obtidos nos experimentos de difração de raios X, que mostram a formação se filmes semicristalinos e com alta concentração de defeitos.
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.
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.
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Palavras-chave
Semicondutores, Sulfeto de Cobre, Dióxido de Estanho, Junção p-n, Semiconductors, Copper Sulfide, Tin oxide, p-n junction