Filmes finos de AZO/ PET depositados por magnetron sputtering: comparação entre RF e fonte pulsada
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Data
2019-08-01
Autores
Oliveira, Lucas Pires Gomes de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Atualmente, tem-se pesquisado óxidos alternativos ao ITO (óxido de índio dopado com estanho) e um potencial candidato é o óxido de zinco dopado com alumínio (AZO), pois é atóxico e deriva de fontes de materiais com baixo custo de produção. Nesse trabalho, filmes finos de AZO (~200 nm de espessura) foram depositados em polietileno tereftalato (PET) à temperatura próxima a ambiente, pela técnica de magnetron sputtering. O plasma foi ativado usando uma fonte de radiofrequência (RF) de 13,56 MHz e uma fonte pulsada de 15 kHz (PMS, do inglês, pulsed magnetron sputtering). As propriedades ópticas dos filmes foram analisadas por meio de um espectrômetro UV-Vis-NIR (190 nm a 2500 nm). Todos os filmes apontaram transmitância média superior a 80% na região visível. A resistividade elétrica dos filmes foi determinada pelo método linear de quatro pontos, alcançando valores em torno de 0,001 Ω.cm para filmes AZO de 200 nm de espessura depositados por PMS. A difratometria de raios-X (DRX) comprovou a cristalinidade dos filmes, apresentando orientação preferencial no plano (002) como o ZnO. A espectroscopia de raios-X de energia dispersiva (EDS) foi utilizada para análise da composição química dos filmes, além da composição das trincas em alguns filmes. A morfologia superficial dos filmes finos de AZO foi caracterizada por microscopia eletrônica de varredura (MEV), sendo avaliada a formação de trincas e imperfeições. Nenhuma trinca foi observada nos filmes crescidos por PMS, além de apresentarem baixos valores de resistividade elétrica, mostrando adequação para serem aplicados em células fotovoltaicas flexíveis.
Nowadays, as an alternative for ITO films, many research groups point out that Al-doped ZnO film (AZO) is a suitable substitute, considering that it is non-toxic and derived from low cost and easily available materials. In the present work, AZO thin films (about 200 nm) were deposited on polyethylene terephthalate (PET) substrate, at room temperature. For the plasma activation, a radiofrequency (RF) of 13.56 MHz and a middle frequency pulsed ac magnetron sputtering (PMS) of 15 kHz were used as the power source. Optical properties were analyzed by UV-Vis-NIR spectroscopy in a wavelength (190 to 2,500 nm). All films presented transmittance values higher than 80% at the visible region. Electrical resistivity was obtained by a four-point probe method. For AZO film produced by PMS, the resistivity was about 0.001 Ω.cm. Morphology of AZO thin films were characterized by scanning electron microscopy (SEM), being analyzed the cracks and imperfections in some films. X-rays diffractometry (XRD), proved the crystallinity of the films, having preferred orientation in the plane (002) as the ZnO. X-rays-energy dispersive spectroscopy (EDS), to analyze the chemical composition of the films, besides the composition of the cracks in some films. No micro-cracks were observed in the thin films deposited by PMS, besides presenting low values of resistivity, showing to be a potential film used in confection in flexible photovoltaic cells
Nowadays, as an alternative for ITO films, many research groups point out that Al-doped ZnO film (AZO) is a suitable substitute, considering that it is non-toxic and derived from low cost and easily available materials. In the present work, AZO thin films (about 200 nm) were deposited on polyethylene terephthalate (PET) substrate, at room temperature. For the plasma activation, a radiofrequency (RF) of 13.56 MHz and a middle frequency pulsed ac magnetron sputtering (PMS) of 15 kHz were used as the power source. Optical properties were analyzed by UV-Vis-NIR spectroscopy in a wavelength (190 to 2,500 nm). All films presented transmittance values higher than 80% at the visible region. Electrical resistivity was obtained by a four-point probe method. For AZO film produced by PMS, the resistivity was about 0.001 Ω.cm. Morphology of AZO thin films were characterized by scanning electron microscopy (SEM), being analyzed the cracks and imperfections in some films. X-rays diffractometry (XRD), proved the crystallinity of the films, having preferred orientation in the plane (002) as the ZnO. X-rays-energy dispersive spectroscopy (EDS), to analyze the chemical composition of the films, besides the composition of the cracks in some films. No micro-cracks were observed in the thin films deposited by PMS, besides presenting low values of resistivity, showing to be a potential film used in confection in flexible photovoltaic cells
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Palavras-chave
AZO, PET, , PMS, Caracterização, Magnetron sputtering