Structural and optical properties of Al-doped ZnO thin films produced by magnetron sputtering

• Published in: Processing and Application of Ceramics Vol. 14; no. 2; pp. 119 - 127
• Main Authors: José César Augusto de Queiroz, João Batista de Azevedo Filho, José Quinzinho de Medeiros Neto, Igor Oliveira Nascimento, Ivan Alves de Souza, Maria Gerlania de Oliveira Queiroz, Emanuel Benedito de Melo, José Daniel Diniz Melo, Thercio Henrique de Carvalho Costa
• Format: Journal Article
• Language: English
• Published: University of Novi Sad 01-01-2020
• Subjects: ab initio calculation; azo thin films; energy band diagram; magnetron sputtering
• ISSN: 1820-6131; 2406-1034
• DOI: 10.2298/PAC2002119Q

Experimental and theoretical investigations of the structure and optical properties of Al-doped ZnO (AZO) thin films produced by magnetron sputtering under different values of electric current were conducted. The XRD results confirm the formation of the AZO thin films with hexagonal wurtzite structure, with preferential orientation along the crystallographic plane (002), direction c. The increment of electric current allowed an increase in average crystallite size. The FE-SEM and AFM images analyses of the AZO films revealed the occurrence of nucleation on the substrate surface that formed films with granular and rough structure. The higher substrate temperature caused by the higher value of electric current had influence on the grain size and thickness (ranging from 974 to 1500 nm) of the formed thin films. Due to the high absorption of free carriers, the optical transmittance of the AZO films was acceptable for the visible spectrum and limited to the near infrared region. The energy band gap values for both AZO films, measured from the optical transmission spectra, were ideal for semiconductor applications. The ab initio calculations using DFT and the method LSDA + U along with the correction of Hubbard were successfully applied to investigate the structural and optical effects. The band structures of the pure ZnO and ZnO:Al, calculated in this work, presented Eg values close to the experimental results. Therefore, these results imply that our methods are reliable and that the calculations are in accordance with the experimental results.