Annealing time induced roughening in ZnO thin films: A fractal and multifractal assessment. (February 2020)

• Record Type: Journal Article
• Authors: Ghosh, Koushik; Pandey, R.K.
• Is Part Of: Materials science in semiconductor processing. Volume 106(2020)
• Publication Date: 2020-02
• Subjects: ZnO thin film -- Sol-gel spin coating -- GIXRD -- Atomic force microscopy -- Fractal analysis -- Multifractal analysis; Semiconductors -- Periodicals; Integrated circuits -- Materials -- Periodicals; Semiconducteurs -- Périodiques; Circuits intégrés -- Matériaux -- Périodiques; Electronic journals; 621.38152
• DOI: 10.1016/j.mssp.2019.104771
• Languages: English
• ISSNs: 1369-8001

Abstract

Abstract: The residual surface micro-morphology and roughening of the sol-gel spin-coated ZnO thin films annealed at 500 °C for 1, 2, 3, and 4 h have been studied in the present work. The glancing incidence x-ray diffraction (GIXRD) patterns show that all the annealed films have a polycrystalline hexagonal wurtzite structure irrespective of the annealing times used in this work. The tensile stress developed, amorphization took place and accordingly the orientation of micro-crystallites changed with the increasing annealing time. The inadequacy of the conventional statistical parameters for surface quality assessment in the sense of both spatial and vertical complexity is insisted analysis of surface morphology with the help of fractal geometrical concepts. The monofractal assessment reveals the statistical self-similarity and long-range correlation properties of surface heights of the ZnO thin films annealed for different time spans. A persistent surface appears in the annealed films and persistency remains for all the annealing times used in this work. The highest persistency has been observed in 2 h annealed films. The fractal dimensions have been found to be inhomogeneous throughout the surface. Therefore, the multifractal technique is employed to understand the local scaling of the surface morphology. The least strength of multifractality and thereby, the lowest surface complexity have been observed in 2 h annealed films. The micro-morphological alterations with the annealing times are discussed in terms of the stress-induced surface instabilities, amorphization, and mass diffusion. Thus, the present work promotes a vigorous understanding of the residual surface micromorphology and roughening in commercially attractive solution-processed ZnO thin films using the monofractal and multifractal techniques. These methods could also be implemented to other solution-processed multifunctional materials to have a better understanding of their residual surface growth, roughening, and micro-morphology.