Thin Films Deposited by Spin Coating Technique: Review

Abstract

Nanostructure thin films have been prepared and deposited onto various substrates such as glass substrate, quartz, GaN (0001) substrate, indium tin oxide coated glass, soda-lime glass, microscope glass slide via spin coating technique. This deposition method has many advantages, such as being cheap, simple, suitable for the low-temperature deposition process. Literature review revealed that the deposition process was carried out at different conditions produced unique properties of films. Structural, morphological, and optical properties were studied by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and UV-Visible spectrophotometer. It was found that the average grain size of the obtained films was in the nanometer scale. The research findings confirmed that these materials could be used for photovoltaic applications. Keywords: spin coating technique, substrate, thin films, photovoltaic applications 1. INTRODUCTION The thin film's development for energy conversion and optoelectronic materials, among other applications, is of great interest [1,2]. Because of the low cost, non-toxic starting materials indicate excellent electrical, photovoltaic, photo catalytically and optical properties [3-6]. Nowadays, there is an extended interest in researching different synthesis methodologies for metal chalcogenide thin films, such as metal selenide, metal sulfide, and metal telluride thin films. Several synthesis methodologies for these materials have been reported including spray pyrolysis [7,8], electrodeposition [9,10], thermal evaporation [11,1 2], chemical bath deposition [13,14], successive ionic layer adsorption and reaction [15,16], atomic layer deposition [17], molecular beam epitaxy [18], pulsed laser deposition [19], and sol-gel method [20]. Researchers conclude that each methodology has advantages and disadvantages [21-24]. Among the main disadvantages are high cost, toxicity, elevated synthesis temperatures, a considerable number of by-products, annealing requirements at high temperatures after synthesis that limit the use of flexible substrates, and films heterogeneity. Several instruments including atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), scanning tunneling microscopy [25,26], Raman spectrometry, real-time reflection high energy electron diffraction [27,28], UV-Visible spectrophotometer (UV-Visible) are used to investigate general properties of films. This work presented a review of the preparation of thin films using a spin coating technique. This method was chosen for simplicity, low cost, low by-product formation, low temperature, and no-annealing requirements. Structural, electrical, optical, and morphological properties of the prepared thin films were discussed. The deposition technique could be divided into chemical deposition technique and physical deposition method. Generally, a higher operational cost is needed to synthesize thin films using the physical method (Figure 1). Thin films have been prepared by using various deposition methods, as highlighted by many researchers. Metal selenide, metal sulphide, and metal telluride thin films were reported as listed in Table (1-3). Characterization of obtained films was carried out by using various tools.