Antireflection TiO2 coatings on textured surface grown by HiPIMS

The aim of this work is to test the technology of the high impulse power magnetron sputtering (HiPIMS) for depositing TiO2 thin films on textured surfaces and to reveal anti-reflection properties of these films. Prior to deposition, the monocrystalline (100) silicon substrates were etched in KOH/IPA solution forming the surface texturization of the pyramidal structure. Thin films of different thicknesses were deposited by HiPIMS on silicon substrates using a titanium target in argon-oxygen atmosphere. In order to compare properties of different TiO2 structures, the additional textured samples were coated by conventional direct current (DC) method, as well. Anti-reflection coatings were characterized by spectrophotometry, ellipsometry, scanning electron microscopy, grazing incidence X-ray diffraction and transmission electron microscopy techniques. The HiPIMS deposited films were found to be characterized by the higher refractive index. These films appeared to be smooth, while uniformly covering the surface of the sample, including the space between pyramids. Moreover, the HiPIMS deposited films show the lowest reflectance in comparison to the DC deposited samples of the same thickness.