Investigation of upward speed and thickness effects on optical and mechanical properties of hard transparent thin films deposited on polycarbonate substrate

Abstract

In the present work, nanomechanical behaviors and optical properties of the nanohybrid thin films coated on the polycarbonate (PC) substrates were investigated. Tetraethyl orthosilicate (TEOS), 3-glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri sec-butoxide were used as main precursors through very simple and repeatable sol-gel process. Optical, chemical, structural, morphological and mechanical characteristics of the samples were studied by ellipsometry, UV/vis spectroscopy, ATR-FTIR, EDS, XRD, FE-SEM, TEM and nanoindentation-nanoscratch methods. It was found that upward speed had an important effect on the nanomechanical properties while optical properties remained constant. The obtained results indicated that the refractive index of the prepared thin films were significantly lower (1.483) than PC substrate (1.58) led to increase the transmittance that was measured 89 % compared to pristine PC (86 %). Nanohybrid thin films increased PC hardness and elastic modulus to 0.45 and 7.4 GPa respectively at upward speed 5 mm/s. The friction coefficient was decreased to 0.23 and the pencil hardness was 5H at 1887 nm thickness coating at 9 mm/s upward speed.