Effect of crystalline structure on optical and electrical properties of IWOH films fabricated by low-damage reactive plasma deposition at room temperature

Abstract

Tungsten and water co-doped indium oxide (IWOH) films were deposited via a low-damage reactive plasma deposition method at room temperature followed by air atmosphere annealing. The structural, electrical, and optical properties of IWOH films with different water flow rates (F H2O ) were systematically investigated before and after annealing. Despite the lower mobility (43.7 cm 2 /V) of IWOH films with high water flow rate (H-F H2O , F H2O ≥ 1.5 sccm) in the as-deposited state, it has increased to 65.2 cm 2 /V, which surpassed IWOH films with low water flow rate (L-F H2O , F H2O < 1.5 sccm) after annealing. Meanwhile, a significant increase in average optical transmittance from 80.9% to 88.8% and from 92.2% to 95.2% in the short wavelength of visible (350–500 nm) and near-infrared region (800–2500 nm), respectively, was obtained for H-F H2O films after annealing. The variation of the optical and electrical properties for IWOH films with different F H2O was attributed to the crystalline structure with a larger crystallite size and lower density of grain boundary. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy analysis revealed that high water flow rate impeded crystallization of IWOH films during reactive plasma deposition, leading to an amorphous structure in the as-deposited state. After annealing, however, the H-F H2O films crystallized and exhibited larger grains than both tungsten-doped indium oxide (IWO) and L-F H2O films. The modified crystalline properties of IWOH films with larger grains hence reducing grain-boundary scattering, which was realized by H-F H2O and annealing treatment, gave rise to enhanced electrical properties without deteriorating optical properties. • Hydrogen-doped indium tungsten oxide was fabricated by reactive plasma deposition at room temperature. • Structural, optical and electrical properties were studied as a function of water flow rate. • Proper water flow rate can enhance the crystalline quality with fewer grain boundary scattering. • The modified crystalline properties with reduced grain boundary led to enhanced mobility.