The Material Growth and Characteristics of Transition Metal Oxide Thin Films Based on Hot Wire Oxidation Sublimation Deposition Technology

Transition-metal oxides (TMOs) possess pronounced optoelectronic properties and are widely exploited in photovoltaics and photocatalysis. Here, we introduce a hot wire oxidation sublimation deposition (HWOSD) that directly converts elemental Mo and W into amorphous MoOx and WOx films on various substrates. Scanning electron microscopy and atomic force microscopy reveal uniform thickness and conformal coverage over textured and planar surfaces. X-ray photoelectron spectroscopy indicates high oxygen contents with stoichiometric ratios of 2.94 (MoOx) and 2.91 (WOx). Optical measurements show transmittances > 94% across 400–1200 nm, yielding optical band gaps of 1.86 eV (MoOx) and 2.67 eV (WOx). The conductivities of MoOx and WOx were 2.58 × 10−6 S cm−1 and 5.14 × 10−7 S cm−1 at room temperature, and the TMO/Si surface potential differences are 200 mV and 114 mV, respectively. Minority-carrier-lifetime measurements indicate that MoOx films confer an additional passivation benefit to the i a-Si:H/c-Si/i a-Si:H stack. Annealing of MoOx and WOx realized their phase transition from an amorphous state to a polycrystalline state, with changes in their optical transmittance in the visible light region. Investigation of the photovoltaic performances of MoOx and WOx as HTLs deposited by HWOSD demonstrates their excellent electronic functionality in optoelectronics. These results establish HWOSD as a scalable, low-temperature method to fabricate high-quality TMO films and expand their potential in advanced optoelectronic devices.