Precursor-driven nucleation and texture control governing resistivity in low-temperature In2O3 films

Abstract

Achieving low resistivity (ρ) and sufficient carrier mobility (μ) in In₂O₃ thin films deposited by plasma-enhanced atomic layer deposition (PEALD) at ≤ 100 °C remains challenging due to limited crystallinity and grain-boundary scattering. This study demonstrates that precursor-controlled nucleation—rather than film thickness or bulk crystallinity—is the key factor governing carrier mobility and resistivity. Two indium precursors, DIP3 (MeIn(Pr)₂NMe) and DIP4 (InMe₃(THF)), were employed to investigate the growth, structure, and optoelectronic properties of In₂O₃ films 30–100 nm thick. Characterization used grazing-incidence XRD, XPS, spectroscopic ellipsometry, UV–Vis, and van der Pauw Hall measurements.Films grown with DIP3, which exhibits a lower nucleation density, maintained a stable (222)/(400) texture up to 80 nm and achieved ρ = 1.1 × 10⁻³ Ω cm and FoM = 1.5 × 10⁻³ Ω⁻¹ without post-annealing. In contrast, DIP4 films showed an earlier onset of random orientation and a pronounced mobility decline beyond 50 nm, attributed to higher nucleation density. Increasing the number of DIP3 dosing pulses per ALD cycle raised the growth per cycle (GPC) by 0.04 Å/cycle and increased resistivity to 6.8 × 10⁻³ Ω cm, accompanied by a rise in the (411) peak intensity.These results confirm that accelerated nucleation promotes random grain orientation, thereby increasing resistivity and reducing mobility. All films exhibited > 80% transmittance in the visible range. Overall, these findings highlight that reducing resistivity in low-temperature PEALD requires controlling nucleation and crystallographic texture rather than simply increasing film thickness.