Pulsed laser deposition and characterization of indium oxide thin films on native-oxide-covered silicon (111) substrates
OA Version
Citation
Abstract
Indium oxide (In2O3) is a transparent conducting oxide with unique electronic properties, including an intrinsic surface electron accumulation layer (SEAL). Despite extensive study on lattice-matched substrates, systematic characterization of PLD-grown In2O3 on native-oxide-covered Si(111) remains limited. This thesis investigates the feasibility and characteristics of PLD-grown In2O3 thin films deposited on as-received Si(111) substrates, for which an approximately 1-2 nm native oxide layer remained present during growth, using a KrF excimer laser (248 nm) at a fluence of 1.61 J/cm^2, substrate temperature of ~550 °C (heater setpoint 600 °C), and oxygen pressure of 0.074 mbar. Two film runs employing 6000 and 8000 laser shots, respectively, were deposited. Both films were characterized by X-ray photoelectron spectroscopy (XPS); the 8000-shot film was additionally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and atomic force microscopy (AFM). XPS analysis of the 6000-shot film revealed good surface-composition uniformity across three measurement spots, with atomic concentrations of approximately 51% In, 41% O, and 8% C. High-resolution In 3d5/2 peak fitting indicated a modest increase in the fitted In3+-O lattice bonding fraction from about 43.0% in the 6000-shot run to about 47.7% in the 8000-shot run, consistent with somewhat more oxide-like near-surface coordination under the 8K process history. XRD analysis of the 8000-shot film confirmed the cubic bixbyite phase (JCPDS 06-0416) through multiple indexed reflections and an elevated I(400)/I(222) ratio (about 1.6 versus the powder reference of 0.35), suggestive of preferential orientation. Scherrer analysis yielded lower-bound crystallite sizes of ~23-38 nm with an average of ~29 nm. SEM imaging of the 8000-shot film revealed continuous film coverage; possible triangular-like surface features were noted in some views, while AFM characterization at the 1 um scan scale yielded an RMS roughness of 1.58 nm and a dominant surface wavelength of approximately 128 nm. Multi-scale measurements (1-30 um) revealed an apparent decrease in roughness with scan size, which is attributed to measurement bandwidth limitations arising from a fixed pixel count. A custom XPS analysis tool developed in Python (Streamlit) was employed for spectral conversion, visualization, and cross-checking of the 6000-shot analysis workflow. The results demonstrate that PLD is a viable route for growing crystalline In2O3 on native-oxide-covered Si(111), while also showing that shot count in the present study should be treated as a relative deposition proxy rather than an independently measured film thickness.
Description
2026