Synthesis of titanium dioxide thin films via thermo- and plasma-enhanced atomic layer deposition

Abstract

Titanium dioxide thin films were deposited onto single-crystalline silicon wafers using thermal and plasma-enhanced atomic layer deposition (TALD and PEALD) techniques. The TiO2 films were subjected to investigation via ellipsometry, X-ray diffraction, Raman spectroscopy, and the use of scanning electron and atomic force microscopy techniques. The research findings enabled the identification of the optimal stages' durations of the ALD processes, which ensure the occurrence of saturated surface chemical reactions between the initial components of the film. Furthermore, the “ALD-window” temperature range for implementing the self-limited growth regime to obtain titanium dioxide coatings that are uniform in thickness and homogeneous in composition and structure for PEALD was identified and found to be T = 200 – 230 °C. In the case of TALD, two distinct “TALD-window” ranges were detected. The temperature ranges were determined to be T1 = 180 – 220 °C and T2 = 230 – 290 °C. Concurrently, titanium dioxide thin films synthesised by the PEALD may be classified as polycrystalline low-porosity coatings with a surface morphology in the form of extensive “plate-like” domain structures. Conversely, TiO2 films produced by the TALD method are classified as nano-grained polycrystalline porous coatings.