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arXiv · 2401.07953

Experimentally informed structure optimization of amorphous TiO2 films grown by atomic layer deposition

Jun Meng·Mehrdad Abbasi·Yutao Dong·Corey Carlosa·Xudong Wang·Jinwoo Hwang·Dane Morgan
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Abstract

Amorphous titanium dioxide TiO2 (a-TiO2) has been widely studied, particularly as a protective coating layer on semiconductors to prevent corrosion and promote electron-hole conduction in photoelectrochemical reactions. The stability and longevity of a-TiO2 is strongly affected by the thickness and structural heterogeneity, implying that understanding the structure properties of a-TiO2 is crucial for improving the performance. This study characterized the structural and electronic properties of a-TiO2 thin films (~17nm) grown on Si by Atomic Layer Deposition (ALD). Fluctuation spectra V(k) and angular correlation functions were determined with 4-dimensional scanning transmission electron microscopy (4D-STEM), which revealed the distinctive medium-range ordering in the a-TiO2 film. A realistic atomic model of a-TiO2 was established guided by the medium-range ordering and the previously reported short-range ordering of a-TiO2 film, as well as the interatomic potential. The structure was optimized by the StructOpt code using a genetic algorithm that simultaneously minimizes energy and maximizes match to experimental short- and medium-range ordering. The StructOpt a-TiO2 model presents an improved agreements with the medium-range ordering and the k-space location of the dominant 2-fold angular correlations compared with a traditional melt-quenched model. The electronic structure of the StructOpt a-TiO2 model was studied by ab initio calculation and compared to the crystalline phases and experimental results. This work uncovered the medium-range ordering in a-TiO2 thin film and provided a realistic a-TiO2 structure model for further investigation of structure-property relationships and materials design. In addition, the improved multi-objective optimization package StructOpt was provided for structure determination of complex materials guided by experiments and simulations.

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Jun Meng, Mehrdad Abbasi, Yutao Dong, Corey Carlosa, Xudong Wang, Jinwoo Hwang, Dane Morgan. 2024-01-15. Experimentally informed structure optimization of amorphous TiO2 films grown by atomic layer deposition. https://doi.org/10.1039/d2nr03614b

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