Phase Evolution and Substrate-Dependent Nucleation of Quartz GeO2 Films Grown by MOCVD on r- and c-Plane Sapphires
Abstract
Ultrawide-bandgap (UWBG) semiconductors, such as GeO2, are gaining significant attention for their potential in high-performance applications, particularly in piezoelectric devices. Despite extensive research, a comprehensive understanding of the growth dynamics and phase evolution of GeO2 films via metal-organic chemical vapor deposition (MOCVD) remains insufficient. In this study, we investigate the growth behavior and morphological evolution of GeO2 thin films on r-plane and c-plane sapphire substrates for the MOCVD growth process. The temporal evolution of crystallization and the amorphous-to-quartz phase transition are systematically elucidated for the first time. As growth time increases, the spherulitic quartz patterns expand in size, and elevated growth temperatures are found to enhance the crystallization rate. Distinct morphological symmetries emerge depending on the substrate orientation: quadrangular patterns on r-plane sapphire and hexagonal patterns on c-plane sapphire. Atomic force microscopy reveals that these spherulitic domains exhibit pyramid-like surface topography, consistent with volumetric contraction during the amorphous-to-quartz phase transition. These findings offer new insights into the phase evolution and substrate-dependent crystallization behavior of GeO2 films grown by MOCVD.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.