van der Waals epitaxy of ferroelectric ε-gallium oxide thin film on flexible synthetic mica

Abstract

This study demonstrates the formation of the van der Waals epitaxy of the ε-gallium oxide (Ga 2 O 3 ) thin film on cleaved synthetic mica via mist chemical vapor deposition. Orthorhombic ε-Ga 2 O 3 (001) was epitaxially grown on synthetic mica (001). The analysis using transmission electron microscopy revealed an in-plane orientation of ε-Ga 2 O 3 [010] || synthetic mica [010]. However, the most thermodynamically stable β-Ga 2 O 3 was grown at the film-substrate interface. The optical direct bandgap of the ε-Ga 2 O 3 thin film grown by van der Waals epitaxy was estimated to be 5.0 eV, which was the same as for the heteroepitaxially grown ε-Ga 2 O 3 thin film on other substrates. Besides, after ε-Ga 2 O 3 thin film was grown on the synthetic mica substrates that are cleaved sufficiently thin, the sample could be bent or cut with scissors. These results denote that the epitaxial ε-Ga 2 O 3 thin films grown by van der Waals epitaxy can be applied to flexible electronics.

Ga2O3polymorphs: tailoring the epitaxial growth conditions

“…This could be an indication that an interlayer could be needed in order to accommodate the substrate-layer strain. The presence of a b-Ga 2 O 3 buffer layer was observed also in the recent reports of e-Ga 2 O 3 layers on ITO/YSZ(111) 87 and of van der Waals epitaxy of e-Ga 2 O 3 on synthetic mica, 95 both via mist-CVD. In particular, the van der Waals epitaxy report of e-Ga 2 O 3 might hint at the fact that, in conditions with very weak chemical bonding between the substrate and epilayer, the growth of an initial layer of the most thermodynamically stable material in the b phase is needed, before obtaining epitaxial e-Ga 2 O 3 .…”

Ultrasensitive Flexible κ-Phase Ga2O3 Solar-Blind Photodetector

“…In the Ga 2 O 3 (122) scan result in Figure c, 12-fold symmetry is evident over the 360° range, indicating the orthorhombic structure rather than the hexagonal structure (so-called ε-phase). , The in-plane rotational symmetry difference between β-Ga 2 O 3 (−401) and κ-Ga 2 O 3 (122) could also be viewed in SI Figure S1c in the SI. It has been reported that in orthorhombic Ga 2 O 3 film grown on various substrates, intermediate β-Ga 2 O 3 film could appear at the interface. , If the detection limit of the XRD scan for ultrathin films is to be considered and an interfacial ultrathin β-Ga 2 O 3 is assumed to be present, this ultrathin film would not affect the PD performance.…”

Transferable Ga2O3 Membrane for Vertical and Flexible Electronics via One-Step Exfoliation

“…We observed slightly higher resistance and Schottky behavior of exfoliated n-Ga 2 O 3 +etching sample compared with the as-grown n-Ga 2 O 3 /mica. This phenomenon could be attributed to (i) material quality difference between the top n-Ga 2 O 3 layer and exfoliated bottom n-Ga 2 O 3 , which may contain polycrystal interfacial layer, 46,47 and (ii) plasma damages after Ar dry etching. 48,49 The vdW-bond-assisted exfoliation demonstrated in this work could be employed to fabricate vertical configuration Ga 2 O 3 devices, including PDs, Schottky barrier diodes (SBD), PN diode, and bottom-gate transistors.…”