Mechanism Behind the Easy Exfoliation of Ga₂O₃ Ultra‐Thin Film Along (100) Surface

Abstract

The transparent wide band gap semiconductor β‐Ga2O3 has gained wide attention due to its suitability to a wide range of applications. Despite not being a van der Waals material and having highly strong ionic bonding, the material can be mechanically cleaved and exfoliated easily along favorable surfaces to make ultra‐thin layers and used in device fabrications. One of the interesting properties of this material is that thin layers preserve the pristine bulk‐like electronic properties, which makes it even more promising for applications in power devices. However, very little is known about the mechanism why such ultra‐thin film or even single bilayer exfoliation is favorable from the bulk. In this letter, we have explained the mechanism of such phenomenon by detailed analyses of different types of Ga–O bonding character. The protocol of methodology used and developed in this study can be utilized in general to understand bond breaking and forming of other complex materials as well. This understanding will give us a better control to fabricate thin film 2D devices.

Phase transition of two-dimensional ferroelectric and paraelectric Ga2O3 monolayers: A density functional theory and machine learning study

“…Unlike the other III 2 IV 3 compounds such as In 2 Se 3 , the bonding in Ga 2 O 3 is mainly ionic in nature [11,58]. The Bader charge analysis [59,60] and the electron localization function [61] on the (meta)stable and saddle configurations indicate an ionicity of 2D Ga 2 O 3 phases similar to bulk β-Ga 2 O 3 , as shown in Fig.…”

“…Although Ga 2 O 3 is not a van der Waals material, twodimensional (2D) β-Ga 2 O 3 can be mechanically exfoliated from the bulk material along the (100) direction, forming thin β-phase layers [9][10][11][12][13]. Quasi-2D Ga 2 O 3 thin films have been mechanically exfoliated with a thickness of ∼20 to 100 nm [10,[14][15][16].…”

Phase Transition of Two-Dimensional Ferroelectric and Paraelectric Ga2O3 Monolayer: A Density Functional Theory and Machine-Learning Study

“…Unlike the other III 2 IV 3 compounds such as In 2 Se 3 , the bonding in Ga 2 O 3 is mainly ionic in nature [11,54]. The Bader charge analysis [55,56] and the electron localization function [57] on the (meta-) stable and saddle configurations indicate a similar ionicity of 2D Ga 2 O 3 phases compared to bulk β-Ga 2 O 3 , as shown in the ESI Fig.…”

“…Within a line growth, a periodic feature of the energy evolution can be seen as the displacement of the front atoms (i.e., atoms 0, 6, 12, 18...) always lead to increase in the potential energy, while the closing atoms (the last atoms completing the concerted movement, i.e. atoms 5,11,17) bring the system to more stable local minima.…”

“…Although Ga 2 O 3 is not a Van der Waals material, the 2D β-Ga 2 O 3 can be mechanically exfoliated from the bulk material along the (100) direction, forming thin βphase layers [9][10][11]. Quasi-2D Ga 2 O 3 thin films have been mechanically exfoliated with the thickness of ∼ 20 to 100 nm [10,[12][13][14].…”