# 2D Indium Oxide at the Epitaxial Graphene/SIC Interface: Synthesis, Structure, Properties, and Devices

## TL;DR

Scientists created a new 2D insulator, InO2, at the graphene/SiC interface, which could be used in high-frequency electronic devices.

## Contribution

The synthesis of a new 2D insulator, monolayer InO2, with a wide bandgap and demonstrated use in Schottky junctions.

## Key findings

- Monolayer InO2 was synthesized over a large area at the EG/SiC interface with a bandgap of 4.1 eV.
- Intercalation of InO2 transforms the EG/n-SiC junction from ohmic to Schottky with a barrier height of 0.87 eV.
- The Schottky junction shows a rectification ratio of ≈10⁴, indicating potential for vertical electronic devices.

## Abstract

Scaled and high‐quality insulators are crucial for fabricating 2D/3D hybrid vertical electronic devices such as metal‐oxide‐semiconductor (MOS) based Schottky diodes and hot electron transistors, the production of which is constrained by the scarcity of bulk layered wide bandgap semiconductors. In this research, the synthesis of a new 2D insulator, monolayer InO2, which differs in stoichiometry from its bulk form is presented, over a large area (>300 µm2) by intercalating at the epitaxial graphene (EG)/SiC interface. By adjusting the lateral size of graphene through optical lithography prior to the intercalation, the thickness of InO2 is tuned such that it is 85% monolayer. The preference for monolayer formation of InO2 is explained using molecular dynamics and density functional theory (DFT) calculations. Additionally, the bandgap of InO2 is calculated to be 4.1 eV, differing from its bulk form (2.7 eV). Furthermore, MOS‐based Schottky diode measurements on InO2 intercalated EG/n‐SiC demonstrate that the EG/n‐SiC junction transforms from ohmic to a Schottky junction upon intercalation, with a barrier height of 0.87 eV and a rectification ratio of ≈105. These findings introduce a new addition to the 2D insulator family, demonstrating the utility of monolayer InO2 as a barrier in vertical electronic devices.

A new monolayer insulator, InO2, is synthesized by intercalating indium beneath patterned epitaxial graphene on SiC, followed by high‐temperature oxidation. This selective confinement yields large‐area, uniform InO2 with a wide bandgap of 4.1 eV. Upon intercalation, the EG/n‐SiC junction transitions from ohmic to Schottky, exhibiting a rectification ratio of ≈10⁴—promising for high‐frequency vertical electronic devices.