Flat bands in ultra-wide gap two-dimensional germanium dioxide

TL;DR

This study uses advanced computational methods to analyze 2D germanium dioxide, revealing ultra-wide band gaps and flat valence bands that are tunable under strain, promising for high-voltage, high-temperature electronic devices.

Contribution

It introduces the first detailed theoretical investigation of 2D GeO2, highlighting its ultra-wide band gaps and tunable flat bands using DFT and BSE methods.

Findings

All 2D GeO2 polymorphs have ultra-wide band gaps.

Strong excitonic effects are observed in these materials.

Flat valence bands can be tuned with strain.

Abstract

We employ first principles density-functional theory (DFT) and the Bethe-Salpeter equation (BSE) in the framework of tight-binding based maximally localized Wannier functions (MLWF-TB) model to investigate the electronic and optical properties of free-standing two-dimensional (2D) germanium dioxide phases. All investigated 2D GeO2 polymorphs exhibit ultra-wide band gaps and strong excitonic effects, with flat O-p-derived valence bands tunable under strain. These features allow the design of flat band materials with ultra large electronic gaps in low-dimensional systems, making these materials promising for devices operation at higher voltages and temperatures than conventional semiconductor materials.