Layer-dependent Band Alignment and Work Function of Few-Layer Phosphorene

TL;DR

This study uses first-principles calculations to analyze how the electronic properties of few-layer phosphorene, including band gap, work function, and band alignment, depend on the number of layers, revealing potential for electronic and energy applications.

Contribution

The paper provides a detailed first-principles analysis of layer-dependent electronic properties of phosphorene, highlighting its direct band gap and carrier characteristics for optoelectronic uses.

Findings

Band gap decreases with layers following a power law

Work function decreases rapidly from monolayer to trilayer

Bilayer phosphorene has a significantly lighter hole effective mass

Abstract

Using first-principles calculations, we study the electronic properties of few-layer phosphorene focusing on layer-dependent behavior of band gap, work function and band alignment and carrier effective mass. It is found that few-layer phosphorene shows a robust direct band gap character, and its band gap decreases with the number of layers following a power law. The work function decreases rapidly from monolayer (5.16 eV) to trilayer (4.56 eV), and then slowly upon further increasing the layer number. Compared to monolayer phosphorene, there is a drastic decrease of hole effective mass along the ridge (zigzag) direction for bilayer phosphorene, indicating a strong interlayer coupling and screening effect. Our study suggests that 1). Few-layer phosphorene with a layer-dependent band gap and a robust direct band gap character is promising for efficient solar energy harvest. 2). Few-layer phosphorene outperforms monolayer counterpart in terms of a lighter carrier effective mass, a higher carrier density and a weaker scattering due to enhanced screening. 3). The layer-dependent band edges and work functions of few-layer phosphorene allow for modification of Schottky barrier with enhanced carrier injection efficiency. It is expected that few-layer phosphorene will present abundant opportunities for a plethora of new electronic applications.