Energy of adsorption at semiconducting surfaces with Fermi level differently pinned -- ab initio study

TL;DR

This study investigates how the adsorption energy at semiconductor surfaces varies with Fermi level pinning and charge transfer, using ab initio DFT simulations to reveal different behaviors for molecular and dissociative adsorption.

Contribution

It demonstrates that adsorption energy depends on charge transfer and Fermi level pinning, providing a detailed ab initio analysis of these effects on semiconductor surfaces.

Findings

Adsorption energy for molecular adsorption is coverage-independent.

Dissociative adsorption energy varies significantly with Fermi level pinning.

Charge transfer influences adsorption energy in open shell systems.

Abstract

It is shown that adsorption energy at semiconductor surfaces critically depends on the charge transfer to or from the adsorbed species. For the processes without the charge transfer, such as molecular adsorption of closed shell systems, the adsorption energy is determined by the bonding only. In the case involving charge transfer, such as open shell systems like metal atoms or the dissociating molecules, the energy attains different value for the Fermi level differently pinned. The DFT simulation of adsorption of ammonia at hydrogen covered GaN(0001) confirms these predictions: the molecular adsorption is independent on the coverage while the dissociative process energy varies by several electronvolts.