The graphene/n-Ge(110) interface: structure, doping, and electronic properties

TL;DR

This study investigates the structure and electronic properties of the graphene/n-Ge(110) interface, revealing weak interaction, doping effects, and the influence of growth conditions on interface quality, with implications for semiconductor device integration.

Contribution

It provides detailed insights into the atomic-scale structure, doping mechanisms, and growth parameters affecting graphene on n-type Ge(110), combining experimental and theoretical approaches.

Findings

Graphene remains nearly undisturbed electronically, with moderate n-doping.

Substrate temperature critically influences graphene alignment during growth.

Dopants segregate at the interface, forming structures that induce doping.

Abstract

The implementation of graphene in semiconducting technology requires the precise knowledge about the graphene-semiconductor interface. In our work the structure and electronic properties of the graphene/$n$-Ge(110) interface are investigated on the local (nm) and macro (from $\mu\mathrm{m}$ to mm) scales via a combination of different microscopic and spectroscopic surface science techniques accompanied by density functional theory calculations. The electronic structure of freestanding graphene remains almost completely intact in this system, with only a moderate $n$-doping indicating weak interaction between graphene and the Ge substrate. With regard to the optimization of graphene growth it is found that the substrate temperature is a crucial factor, which determines the graphene layer alignment on the Ge(110) substrate during its growth from the atomic carbon source. Moreover, our results demonstrate that the preparation routine for graphene on the doped semiconducting material ($n$-Ge) leads to the effective segregation of dopants at the interface between graphene and Ge(110). Furthermore, it is shown that these dopant atoms might form regular structures at the graphene/Ge interface and induce the doping of graphene. Our findings help to understand the interface properties of the graphene-semiconductor interfaces and the effect of dopants on the electronic structure of graphene in such systems.