[Paper Review] Initial stages of the graphite-SiC(0001) interface formation studied by photoelectron spectroscopy

K. V. Emtsev, Thomas Seyller+5 more|arXiv (Cornell University)|Sep 15, 2006

Silicon Carbide Semiconductor Technologies4 citations

TL;DR

This study investigates the initial formation of the graphite-SiC(0001) interface using photoelectron spectroscopy, revealing that the 6√3 reconstructed surface exhibits sp²-bonded carbon with modified pi-bands due to substrate interaction. At 1250–1300 °C, a graphene layer forms with unperturbed electronic structure, and the interface structure closely resembles the 6√3 phase, indicating a stable, well-ordered interface critical for graphene growth on SiC.

ABSTRACT

Graphitization of the 6H-SiC(0001) surface as a function of annealing temperature has been studied by ARPES, high resolution XPS, and LEED. For the initial stage of graphitization - the 6root3 reconstructed surface - we observe sigma-bands characteristic of graphitic sp2-bonded carbon. The pi-bands are modified by the interaction with the substrate. C1s core level spectra indicate that this layer consists of two inequivalent types of carbon atoms. The next layer of graphite (graphene) formed on top of the 6root3 surface at TA=1250-1300 degree C has an unperturbed electronic structure. The annealing at higher temperatures results in the formation of a multilayer graphite film. It is shown that the atomic arrangement of the interface between graphite and the SiC(0001) surface is practically identical to that of the 6root3 reconstructed layer.

Motivation & Objective

• To understand the atomic and electronic structure of the initial graphite-SiC(0001) interface during early-stage graphitization.
• To determine how the SiC substrate influences the electronic properties of the first carbon layers.
• To identify the structural and electronic evolution of the interface as a function of annealing temperature.
• To establish the relationship between the 6√3 reconstructed surface and the subsequent formation of graphene.
• To assess the stability and electronic integrity of the graphene layer grown on SiC(0001).

Proposed method

• Angle-resolved photoemission spectroscopy (ARPES) was used to probe the electronic band structure of the interface.
• High-resolution X-ray photoelectron spectroscopy (XPS) analyzed the chemical states and core level shifts of carbon atoms.
• Low-energy electron diffraction (LEED) confirmed surface reconstruction and structural order.
• Annealing of 6H-SiC(0001) samples at temperatures from 1250 °C to 1400 °C was used to control graphitization stages.
• The evolution of the C1s core level spectra revealed two inequivalent carbon species in the initial 6√3 phase.
• Comparative analysis of electronic structure across temperature stages identified the onset of graphene formation.

Experimental results

Research questions

• RQ1 How does the electronic structure of the first carbon layer on SiC(0001) evolve during initial graphitization?
• RQ2 What is the role of the 6√3 reconstructed surface in mediating the interface between graphite and SiC?
• RQ3 At what annealing temperature does a graphene layer with unperturbed electronic structure form?
• RQ4 How do the sigma- and pi-bands of the interfacial carbon layer differ from those of bulk graphite?
• RQ5 Is the atomic arrangement of the graphite-SiC interface identical to that of the 6√3 reconstructed surface?

Key findings

• The 6√3 reconstructed surface exhibits sigma-bands characteristic of sp²-bonded carbon, confirming its graphitic nature.
• Pi-bands in the 6√3 phase are modified by interaction with the SiC substrate, indicating strong electronic coupling.
• C1s core level spectra show two inequivalent carbon atoms in the 6√3 layer, indicating structural and electronic inhomogeneity.
• At 1250–1300 °C, a graphene layer forms with an unperturbed electronic structure, indicating minimal substrate interaction.
• Annealing above 1300 °C leads to multilayer graphite growth, with the interface structure remaining consistent with the 6√3 phase.
• The atomic arrangement of the graphite-SiC(0001) interface is nearly identical to that of the 6√3 reconstructed surface, confirming structural stability.