• Introduction

• SiC substrate

• Process

• Expitaxial graphene on Si – face

• Expitaxial graphene on C – face

• Summary

Graphene synthesis on SiC

Graphene synthesis methods

Graphene Synthesis

Top down Bottom Up

Mechanical exfoliation

Chemical exfoliation

Chemical synthesis

Pyrolysis

Epitaxial Growth

CVD

Other methods

Epitaxial growth

• Single crystalline film on a single crystalline substrate.

• SiC substrate graphene

• Feasibility and scalability• High temperature process, difficult graphene

transfer from SiC to other sub, expensive substrate.

Anneal

Si

SiC substrate

• Hexagonal polytypism. (4H, 6H)• 3 carbon – 1 Si ( bilayer ) – 1 carbon linking

another layer• Polar: Si – face (0001), C – face (000ī)

A

B

C

B

• Surface cleaning ( H2 etching, furnace, Ar + H2, ~1 atm ) or CMP

• Surface oxide removing ( heating ~1000°C, UHV, Si flux ) SiO gas

• Graphene formation - UHV, high temp - Ar overpressure, more high temp

Process

Si – face (0001)

• Unit vector: SiC 3.08A, graphene 2.46A

• Rotating 30°C formation to align

• First graphene layer covalent bonding with Si.

• Structural graphene but no electrical property (ZLG)

• From 2nd graphene layer (MLG), forming π bonding.

• Intrinsic doping n~10^13 due to the ZLG-SiC interface.

• Bilayer intrinsic doping and band gap opening

Si – face (0001)

• Transfer doping - Deposit electron acceptor - ex. Antimony, bismuth, F4-TCNQ ( electron acceptor molecule.

• Intercalation - Decoupling ZLG from SiC by putting other

Si – face (0001)

• Rotating 30° or ± 2.2° [10ī0] formation.

• Electrically decoupled between layers

• Stacks of layer single layer electronic properties.

C – face (000ī)

Si – face C - face

-Uniform single layer thickness control( Ar overpressure )

-No effect of Ar overpressure-Uniformity control difficult

-Defect free from SIC substrate -Surface defect

-High crystal quality -Process control difficult

-2000 cm2/VS (N-doped)-30000 cm2/VS (charge-neutral)

-5000 cm2/VS (N-doped)-150,000 cm2/VS (charge-neutral)

SUMMARY

• J. Hass, et al. PRL 100, 125504 (2008)• C. Riedl, et al. J. Phys. D: Appl. Phys. 43 (2010) 374009• Zachary R. Robinson, et al. CARBON 81 (2015) 73-82• J. Hass, et al. J. Phys: Condens. Matter 20 (2008) 323202• U. Starke, et al. MRS Bulletin 37 (DEC. 2012)• Phillip N. First, et al. MRS Bulletin 35 (APR. 2010)

Reference