n-type behavior of graphene supported on Si/SiO2 substrates

Hugo E. Romero, Ning Shen, Prasoon Joshi, Humberto R. Gutierrez, Srinivas A. Tadigadapa, Jorge O. Sofo, Peter C. Eklund

Research output: Contribution to journalArticle

206 Citations (Scopus)

Abstract

Results are presented from an experimental and theoretical study of the electronic properties of back-gated graphene field effect transistors (FETs) on Si/SiO2 substrates. The excess charge on the graphene was observed by sweeping the gate voltage to determine the charge neutrality point in the graphene. Devices exposed to laboratory environment for several days were always found to be initially p-type. After ∼20 h at 200 °C in ∼5 × 10-7 Torr vacuum, the FET slowly evolved to n-type behavior with a final excess electron density on the graphene of ∼4 × 1012 e/cm2. This value is in excellent agreement with our theoretical calculations on SiO2, where we have used molecular dynamics to build the SiO2 structure and then density functional theory to compute the electronic structure. The essential theoretical result is that the SiO2 has a significant surface state density just below the conduction band edge that donates electrons to the graphene to balance the chemical potential at the interface. An electrostatic model for the FET is also presented that produces an expression for the gate bias dependence of the carrier density.

Original languageEnglish (US)
Pages (from-to)2037-2044
Number of pages8
JournalACS nano
Volume2
Issue number10
DOIs
StatePublished - Oct 1 2008

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Graphene
graphene
Field effect transistors
Substrates
field effect transistors
Carrier concentration
Chemical potential
Surface states
Conduction bands
Electronic properties
Electronic structure
Density functional theory
Molecular dynamics
Electrostatics
conduction bands
Vacuum
electrostatics
molecular dynamics
density functional theory

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

Romero, H. E., Shen, N., Joshi, P., Gutierrez, H. R., Tadigadapa, S. A., Sofo, J. O., & Eklund, P. C. (2008). n-type behavior of graphene supported on Si/SiO2 substrates. ACS nano, 2(10), 2037-2044. https://doi.org/10.1021/nn800354m
Romero, Hugo E. ; Shen, Ning ; Joshi, Prasoon ; Gutierrez, Humberto R. ; Tadigadapa, Srinivas A. ; Sofo, Jorge O. ; Eklund, Peter C. / n-type behavior of graphene supported on Si/SiO2 substrates. In: ACS nano. 2008 ; Vol. 2, No. 10. pp. 2037-2044.
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Romero, HE, Shen, N, Joshi, P, Gutierrez, HR, Tadigadapa, SA, Sofo, JO & Eklund, PC 2008, 'n-type behavior of graphene supported on Si/SiO2 substrates', ACS nano, vol. 2, no. 10, pp. 2037-2044. https://doi.org/10.1021/nn800354m

n-type behavior of graphene supported on Si/SiO2 substrates. / Romero, Hugo E.; Shen, Ning; Joshi, Prasoon; Gutierrez, Humberto R.; Tadigadapa, Srinivas A.; Sofo, Jorge O.; Eklund, Peter C.

In: ACS nano, Vol. 2, No. 10, 01.10.2008, p. 2037-2044.

Research output: Contribution to journalArticle

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AU - Romero, Hugo E.

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AU - Tadigadapa, Srinivas A.

AU - Sofo, Jorge O.

AU - Eklund, Peter C.

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N2 - Results are presented from an experimental and theoretical study of the electronic properties of back-gated graphene field effect transistors (FETs) on Si/SiO2 substrates. The excess charge on the graphene was observed by sweeping the gate voltage to determine the charge neutrality point in the graphene. Devices exposed to laboratory environment for several days were always found to be initially p-type. After ∼20 h at 200 °C in ∼5 × 10-7 Torr vacuum, the FET slowly evolved to n-type behavior with a final excess electron density on the graphene of ∼4 × 1012 e/cm2. This value is in excellent agreement with our theoretical calculations on SiO2, where we have used molecular dynamics to build the SiO2 structure and then density functional theory to compute the electronic structure. The essential theoretical result is that the SiO2 has a significant surface state density just below the conduction band edge that donates electrons to the graphene to balance the chemical potential at the interface. An electrostatic model for the FET is also presented that produces an expression for the gate bias dependence of the carrier density.

AB - Results are presented from an experimental and theoretical study of the electronic properties of back-gated graphene field effect transistors (FETs) on Si/SiO2 substrates. The excess charge on the graphene was observed by sweeping the gate voltage to determine the charge neutrality point in the graphene. Devices exposed to laboratory environment for several days were always found to be initially p-type. After ∼20 h at 200 °C in ∼5 × 10-7 Torr vacuum, the FET slowly evolved to n-type behavior with a final excess electron density on the graphene of ∼4 × 1012 e/cm2. This value is in excellent agreement with our theoretical calculations on SiO2, where we have used molecular dynamics to build the SiO2 structure and then density functional theory to compute the electronic structure. The essential theoretical result is that the SiO2 has a significant surface state density just below the conduction band edge that donates electrons to the graphene to balance the chemical potential at the interface. An electrostatic model for the FET is also presented that produces an expression for the gate bias dependence of the carrier density.

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Romero HE, Shen N, Joshi P, Gutierrez HR, Tadigadapa SA, Sofo JO et al. n-type behavior of graphene supported on Si/SiO2 substrates. ACS nano. 2008 Oct 1;2(10):2037-2044. https://doi.org/10.1021/nn800354m