Band alignment determination of bulk h-BN and graphene/h-BN laminates using photoelectron emission microscopy

Because graphene stacked on hexagonal boron nitride (h-BN) exhibits high electron mobility, it is expected to be applied to next-generation high-speed transistors and electron emitters. To further improve the performance of graphene/h-BN devices, it is necessary to determine the band alignment of gr...

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Bibliographic Details
Published in:Journal of applied physics 2019-04, Vol.125 (14)
Main Authors: Ogawa, Shuichi, Yamada, Takatoshi, Kadowaki, Ryo, Taniguchi, Takashi, Abukawa, Tadashi, Takakuwa, Yuji
Format: Article
Language:English
Subjects:
Affinity
Alignment
Applied physics
Boron nitride
Crystals
Electron affinity
Electron mobility
Electrons
Emission microscopy
Emitters
Emitters (electron)
Graphene
Laminates
Laminating
Micrometers
Microscopy
Negative electron affinity
Performance enhancement
Photoelectric emission
Photoelectron spectroscopy
Photoelectrons
Semiconductor devices
Silicon substrates
Single crystals
Spectroscopic analysis
Spectrum analysis
Transistors
Ultraviolet spectra
Valence band
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Summary:Because graphene stacked on hexagonal boron nitride (h-BN) exhibits high electron mobility, it is expected to be applied to next-generation high-speed transistors and electron emitters. To further improve the performance of graphene/h-BN devices, it is necessary to determine the band alignment of graphene/h-BN laminates. However, because mechanically peeled h-BN single crystals transferred onto Si substrates are small, pinpoint observation of h-BN with ordinary photoelectron spectroscopy is difficult. In this study, the electric structure of a graphene/h-BN laminate was identified by photoemission electron microscopy and local measurements of valence band and secondary electron spectra using micro-ultraviolet photoelectron spectroscopy were performed. From these measurements, we determined the band alignment of a graphene/h-BN laminate with a crystal size of a few tens of micrometers. The work function and electron affinity measured by photoelectron spectroscopy of single-crystal h-BN were 4.6 and −0.5 eV, respectively. Laminating graphene on h-BN caused the Fermi level of h-BN to rise 0.85 eV above that of nonlaminated h-BN. In addition, it was found that graphene on h-BN displayed weak n-type conductivity. The results obtained in this research are expected to be widely applied in the field of electronics such as electron emitters using h-BN with negative electron affinity.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5093430