Band alignment determination of bulk h-BN and graphene/h-BN laminates using photoelectron emission microscopy
Band alignment determination of bulk h-BN and graphene/h-BN laminates using photoelectron emission microscopy
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DOI：
10.1063/1.5093430
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发表时间：
2019-04
影响因子：
3.2
通讯作者：
S. Ogawa;T. Yamada;Ryo Kadowaki;T. Taniguchi;T. Abukawa;Y. Takakuwa
中科院分区：
文献类型：
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作者：
S. Ogawa;T. Yamada;Ryo Kadowaki;T. Taniguchi;T. Abukawa;Y. Takakuwa
由于堆叠在六方氮化硼（h-BN）上的石墨烯表现出高电子迁移率，因此有望应用于下一代高速晶体管和电子发射器。为了进一步提高石墨烯/h-BN器件的性能，有必要确定石墨烯/h-BN层压材料的能带排列。然而，由于机械剥离转移到Si衬底上的h-BN单晶很小，因此用普通光电子能谱对h-BN进行精确观察很困难。在这项研究中，通过光电发射电子显微镜识别了石墨烯/h-BN层压板的电结构，并使用微紫外光电子能谱对价带和二次电子能谱进行了局部测量。通过这些测量，我们确定了晶体尺寸为几十微米的石墨烯/h-BN 层压材料的能带排列。通过光电子能谱测量单晶h-BN的功函数和电子亲和势分别为4.6和-0.5 eV。在 h-BN 上层压石墨烯导致 h-BN 的费米能级比未层压的 h-BN 上升 0.85 eV。此外，还发现h-BN上的石墨烯表现出弱的n型导电性。这项研究获得的成果有望广泛应用于使用具有负电子亲和力的h-BN的电子发射器等电子领域。由于堆叠在六方氮化硼（h-BN）上的石墨烯表现出高电子迁移率，因此有望应用于下一代高速晶体管和电子发射器。为了进一步提高石墨烯/h-BN器件的性能，有必要确定石墨烯/h-BN层压材料的能带排列。然而，由于机械剥离转移到Si衬底上的h-BN单晶很小，因此用普通光电子能谱对h-BN进行精确观察很困难。在这项研究中，通过光电发射电子显微镜识别了石墨烯/h-BN层压板的电结构，并使用微紫外光电子能谱对价带和二次电子能谱进行了局部测量。通过这些测量，我们确定了晶体尺寸为几十微米的石墨烯/h-BN 层压材料的能带排列。通过光电子能谱测量单晶h-BN的功函数和电子亲和势分别为4.6和-0.5 eV...
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.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...