Influence of interface dipole layers on the performance of graphene field effect transistors

Abstract

The linear band dispersion of graphene's bands near the Fermi level gives rise to its unique electronic properties, such as a giant carrier mobility, and this has triggered extensive research in applications, such as graphene field-effect transistors (GFETs). However, GFETs generally exhibit a device performance much inferior compared to the expected one. This has been attributed to a strong dependence of the electronic properties of graphene on the surrounding interfaces. Here we study the interface between a graphene channel and SiO2, and by means of photoelectron spectromicroscopy achieve a detailed determination of the course of band alignment at the interface. Our results show that the electronic properties of graphene are modulated by a hydrophilic SiO2 surface, but not by a hydrophobic one. By combining photoelectron spectromicroscopy with GFET transport property characterization, we demonstrate that the presence of electrical dipoles in the interface, which reflects the SiO2 surface electrochemistry, determines the GFET device performance. A hysteresis in the resistance vs. gate voltage as a function of polarity is ascribed to a reversal of the dipole layer by the gate voltage. These data pave the way for GFET device optimization.

Spectrum adapted expectation-conditional maximization algorithm for extending high–throughput peak separation method in XPS analysis

“…These peaks represent the contaminant, and graphene sp 2 component, respectively. The component of contamination would arise lithographic processing [33,34]. The peak of graphene sp 2 component (284.28 eV) was very close to the value reported in Nagamura et al [33] (284.23 eV).…”

“…The component of contamination would arise lithographic processing [33,34]. The peak of graphene sp 2 component (284.28 eV) was very close to the value reported in Nagamura et al [33] (284.23 eV). As the mixture ratio (λ 1 and λ 2 ) were 0.63 and 0.38, respectively, the contaminant component occupies larger part of the data than that of the graphene sp 2 component.…”

“…As the mixture ratio (λ 1 and λ 2 ) were 0.63 and 0.38, respectively, the contaminant component occupies larger part of the data than that of the graphene sp 2 component. Such relatively large contaminant component was also observed in Nagamura et at al [33]. The degree of the asymmetry of the graphene sp 2 component (α 1 ) was 0.29, whereas the asymmetric parameter of the graphene C 1s peak is generally assumed to be about 0.1 [35][36][37].…”

“…The W 4 f core-level spectrum was taken by a mechanically exfoliated WSe 2 sheet in a 2D heterostructure tunnel field effect transistor [32]. Also, the C 1s core-level photoelectron spectrum was taken by a graphene sheet on a 90 nm SiO 2 /p + -Si(100) substrate [33]. Both spectral data were acquired using a VG Scienta R3000 spectrometer in the scanning photoelectron microscopy system (3D nano-ESCA) installed at the University of Tokyo outstation beamline, BL07LSU at SPring-8.…”

Micrometer-scale monolayer SnS growth by physical vapor deposition

“…In this article, we address monolayer SnS growth on an atomically flat mica substrate from different powders to identify the mechanism for micrometer-scale monolayer growth. Since chemical characterization of the nanoscale microstructure is determinant in this study, a core-level photoelectron spectromicroscopic apparatus installed at the synchrotron radiation facility of SPring-8, called "3D nano-ESCA," 35,36 is utilized, with which we can scan the sample with a high lateral spatial resolution of ~70 nm to record photoelectron spectra for quantitative analysis of the chemical states.…”