Highly Monochromatic Electron Emission from Graphene/Hexagonal Boron Nitride/Si Heterostructure

Abstract

In this work, a planar electron emission device based on a graphene/hexagonal boron nitride (h-BN)/n-Si heterostructure is fabricated to realize highly monochromatic electron emission from a flat surface. The h-BN layer is used as an insulating layer to suppress electron inelastic scattering within the planar electron emission device. The energy spread of the emission device using the h-BN insulating layer is 0.28 eV based on the full-width at half-maximum (FWHM), which is comparable to a conventional tungsten field emitter. The characteristic spectral shape of the electron energy distributions reflected the electron distribution in the conduction band of the n-Si substrate. The results indicate that the inelastic scattering of electrons at the insulating layer is drastically suppressed by the h-BN layer. Furthermore, the maximum emission current density reached 2.4 A/cm2, which is comparable to that of a conventional thermal cathode. Thus, the graphene/h-BN heterostructure is a promising material for planar electron emission devices to obtain a highly monochromatic electron beam and a high electron emission current density.

Mechanism of Highly Efficient Electron Emission from a Graphene/Oxide/Semiconductor Structure

“…In our recent study, we demonstrated the electron emission from a graphene/h-BN/n-Si heterostructure. 32 This result indicates that h-BN can be used as the insulating layer of planar-type electron emission devices. High-quality graphene can be epitaxially grown on the h-BN surface because h-BN has a similar crystal structure to that of graphene.…”

“…The energy spectra of the emitted electrons of the GOS structure were obtained using a hemispherical electron energy analyzer. The detailed measurement set-up of the electron energy distributions of the GOS device is described in a previous paper …”

“…The detailed measurement set-up of the electron energy distributions of the GOS device is described in a previous paper. 32 ■ RESULTS AND DISCUSSION Figure 2a shows the emission current, cathode current, and electron emission efficiency of the GOS emission device with an electron emission area of 100 μm × 100 μm and a 1 nm thick graphene electrode fabricated by catalyst-free LPCVD as a function of the applied gate voltage. The emission current appeared at a gate voltage of approximately 7 V and increased with an increasing gate bias voltage, reaching a maximum of 3.36 nA at 10 V. The maximum emission efficiency was 48.5% at 8.7 V and remained almost constant for higher gate bias voltage.…”

Electron transmission through suspended graphene membranes measured with a low-voltage gated Si field emitter array

“…Measuring the electron transparencies at lower energies is difficult due to the strong electrostatic field needed to extract electrons by field emission. Planar graphene devices have been demonstrated for low-energy electron field emission measurements from graphene; however these devices do not provide an independent measure of electron transmission through graphene membranes with different number of layers [14]. In this work, we instead use atomically sharp Si emitters with self-aligned gates to extract electrons at voltages of less than 20 V as a separate electron source.…”

Fabrication of Pt- and Au-coated W Nano Tip with Electroplated Films as a Noble-metal Source toward Viable Application for Long-life Electron Source

“…The development of next-generation electron sources is crucial for improving the efficiency of electron microscopes. Materials such as strained superlattice GaAs/GaAsP semiconductor photocathodes [1], graphene/h-BN/n-Si heterostructure planar electron emission devices [2], Co2MnGa❬100❭ tip [3], LaB 6 ❬100❭ nanowire [4], CeB 6 ❬310❭ tip [5], and amorphous carbon-coated metal tip [6,7] have been investigated in this direction. One of the important factors that determines the efficiency (probe diameter or coherence) of an electron optical device is the brightness of the electron source.…”