Robust Nanocapacitors Based on Wafer-Scale Single-Crystal Hexagonal Boron Nitride Monolayer Films

Abstract

Two-dimensional wafer-scale and single-crystal hexagonal boron nitride (h-BN) films are considered a crucial part of the next generation of van der Waals (vdW) electronic devices. Progress has been made in the synthesis process recently, leading to the demonstration of electronic devices. In this work, we report an effective method to synthesize high-quality single-crystal h-BN monolayer films. Single-crystal metal substrates were produced by thermal annealing of Ni foils, followed by electropolishing to remove the passivated surface layer. Molecular beam epitaxy was employed to synthesize 1 in.2 monolayer single-crystal h-BN films. We discovered that electropolishing plays an important role in drastically increasing the speed of h-BN film growth. Robust nanocapacitors were fabricated using as-grown monolayer h-BN films. The nanocapacitance effect and tunneling current mechanism were studied in detail, and the “effective distance” concept is introduced to explain the quantum phenomenon in the (vdW) metal–insulator–metal devices using atomically thin dielectric h-BN films.

Static and Small-Signal Modeling of Radiofrequency Hexagonal Boron Nitride Switches

“…C ON values have not been reported previously for ECs of hBN switches in the literature and are obtained here by considering a correct description of S 21,int in the ON-state for each switch. The values of C ON obtained for the hBN devices are similar to the ones reported elsewhere for fabricated hBN-based MIMs, i.e., few pF [27], [28]. Furthermore, this capacitive effect at ON-state has not been observed in other 2D monolayer RF switches [4], [5] and hence it is suggested here to be associated to the charge storaged within the hBN layer during the filament-based resistive switching [15] rather than to the thickness of the monolayer as suggested elsewhere [6].…”

The role of oxygen incorporation in Ni (111) substrates on the growth of hexagonal boron nitride monolayers

“…The specific capacitance of these capacitors of different sizes are summarized in figure 8(i) with great distribution consistency. The smaller measured average specific capacitance of 0.008 m -pF m 2 than theoretical geometric capacitance of 0.087 m -pF m 2 is attributed to series capacitances from geometric capacitance (C g ) and vacuum capacitance (C v ), which is due to extra geometric distance between two electrodes from van der Waals interaction of the interface between the h-BN and metal electrodes [72], and vacuum layer from surface corrugation and reconstruction [5,[73][74][75][76][77], respectively.…”

“…is attributed to the built-in voltage at equilibrium across the h-BN, which is in good agreement with the theoretical values. High breakdown electric field is calculated to be ∼11.2 MV cm −1 based on 0.74 V breakdown voltage and atomic distance between two metal electrodes separated by h-BN monolayer [5]. Figure 8(g) shows the temperature-dependent forward breakdown characteristics in the 100 × 100 mm 2 devices with a compliance current of 100 mA from room temperature (25 °C) to 200 °C.…”

“…Cheng et al demonstrated the plasma-assisted MBE growth of mono-and few-layer h-BN on highly orientated pyrolytic graphite (HOPG) substrates at high temperatures ∼ 1390 °C [38]. Our previous effort also led to the synthesis of a largearea single-crystal h-BN monolayer on an annealed singlecrystal Ni (111) substrate [5]. However, these successful growths of h-BN relied on the preparation of perfect highpurity single-crystal metal substrates, which are rather complicated and expensive.…”

“…Atomically thin hexagonal boron nitride (h-BN) has drawn tremendous attention for next-generation electronics owing to its excellent properties, wide bandgap (∼5.9 eV) [1], high electric breakdown strength (∼12 MV cm −1 ), high thermal conductivity (∼600 Wm −1 K −1 ), excellent thermal/chemical stability, and a surface free of dangling bonds [2][3][4]. Due to these remarkable properties, h-BN has been adopted perfectly as an insulating layer in capacitors [5,6], transistors [7][8][9][10][11] an active layer for resistive switching memristors [12][13][14][15][16], single-photon emitters [17][18][19], and ultra-flat anti-scattering substrate and encapsulation layer [20][21][22][23][24] for van der Waals materials nanodevices. All of these applications propose strict requirements on h-BN quality and demand for large-scale reliable and controllable synthesis methodologies to achieve high quality 2D h-BN films [25].…”