Inclined Ultrathin Bi₂O₂Se Films: A Building Block for Functional van der Waals Heterostructures

Abstract

As an emerging ultrathin semiconductor material, Bi2O2Se exhibits prominent performances in electronics, optoelectronics, ultrafast optics, etc. However, until now, the in-plane growth of Bi2O2Se thin films is mostly fulfilled on atomically flat mica substrates with interfacial electrostatic forces setting obstacles for Bi2O2Se transfer to fabricate functional van der Waals heterostructures. In this work, controlled growth of inclined Bi2O2Se ultrathin films is realized with apparently reduced interfacial contact areas upon mica flakes. Consequently, the transfer of Bi2O2Se could be facile by overcoming weaker electrostatic interactions. From cross-sectional characterizations at the Bi2O2Se/mica interfaces, it is found that there are no oxide buffer layers in existence for both in-plane and inclined growths, while the un-neutralized charge density is apparently decreased for inclined films. By mechanical pressing, inclined Bi2O2Se could be transferred onto SiO2/Si substrates, and back-gated Bi2O2Se field effect transistors are fabricated, outperforming previously reported in-plane Bi2O2Se devices transferred with the assistance of corrosive acids and adhesive polymers. Furthermore, Bi2O2Se/graphene heterostructures are fulfilled by a probe tip to fabricate hybrid phototransistors with pristine interfaces, exhibiting highly efficient photoresponses. The results in this work demonstrate the potential of inclined Bi2O2Se to act as a building block for prospective van der Waals heterostructures.

Bi2O2Se-Based Memristor-Aided Logic

“…To check the material phonon vibration, Bi 2 O 2 Se was probed via Raman spectra. As shown in Figure f, the characteristic A 1g phonon vibration peak was observed at 159 cm –1 via Raman spectrum probing, which is consistent with previous reports. , The grain size is approximately 35 μm, which is sufficient for its subsequent use in device fabrication. The Bi 2 O 2 Se crystal in a tetragonal phase ( I 4/ mmm , a = 3.891 Å, c = 12.21 Å, and Z = 2) is shown in Figure d.…”

High Mobility Two-Dimensional Bismuth Oxyselenide Single Crystals with Large Grain Size Grown by Reverse-Flow Chemical Vapor Deposition

“…The bare mica substrate exhibits three Raman modes at 190, 200, and 320 cm –1 owing to its layered structure nature. The Bi 2 O 2 Se nanoplates show a typical Raman A 1g mode at 159 cm –1 . ,− It is worth mentioning that the intensity of A 1g peaks monotonically increase as the thickness of the Bi 2 O 2 Se film increases, but its position remains almost unchanged, as shown in Figures a and S6. We also performed Raman mapping of the A 1g mode intensity to show the homogeneity of the as-grown Bi 2 O 2 Se flake, as shown in Figure b.…”

Recent advances in the fabrication of 2D metal oxides

“…Fifthly, 2D multi-anionic oxygenated compound materials, including single metal oxychalcogenides (e.g. Bi 2 O 2 Se) ( Hong et al., 2020 ; Wang et al., 2021a ; Wei et al., 2019 ; Wu et al., 2017 ), bication oxychalcogenides (e.g. Y 2 Ti 2 O 5 S 2 ) ( Wang et al., 2019 ), bication oxyhalides (e.g.…”