Controlled Vapor–Solid Deposition of Millimeter‐Size Single Crystal 2D Bi₂O₂Se for High‐Performance Phototransistors

Abstract

Atomically thin 2D materials have received intense interest both scientifically and technologically. Bismuth oxyselenide (Bi 2 O 2 Se) is a semiconducting 2D material with high electron mobility and good stability, making it promising for high-performance electronics and optoelectronics. Here, an ambient-pressure vapor-solid (VS) deposition approach for the growth of millimeter-size 2D Bi 2 O 2 Se single crystal domains with thicknesses down to one monolayer is reported. The VS-grown 2D Bi 2 O 2 Se has good crystalline quality, chemical uniformity, and stoichiometry. Field-effect transistors (FETs) are fabricated using this material and they show a small contact resistivity of 55.2 Ω cm measured by a transfer line method. Upon light irradiation, a phototransistor based on the Bi 2 O 2 Se FETs exhibits a maximum responsivity of 22 100 AW −1 , which is a record among currently reported 2D semiconductors and approximately two orders of magnitude higher than monolayer MoS 2 . The Bi 2 O 2 Se phototransistor shows a gate tunable photodetectivity up to 3.4 × 10 15 Jones and an on/off ratio up to ≈10 9 , both of which are much higher than phototransistors based on other 2D materials reported so far. The results of this study indicate a method to grow large 2D Bi 2 O 2 Se single crystals that have great potential for use in optoelectronic applications.

High‐Fidelity Transfer of 2D Bi2O2Se and Its Mechanical Properties

“…Few-layer and single-crystalline Bi 2 O 2 Se flakes on mica substrate were synthesized with vapor-solid (VS) deposition following our previous work (please see the Experimental Section for details). [8] Transfer of Bi 2 O 2 Se flakes is essential for subsequent measurements of physical properties and further applications. The schematic illustration of the proposed PDMS-mediated and the previous established PMMA-assisted transfer [8,29] processes are shown in Figure 1.…”

“…[1][2][3] Bismuth oxyselenide (Bi 2 O 2 Se), a semiconducting 2D material featured by narrow bandgap (≈0.8 eV), high electronic mobility (20 000 cm 2 V −1 s −1 at 2 K), and good air stability, shows great potential for applications in high-performance electronics, optoelectronics, and flexible devices. [4][5][6][7][8][9][10] For example, the photodetectors based on Bi 2 O 2 Se with ultrabroadband responses, [7] high on/off ratio, and ultrahigh photodetectivity [8] have been demonstrated. Bi 2 O 2 Se is also an important material to fabricate three-terminal memristors with high speed and low energy consumption for neuromorphic functions.…”

Molecular Beam Epitaxy and Electronic Structure of Atomically Thin Oxyselenide Films

“…Oxychalcogenides, which can be regarded as mixing and bridging chalcogenides and oxides together, reactivate their research booms for the remarkable phenomena such as high carrier mobility, [9] thermoelectricity, [10][11][12] ferroelectricity, [13] and superconductivity. [2,9,13,[15][16][17][18][19][20][21][22][23] For example, the bulk Bi 2 O 2 Se crystals show an ultrahigh Hall mobility of ≈280 000 cm 2 V −1 s −1 at low temperature [9] and robust bandgap (immune to Se vacancies) after cleavage. [2,9,13,[15][16][17][18][19][20][21][22][23] For example, the bulk Bi 2 O 2 Se crystals show an ultrahigh Hall mobility of ≈280 000 cm 2 V −1 s −1 at low temperature [9] and robust bandgap (immune to Se vacancies) after cleavage.…”

“…[14] Bi 2 O 2 Se, a representative of oxychalcogenides family, emerged as an air-stable highmobility layered semiconductor, which holds promise for next-generation digital devices and optoelectronics. [17] Nanoplates and thin films of Bi 2 O 2 Se were successfully prepared by chemical vapor deposition (CVD), [9,15,21,23] displaying excellent switching behavior of I on /I off and high Hall mobility (up to 450 cm 2 V −1 s −1 ) at room temperature. [17] Nanoplates and thin films of Bi 2 O 2 Se were successfully prepared by chemical vapor deposition (CVD), [9,15,21,23] displaying excellent switching behavior of I on /I off and high Hall mobility (up to 450 cm 2 V −1 s −1 ) at room temperature.…”

“…[2,9,13,[15][16][17][18][19][20][21][22][23] For example, the bulk Bi 2 O 2 Se crystals show an ultrahigh Hall mobility of ≈280 000 cm 2 V −1 s −1 at low temperature [9] and robust bandgap (immune to Se vacancies) after cleavage. [16,18,[23][24][25] The present research is mainly focused on the bulk crystals and few-layer or multiplayer samples due to the challenge to faithfully achieve the growth of atomically thin Bi 2 O 2 Se films. Outstanding optoelectronic properties were recently observed in CVD-grown Bi 2 O 2 Se nanoplates.…”