Molecular Beam Epitaxy and Electronic Structure of Atomically Thin Oxyselenide Films

Abstract

over decades. 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. [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. [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. [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. Outstanding optoelectronic properties were recently observed in CVD-grown Bi 2 O 2 Se nanoplates. [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. The atomically thin counterpart down to one-unit-cell (1-UC) Atomically thin oxychalcogenides have been attracting intensive attention for their fascinating fundamental properties and application prospects. Bi 2 O 2 Se, a representative of layered oxychalcogenides, has emerged as an air-stable high-mobility 2D semiconductor that holds great promise for next-generation electronics. The preparation and device fabrication of high-quality Bi 2 O 2 Se crystals down to a few atomic layers remains a great challenge at present. Here, molecular beam epitaxy (MBE) of atomically thin Bi 2 O 2 Se films down to monolayer on SrTiO 3 (001) substrate is achieved by co-evaporating Bi andSe precursors in oxygen atmosphere. The interfacial atomic arrangements of MBE-grown Bi 2 O 2 Se/SrTiO 3 are unambiguously revealed, showing an atomically sharp interface and atom-to-atom alignment. Importantly, the electronic band structures of one-unit-cell (1-UC) thick Bi 2 O 2 Se films are observed by angle-resolved photoemission spectroscopy (ARPES), showing low effective mass of ≈0.15 m 0 and bandgap of ≈0.8 eV. These results may be constructive to the synthesis of other 2D oxychalcogenides and investigation of novel physical properties. Ultrathin FilmsThanks to their rich physics and fascinating application prospects, atomically thin metal oxides/chalcogenides (sulfide, selenide, or telluride) and their heterostructures, such as transition metal dichalcogenides (TMDs), [1,2] superconducting β-phase FeSe, [3,4] topological insulator (Bi 2 Se 3 , Bi 2 Te 3 ), [5,6] and LaAlO 3 /SrTiO 3 , [7,8] have been attracting tremendous interest

Progress Report on Property, Preparation, and Application of Bi2O2Se

“…Peng et al obtained thin films of Bi 2 O 2 Se on SrTiO 3 via MBE, through co‐evaporating Bi and Se precursors in oxygen atmosphere at 290 °C. [ 55 ] Terrace‐like Bi 2 O 2 Se films can be obtained on a TiO 2 ‐terminated SrTiO 3 surface (as shown in Figure a–d), and precise control over thickness from single layer to twenty layers is achievable through controlling the growth time. Jiang et al used PLD to realize the parallel growth of Bi 2 O 2 Se films on SrTiO 3 substrates, the film thickness is also adjustable through the growth time.…”

“…In this section, we summarize the typical applications of Bi 2 O 2 Se nanocrystals, including its 2D structures, polycrystalline powders, and quantum dots. [55] Copyright 2019, Wiley-VCH. e) Schematic diagram for CVT preparation of Bi 2 O 2 Se nanosheets on mica, f) an optical image of the obtained Bi 2 O 2 Se nanosheets via CVT, showing a lateral size of ≈300 nm, and g) a typical optical image of a millimeter-sized Bi 2 O 2 Se nanosheet.…”

Self‐Driven WSe2/Bi2O2Se Van der Waals Heterostructure Photodetectors with High Light On/Off Ratio and Fast Response

“…has gained wide interest due to its excellent electron mobility and good ambient stability. [ 16,17 ] Tremendous progress has been achieved in the structural analysis, [ 17–19 ] controlled synthesis, [ 20–23 ] precision etching, [ 24 ] noncorrosive transfer, [ 23,25 ] and large area growth [ 26,27 ] of 2D Bi 2 O 2 Se, which paved the way for advanced electronics and optoelectronics device applications. [ 28–31 ] The 2D Bi 2 O 2 Se exhibits an ultra‐high mobility (≈20 000 cm 2 V −1 s −1 ) comparable to graphene and proper band gap of 0.8 eV, it is thus worth exploring its merits in high‐performance photodetection applications.…”

Exploiting Two‐Dimensional Bi2O2Se for Trace Oxygen Detection

“…Bi 2 O 2 Se, [5] an emerging layered semiconductor formed by alternated layers of [Se] n 2nÀ and [Bi 2 O 2 ] n 2n+ with high carrier mobility at room temperature and moderate band gap of about 0.8 eV,o ffers ap ossibility to be fabricated into in an ultra-sensitive resistance-type sensor with ah igh signal-tonoise ratio. [1c,e,5a, 6] Moreover,w afer-scale growth of 2D Bi 2 O 2 Se single crystals is recently achieved by chemical vapor deposition (CVD) and molecular beam epitaxy,f acilitating further integration of 2D Bi 2 O 2 Se sensors by utilizing Si integration technology.…”