A 2D Bismuth-Induced Honeycomb Surface Structure on GaAs(111)

Abstract

Two-dimensional (2D) topological insulators have fascinating physical properties which are promising for applications within spintronics. In order to realize spintronic devices working at room temperature, materials with a large nontrivial gap are needed. Bismuthene, a 2D layer of Bi atoms in a honeycomb structure, has recently attracted strong attention because of its record-large nontrivial gap, which is due to the strong spin−orbit coupling of Bi and the unusually strong interaction of the Bi atoms with the surface atoms of the substrate underneath. It would be a significant step forward to be able to form 2D materials with properties such as bismuthene on semiconductors such as GaAs, which has a band gap size relevant for electronics and a direct band gap for optical applications. Here, we present the successful formation of a 2D Bi honeycomb structure on GaAs, which fulfills these conditions. Bi atoms have been incorporated into a clean GaAs(111) surface, with As termination, based on Bi deposition under optimized growth conditions. Low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/S) demonstrates a well-ordered large-scale honeycomb structure, consisting of Bi atoms in a √3 × √3 30°reconstruction on GaAs(111). X-ray photoelectron spectroscopy shows that the Bi atoms of the honeycomb structure only bond to the underlying As atoms. This is supported by calculations based on density functional theory that confirm the honeycomb structure with a large Bi−As binding energy and predict Biinduced electronic bands within the GaAs band gap that open up a gap of nontrivial topological nature. STS results support the existence of Bi-induced states within the GaAs band gap. The GaAs:Bi honeycomb layer found here has a similar structure as previously published bismuthene on SiC or on Ag, though with a significantly larger lattice constant and only weak Bi−Bi bonding. It can therefore be considered as an extreme case of bismuthene, which is fundamentally interesting. Furthermore, it has the same exciting electronic properties, opening a large nontrivial gap, which is the requirement for room-temperature spintronic applications, and it is directly integrated in GaAs, a direct band gap semiconductor with a large range of (opto)electronic devices.

Electric Control of Helicity-Dependent Photocurrent and Surface Polarity Detection on Two-Dimensional Bi2O2Se Nanosheets

“…Here φ is the angle between the polarization direction of the incident light and the optical axis of the quarter wave plate. The total photocurrent J x can be generally expressed by the phenomenological formula (1) which is demonstrated to be useful in studying semiconductor quantum wells, transition-metal dichalcogenides (TMDCs), and topological insulators by the previous reports. 23 −29 Here, the coefficient C that parametrizes HDPC with the functional form sin 2φ is generated through a spin-dependent process, i.e., CPGE and CPDE.…”

“…Controlling and manipulating electron spins in nonmagnetic semiconductor materials with a strong spin orbit interaction (SOI) have received intense interest in the field of spintronics. − Bismuth oxyselenide (Bi 2 O 2 Se) is a two-dimensional (2D) layered semiconductor material with high electron Hall mobility and good environmental stability, which exhibits excellent electron transport and optical properties for photoelectric applications. − Recently, the existence of strong SOI has been experimentally demonstrated in Bi 2 O 2 Se nanosheets, which inaugurates the possibility of Bi 2 O 2 Se for application in spintronics and quantum devices. , Previous research has established that Bi 2 O 2 Se is composed of Bi–O 2 –Bi trilayers with positively charged and Se atomic layers with a compensating negative charge, which may lead to the metallic Rashba-split surface states on the polar surfaces. − These surface states stem from huge potential bending, positive or negative, depending on surface polarity, and reside partially in the bulk band gap, leaving appropriate space for multifunctional electrical tuning. , However, so far, there is no method that can differentiate between the Bi- or Se-terminated surfaces. Since the lattice polarity is a very important issue for the study of Bi 2 O 2 Se, which will lead to different surface electronic structures, it is necessary to carry out systematic investigations to distinguish the lattice polarity of Bi 2 O 2 Se.…”

Recent advances in ecofriendly 2D monoelemental bismuthene as an emerging material for energy, catalysis and biomedical applications

“…Bismuthene has attracted attention due to its large nontrivial gap due to the strong spin orbit coupling of Bi and unusual strong interaction between Bi atoms and surface atoms of the substrate. In this case, Liu et al 100 prepared bismuthene on GaAs, which possessed a large Bi-As binding energy, and as expect bismuthene, induced an electronic band in the band gap of GaAs, opening a gap that has a nontrivial topological nature. Abdelfatah et al 101 doped the p-type dopant tetrafluoro-tetracyanoquinodimethane (F4TCNQ) in bismuthene to achieve surface charge transfer.…”

Emergence of quasi-1D spin-polarized states in ultrathin Bi films on InAs(111)A for spintronics applications

“…In contrast to silicon and germanium, III–V semiconductors are quite promising for a large number of electronic and optical applications because they have a direct band gap and high charge carrier mobility, providing great flexibility in the integration of different materials. 31–33 It was recently discovered that GaAs(111)-B facilitates the formation of a honeycomb bismuthene holding topological spin-polarised states, 34 while InAs(111)A and B substrates were found to promote the growth of Bi crystalline films of 2 ML and 12 ML thickness. 35 A Bi film of ∼30 ML thickness has been successfully grown on the InAs(111)A and B sides, forming a high-quality Bi monocrystal.…”