Spontaneous Seed Formation during Electrodeposition Drives Epitaxial Growth of Metastable Bismuth Selenide Microcrystals

Abstract

Materials with metastable phases can exhibit vastly different properties from their thermodynamically favored counterparts. Methods to synthesize metastable phases without the need for high-temperature or high-pressure conditions would facilitate their widespread use. We report on the electrochemical growth of microcrystals of bismuth selenide, Bi2Se3, in the metastable orthorhombic phase at room temperature in aqueous solution. Rather than direct epitaxy with the growth substrate, the spontaneous formation of a seed layer containing nanocrystals of cubic BiSe enforces the metastable phase. We first used single-crystal silicon substrates with a range of resistivities and different orientations to identify the conditions needed to produce the metastable phase. When the applied potential during electrochemical growth is positive of the reduction potential of Bi3+, an initial, Bi-rich seed layer forms. Electron microscopy imaging and diffraction reveal that the seed layer consists of nanocrystals of cubic BiSe embedded within an amorphous matrix of Bi and Se. Using density functional theory calculations, we show that epitaxial matching between cubic BiSe and orthorhombic Bi2Se3 can help stabilize the metastable orthorhombic phase over the thermodynamically stable rhombohedral phase. The spontaneous formation of the seed layer enables us to grow orthorhombic Bi2Se3 on a variety of substrates including single-crystal silicon with different orientations, polycrystalline fluorine-doped tin oxide, and polycrystalline gold. The ability to stabilize the metastable phase through room-temperature electrodeposition in aqueous solution without requiring a single-crystal substrate broadens the range of applications for this semiconductor in optoelectronic and electrochemical devices.

Metastable Metal–Alloy Interface in RuNi Nanoplates Boosts Highly Efficient Hydrogen Electrocatalysis

“…Normally, Ni nanocrystals can crystallize in two lattice forms: the metastable phase and the stable phase. Metastable materials enable substantial improvements for different catalytic reactions due to its high Gibbs energy, unique atom ordering, and surface environment. − However, the native thermodynamics instability property of the metastable structure makes the construction of metastable interfaces fraught with difficulties. , Designing a unique interface provides an effective and powerful strategy to tackle this challenge, where the different components in interfacial structure may show the synergistic effect on improving the activity and stability. ,, However, constructing the stabilized interface between two metastable structures remains a great challenge.…”

Enhanced Electrical, Thermal, and Mechanical Properties of SnTe through Equimolar Multication Alloying for Suitable Device Applications

“…48,49 Bi 4f 5/2 (163.0 eV) and 4f 7/2 (157.7 eV) main peaks with a SOS of 5.3 eV are assigned to the Bi 3+ oxidation state, whereas the shoulders at higher binding energies (164.5, 159.2 eV) are labeled as Bi (3+x)+ as previously reported to arise from binding with residual oxygen. 50 Cu 2p 1/2 (952.8 eV) and 2p 3/2 (933.0 eV) spectra with a separation of 19.8 eV show good agreement with the Cu + state. 51 Finally, In 3d 3/2 (452.5 eV) and 3d 5/2 (444.9 eV) peaks with a separation of 7.6 eV are consistent with the In 3+ state.…”

“…Sn 3d 3/2 and 3d 5/2 peaks at a binding energy of 495.2 and 486.7 eV, respectively, and a separation of 8.5 eV can be assigned to the Sn 2+ state . The Te 3d 3/2 (583.2 eV) and 3d 5/2 (572.8 eV) doublets with an SOS of 10.4 eV can be assigned to the Te 2– state and at higher binding energies of the Te 3d spectrum; the minor peaks (586.9, 576.4 eV) are assigned to the Te 4+ state from the TeO 2 surface oxides. , Bi 4f 5/2 (163.0 eV) and 4f 7/2 (157.7 eV) main peaks with a SOS of 5.3 eV are assigned to the Bi 3+ oxidation state, whereas the shoulders at higher binding energies (164.5, 159.2 eV) are labeled as Bi (3+ x )+ as previously reported to arise from binding with residual oxygen . Cu 2p 1/2 (952.8 eV) and 2p 3/2 (933.0 eV) spectra with a separation of 19.8 eV show good agreement with the Cu + state .…”

Fundamental Understanding on Selenium Electrochemistry: From Electrolytic Cell to Advanced Energy Storage

“…b) SEM images of Bi 2 Se 3 films grown on Si (111) electrodes at a potential of À0.45 V versus Ag/AgCl for different charge densities. Reproduced with permission from Luo et al [67] Copyright 2022, American Chemical Society.…”

“…Recently, the morphological evolution of Bi 2 Se 3 films with the orthorhombic phase was investigated at a potential of −0.45 V versus Ag/AgCl when applying different charge densities, as presented in Figure 7b. [ 67 ] With the increase of total charge densities, the elemental Se:Bi ratio delivered an increasing trend from 1.3 to 1.8. Meanwhile, the electrodeposited Bi 2 Se 3 films exhibited a layer of sub‐micrometer‐sized hemispherical seeds for a charge density of 0.3 C cm −2 .…”