Investigation of GaAs surface treatments for ZnSe growth by molecular beam epitaxy without a buffer layer

Zhang, Chaomin; Alberi, Kirstin; Honsberg, Christiana B.; Park, Kwang-Wook

doi:10.1016/j.apsusc.2021.149245

Cited by 10 publications

(4 citation statements)

References 48 publications

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“…The 450 nm should be corresponding to the band gap of ZnSe while the 650 nm is contributed by defect energy level. 41 The curves of the composites are similar to that of CuSe except that the absorption intensity shows some as different. As the ratio of ZnSe increases, the absorption intensity decreases more or less.…”

Section: Xps and Uv−vis Drsmentioning

confidence: 65%

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High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

Chen

Zhang

Xiong

et al. 2022

ACS Appl. Energy Mater.

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ZnSe nanoparticles were loaded on {001} facets-exposed CuSe nanosheets to construct a 0D/2D ZnSe/(001)CuSe heterojunction catalyst. This ZnSe/(001)CuSe catalyst exhibits high photoelectrochemical (PEC) and hydrogen evolution reaction (HER) properties. The photocurrent of the heterojunction catalyst displays 600% enhancement, whereas in the HER the heterojunction catalyst shows a Tafel slope as low as 57 mV/dec that decreases 367% compared with CuSe. Hydroxyl has been confirmed to be the active group, which confirms the heterojunction catalyst remains the high valence band (VB) potential of ZnSe. It is considered that the exposed {001} facets of CuSe are crucial. Double heterojunctions are formed between the ZnSe/ (001)CuSe: a crystal facets heterojunction between the {101} and {001} facets of CuSe will separate the carriers in CuSe, then a semiconductor heterojunction between ZnSe and CuSe can cause a photoinduced electron flow from the conduction band (CB) of ZnSe to that of CuSe. Most importantly, the photoinduced holes in the VB of ZnSe can hardly flow into that of CuSe due to the crystal facets' heterojunction to prevent carriers' recombination in CuSe. This double heterojunctions structure can sharply reduce the internal resistance and improve the carrier separation efficiency in order to improve the PEC and HER performances.

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Section: Xps and Uv−vis Drsmentioning

confidence: 65%

“…The absorption curve of ZnSe shows two obvious steps at 450 and 650 nm. The 450 nm should be corresponding to the band gap of ZnSe while the 650 nm is contributed by defect energy level . The curves of the composites are similar to that of CuSe except that the absorption intensity shows some as different.…”

Section: Resultsmentioning

confidence: 86%

High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

Chen

Zhang

Xiong

et al. 2022

ACS Appl. Energy Mater.

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“…Mudiyanselage et al utilized in situ AES to quantitatively monitor elemental flux ratios during growth, providing valuable insight into the growth process [23] . Madisetti et al employed AES to monitor the removing traces of carbon and oxides on the surface by heating the samples to a high temperature of 850 °C for 1 h [180] . Zhang et al used AES to investigate the effect of different surface cleanliness on GaAs growth [181] .…”

Section: Other Spectroscopic Techniquesmentioning

confidence: 99%

Development of in situ characterization techniques in molecular beam epitaxy

Shen,

Zhan,

et al. 2024

J. Semicond.

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Ex situ characterization techniques in molecular beam epitaxy (MBE) have inherent limitations, such as being prone to sample contamination and unstable surfaces during sample transfer from the MBE chamber. In recent years, the need for improved accuracy and reliability in measurement has driven the increasing adoption of in situ characterization techniques. These techniques, such as reflection high-energy electron diffraction, scanning tunneling microscopy, and X-ray photoelectron spectroscopy, allow direct observation of film growth processes in real time without exposing the sample to air, hence offering insights into the growth mechanisms of epitaxial films with controlled properties. By combining multiple in situ characterization techniques with MBE, researchers can better understand film growth processes, realizing novel materials with customized properties and extensive applications. This review aims to overview the benefits and achievements of in situ characterization techniques in MBE and their applications for material science research. In addition, through further analysis of these techniques regarding their challenges and potential solutions, particularly highlighting the assistance of machine learning to correlate in situ characterization with other material information, we hope to provide a guideline for future efforts in the development of novel monitoring and control schemes for MBE growth processes with improved material properties.

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“…[ 16 ] 3) The conduction band offset between buffer layer and absorber layer should be spike‐like Type‐II heterojunction and less than 0.4 eV. [ 22–24 ] The currently developed alternative binary buffer layer materials, such as ZnO, [ 17 ] ZnS, [ 18 ] ZnSe, [ 19 ] In 2 S 3 , [ 20 ] MoS 2 , [ 21 ] and so on. These binary buffer layer materials have the characteristics of simple preparation process and flexible application structure.…”

Section: Introductionmentioning

confidence: 99%

ZnO₁₋_xS_x Solid Solution as Potential Buffer Layer Materials for Cu₂ZnSnS₄‐Based Thin Film Solar Cells: Structural and Interfacial Properties

Zhang

Jia

Zhao

et al. 2022

Adv Materials Inter

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>10 5 cm -1 in the visible light region), [1] a proper bandgap (≈1.5 eV), [2] suitable band edge (valence band maximum: 0.8 eV; conduction band minimum: −0.7 eV, vs NHE), [3] adjustability of structure and properties, [4] and so on. In the past decade, CZTS-based TFSCs have made significant advances in laboratory research. [5] Recently, the certified record conversion efficiency of CZTS-and CZTSSe-based TFSCs have reached 11.0% and 13.0%, respectively. [6] However, these conversion efficiencies are far lower than its theoretical conversion efficiency limit (32.2%). [7] The current research hotspots to improve the conversion efficiency mainly focus on the following two directions: one is the modification of CZTS absorbing materials, and the other is the optimization of device structure of CZTS-based TFSCs. [4] CZTS-based solar cells suffer from low open-circuit voltage (V oc ). The following several factors lead to the low V oc : secondary phases inside the absorber layer and on its boundaries, bandgap fluctuations caused by structural or compositional in-homogeneities, electrostatic potential fluctuations caused by charged defects, and recombination of photogenerated electron-hole pairs via interface states. [8] Compared with other influencing factors, the carrier recombination via interface states is relatively easy to be eliminated through interface engineering. [9] The schematic diagram for device structure of CZTS-based solar cells is shown in Figure 1. The top is window layer containing Al-doped ZnO and intrinsic ZnO (i-ZnO), followed by buffer layer, CZTS absorber layer, Mo back contact and substrate. Among them, the buffer layer plays an important role. The buffer layer is a transition layer between CZTS absorption layer with narrow bandgap and ZnO window layer with wide bandgap. It reduces the bandgap misalignment and lattice mismatch between these two layers, and can prevent the damage to CZTS absorption layer when sputtering ZnO window layer in the process of device fabrication. Furthermore, the buffer layer is also the determinant of the separation and transfer behavior of photogenerated carriers. Therefore, the buffer layer plays an important role in improving the performance of CZTS-based TFSCs. [10] In general, there is a certain potential barrier between the CZTS absorption layer and the carrier transfer layer, which hinders the further improvement of the The current low conversion efficiency of Cu 2 ZnSnS 4 (CZTS)-based thin film solar cells is mainly blamed on the high carrier recombination via interface states at the absorber-buffer. In this work, ZnO 1−x S x solid solution is exploited as the potential buffer layer materials to solve this issue by using density functional theory calculations. With the varying of solid solubility, the lattice constant of ZnO 1−x S x solid solution follows the first-order Vegard's Law, while its bandgap follows the second-order Vegard's Law. Based on the systematical analysis of crystal structure and electronic properties of ZnO 1−x S x solid solution, ZnO 0.375...

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Investigation of GaAs surface treatments for ZnSe growth by molecular beam epitaxy without a buffer layer

Cited by 10 publications

References 48 publications

High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

Development of in situ characterization techniques in molecular beam epitaxy

ZnO₁₋_xS_x Solid Solution as Potential Buffer Layer Materials for Cu₂ZnSnS₄‐Based Thin Film Solar Cells: Structural and Interfacial Properties

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Investigation of GaAs surface treatments for ZnSe growth by molecular beam epitaxy without a buffer layer

Cited by 10 publications

References 48 publications

High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

High Photo-electrochemical and Hydrogen Evolution Reaction Activities from 0D/2D ZnSe/(001)CuSe Heterojunction Catalysts Constructed by ZnSe Nanoparticles and {001} Facets-Exposed CuSe Nanosheets

Development of in situ characterization techniques in molecular beam epitaxy

ZnO1−xSx Solid Solution as Potential Buffer Layer Materials for Cu2ZnSnS4‐Based Thin Film Solar Cells: Structural and Interfacial Properties

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ZnO₁₋_xS_x Solid Solution as Potential Buffer Layer Materials for Cu₂ZnSnS₄‐Based Thin Film Solar Cells: Structural and Interfacial Properties