scholarly journals Электронная структура наноинтерфейса Cs/n-GaN(0001)

2018 ◽  
Vol 44 (6) ◽  
pp. 50
Author(s):  
Г.В. Бенеманская ◽  
М.Н. Лапушкин ◽  
Д.Е. Марченко ◽  
С.Н. Тимошнев
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Surface States ◽  
Valence Band Maximum ◽  
Surface Electron ◽  
Electron States ◽  
Band Maximum ◽  
Metallic Character ◽  
First Time

AbstractElectronic structures of the n -GaN(0001) surface and Cs/ n -GaN(0001) interface with submonolayer Cs coverages were studied for the first time in situ by the photoelectron spectroscopy (PES) method. The spectra of photoemission from the valence band, surface electron states, and core levels (Ga 3 d , Cs 4 d , Cs 5 p ) under synchrotron excitation were measured in a range of photon energies within 50–150 eV. Evolution of the spectrum of surface states near the valence-band maximum was revealed by PES during the adsorption of Cs atoms. A metallic character of the Cs/ n -GaN(0001) nano-interface is demonstrated.

Compositionally Dependent Band Offsets In Aln/AlxGa1-xN Heterojunctions Measured By Using X-Ray Photoelectron Spectroscopy

1997 ◽  
Vol 482 ◽  
Author(s):  
R.A. Beach ◽  
E.C. Piquette ◽  
R.W. Grant ◽  
T.C. McGill
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Valence Band Maximum ◽  
Core Level ◽  
Band Offset ◽  
Valence Band Offset ◽  
Band Offsets ◽  
Band Maximum ◽  
X Ray ◽  
Al Content

AbstractAlthough GaN has been extensively studied for applications in both light emitting and high power devices, the AlN/GaN valence band offset remains an area of contention. Values quoted in the literature range from 0.8eV (Martin)[1] to 1.36eV (Waldrop)[2]. This paper details an investigation of the AIN/AlxGa1-xN band offset as a function of alloy composition. We find an AlN/AlxGa1-xN valence band offset that is nearly linear with Al content and an end point offset for AlN/GaN of 1.36 ± 0.1 eV. Samples were grown using radio frequency plasma assisted molecular beam epitaxy and characterized with x-ray photoelectron spectroscopy(XPS). Core-level and valence-band XPS data for AIN (0001) and AlxGa1-xN (0001) samples were analyzed to determine core-level to valence band maximum (VBM) energy differences. In addition, oxygen contamination effects were tracked in an effort to improve accuracy. Energy separations of core levels were obtained from AlN/AlxGa1-xN(0001) heterojunctions. From this and the core-level to valence band maximum separations of the bulk materials, valence band offsets were calculated.

scholarly journals XPS Study of Oxygen Adsorption on (3×3) Reconstructed MBE Grown Gan Surfaces

1999 ◽  
Vol 4 (S1) ◽  
pp. 648-652 ◽  
Author(s):  
R. A. Beach ◽  
E. C. Piquette ◽  
T. C. McGill ◽  
T. J. Watson
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Oxygen Adsorption ◽  
Valence Band Maximum ◽  
Core Level ◽  
Energy Separation ◽  
Metallic Component ◽  
Band Maximum ◽  
Bulk Gan ◽  
Reconstructed Surface

The incorporation of oxygen onto the (3×3) reconstructed surface of GaN(0001) has been studied using X-ray Photoelectron Spectroscopy (XPS). It was found that the (3×3) reconstruction corresponds to a fractional Ga adlayer atop a Ga terminated GaN surface. Our measurements indicate a surface coverage of 1.15 ± 0.2 monolayers of relaxed Ga on the surface. The binding energy separation between the relaxed surface Ga3d core level and bulk Ga3d level was measured to be 1.1 ± 0.1 eV. A metallic component extending from the bulk GaN valence band maximum out to 0 eV was also present in the XPS spectrum. The separation between the bulk valence band maximum and the Fermi level of the metallic component was found to be 2.1 ± 0.1 eV. The relaxation of the surface Ga was found to decrease with oxygen exposure indicating Ga-O bonding, with oxygen adsorption terminating at 1.3 ± 0.2 monolayers. The O1s core level was found to have a FWHM of 2.0 ± 0.1 eV.

scholarly journals Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy: Variation with Photon Energy

2017 ◽  
Vol 121 (48) ◽  
pp. 26655-26666 ◽  
Author(s):  
Bertrand Philippe ◽  
T. Jesper Jacobsson ◽  
Juan-Pablo Correa-Baena ◽  
Naresh K. Jena ◽  
Amitava Banerjee ◽  
...  
Keyword(s):  
Valence Band ◽  
Photon Energy ◽  
Photoelectron Spectroscopy ◽  
Valence Band Maximum ◽  
Band Maximum ◽  
Perovskite Material ◽  
Valence Level

scholarly journals Influence of Graphite Layer on Electronic Properties of MgO/6H-SiC(0001) Interface

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4189
Author(s):  
R. Lewandków ◽  
P. Mazur ◽  
A. Trembułowicz ◽  
A. Sabik ◽  
R. Wasielewski ◽  
...  
Keyword(s):  
Energy Level ◽  
Photoelectron Spectroscopy ◽  
Valence Band Maximum ◽  
Graphite Layer ◽  
Band Maximum ◽  
X Ray ◽  
Mgo Layers ◽  
Uv Photoelectron Spectroscopy ◽  
Potential Use

This paper concerns research on magnesium oxide layers in terms of their potential use as a gate material for SiC MOSFET structures. The two basic systems of MgO/SiC(0001) and MgO/graphite/SiC(0001) were deeply investigated in situ under ultrahigh vacuum (UHV). In both cases, the MgO layers were obtained by a reactive evaporation method. Graphite layers terminating the SiC(0001) surface were formed by thermal annealing in UHV. The physicochemical properties of the deposited MgO layers and the systems formed with their participation were determined using X-ray and UV photoelectron spectroscopy (XPS, UPS). The results confirmed the formation of MgO compounds. Energy level diagrams were constructed for both systems. The valence band maximum of MgO layers was embedded deeper on the graphitized surface than on the SiC(0001).

scholarly journals Xps Study of Oxygen Adsorption on (3X3) Reconstructed MBE Grown GaN Surfaces

1998 ◽  
Vol 537 ◽  
Author(s):  
R. A. Beach ◽  
E. C. Piquette ◽  
T. C. McGill ◽  
T. J. Watson
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Oxygen Adsorption ◽  
Valence Band Maximum ◽  
Core Level ◽  
Energy Separation ◽  
Metallic Component ◽  
Band Maximum ◽  
Bulk Gan ◽  
Reconstructed Surface

AbstractThe incorporation of oxygen onto the (3x3) reconstructed surface of GaN(0001) has been studied using X-ray Photoelectron Spectroscopy (XPS). It was found that the (3x3) reconstruction corresponds to a fractional Ga adlayer atop a Ga terminated GaN surface. Our measurements indicate a surface coverage of 1.15 ± 0.2 monolayers of relaxed Ga on the surface. The binding energy separation between the relaxed surface Ga3d core level and bulk Ga3d level was measured to be 1.1 ± 0.1 eV. A metallic component extending from the bulk GaN valence band maximum out to 0 eV was also present in the XPS spectrum. The separation between the bulk valence band maximum and the Fermi level of the metallic component was found to be 2.1 ± 0. 1 eV. The relaxation of the surface Ga was found to decrease with oxygen exposure indicating Ga-O bonding, with oxygen adsorption terminating at 1.3 ± 0.2 monolayers. The Ols core level was found to have a FWHM of 2.0 ± 0.1 eV.

scholarly journals An antibonding valence band maximum enables defect-tolerant and stable GeSe photovoltaics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shun-Chang Liu ◽  
Chen-Min Dai ◽  
Yimeng Min ◽  
Yi Hou ◽  
Andrew H. Proppe ◽  
...  
Keyword(s):  
Solar Cells ◽  
Valence Band ◽  
Surface Passivation ◽  
Defect Density ◽  
Perovskite Solar Cells ◽  
Valence Band Maximum ◽  
Ambient Conditions ◽  
Band Maximum ◽  
Point Tracking ◽  
Power Point

AbstractIn lead–halide perovskites, antibonding states at the valence band maximum (VBM)—the result of Pb 6s-I 5p coupling—enable defect-tolerant properties; however, questions surrounding stability, and a reliance on lead, remain challenges for perovskite solar cells. Here, we report that binary GeSe has a perovskite-like antibonding VBM arising from Ge 4s-Se 4p coupling; and that it exhibits similarly shallow bulk defects combined with high stability. We find that the deep defect density in bulk GeSe is ~1012 cm−3. We devise therefore a surface passivation strategy, and find that the resulting GeSe solar cells achieve a certified power conversion efficiency of 5.2%, 3.7 times higher than the best previously-reported GeSe photovoltaics. Unencapsulated devices show no efficiency loss after 12 months of storage in ambient conditions; 1100 hours under maximum power point tracking; a total ultraviolet irradiation dosage of 15 kWh m−2; and 60 thermal cycles from −40 to 85 °C.

scholarly journals Synthesis of ZnO doped high valence S element and study of photogenerated charges properties

RSC Advances ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 4422-4427 ◽  
Author(s):  
Lijing Zhang ◽  
Xiufang Zhu ◽  
Zhihui Wang ◽  
Shan Yun ◽  
Tan Guo ◽  
...  
Keyword(s):  
Uniform Distribution ◽  
Valence Band ◽  
Valence Band Maximum ◽  
Band Maximum

The uniform distribution of S dopants elevated the valence band maximum by mixing S 3p with the upper valence band states of ZnO. The valence band maxima of S–ZnO was 0.37 eV higher than that of ZnO.

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