CdS and Cd-Free Buffer Layers on Solution Phase Grown Cu2ZnSn(SxSe1- x)4 :Band Alignments and Electronic Structure Determined with Femtosecond Ultraviolet Photoelectron Spectroscopy

2014 ◽  
Vol 1638 ◽  
Author(s):  
Richard Haight ◽  
Aaron Barkhouse ◽  
Wei Wang ◽  
Yu Luo ◽  
Xiaoyan Shao ◽  
...  
Keyword(s):  
Fermi Level ◽  
Photoelectron Spectroscopy ◽  
Solution Phase ◽  
Buffer Layers ◽  
Photoemission Spectroscopy ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Band Bending ◽  
Pump Probe ◽  
Fermi Level Pinning ◽  
Band Alignments

ABSTRACTThe heterojunctions formed between solution phase grown Cu2ZnSn(SxSe1- x)4 (CZTS,Se) and a number of important buffer materials including CdS, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission spectroscopy (fs-UPS) and photovoltage spectroscopy. With this approach we extract the magnitude and direction of the CZTS,Se band bending, locate the Fermi level within the band gaps of absorber and buffer and measure the absorber/buffer band offsets under flatband conditions. We will also discuss two-color pump/probe experiments in which the band bending in the buffer layer can be independently determined. Finally, studies of the bare CZTS,Se surface will be discussed including our observation of mid-gap Fermi level pinning and its relation to Voc limitations and bulk defects.

Built-in Potential of a Pentacene Pin Homojunction Studied by Ultraviolet Photoemission Spectroscopy

2010 ◽  
Vol 1270 ◽  
Author(s):  
Selina Olthof ◽  
Hans Kleemann ◽  
Björn Lüssem ◽  
Karl Leo
Keyword(s):  
Small Molecules ◽  
Work Function ◽  
Photoelectron Spectroscopy ◽  
Photoemission Spectroscopy ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Organic P ◽  
Band Bending ◽  
Silver Substrate ◽  
N Doping ◽  
Ultraviolet Photoemission Spectroscopy

AbstractIn this paper we investigate the energetic alignment in an organic p-i-n homojunction using ultraviolet photoelectron spectroscopy. The device is made of pentacene and we emploay the small molecules NDN1 for n-doping and NDP2 for p-doping the layers. The full p-i-n structure is deposited stepwise on a silver substrate to learn about the interface dipoles and band bending effects present in the device. From the change in work function between the p- and n-doped layers we gain knowledge of the built-in potential of this junction.

Fermi level pinning and band bending in δ-doped BaSnO3

2021 ◽  
Vol 118 (5) ◽  
pp. 052101
Author(s):  
Youjung Kim ◽  
Hyeongmin Cho ◽  
Kookrin Char
Keyword(s):  
Fermi Level ◽  
Band Bending ◽  
Fermi Level Pinning

SHG(Second Harmonic Generation) in Reflection from GaAs Surfaces during Sulfur Passivation and Photochemical Washing Processes

1992 ◽  
Vol 259 ◽  
Author(s):  
Chikashi Yamada ◽  
Takahiro Kimura ◽  
Peter Fuqua
Keyword(s):  
Second Harmonic Generation ◽  
Fermi Level ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Band Bending ◽  
Remarkable Similarity ◽  
Fermi Level Pinning ◽  
Sulfur Passivation ◽  
Intensity Changes ◽  
Pl Intensity

ABSTRACTA passivation processes using Na2S and photochemical washing of GaAs (100) surfaces was studied in real time by a second-harmonic generation (SHG) technique. The intensities of surface-specific SHG signals were compared with those of photoluminescence (PL) signals. We found a remarkable similarity between the SHG and PL intensity changes during these processes. A band-bending model due to Fermi-level pinning at the surface has been applied in order to account for both the SHG and the PL intensity changes.

Electronic Properties of Chemically Etched CdTe Thin Films: Role of Te for Back-Contact Formation

2001 ◽  
Vol 668 ◽  
Author(s):  
D. Kraft ◽  
A. Thiβen ◽  
M. Campo ◽  
M. Beerbom ◽  
T. Mayer ◽  
...  
Keyword(s):  
Fermi Level ◽  
Electronic Properties ◽  
Photoelectron Spectroscopy ◽  
Valence Band Maximum ◽  
Ex Situ ◽  
Back Contact ◽  
Experimental Conditions ◽  
Band Bending ◽  
Fermi Level Position ◽  
Contact Formation

ABSTRACTImprovement of electric back contact formation is one of the major issues of the CdTe thin film solar cell research. Chemical etching of CdTe before metallization is accepted to improve contact formation. It is believed that a CdTe/Te contact is formed by this procedure leading to a Fermi level position in the CdTe close to the valence band maximum for low contact resistance. We have studied the electronic properties of chemically etched CdTe surfaces with photoelectron spectroscopy. Etching of the samples was performed in air (“ex-situ“) as well as in an electrochemical setup directly attached to the UHV system (“in-situ“). The formation of a Te layer is clearly shown by (S)XPS. In contrast to previous studies we could not detect the formation of a p-CdTe surface for different experimental conditions. The detected Fermi level position indicates still band bending and hence a blocking Schottky barrier.

Controlled Surface Fermi-level on the SeS2-passivated n-GaAs (100)

1998 ◽  
Vol 510 ◽  
Author(s):  
Jing xi Sun ◽  
F. J. Himpsel ◽  
T. F. Kuech
Keyword(s):  
Fermi Level ◽  
Photoemission Spectroscopy ◽  
Ambient Conditions ◽  
Surface Band ◽  
Band Bending ◽  
Term Stability ◽  
Long Term Stability ◽  
Synchrotron Radiation Photoemission ◽  
Surface Fermi Level

AbstractSelenium disulfide surface treatment can unpin the surface Fermi-level on n-GaAs (100) surfaces, resulting in a reduction in the surface band bending. The long-term stability of the surface Fermi-level unpinning has been studied using photoreflectance spectroscopy under room ambient conditions. Our results show that the SeS2-treated n-GaAs (100) surface is stable up to four months with negligible shift in the surface Fermi-level being noted. The mechanism of the long-term stability is attributed to the layered surface structure formed on the SeS2-treated n- GaAs (100) surface. The chemical structure of the passivated surface was determined by synchrotron radiation photoemission spectroscopy. The outermost layer of sulfur and arsenicbased sulfides and selenides may protect the electronic passivating layer, which consists of gallium-based selenides, from interaction with the atmosphere.

scholarly journals Инфракрасное фотоотражение полупроводниковых материалов A-=SUP=-3-=/SUP=-B-=SUP=-5-=/SUP=- ( О б з о р )

2021 ◽  
Vol 63 (8) ◽  
pp. 991
Author(s):  
О.С. Комков
Keyword(s):  
Fermi Level ◽  
Decisive Role ◽  
Infrared Range ◽  
Orbit Splitting ◽  
Band Bending ◽  
Fermi Level Pinning ◽  
Surface And Interface ◽  
Spin Orbit Splitting ◽  
Wide Wavelength Range ◽  
Excitonic Effects

Photoreflectance is a contactless type of modulation optical spectroscopy. It is used to study the band structure features of monocrystalline semiconductors, their doping level, the composition of alloys, as well as surface and interface band bending. Using high-quality GaAs as an example, the possibilities of describing the photoreflectance lineshape by one-electron and exciton models are demonstrated. The spectra of ultrapure samples of this material exhibit an oscillating structure well described by excitonic effects. For III-V alloys, a review of photoreflectance results concerning the effect of composition and temperature on the band gap and spin-orbit splitting is carried out. Determination of the position of the Fermi level on the surface (Fermi level pinning) for III-V crystals is considered. The currently developing technique for measuring photoreflectance in the mid-infrared range (photomodulation Fourier transform infrared spectroscopy) is described in detail. It is shown that phase correction plays a decisive role in such measurements. Original results demonstrate the capabilities of this method in a wide wavelength range.

Band bending, Fermi level pinning, and surface fixed charge on chemically prepared GaAs surfaces

1989 ◽  
Vol 54 (6) ◽  
pp. 555-557 ◽  
Author(s):  
E. Yablonovitch ◽  
B. J. Skromme ◽  
R. Bhat ◽  
J. P. Harbison ◽  
T. J. Gmitter
Keyword(s):  
Fermi Level ◽  
Fixed Charge ◽  
Band Bending ◽  
Fermi Level Pinning
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