scholarly journals Structure-Dependent 4-Tert-Butyl Pyridine-Induced Band Bending at TiO2Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Mats Göthelid ◽  
Shun Yu ◽  
Sareh Ahmadi ◽  
Chenghua Sun ◽  
Marcelo Zuleta
Keyword(s):  
Fermi Level ◽  
Photoelectron Spectroscopy ◽  
Oxygen Vacancies ◽  
Conduction Band Edge ◽  
Excess Charge ◽  
Positive Role ◽  
Surface Band ◽  
Band Bending ◽  
Tert Butyl ◽  
Cell Electrolytes

The role of 4-tert butyl pyridine (4TBP) adsorption on TiO2surface band bending has been studied using photoelectron spectroscopy. Surface oxygen vacancies pin the Fermi level near the conduction band edge on rutile (110). 4TBP preferentially adsorbs in those vacancies and shift the Fermi level to lower binding energy in the band gap. This is done by transferring vacancy excess charge into the emptyπ∗orbital in the pyridine ring. The anatase (100) surface contains much less oxygen vacancies although the surface is much rougher than the rutile (110). 4TBP adsorption does not have any significant effect on the surface band bending. Thus the positive role associated with 4TBP addition to solar cell electrolytes is suggested to protection against adsorption of other electrolyte components such as Li and I.

Passivation of Gaas by Novel P2S5/(NH4)2Sx Sulfurization Techniques

1992 ◽  
Vol 281 ◽  
Author(s):  
J. T. Hsieh ◽  
C. Y. Sun ◽  
H. L. Hwang
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface Passivation ◽  
Schottky Diodes ◽  
Lower Surface ◽  
State Density ◽  
Surface Band ◽  
Band Bending ◽  
Barrier Heights ◽  
Effective Barrier ◽  
Metal Work

ABSTRACTA new surface passivation technique using P2S5/(NH4)2S on GaAs was investigated, and the results are compared with those of the (NH4)2Sx treatment. With this new surface treatment, the effective barrier heights for both Al- and Au—GaAs Schottky diodes were found to vary with the metal work functions, which is a clear evidence of the lower surface state density. Results of I—V measurements show that P2S5/(NH4)2S—passivated diodes have lower reverse leakage current and higher effective barrier height than those of the (NH4)2Sx -treated ones. Auger Electron Spectroscopy, X—ray photoelectron spectroscopy and Raman scattering measurements were done to characterize the surfaces including their compositions and surface band bending. In this paper, interpretations on this novel passivation effect is also provided.

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.

Role of Surfaces and Interfaces for the Electronic Properties of Conducting Oxides

2001 ◽  
Vol 666 ◽  
Author(s):  
Andreas Klein
Keyword(s):  
Work Function ◽  
Electronic Properties ◽  
Photoelectron Spectroscopy ◽  
Band Alignment ◽  
Surface Band ◽  
Band Bending ◽  
Conducting Oxides ◽  
Degenerate Semiconductors ◽  
Surfaces And Interfaces

ABSTRACTTransparent conductive oxides (TCOs) are generally considered as degenerate semiconductors doped intrinsically by oxygen vacancies and by intentionally added dopants. For some applications a high work function is required in addition to high conductivity and it is desired to tune both properties independently. To increase the work function, the distance between the Fermi energy and the vacuum level must increase, which can be realized either by electronic surface dipoles or by space charge layers. Photoelectron spectroscopy data of in-situ prepared samples clearly show that highly doped TCOs can show surface band bending of the order of 1 eV. It is further shown that the band alignment at heterointerfaces between TCOs and other materials, which are crucial for many devices, are also affected by such band bending. The origin of the band bending, which seems to be general to all TCOs, depends on TCO thin film and surface processing conditions. The implication of surface band bending on the electronic properties of thin films and interfaces are discussed.

scholarly journals Surface band bending in semimetal Td-WTe2

2020 ◽  
Author(s):  
Aixi Chen ◽  
Huifang Li ◽  
Rong Huang ◽  
Yanfei Zhao ◽  
Tong Liu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electric Polarization ◽  
Property A ◽  
Surface Band ◽  
Band Bending ◽  
Xps Spectra ◽  
Surface Polarization ◽  
Out Of Plane ◽  
Microscopic Origin ◽  
Ferroelectric Switching

Abstract Recently, spontaneous out-of-plane electric polarization and ferroelectric switching were found in WTe2 devices. On single crystal with ferroelectric property, a built-in electric field and corresponding band bending would be expected at the surface. However, such band bending in WTe2 hasn’t directly been observed experimentally. Here, by fitting angle-dependent X-ray photoelectron spectroscopy (XPS) spectra on WTe2 surface, we clearly observed downward band bending after slightly exposure to air, verifying appearance of surface polarization. Such band bending can’t be observed on pristine WTe2 surface and will disappear on fully oxidized sample. It suggests strong correlation between surface band bending and oxidation. Ionized donors from oxide species pinned at surface may contribute to the formation of surface band bending and polarization. Our study here offers new insight to figure out the microscopic origin of ferroelectric in WTe2.

scholarly journals H-Terminated Diamond Surface Band Bending Characterization by Angle-Resolved XPS

Surfaces ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Gonzalo Alba ◽  
David Eon ◽  
M. Pilar Villar ◽  
Rodrigo Alcántara ◽  
Gauthier Chicot ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Vapour ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Surface Band ◽  
Band Bending ◽  
New Approach ◽  
Shallow Acceptors ◽  
New Interpretation ◽  
P Type

Concerning diamond-based electronic devices, the H-terminated diamond surface is one of the most used terminations as it can be obtained directly by using H2 plasma, which also is a key step for diamond growth by chemical vapour deposition (CVD). The resultant surfaces present a p-type surface conductive layer with interest in power electronic applications. However, the mechanism for this behavior is still under discussion. Upward band bending due to surface transfer doping is the most accepted model, but has not been experimentally probed as of yet. Recently, a downward band bending very near the surface due to shallow acceptors has been proposed to coexist with surface transfer doping, explaining most of the observed phenomena. In this work, a new approach to the measurement of band bending by angle-resolved X-ray photoelectron spectroscopy (ARXPS) is proposed. Based on this new interpretation, a downward band bending of 0.67 eV extended over 0.5 nm was evidenced on a (100) H-terminated diamond surface.

Surface band-bending and Fermi-level pinning in doped Si observed by Kelvin force microscopy

2014 ◽  
Vol 104 (13) ◽  
pp. 132103 ◽  
Author(s):  
Makoto Arita ◽  
Kazuhisa Torigoe ◽  
Takashi Yamauchi ◽  
Takashi Nagaoka ◽  
Toru Aiso ◽  
...  
Keyword(s):  
Fermi Level ◽  
Surface Band ◽  
Band Bending ◽  
Force Microscopy ◽  
Fermi Level Pinning

Surface Electronic Structure of Nitric-oxide-treated Indium Tin Oxide

2003 ◽  
Vol 796 ◽  
Author(s):  
Hu Jianqiao ◽  
Pan Jisheng ◽  
Furong Zhu ◽  
Gong Hao
Keyword(s):  
Nitric Oxide ◽  
Binding Energy ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Surface Region ◽  
Valence Band Maximum ◽  
Surface Band ◽  
Band Bending ◽  
Surface Electronic Structure

ABSTRACTThe surface electronic properties of the nitric oxide (NO) treated indium tin oxide (ITO) are examined in-situ by a four-point probe and X-ray photoelectron spectroscopy (XPS). The XPS N1s peak emerged at a high binding energy of 404 eV indicating that NO is reactive with ITO. NO adsorption induces an increase of film sheet resistance, arising from an oxygen rich layer near the ITO surface region, with approximately 2.5 nm thick. This implies that the interaction of NO with ITO is occurred around surface region. Valence band maximum measured for NO-absorbed ITO was shifted to the low binding energy side. This is related to the upward surface band bending.

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