Study of Band Alignment at CBD-CdS/Cu(In1-xGax)Se2 (x = 0.2 - 1.0) Interfaces by Photoemission and Inverse Photoemission Spectroscopy

2007 ◽  
Vol 1012 ◽  
Author(s):  
Shimpei Teshima ◽  
Hirotake Kashiwabara ◽  
Keimei Masamoto ◽  
Kazuya Kikunaga ◽  
Kazunori Takeshita ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Valence Band Maximum ◽  
Band Gap Energy ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Gap Energy ◽  
Conduction Band Offset ◽  
Inverse Photoemission ◽  
Inverse Photoemission Spectroscopy

AbstractDependence of band alignments at interfaces between CdS by chemical bath deposition and Cu(In1-xGax)Se2 by conventional 3-stage co-evaporation on Ga substitution ratio x from 0.2 to 1.0 has been systematically studied by means of photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). For the specimens of the In-rich CIGS, conduction band minimum (CBM) by CIGS was lower than that of CdS. Conduction band offset of them was positive about +0.3 ~ +0.4 eV. Almost flat conduction band alignment was realized at x = 0.4 ~ 0.5. On the other hand, at the interfaces over the Ga-rich CIGS, CBM of CIGS was higher than that of CdS, and CBO became negative. The present study reveals that the decrease of CBO with a rise of x presents over the wide rage of x, which results in the sign change of CBO around 0.4 ~ 0.45. In the Ga-rich interfaces, the minimum of band gap energy, which corresponded to energy spacing between CBM of CdS and valence band maximum of CIGS, was almost identical against the change of band gap energy of CIGS. Additionally, local accumulation of oxygen related impurities was observed at the Ga-rich samples, which might cause the local rise of band edges in central region of the interface.

Study of Band Alignment at the Interface between CBD-CdS and CIGS grown by H2O-introduced co-evaporation

2007 ◽  
Vol 1012 ◽  
Author(s):  
Norio Terada ◽  
Hirotake Kashiwabara ◽  
Kazuya Kikunaga ◽  
Shimpei Teshima ◽  
Tetsuji Okuda ◽  
...  
Keyword(s):  
Conduction Band ◽  
Valence Band Maximum ◽  
Band Gap Energy ◽  
Band Alignment ◽  
Type I ◽  
Conduction Band Offset ◽  
Substitution Ratio ◽  
Band Alignments ◽  
Inverse Photoemission Spectroscopy ◽  
Ga Substitution

AbstractFor understanding the origin of the improvements of properties in the CIGS-based cells, of which the CIGS absorber has been fabricated by H2O-introduced co-evaporation [CIGS-H2O], band alignment at the interfaces between chemical bath deposited CdS and CIGS-H2O with Ga substitution ratio ~ 40 % has been studied by photoemission and inverse photoemission spectroscopy. The CdS layer over the CIGS-H2O showed an identical electronic structure with that of CdS on the conventionally grown CIGS; band gap energy of 2.3 ~ 2.4 and a location of conduction band minimum (CBM) and valence band maximum (VBM) relative to Fermi level were + 0.75 eV and -1.6 ~ -1.7 eV, respectively. In the interface region, decreases of CBM and a rise of VBM were observed. Total amount of the decrease of CBM over the interface was 0.2 ~ 0.3 eV. XPS measurements of the core-level signals over the interface showed a small upward bend bending of 0.1 ~ 0.2 eV. Consequently, the conduction band offset (CBO) and valence bad offset (VBO) at the CBD-interface over the CIGS-H2O (Ga~40%) are about +0.1, and 0.9 ~ 1.1 eV, respectively. This positive CBO is contrast with a slightly negative CBO at the interface between CBD-CdS/conventionally grown CIGS with Ga ~ 40 % measured previously. These results indicate that the H2O introduction is effective to extend the upper limit of the Ga substitution ratio where the Type-I conduction band alignment is maintained. The observed band alignments are consistent with the rise of Voc and efficiency in the CIGS-H2O based cells.

Band alignment at CdS/wide-band-gap Cu(In,Ga)Se2 hetero-junction by using PES/IPES

2005 ◽  
Vol 865 ◽  
Author(s):  
S.H. Kong ◽  
H. kashiwabara ◽  
K. Ohki ◽  
K. Itoh ◽  
T. Okuda ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Ion Beam ◽  
Wide Band ◽  
Valence Band Maximum ◽  
Conduction Band Minimum ◽  
Band Alignment ◽  
Interface Region ◽  
Photoemission Spectroscopy ◽  
Wide Gap

AbstractDirect characterization of band alignment at chemical bath deposition (CBD)-CdS/Cu0.93 (In1-xGax)Se2 has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 350 eV yields a removal of surface contamination as well as successful measurement of the intrinsic properties of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of 1.4 ∼ 1.6 eV were successfully exposed. IPES spectra revealed that the conduction band offset (CBO) at the interface region of the wide gap CIGS with x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that the energy spacing between conduction band minimum (CBM) of CdS layer and valence band maximum (VBM) of Cu0.93(In0.25Ga0.75)Se2 layer at interface region was no wider than that of the interface over the Cu0.93(In0.60Ga0.40)Se2 layer.

LITAO3 CHARACTERIZATION OF RUBIDIUM ON TEMPERATURE VARIATIONS

2018 ◽  
Vol 1 (02) ◽  
pp. 54-59
Author(s):  
Agus Ismangil ◽  
Teguh Puja Negara
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
Transmission Rate ◽  
Ferroelectric Material ◽  
Band Gap Energy ◽  
Ferroelectric Materials ◽  
Annealing Process ◽  
Optical Modulators ◽  
Gap Energy

One of the studies that recently attracted the attention of physicists is research on ferroelectric material because this material is very promising for the development of new generation devices in connection with the unique properties it has. Ferroelectric materials, especially those based on a mixture of lithium tantalite (LiTaO3), are expected to be applied to the infrared sensor. Lithium tantalate (LiTaO3) is a ferroelectric material that is unique in terms of pyroelectric and piezoelectric properties that are integrated with good mechanical and chemical stability. Therefore LiTaO3 is often used for several applications such as electro-optical modulators and pyroelectric detectors. LiTaO3 is a non-hygroscopic crystal, colorless, soluble in water, has a high transmission rate and does not easily damage its optical properties. LiTaO3 is a material that has a high dielectric constant and a high load storage capacity. This research has succeeded in determining the band gap energy of the LiTaO3 film in the rubidium chamber obtained in the range of values 2.02-2.98 eV as shown in figure 4. The LiTaO3 film after the annealing process at a temperature of 650 oC, has the highest band gap energy of 2.98 eV. Large energy is needed on the electrons to be excited from the valence band to the conduction band. Whereas in the LiTaO3 film after an annealing process of 800 oC, the band gap energy obtained is 2.02 eV. This makes it easier for electrons to be excited from the valence band to the conduction band because the energy needed is not too large.

Conduction-band electronic structure of 1T-TaS2revealed by angle-resolved inverse-photoemission spectroscopy

2014 ◽  
Vol 89 (15) ◽  
Author(s):  
Hitoshi Sato ◽  
Masashi Arita ◽  
Yuki Utsumi ◽  
Yutaka Mukaegawa ◽  
Minoru Sasaki ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Conduction Band ◽  
Photoemission Spectroscopy ◽  
Inverse Photoemission ◽  
Inverse Photoemission Spectroscopy

scholarly journals The Effect of Niobium and Rubidium Doping on the Energy Band Gap of a Lithium Tantalate (LiTaO3) Thin Film

2021 ◽  
Vol 32 (2) ◽  
pp. 1-5
Author(s):  
Agus Ismangil ◽  
Fatimah Arofiati Noor ◽  
Toto Winata
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
Chemical Solution Deposition ◽  
Band Gap Energy ◽  
Chemical Solution ◽  
Energy Band Gap ◽  
Solution Deposition ◽  
Gap Energy ◽  
Niobium Doped

Chemical solution deposition (CSD) is a technique for making a film by keeping synthetic arrangements on the outer layer of the substrate. The outcomes show that the band gap energy of the LiTaO3 film is 1 eV. Electrons are more effectively invigorated to the valence band than to the conduction band on the grounds that the energy required is not excessively huge. Niobium-doped LiTaO3 film has a band gap energy of 1.15 eV. A large amount of energy is needed for electrons to be energized from the valence band to the conduction band. The rubidium-doped LiTaO3 film has a band gap energy of 1.30 eV.

Band Alignment of CdS/Cu2ZnSnSe4 Heterointerface and Solar Cell Performances

MRS Advances ◽  
2017 ◽  
Vol 2 (53) ◽  
pp. 3157-3162 ◽  
Author(s):  
Takehiko Nagai ◽  
Shinho Kim ◽  
Hitoshi Tampo ◽  
Kang Min Kim ◽  
Hajime Shibata ◽  
...  
Keyword(s):  
Conduction Band ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Band Offset ◽  
Valence Band Offset ◽  
X Ray ◽  
Heterojunction Solar Cells ◽  
Conduction Band Offset ◽  
Ultraviolet Photoemission Spectroscopy ◽  
Large Spike

ABSTRACTWe determined that the conduction band offset (CBO) and the valence band offset (VBO) at the CdS/ Cu2ZnSnSe4 (CZTSe) heterointerface are +0.56 and +0.89eV, respectively, by using X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and inversed photoemission spectroscopy (IPES). A positive CBO value, so-called “spike” structure, means that the position of conduction band becomes higher than that of absorber layer. The evaluated CBO of +0.56 eV suggests that the conduction band alignment at CdS/CZTSe interface is enough to become an electron barrier. Despite such a large spike structure in the conduction band at the interface, a conversion efficiency of 8.7 % could be obtained for the CdS/CZTSe heterojunction solar cells.

Band Bending of n-GaP(001) and p-InP(001) Surfaces with and without Sulfur Treatment Studied by Photoemission (PES) and Inverse Photoemission Spectroscopy (IPES)

2011 ◽  
Vol 222 ◽  
pp. 56-61
Author(s):  
K.Z. Liu ◽  
Masaru Shimomura ◽  
Y. Fukuda
Keyword(s):  
Conduction Band ◽  
Surface States ◽  
Conduction Band Edge ◽  
Photoemission Spectroscopy ◽  
Clean Surface ◽  
Dangling Bond ◽  
Xps Spectra ◽  
Flat Bands ◽  
Inverse Photoemission ◽  
Inverse Photoemission Spectroscopy

Surface electronic structures of n-GaP(001) and p-InP(001) with and without sulfur treatment have been studied by X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoemission spectroscopy (SRPES), and inverse photoemission spectroscopy (IPES). The Fermi level (EF) of a clean n-GaP(001)-(2x4) surface is found to be pinned at 0.2 eV above the valence band maximum (VBM), suggesting that the surface electronic bands are bent upward. XPS spectra reveal that the EF is moved to 2.3 eV above the VBM by the sulfur treatment, implying that the sulfur-treated surface has flat bands. The IPES result shows that empty dangling bond states on Ga atoms at the surface are located at the conduction band minimum (CBM) and they disappeared with the treatment. SRPES spectra of a clean p-InP(001)-(2x4) surface indicate that the EF is located at 0.3 eV above the VBM and surface states due to phosphorus atoms are at –0.9 eV below the EF. The result implies that the surface has almost flat bands. Empty dangling bond states on In atoms at the clean surface are found to be located at the conduction band edge. Surface states due to the In-S bonds are found at –3.5 eV below the EF for the sulfur-treated surface. The sulfur treatment of the clean surface leads to a little shift (0.1 –0.2 eV) of the EF and to considerable reduction of the empty states in the band gap. A type conversion of p- to n- is not observed in the present work. This is discussed in terms of the thickness of a sulfide layer.

Compositional dependence of band‐gap energy and conduction‐band effective mass of In1−x−yGaxAlyAs lattice matched to InP

1982 ◽  
Vol 41 (5) ◽  
pp. 476-478 ◽  
Author(s):  
D. Olego ◽  
T. Y. Chang ◽  
E. Silberg ◽  
E. A. Caridi ◽  
A. Pinczuk
Keyword(s):  
Band Gap ◽  
Effective Mass ◽  
Conduction Band ◽  
Band Gap Energy ◽  
Compositional Dependence ◽  
Gap Energy ◽  
Lattice Matched
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