Spectroscopic states of PTCDA negative ions and their relation to the maxima of unoccupied state density in the conduction band

2011 ◽  
Vol 56 (6) ◽  
pp. 754-759 ◽  
Author(s):  
S. A. Pshenichnyuk ◽  
A. V. Kukhto ◽  
I. N. Kukhto ◽  
A. S. Komolov
Keyword(s):  
Conduction Band ◽  
Negative Ions ◽  
State Density ◽  
Unoccupied State

Optical Properties of the Pb Center at the Si/SiO2 Interface

1985 ◽  
Vol 46 ◽  
Author(s):  
Arthur H. Edwards ◽  
W. Beall Fowler
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
Defect State ◽  
Polarization Effects ◽  
Unoccupied State ◽  
Cluster Calculations ◽  
Occupied State ◽  
Order Of Magnitude ◽  
Neutral Defect ◽  
Theoretical Results

AbstractWe present theoretical results for the optical prooerties of the Pb center at the Si/SiO2 interface. Using wave functions obtainec from semiempirical (MINDO/3) cluster calculations, we have calculated electric dipole matrix elements connecting the singly occupied (neutral) defect state to the unoccupied conduction-band-like states, as well as those connecting the occupied valence-band-like states to the singly occupied defect state and to the unoccupied defect state. We predict the absorption cross section for excitation from the valence band to the unoccupied state to be of order 10−19 cm2 and that for excitation from the valence band to the occupied state and from the occupied state to the conduction band to be an order of magnitude larger. We also predict that the absorption will in some cases be strongly dependent on the direction of the polarization. Effects of symmetry lowering in the oxide and of distortions in the silicon are discussed.

Improved Interface Trap Density Close to the Conduction Band Edge of a-Face 4H-SiC MOSFETs Revealed Using the Charge Pumping Technique

2017 ◽  
Vol 897 ◽  
pp. 143-146 ◽  
Author(s):  
Gerald Rescher ◽  
Gregor Pobegen ◽  
Thomas Aichinger ◽  
Tibor Grasser
Keyword(s):  
Silicon Carbide ◽  
Conduction Band ◽  
State Density ◽  
Trap Density ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Power Mosfets ◽  
Charge Pumping ◽  
Wide Range ◽  
Reduced Mobility

We study the interface properties of 4H silicon carbide Si-face 0001 and a-face 11220 power MOSFETs using the charge pumping technique. MOSFETs produced on the a-face show a higher electron mobility than Si-face devices, although their charge pumping signal is 5 times higher, indicating a higher interface/border trap density. We show the main contribution to the interface/border trap density on a-face devices originates from deep states in a wide range around midgap, whereas Si-face devices show a higher and exponentially increasing interface/border state density close to the conduction band edge of 4H silicon carbide, resulting in reduced mobility.

scholarly journals Влияние фтора на плотность состояний на границе раздела анодный оксидный слой/In-=SUB=-0.53-=/SUB=-Ga-=SUB=-0.47-=/SUB=-As

2021 ◽  
Vol 47 (10) ◽  
pp. 11
Author(s):  
М.С. Аксенов ◽  
Н.А. Валишева ◽  
А.П. Ковчавцев
Keyword(s):  
Fermi Level ◽  
Band Gap ◽  
Conduction Band ◽  
Annealing Temperature ◽  
State Density ◽  
The State ◽  
Conduction Band Bottom

It is shown that the fluorine-containing anodic layers on the n-In0.53Ga0.47As surface, in contrast to the anodic layers without fluorine, form a SiO2/InGaAs interface with an unpinned Fermi level, the state density on which decreases during annealing at a temperature of 300 °C to values (2-4) 1011 and (4-5) 1012 eV-1cm-2 near conduction band bottom and the band gap middle, respectively. An increase in the annealing temperature leads to a reverse increase in the state density (350 ºС) and pinning of the Fermi level (400 ºС).

scholarly journals Electrical Characterization of Si/ZnO Nanorod PN Heterojunction Diode

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Sadia Muniza Faraz ◽  
Wakeel Shah ◽  
Naveed Ul Hassan Alvi ◽  
Omer Nur ◽  
Qamar Ul Wahab
Keyword(s):  
Conduction Band ◽  
Zno Nanorods ◽  
Electrical Characterization ◽  
Interface State ◽  
State Density ◽  
Average Height ◽  
Zno Nanorod ◽  
Heterojunction Diode ◽  
Rectification Factor

The electrical characterization of p-Silicon (Si) and n-Zinc oxide (ZnO) nanorod heterojunction diode has been performed. ZnO nanorods were grown on p-Silicon substrate by the aqueous chemical growth (ACG) method. The SEM image revealed high density, vertically aligned hexagonal ZnO nanorods with an average height of about 1.2 μm. Electrical characterization of n-ZnO nanorods/p-Si heterojunction diode was done by current-voltage (I-V), capacitance-voltage (C-V), and conductance-voltage (G-V) measurements at room temperature. The heterojunction exhibited good electrical characteristics with diode-like rectifying behaviour with an ideality factor of 2.7, rectification factor of 52, and barrier height of 0.7 V. Energy band (EB) structure has been studied to investigate the factors responsible for small rectification factor. In order to investigate nonidealities, series resistance and distribution of interface state density (NSS) below the conduction band (CB) were extracted with the help of I-V and C-V and G-V measurements. The series resistances were found to be 0.70, 0.73, and 0.75 KΩ, and density distribution interface states from 8.38 × 1012 to 5.83 × 1011 eV−1 cm−2 were obtained from 0.01 eV to 0.55 eV below the conduction band.

scholarly journals Fullerene Negative Ions: Formation and Catalysis

2020 ◽  
Vol 21 (9) ◽  
pp. 3159
Author(s):  
Zineb Felfli ◽  
Kelvin Suggs ◽  
Nantambu Nicholas ◽  
Alfred Z. Msezane
Keyword(s):  
Transition State ◽  
Cross Sections ◽  
Water Oxidation ◽  
Density Functional ◽  
Regge Pole ◽  
Negative Ions ◽  
State Density ◽  
Negative Ion ◽  
Functional Theory ◽  
Total Cross Sections

We first explore negative-ion formation in fullerenes C44 to C136 through low-energy electron elastic scattering total cross sections calculations using our Regge-pole methodology. Then, the formed negative ions C44ˉ to C136ˉ are used to investigate the catalysis of water oxidation to peroxide and water synthesis from H2 and O2. The exploited fundamental mechanism underlying negative-ion catalysis involves hydrogen bond strength-weakening/breaking in the transition state. Density Functional Theory transition state calculations found C60ˉ optimal for both water and peroxide synthesis, C100ˉ increases the energy barrier the most, and C136ˉ the most effective catalyst in both water synthesis and oxidation to H2O2.

scholarly journals Nitrogen Passivation of the Interface States Near the Conduction Band Edge in 4H-Silicon Carbide

2000 ◽  
Vol 640 ◽  
Author(s):  
J. R. Williams ◽  
G. Y. Chung ◽  
C. C. Tin ◽  
K. McDonald ◽  
D. Farmer ◽  
...  
Keyword(s):  
Conduction Band ◽  
Interface State ◽  
Interface States ◽  
State Density ◽  
Interface State Density ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Breakdown Field ◽  
Inversion Mode ◽  
Passivation Process

ABSTRACTThis paper describes the development of a nitrogen-based passivation technique for interface states near the conduction band edge [Dit(Ec)] in 4H-SiC/SiO2. These states have been observed and characterized in several laboratories for n- and p-SiC since their existence was first proposed by Schorner, et al. [1]. The origin of these states remains a point of discussion, but there is now general agreement that these states are largely responsible for the lower channel mobilities that are reported for n-channel, inversion mode 4H-SiC MOSFETs. Over the past year, much attention has been focused on finding methods by which these states can be passivated. The nitrogen passivation process that is described herein is based on post-oxidation, high temperature anneals in nitric oxide. An NO anneal at atmospheric pressure, 1175°C and 200–400sccm for 2hr reduces the interface state density at Ec-E ≅0.1eV in n-4H-SiC by more than one order of magnitude - from > 3×1013 to approximately 2×1012cm−2eV−1. Measurements for passivated MOSFETs yield effective channel mobilities of approximately 30–35cm2/V-s and low field mobilities of around 100cm2/V-s. These mobilities are the highest yet reported for MOSFETs fabricated with thermal oxides on standard 4H-SiC and represent a significant improvement compared to the single digit mobilities commonly reported for 4H inversion mode devices. The reduction in the interface state density is associated with the passivation of carbon cluster states that have energies near the conduction band edge. However, attempts to optimize the the passivation process for both dry and wet thermal oxides do not appear to reduce Dit(Ec) below about 2×1012cm−2eV−1 (compared to approximately 1010cm−2eV−1 for passivated Si/SiO2). This may be an indication that two types of interface states exist in the upper half of the SiC band gap – one type that is amenable to passivation by nitrogen and one that is not. Following NO passivation, the average breakdown field for dry oxides on p-4H-SiC is higher than the average field for wet oxides (7.6MV/cm compared to 7.1MV/cm at room temperature). However, both breakdown fields are lower than the average value of 8.2MV/cm measured for wet oxide layers that were not passivated. The lower breakdown fields can be attributed to donor-like states that appear near the valence band edge during passivation.

Effects of Strain on Optical Properties of BiFeO3: A First-Principles Study

2016 ◽  
Vol 703 ◽  
pp. 224-229
Author(s):  
Zhen Ye Zhu ◽  
Si Qi Wang ◽  
Qian Wang
Keyword(s):  
Optical Properties ◽  
Conduction Band ◽  
First Principles ◽  
State Density ◽  
Low Energy ◽  
Optical Absorption Coefficient ◽  
First Principles Calculations ◽  
Photovoltaic Application ◽  
Density Peaks ◽  
Optical Applications

In order to investigate the effects of strain on optical properties of BiFeO3, electronic structure, dielectric properties and optical properties of BiFeO3 under different strain conditions were performed by first-principles calculations. Results show that the optical spectra of BiFeO3 is mainly determined by the contributions from transition from valence band O 2p to conduction band Fe 3d levels or even higher conduction band Bi 6s states in the low-energy region. Compared with equilibrium state, state density peaks shift to left side and state density peaks become broader and lower, and band gap becomes smaller under strain states. Furthermore, strain increases optical absorption coefficient peaks, energy loss coefficient peaks and reflectivity coefficient peaks, and extinction coefficient peaks, exhibiting that optical properites of BiFeO3 is improved under strain states. Our research provides theoretical guidance for future optical applications of BiFeO3, especially photovoltaic application.

A Study on the Electronic Properties of Nitric Oxide Annealed MOS Structures Processed on 4H-SiC

2011 ◽  
Vol 1305 ◽  
Author(s):  
Kerlit Chew ◽  
Chin-Che Tin ◽  
Claude Ahyi ◽  
Kim Nie Chong ◽  
Meng Suan Liang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Conduction Band ◽  
Drain Current ◽  
Interface State ◽  
State Density ◽  
Interface State Density ◽  
Flat Band ◽  
Mos Capacitor ◽  
Uv Illumination ◽  
Thermal Oxide

ABSTRACTInterface state density profiling of the thermal oxide / n-type 4H-SiC interface which underwent post-oxidation nitric-oxide (NO) annealing showed that an interface state density of approximately 1×1011 cm−2eV−1 could be achieved at around 0.2 eV below the conduction band. It decreased exponentially by two orders to 1×109 cm-2eV-1 at around 0.9 eV from the conduction band. The values are comparable or better than other published work. The low interface state density achieved near the conduction band is important towards improved channel carrier mobility in SiC MOSFETs. A positive flat-band voltage shift of the SiC based MOS capacitor was also observed. The shift reduced under UV illumination. It could be attributed to slow acceptor-like (negatively-charged) traps, which may have contributed to the instabilities observed in drain current and threshold voltage suffered by SiC MOSFETs.

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