New Type of Defects Explored by Theory: Silicon Interstitial Clusters in SiC

2008 ◽  
Vol 600-603 ◽  
pp. 413-416
Author(s):  
Adam Gali ◽  
T. Hornos ◽  
Nguyen Tien Son ◽  
Erik Janzén
Keyword(s):  
Ab Initio ◽  
High Temperatures ◽  
Vibration Modes ◽  
Local Vibration ◽  
Ionization Energies ◽  
New Type ◽  
Carbon Interstitial ◽  
Small Clusters

We have studied the small clusters of silicon and carbon interstitials by ab initio supercell calculations in 4H-SiC. We found that silicon interstitials can form stable and electrically active complexes with each other or with a carbon interstitial. Local vibration modes and ionization energies were also calculated in order to help the identification of the defects. We propose that silicon interstitials can emit from these clusters at relatively high temperatures, which may play an important role in the formation of the DI center.

Ab initio Study on Ionization Energies of 3-Amino-1-propanol

2011 ◽  
Vol 24 (3) ◽  
pp. 315-318 ◽  
Author(s):  
Ke-dong Wang ◽  
Ying-bin Jia ◽  
Zhen-jiang Lai ◽  
Yu-fang Liu
Keyword(s):  
Ab Initio ◽  
Ab Initio Study ◽  
Ionization Energies

A study of the vacuum pyrolysis of 1,2,3-benzotriazines. The Hel ultraviolet photoelectron spectra of benzazete and o-benzyne

1995 ◽  
Vol 73 (1) ◽  
pp. 146-149 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Chandra Deo Roy ◽  
Jiangong Ma
Keyword(s):  
Heat Source ◽  
Ab Initio ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Ionization Energies ◽  
Vacuum Pyrolysis ◽  
Ab Initio Hf

A CW CO2 laser is used as a directed heat source to carry out the vacuum pyrolysis of 1,2,3-benzo-triazine (1a) and 4-methyl-1,2,3-benzotriazine (1b). We report the first HeI photoelectron (pe) spectrum of benzazete (2a), which correlates with ionization energies calculated with HAM/3 using an equilibrium geometry obtained at the ab initio HF/6-31G** level of the theory. The pe spectrum of o-benzyne (3) obtained in this study correlates with the spectrum published by Zhang and Chen, but not with the spectra reported in two earlier publications. Keywords: 1,2,3-benzotriazines, vacuum pyrolysis, HeI ultraviolet photoelectron spectra, benzazete, benzyne.

Theory of DX Centers in AlxGa1-x Alloys

1989 ◽  
Vol 163 ◽  
Author(s):  
D. J. Chadi ◽  
S. B. Zhang
Keyword(s):  
Theoretical Model ◽  
Ab Initio ◽  
Electronic Properties ◽  
Lattice Distortion ◽  
Substitutional Site ◽  
Ionization Energies ◽  
Dx Centers ◽  
Large Lattice ◽  
Self Consistent ◽  
Pseudo Potential

AbstractA theoretical model for DX centers which explains their unusual electronic properties in terms of two distinct bonding configurations for donor impurities in AlxGa1-x As alloys is examined. The results of our ab initio self-consistent pseudo-potential calculations show that for x > ≃20%, the normal fourfold coordinated substitutional site becomes unstable with respect to a large lattice distortion. The model explains the large difference between the thermal and optical ionization energies of DX centers.

scholarly journals Properties of Ambient-Cured Normal and Heavyweight Geopolymer Concrete Exposed to High Temperatures

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 740 ◽  
Author(s):  
Farhad Aslani ◽  
Zohaib Asif
Keyword(s):  
Mass Loss ◽  
High Temperatures ◽  
Offshore Structures ◽  
Normal Weight ◽  
Geopolymer Concrete ◽  
Coarse Aggregates ◽  
Residual Properties ◽  
New Type ◽  
Heavyweight Concrete ◽  
Underwater Structures

Ambient-cured heavyweight geopolymer concrete (HWGC) is a new type of concrete that combines the benefits of both heavyweight concrete (HWC) and geopolymer concrete (GC). HWGC provides proper protection from the sources that emit harmful radiations in medical and nuclear industries. Furthermore, HWGC may also be used in offshore structures for pipeline ballasting and similar underwater structures. In this study, heavyweight aggregates (magnetite) have been used and replaced by normal-weight coarse aggregates in GC at volume ratios of 50, 75, and 100% to attain heavyweight classification according to British standards. This study investigates the impacts of high temperatures on standard ambient-cured geopolymer concrete and ambient-cured HWGC through its residual properties regarding compressive and tensile strengths, mass loss, spalling intensity, and flexural strength. The residual properties were examined by heating 100 × 200 mm cylinder specimens to 100, 300, 600, and 900 °C. The results indicated that the maximum compressive strengths of 40.1 and 39.0 MPa were achieved by HWGC at 300 and 100 °C, respectively. The overall result shows that the strength of HWGC increases by increasing magnetite aggregate proportion, while the mass loss, intensity of spalling, and loss of strengths is proportional to temperature after a certain point. Minor spalling with holes and cracking was observed only at 900 °C in HWGC.

Silicon-Hydrogen Bonds in Boron and Phosphorous Doped Polycrystalline Silicon Thin Films

2004 ◽  
Vol 808 ◽  
Author(s):  
R. Saleh ◽  
N. H. Nickel
Keyword(s):  
Binding Energy ◽  
Polycrystalline Silicon ◽  
Binding Energies ◽  
Vibration Modes ◽  
Laser Crystallization ◽  
Hydrogen Binding ◽  
Local Vibration ◽  
Silicon Thin Films ◽  
The One ◽  
Hydrogen Effusion

ABSTRACTHydrogen bonding in laser crystallized boron and phosphorous doped polycrystalline silicon is investigated using Raman spectroscopy and hydrogen effusion measurements. During laser crystallization the intensity of the local vibration modes near 2000 and 2100 cm−1 decreases. The intensity of vibration mode at 2000 cm−1 decreases faster than the one at 2100 cm−1. From H effusion measurements, the hydrogen density-of-states (H DOS) distribution is derived. For undoped amorphous silicon the H DOS exhibits two prominent peaks at hydrogen binding energies of E– μH = –1.1 and –1.5 eV. In B doped a-Si:H the peak at –1.1 eV is less pronounced while in P doped a-Si:H the H binding energy increases by about 0.1 eV. In all samples laser crystallization causes an increase of the H binding energy by about 0.2 – 0.3 eV. However, the peaks in the H DOS observed in B-doped samples are preserved during laser crystallization.

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