Ab Initio Studies of Local Vibrations of Small Self-Interstitials Aggregates in Silicon

2005 ◽  
Vol 108-109 ◽  
pp. 175-180
Author(s):  
A. Carvalho ◽  
R. Jones ◽  
J. Coutinho ◽  
Vitor J.B. Torres ◽  
Patrick R. Briddon
Keyword(s):  
Ab Initio ◽  
Optical Activity ◽  
Density Functional ◽  
Vibrational Modes ◽  
Functional Modeling ◽  
Modeling Studies ◽  
Metastable Form ◽  
Local Vibrational Modes ◽  
Vibronic Transitions

We report on the energetics, electrical and optical activity of small self-interstitial (I3 and I4) clusters in Si, found from ab-initio density-functional modeling studies. I4 possesses nine local vibrational modes above the Raman edge, which account for up to three dipole-allowed vibronic transitions observed in recent experiments associated with the X-photoluminescent line. Another prominent photoluminescent line (known as the W-line) that shows a trigonal stress-induced splitting pattern, has been previously assigned to I3. Our analysis of the LVMs of a metastable form of I3 support this assignment.

Metastable VO2 Complexes in Silicon: Experimental and Theoretical Modeling Studies

2005 ◽  
Vol 108-109 ◽  
pp. 223-228 ◽  
Author(s):  
L.I. Murin ◽  
J. Lennart Lindström ◽  
Vladimir P. Markevich ◽  
I.F. Medvedeva ◽  
Vitor J.B. Torres ◽  
...  
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Interstitial Oxygen ◽  
Vibrational Modes ◽  
Acceptor Level ◽  
Acceptor State ◽  
Metastable Form ◽  
Local Vibrational Modes ◽  
Co Doped

We report on a combined experimental and theoretical study of the metastable form of the vacancy-dioxygen defect in Si labeled VO∗ 2. Important new experimental observations are the detection of mixed local vibrational modes of VO∗ 2 in 16O,18O co-doped samples, the determination of the position of LVM bands for the negatively charged defect, and an assignment of an acceptor level at about Ec − 0.05 eV. Defect energetics, electrical levels and LVM frequencies of the VO∗ 2 complex are also investigated by ab-initio density-functional modeling.We find it to be a bistable defect which accounts well for the experimental data. The metastable form produces an acceptor state at 0.05 eV below Ec, and can be thought of as a VO defect perturbed by interstitial oxygen.

scholarly journals Phonons in Short-Period GaN/AlN Superlattices: Group-Theoretical Analysis, Ab initio Calculations, and Raman Spectra

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 286
Author(s):  
Valery Davydov ◽  
Evgenii Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Raman Spectra ◽  
Density Functional ◽  
Structural Characteristics ◽  
Vibrational Modes ◽  
Phonon Modes ◽  
Short Period ◽  
Group Theoretical Analysis

We report the results of experimental and theoretical studies of phonon modes in GaN/AlN superlattices (SLs) with a period of several atomic layers, grown by submonolayer digital plasma-assisted molecular-beam epitaxy, which have a great potential for use in quantum and stress engineering. Using detailed group-theoretical analysis, the genesis of the SL vibrational modes from the modes of bulk AlN and GaN crystals is established. Ab initio calculations in the framework of the density functional theory, aimed at studying the phonon states, are performed for SLs with both equal and unequal layer thicknesses. The frequencies of the vibrational modes are calculated, and atomic displacement patterns are obtained. Raman spectra are calculated and compared with the experimental ones. The results of the ab initio calculations are in good agreement with the experimental Raman spectra and the results of the group-theoretical analysis. As a result of comprehensive studies, the correlations between the parameters of acoustic and optical phonons and the structure of SLs are obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy. The results obtained can be used to optimize the growth technologies aimed to form structurally perfect short-period GaN/AlN SLs.

High Energy Local Vibrational Modes of Carbon Aggregates in SiC: Experimental and Theoretical Insight

2006 ◽  
Vol 527-529 ◽  
pp. 465-468 ◽  
Author(s):  
Alexander Mattausch ◽  
M. Bockstedte ◽  
Oleg Pankratov ◽  
John W. Steeds ◽  
S.A. Furkert ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
High Energy ◽  
Vibrational Modes ◽  
Energy Mode ◽  
Local Vibrational Modes ◽  
Theoretical Insight

We observe new photoluminescence centers in electron-irradiated 6H-SiC with phonon replicas up to 250 meV and clear threefold isotope splitting of the highest energy mode. Based on ab initio calculations, we discuss the tri-carbon anti-site (C3)Si and the di-interstitial (C2)Hex as models for these centers.

Assignment of Raman-active vibrational modes of tetragonal mackinawite: Raman investigations and ab initio calculations

RSC Advances ◽  
2014 ◽  
Vol 4 (49) ◽  
pp. 25827-25834 ◽  
Author(s):  
Y. El Mendili ◽  
B. Minisini ◽  
A. Abdelouas ◽  
J.-F. Bardeau
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Direct Methods ◽  
Vibrational Modes ◽  
Dispersion Correction ◽  
Density Functional Perturbation Theory ◽  
Calculation Results

We report on the first assignment of the Raman-active vibrational modes of mackinawite using Density Functional Perturbation Theory and direct methods with BLYP + dispersion correction. Based on experimental data and calculation results, the Raman bands were assigned as 236 cm−1 (B1g), 256 cm−1 (Eg), 376 cm−1 (A1g) and 395 cm−1 (Eg).

Local Vibrational Modes of Zn-H-P in GaP, InP and ZnTe

2007 ◽  
Vol 261-262 ◽  
pp. 31-36
Author(s):  
Vitor J.B. Torres ◽  
J. Coutinho ◽  
Patrick R. Briddon
Keyword(s):  
Experimental Data ◽  
Total Energy ◽  
Phosphorus Atom ◽  
Density Functional ◽  
Vibrational Modes ◽  
The Core ◽  
Valence Electrons ◽  
Core Electrons ◽  
Local Vibrational Modes ◽  
Experimental Values

We have investigated the hydrogenation of the zinc acceptor in GaP and InP, and of the phosphorus acceptor in ZnTe, by computer modeling. We used a density-functional supercell code and pseudopotentials to deal with the core electrons. However zinc 3d electrons were explicitly taken to be valence electrons. We have determined the relaxed atomic geometry for seven hydrogen sites. We have found that, in the lowest total energy configuration, hydrogen sits in a bond centered position between zinc and arsenic atoms in all GaP, InP and ZnTe semiconductors and is bonded to the phosphorus atom. We found metastable states, by 0.4, 0.4 and 0.5 eV, for structures where H is antibonding to the phosphorus atom for GaP, InP and ZnTe, respectively. The calculated local vibrational modes (LVM) for the bond-centered configuration agree, within 1%, with the experimental values of 2379.0 cm-1 for GaP:Zn-H, 2287.7 cm-1 for InP:Zn-H and 2193 cm-1 for ZnTe:P-H. The isotopic shift due to the replacement of deuterium by hydrogen is reproduced by less than 2.5% using experimental data. The decrease in the LVM when going from GaP to ZnTe, as the perfect bond length increases, is also well-reproduced. A wag mode at 496 cm-1 and lower LVM, a doublet at 329 cm-1 and a singlet at 242 cm-1, are predicted for P-H in ZnTe.

Sign in / Sign up

Export Citation Format

Share Document