scholarly journals The Effect of Interface Diffusion on Raman Spectra of Wurtzite Short-Period GaN/AlN Superlattices

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2396
Author(s):  
Valery Davydov ◽  
Evgenii M. Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  

We present an extensive theoretical and experimental study to identify the effect on the Raman spectrum due to interface interdiffusion between GaN and AlN layers in short-period GaN/AlN superlattices (SLs). The Raman spectra for SLs with sharp interfaces and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of the random-element isodisplacement model. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, showed that the bands related to A1(LO) confined phonons are very sensitive to the degree of interface diffusion. As a result, a correlation between the Raman spectra in the range of A1(LO) confined phonons and the interface quality in SLs is obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy.

2021 ◽  
Vol 2103 (1) ◽  
pp. 012147
Author(s):  
Yu V Davydov ◽  
E M Roginskii ◽  
Yu E Kitaev ◽  
A N Smirnov ◽  
I A Eliseyev ◽  
...  

Abstract The results of joint theoretical and experimental studies aimed at revealing features in the Raman spectra, which can be used for evaluation of the interface quality between GaN and AlN layers in short-period GaN/AlN superlattices (SLs) are presented. The Raman spectra for SLs with sharp interface and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of random-element isodisplacement model, respectively. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, leads to conclusion that the spectral region of the A1(LO) confined phonons is very sensitive to the degree of interface sharpness. As a result of comprehensive studies, the correlations between the parameters of the A1(LO) confined phonons and the structure of SLs are obtained. The results of the complex studies can be used to optimize the parameters of the growth process in order to form structurally perfect short-period GaN/AlN SLs.


Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 286
Author(s):  
Valery Davydov ◽  
Evgenii Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  

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.


2000 ◽  
Vol 660 ◽  
Author(s):  
J. Casado ◽  
H. E. Katz ◽  
V. Hernández ◽  
J.T. López Navarrete

ABSTRACTIn this paper, the vibrational FT-Raman spectra obtained at different anodic potentials chosen in the oxidation and reduction branches of the voltamperometric waves of two α,α'-sexithiophenes end capped with n-hexyl and n-thiohexyl groups are investigated. In order to analyze the evolution of the atomic charges and bonth lengths on going from the neutral to the doped species some theoretical calculations have been carried out.


1970 ◽  
Vol 48 (14) ◽  
pp. 1664-1674 ◽  
Author(s):  
D. W. Lepard

This paper presents a method for calculating the relative intensities and Raman shifts of the rotational structure in electronic Raman spectra of diatomic molecules. The method is exact in the sense that the wave functions used for the calculations may belong to any intermediate case of Hund's coupling schemes. Using this method, theoretical calculations of the pure rotational and electronic Raman spectrum of NO, and the pure rotational Raman spectrum of O2, are presented. Although a calculated stick spectrum for NO was previously shown by Fast et al., the details of this calculation are given here for the first time.


1995 ◽  
Vol 36 (3) ◽  
pp. 426-431 ◽  
Author(s):  
A. P. Zhukovskii ◽  
L. V. Shurupova ◽  
M. A. Zhukovskii

1999 ◽  
Vol 14 (8) ◽  
pp. 727-730 ◽  
Author(s):  
Fujia Zhang ◽  
Dejiang Zhang ◽  
Jie Zhang ◽  
Jing Qi ◽  
Yanyun Wang ◽  
...  

2010 ◽  
Vol 24 (06n07) ◽  
pp. 667-675 ◽  
Author(s):  
M. ŠĆEPANOVIĆ ◽  
S. AŠKRABIĆ ◽  
M. GRUJIĆ-BROJČIN ◽  
A. GOLUBOVIĆ ◽  
Z. DOHČEVIĆ-MITROVIĆ ◽  
...  

Pure titania ( TiO 2) nanopowders and TiO 2 doped with 10 mol % of vanadium ions ( V 3+) are synthesized by sol-gel method. The dependence of structural characteristics of nanopowders on synthesis conditions is investigated by X-ray diffraction and Raman spectroscopy. Very intensive modes observed in Raman spectra of all nanopowders are assigned to anatase phase of TiO 2. Additional Raman modes of extremely low intensity which can be related to the presence of small amount of brookite amorphous phase are observed in pure TiO 2 nanopowders. In V -doped nanopowders anatase was the only TiO 2 phase detected. The variations in duration and heating rate of calcination influence slightly the Raman spectra of pure TiO 2, but have a great impact on Raman modes of anatase, as well as the additional Raman modes related to the presence of vanadium oxides in V -doped samples.


2000 ◽  
Vol 640 ◽  
Author(s):  
E. F. Bezerra ◽  
A. G. Souza Filho ◽  
J. Mendes Filho ◽  
V. Lemos ◽  
V. N. Freire ◽  
...  

ABSTRACTTheoretical calculations are performed on the role of smooth interfaces in the Raman spectra of Si/3C-SiC superlattices. The dispersion relations were obtained using a linear chain model with the alloyed interface δ-(3C-SiC)0.5(Si)0.5 described in the virtual crystal approximation. A modified bond-polarizability model was used to calculate the Raman spectra. The main results are the enhancement of the Raman spectra and the appearance of new peaks in between those related to the Si quasi confined and the 3C-SiC-confined modes with increasing number δ?of interfacial monolayers (3C-SiC)0.5(Si)0.5. Some of the smooth interface related Raman peaks have intensity comparable with those of an abrupt Si/3C-SiC superlattice.


2021 ◽  
Vol 39 (6) ◽  
pp. 063406
Author(s):  
Md Nazmul Alam ◽  
Joseph R. Matson ◽  
Patrick Sohr ◽  
Joshua D. Caldwell ◽  
Stephanie Law

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