M. B. Smirnov

Bio: M. B. Smirnov is an academic researcher from Saint Petersburg State University. The author has contributed to research in topics: Raman spectroscopy & Ab initio. The author has an hindex of 8, co-authored 24 publications receiving 921 citations. Previous affiliations of M. B. Smirnov include Lucideon.

Phonon dispersion and Raman scattering in hexagonal GaN and AlN

Abstract: We present the results of room- and low-temperature measurements of second-order Raman scattering for perfect GaN and AlN crystals as well as the Raman-scattering data for strongly disordered samples. A complete group-theory analysis of phonon symmetry throughout the Brillouin zone and symmetry behavior of phonon branches, including the analysis of critical points, has been performed. The combined treatment of these results and the lattice dynamical calculations based on the phenomenological interatomic potential model allowed us to obtain the reliable data on the phonon dispersion curves and phonon density-of-states functions in bulk GaN and AlN. @S0163-1829~98!06840-4#

Lattice dynamics of β-V2O5: Raman spectroscopic insight into the atomistic structure of a high-pressure vanadium pentoxide polymorph.

Abstract: We report here the Raman spectrum and lattice dynamics study of a well-crystallized β-V2O5 material prepared via a high-temperature/high-pressure (HT/HP) route, using α-V2O5 as the precursor. Periodic quantum-chemical density functional theory calculations show good agreement with the experimental results and allow one to assign the observed spectral features to specific vibrational modes in the β-V2O5 polymorph. Key structure–spectrum relationships are extracted from comparative analysis of the vibrational states of the β-V2O5 and α-V2O5 structures, and spectral patterns specific to the basic units of the two V2O5 phases are proposed for the first time. Such results open the way for the use of Raman spectroscopy for the structural characterization of vanadium oxide-based host lattices of interest in the field of lithium batteries and help us to greatly understand the atomistic mechanism involved in the α-to-β phase transition of vanadium pentoxide.

Ab initio study of the nonlinear optical susceptibility of Te O 2 -based glasses

Abstract: To gain a better insight into the origin of the outstanding nonlinear optic susceptibilities of $\mathrm{Te}{\mathrm{O}}_{2}$-based glasses whose numerical characteristics are almost two orders of magnitude higher than those of $\mathrm{Si}{\mathrm{O}}_{2}$-based glasses, a comparative computer simulation of their dielectric properties was performed using ab initio studies of a series of ${(\mathrm{Si}{\mathrm{O}}_{2})}_{p}$ and ${(\mathrm{Te}{\mathrm{O}}_{2})}_{p}$ polymer molecules. This comparison showed that these properties are reproducible only in a $\mathrm{Te}{\mathrm{O}}_{2}$ glass simulated as an ensemble of chainlike ${(\mathrm{Te}{\mathrm{O}}_{2})}_{p}$ polymer molecules with $p\ensuremath{\rightarrow}\ensuremath{\infty}$, which was interpreted as evidence for the essential nonlocality of the electronic polarizability mechanism in that glass. The relevant model calculations showed the reasonableness of this hypothesis, which was subsequently used to explain the influence of modifier content on the nonlinear optic susceptibility of the tellurite glasses.

Lattice dynamics and a magnetic-structural phase transition in the nickel orthoborate N i 3 ( B O 3 ) 2

Abstract: Nickel orthoborate $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ having a complex orthorhombic structure Pnnm (No. 58, $Z=2$) of the kotoite type is known for quite a long time as an antiferromagnetic material below ${T}_{\mathrm{N}}=46\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, but up to now its physical properties including the lattice dynamics have not been explored. Six $[\mathrm{Ni}{\mathrm{O}}_{6}]$ units of $2a$ and $4f$ types are linked via rigid $[\mathrm{B}{\mathrm{O}}_{3}]$ groups and these structural particularities impose restrictions on the lattice dynamics and spin-phonon interactions. We performed the symmetry analysis of the phonon modes at the center of the Brillouin zone. The structural parameters and phonon modes were calculated using the dmol3 program. We report and analyze results of infrared and Raman studies of phonon spectra measured in all required polarizations. Most of the even and odd phonons predicted on the basis of the symmetry analysis and theoretical calculations were reliably identified in the measured spectra. Clear evidence of the spin-phonon interaction was found for some particular phonons below ${T}_{\mathrm{N}}$. An unexpected emergence of several very narrow and weak phonon lines was observed in the infrared absorption spectra exactly at the magnetic ordering temperature ${T}_{\mathrm{N}}$. Moreover, anomalous behavior was found for some Raman phonons. The emergence of new phonon modes in the infrared and Raman spectra exactly at ${T}_{\mathrm{N}}$ proves the existence of a magnetostructural phase transition of a new type in $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$. A possible nature of this transition is discussed.

Band parameters for nitrogen-containing semiconductors

Abstract: We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Optical bandgap energy of wurtzite InN

Abstract: Wurtzite InN films were grown on a thick GaN layer by metalorganic vapor phase epitaxy. Growth of a (0001)-oriented single crystalline layer was confirmed by Raman scattering, x-ray diffraction, and reflection high energy electron diffraction. We observed at room temperature strong photoluminescence (PL) at 0.76 eV as well as a clear absorption edge at 0.7–1.0 eV. In contrast, no PL was observed, even by high power excitation, at ∼1.9 eV, which had been reported as the band gap in absorption experiments on polycrystalline films. Careful inspection strongly suggests that a wurtzite InN single crystal has a true bandgap of 0.7–1.0 eV, and the discrepancy could be attributed to the difference in crystallinity.

Nitrogen-related local vibrational modes in ZnO:N

Abstract: We study the influence of nitrogen, a potential acceptor in ZnO, on the lattice dynamics of ZnO. A series of samples grown by chemical vapor deposition (CVD) containing different nitrogen concentrations, as determined by secondary ion mass spectroscopy (SIMS), was investigated. The Raman spectra revealed vibrational modes at 275, 510, 582, 643, and 856 cm−1 in addition to the host phonons of ZnO. The intensity of these additional modes correlates linearly with the nitrogen concentration and can be used as a quantitative measure of nitrogen in ZnO. These modes are interpreted as local vibrational modes. Furthermore, SIMS showed a correlation between the concentration of incorporated nitrogen and unintentional hydrogen, similar to the incorporation of the p-dopant magnesium and hydrogen in GaN during metalorganic CVD.

Layered boron nitride as a release layer for mechanical transfer of GaN-based devices

Abstract: Introducing an extremely thin layer of boron nitride between a sapphire substrate and the gallium nitride semiconductor grown on it is shown to facilitate the transfer of the resulting nitride structures to more flexible and affordable substrates. Nitride semiconductors are renowned for their excellent electronic and optical properties and are the materials of choice for many optical devices, including BluRay players. But they have an important practical drawback: they are very particular about the substrates (typically sapphire) on which they can be grown. This has stimulated the search for new ways of transferring such materials from one substrate to another. Here Kobayashi et al. demonstrate, using a gallium nitride-based device, that the addition of an extremely thin layer of hexagonal boron nitride to the initial growth surface facilitates the straightforward mechanical release of the resulting nitride structures, as well as subsequent transfer to any suitable substrate, including metals, glass and transparent plastics. Nitride semiconductors are the materials of choice for a variety of device applications, notably optoelectronics1,2 and high-frequency/high-power electronics3. One important practical goal is to realize such devices on large, flexible and affordable substrates, on which direct growth of nitride semiconductors of sufficient quality is problematic. Several techniques—such as laser lift-off4,5—have been investigated to enable the transfer of nitride devices from one substrate to another, but existing methods still have some important disadvantages. Here we demonstrate that hexagonal boron nitride (h-BN) can form a release layer that enables the mechanical transfer of gallium nitride (GaN)-based device structures onto foreign substrates. The h-BN layer serves two purposes: it acts as a buffer layer for the growth of high-quality GaN-based semiconductors, and provides a shear plane that makes it straightforward to release the resulting devices. We illustrate the potential versatility of this approach by using h-BN-buffered sapphire substrates to grow an AlGaN/GaN heterostructure with electron mobility of 1,100 cm2 V−1 s−1, an InGaN/GaN multiple-quantum-well structure, and a multiple-quantum-well light-emitting diode. These device structures, ranging in area from five millimetres square to two centimetres square, are then mechanically released from the sapphire substrates and successfully transferred onto other substrates.

Raman spectroscopy of GaN, AlGaN and AlN for process and growth monitoring/control

Abstract: The use of micro-Raman spectroscopy to monitor non-invasively GaN, AlGaN and AlN material parameters for process and growth monitoring/control is demonstrated. Concepts to determine the crystalline quality, the stress, the free carrier concentration, the aluminium composition and the temperature from the Raman modes are reviewed. Raman monitoring of processing and growth is illustrated on selected examples: the high-temperature processing of ion-implanted and non-implanted GaN layers, the Raman monitoring of AlGaN/GaN heterostructure field-effect transistors and the in situ Raman monitoring of GaN growth at elevated temperatures. Ultraviolet Raman spectroscopy has been employed to characterize material properties of GaN surface layers and GaN/AlGaN interfaces. Raman mapping is illustrated on bulk AlN crystals to investigate stress fields related to growth striations and defects. Copyright © 2001 John Wiley & Sons, Ltd.