Sarikov A.,Institute of Semiconductor Physics of Ukraine
Applied Physics Letters | Year: 2011
A thermodynamic mechanism explaining the universal role of metal catalyst in the transformation of Si in the crystalline state and the preferential growth of Si wire-like crystals in the vapor-liquid-solid and relative processes is proposed based on the mechanism of the metal induced crystallization of amorphous Si. It includes metal stimulated crystallization of disordered Si formed on the catalyst and substrate surfaces and the wire-like crystal sidewalls, driven by the chemical potential difference of Si in the disordered and crystalline states. Obtained results have general nature and are applicable to the metal catalyzed wire-like crystal growth in different metal/semiconductor systems. © 2011 American Institute of Physics.
Vasko F.T.,Institute of Semiconductor Physics of Ukraine
Physical Review B - Condensed Matter and Materials Physics | Year: 2010
The transient response of an intrinsic graphene, which is caused by the ultrafast interband transitions, is studied theoretically for the range of pumping correspondent to the saturated absorption regime. Spectral and temporal dependencies of the photoexcited concentration as well as the transmission and relative absorption coefficients are considered for mid-IR and visible (or near-IR) spectral regions at different durations of pulse and broadening energies. The characteristic intensities of saturation are calculated and the results are compared with the experimental data measured for the near-IR lasers with a saturable absorber. The negative absorption of a probe radiation during cascade emission of optical phonons is obtained. © 2010 The American Physical Society.
Linnik T.L.,Institute of Semiconductor Physics of Ukraine
Journal of Physics Condensed Matter | Year: 2012
Based on the symmetry properties of the graphene lattice, we derive the effective Hamiltonian of graphene under spatially nonuniform acoustic and optical strains. Comparison with the published results of the first-principles calculations allows us to determine the values of some Hamiltonian parameters, and suggests the validity of the derived Hamiltonian for acoustical strain up to 10%. The results are generalized for the case of graphene with broken plane reflection symmetry, which corresponds, for example, to the case of graphene placed on a substrate. Here, essential modifications to the Hamiltonian give rise, in particular, to the gap opening in the spectrum in the presence of the out-of-plane component of optical strain, which is shown to be due to the lifting of the sublattice symmetry. The developed effective Hamiltonian can be used as a convenient tool for analysis of a variety of strain-related effects, including electronphonon interaction or pseudo-magnetic fields induced by the nonuniform strain. © 2012 IOP Publishing Ltd.
Vasko F.T.,Institute of Semiconductor Physics of Ukraine |
Zozoulenko I.V.,Linkoping University
Applied Physics Letters | Year: 2010
We study the conductivity of a graphene strip taking into account electrostatically induced charge accumulation on its edges. Using a local dependency of the conductivity on the carrier concentration we find that the electrostatic size effect in doped graphene strip of the width of 0.5-3 μm can result in a significant (about 40%) enhancement of the effective conductivity in comparison to the infinitely wide samples. This effect should be taken into account both in the device simulation as well as for verification of scattering mechanisms in graphene. © 2010 American Institute of Physics.
Glushko E.Ya.,Institute of Semiconductor Physics of Ukraine
Optics Express | Year: 2010
We theoretically study a 1D elastic photonic crystal containing air voids as an opto-pneumatic medium. This medium is sensitive to weak deviations of the external pressure and, owing to its elasticity, can vary its geometry depending on the external conditions. We show that the reflectivity can be drastically changed at a chosen working frequency near the photonic band-gap edge or the reflection window. The resonance properties of such pneumatic photonic crystals made of glass, silicon, and mica with directly excited eigenmodes in the infrared region of frequencies are analyzed. The ways to determine small changes in the pressure on the micro- and nanobar scale are discussed. © 2010 Optical Society of America.