B. Hejda

Czech Academy of Sciences, Institute of Physics

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J. Pastrňák

Czech Academy of Sciences, Institute of Physics

K. Král

Czech Academy of Sciences, Institute of Physics

Jiřı́ Málek

University of Pardubice

Stanislav Záliš

Czech Academy of Sciences, J. Heyrovský Institute of Physical Chemistry

Z. Khás

Czech Academy of Sciences

V. Drchal

Czech Academy of Sciences, Institute of Physics

K. Kra ́l

Czech Academy of Sciences, Institute of Physics

Jin K.

Wayne State University

K. Hauptmanová

University of Veterinary Sciences Brno

R. A. Ėvarestov

St Petersburg University

Cooperative Institutions

Czech Academy of Sciences, Institute of Physics

Czech Academy of Sciences

Institute of Physics

Czech Academy of Sciences, Institute of Plasma Physics

Pennsylvania State University

Institute of Theoretical and Applied Mechanics

Czech Academy of Sciences, J. Heyrovský Institute of Physical Chemistry

Technical University of Liberec

St Petersburg University

Pushkin Leningrad State University

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Infrared Absorption of AlN Single Crystals in the Two‐Phonon Region

physica status solidi (b) (1969)

J. Pastrňák B. Hejda

Abstract Two‐phonon infrared absorption was measured on AlN single crystals in polarized light. Contrary to previous results obtained from other materials with wurtzite structure, the full polarization of some absorption bands was found. The results are interpreted with the help of the fundamental frequencies of the BZE 738, 668, 658, 627, 507, 444, and 413 cm −1 .

Wurtzite crystal structure

10.1002/pssb.19690350246

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Citations (10)

The Symmetrized Combinations of Plane Waves for Wurtzite

physica status solidi (b) (1967)

B. Hejda

Abstract Tables of the coefficients of the symmetrized combinations of plane waves for wurtzite structure are constructed.

Wurtzite crystal structure

10.1002/pssb.19670240228

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Citations (1)

Two-stage relaxation of the electron-phonon system in polar semiconductors

physica status solidi (b) (1992)

K. Král B. Hejda

Abstract The effect of acoustic phonon bottleneck is studied theoretically in the hot electron‐phonon system in the approximation of dispersionless longitudinal optical phonons in polar semiconductors. Kinetic equations for electrons, LO‐phonons, and second generation acoustic phonons are solved numerically for CdSe. The fusion lifetime of acoustic phonons is estimated for the processes of anharmonic acoustic‐optical phonon coupling. The fusion processes are found to be critical for the occurrence of the acoustic phonon bottleneck.

10.1002/pssb.2221740121

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Citations (13)

Supermolecular CNDO/S calculation of parameters for extended hubbard hamiltonian of TCNQ dimers

Chemical Physics (1980)

K. Král Jiřı́ Málek B. Hejda Stanislav Záliš

CNDO/2

Hamiltonian (control theory)

Unpaired electron

10.1016/0301-0104(80)85172-x

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Citations (12)

Infrared Absorption of AIN in the One‐Phonon Region and Finite Size Effects

physica status solidi (b) (1969)

J. Pastrňák B. Hejda

Abstract The absorption of single crystals and microcrystalline samples of AlN, pressed in pellets of halides, has been measured in the region of 1000 to 400 cm −1 . Three intensive absorption maxima have been found in the region between ω T and ω L . They are connected with the finite size and shape effects and their location depends on the material of the surrounding medium. Further, intensive maxima at 610 and 590 cm −1 occur in microcrystalline samples. The absorption by surface modes may be interpreted with the help of Englman and Ruppin's theory assuming that the frequencies ω T ( A 1 ) = 622 cm −1 and ω T ( E 1 ) = 660 cm −1 . It is shown that it is necessary to distinguish between surface and bulk modes for the absorption measurement of microcrystalline samples and that the absorption in the region of surface modes is decisive in materials with sufficiently fine grains, i.e. in measurements with pressed pellets.

Microcrystalline

Maxima

10.1002/pssb.19690350245

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Citations (26)

Energy Band Structure of AlN

physica status solidi (b) (1969)

B. Hejda K. Hauptmanová

Watson

10.1002/pssb.19690360250

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Citations (27)

CNDO/S-CI calculation of Hubbard parameters for doubly charged TCNQ tetramer

Czechoslovak Journal of Physics (1982)

Jiřı́ Málek V. Drchal B. Hejda Stanislav Záliš

CNDO/2

Tetramer

Unpaired electron

10.1007/bf01597543

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Citations (2)

The transmittivity of Cu2O powder samples in the infrared region

physica status solidi (a) (1972)

J. Pastrňák B. Hejda

The transmittivity of Cu2O powder samples has been measured in the infrared spectral region in the vicinity of the optically active vibrational modes ωTo 1 = 610 cm−1 and ωTO 2 = 145 cm−1 for various surrounding media. The theory of optical phonons in finite ionic crystals by Englman and Ruppin has been used for the calculation of the transmittivity. The comparison between theory and experiment shows, that this theory may be used in spite of the great portion of covalent binding in Cu2O. Die Transmission von Cu2O-Pulverproben wurde im infraroten Spektralbereich in der Nähe der optisch aktiven Schwingungsmoden ωTO 1 = 610 cm−1 and ωTO 2 = 145 cm−1 bei verschiedenen Umgebungsmedien gemessen. Für die Berechnung der Transmission wurde die Theorie der optischen Phononen in endlichen Ionenkristallen von Englman und Ruppin benutzt. Der Vergleich zwischen Theorie und Experiment zeigt, daß diese Theorie trotz des großen kovalenten Bindungsanteils von Cu2O benutzt werden kann.

10.1002/pssa.2210100217

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Citations (6)

Hot LO‐Phonon Quasi‐Steady State Distribution Function in Polar Semiconductors

physica status solidi (b) (1990)

K. Král B. Hejda Z. Khás

Abstract The quasi‐steady state hot LO‐phonon distribution function, as it is produced by hot electron cooling in laser excitation experiments, is calculated induding the effect of electron energy collision broadening (EECB) and screeing. Numerical computations performed in several compound polar semiconductors reveal a rather strong effect of EECB.

Hot electron

10.1002/pssb.2221570219

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Citations (7)

Long-wavelength LO-phonon generation during hot-electron cooling in polar semiconductors

Physical review. B, Condensed matter (1993)

K. Král B. Hejda

In a hot-electron system in polar semiconductors a new mechanism is studied theoretically for long-wavelength LO-phonon generation, based on the fusion of hot acoustic phonons. The anharmonic mechanism of the LO-phonon decay into pairs of acoustic phonons is considered together with the reverse process of the fusion of acoustic phonons into the LO ones. Corresponding kinetic equations for the electronic temperature and for the distribution functions of both kinds of phonons are solved numerically in GaAs and CdSe. The relation of the numerical results on the long-wavelength LO-phonon generation, to the recent experiments by Tsen et al. in ultrathin GaAs/AlAs multiple quantum wells is discussed.

10.1103/physrevb.48.11461

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Citations (5)