scispace - formally typeset
Search or ask a question

Showing papers in "Physica Status Solidi B-basic Solid State Physics in 1977"


Journal ArticleDOI
TL;DR: In this paper, the Raman-active lattice vibrations of Bi2Se3, Bi2Te3, Sb2T3, and SbT3 were investigated by Raman scattering and three of the four expected Raman modes, Eg and A1g, could be determined.
Abstract: The Raman-active lattice vibrations of Bi2Se3, Bi2Te3, Sb2Te3, and their solid slutions, whose symmetries correspond to the R3m space group, are investigated by Raman scattering. Three of the four expected Raman modes, Eg and A1g, could be determined. The FIR optical properties of Bi2Te3 crystal surfaces of improved quality (E ∥ c and E ⟂ c) and Bi2Se3 (E ⟂ c) are re-examined near helium and room temperature with a Fourier spectrometer, allowing a determination of the infrared-active mode frequencies with higher accuracy. The results for Bi2Te3 are compared to the predicted frequencies from the lattice dynamical model, given by Jenkins et al. The frequncy shifts of the Raman-active modes in the mixed crystals show single-mode and two-mode behaviour, which is in agreement with simple models for the substitution of antimony and selenium atoms for bismuth and tellurium, respectively, in Bi2Te3.

473 citations


Journal ArticleDOI
TL;DR: In this paper, the temperature dependence of the phonon and electron contribution to the dielectric constant, e.g., in the c-and α-axes, was determined and compared to the capacitance measurements.
Abstract: Measurements of all A1 and E transverse and longitudinal phonons in BaTiO3 are reported in the temperature range 10 to 132 °C where the crystal is in the tetragonal phase. A least squares fitting of the spectral shapes is done and the resulting temperature dependence of the frequencies, linewidths and coupling parameters is presented. The temperature dependence of the phonon and electron contribution to the dielectric constant, e, in the c- and α-axes is determined and compared to the capacitance measurements. It is found that the dielectric constant discrepancy is highly anisotropic.

291 citations


Journal ArticleDOI
TL;DR: In this paper, the electrical conductivity and Hall coefficient perpendicular to the c-axis of hexagonal MoS2, MoSe2, and WSe2 were measured over the temperature ranges 120 to 1170 K and 140 to 820 K, respectively.
Abstract: The electrical conductivity and Hall coefficient perpendicular to the c-axis of hexagonal MoS2, MoSe2, and WSe2 are measured over the temperature ranges 120 to 1170 K and 140 to 820 K, respectively. The derived temperature-dependent carrier densities are described by n ∼ exp (–E/kT) for temperatures less than 800 K indicating (thermal) energy gaps of 0.38 eV in n-type MoS2, 0.27 eV in n-type MoSe2, and 0.19 eV in p-type WSe2. Above room temperature the carrier mobilities are given by μ ∼ T−α, where α ≈ 1.5 in MoS2, MoSe2 and 2.7 in WSe2. The high-temperature (>800 K) thermal activation energies of conduction correspond to energy gaps of 1.27, 0.95, and 1.33 eV in MoS2, MoSe2, and WSe2, respectively. Similar measurements on MoTe2 crystals grown by bromine vapour transport demonstrate the effects of included bromine on the low-temperature conduction processes.

144 citations



Journal ArticleDOI
TL;DR: In this paper, the magnetic field and temperature dependence of both guest and host fluorescence in penta-eene-doped tetracene single crystals are studied, and it is concluded that pentacene enters substitutionally into the host lattice sites and that thermally activated heterofission is site-dependent with activation energies ≈ (0.13 ± 0.01) e V and ≦ 0.06 eV.
Abstract: The magnetic field and the temperature dependence of both guest and host fluorescence in penta-eene-doped tetracene single crystals is studied. From an analysis of the experimental results it is concluded that pentacene enters substitutionally into the host lattice sites and that thermally activated heterofission is site-dependent with activation energies ≈ (0.13 ± 0.01) e V and ≦ 0.06 eV. From a kinetic fit to the temperature dependence of the green and red fluorescence, a thermally activated host singlet exciton diffusion coefficient ≈ 2 × 10−2 cm2/s is inferred; its activation energy is estimated to be (0.018 ± 0.001) eV. The heterofission rate of ≈(4.7 ± 0.5) × l0−10 cm3 s−1 is determined and location of the pentacene triplet level is found to be at (0.86 ± 0.03) eV. Es wird die Abhangigkeit sowohl der Gast- als auch der Wirts-Fluoreszenz in pentazendotierten Tetrazeneinkristallen vom Magnetfeld und von der Temperatur untersucht. Aus einer Analyse der experimentellen Ergebnisse wird geschlossen, das Pentazenzentren substitutionell auf Wirts-gitterplatze eingebaut werden und das die thermisch aktivierte Heterospaltung gitterplatzabhan-gig ist mit Aktivierungsenergien von etwa (0,13 ± 0,01 )eV und ≦ 0,06 eV. Aus einer kinetischen Anpassung an die Temperaturabhangigkeit der grunen und roten Fluoreszenz wird ein thermisch aktivierter Diffusionskoeffizient fur ein Wirts-Singulett-Exziton von ≈ 2 × 10−2 cm2/s bestimmt; seine Aktivierungsenergie wird zu (0,018 ± 0,001) eV berechnet. Die Heterospaltungsrate von ≈ (4,7 ± 0,5) × 10−10 cm3 s−1 wird bestimmt, und es wird gefunden, das das Pentazentri-plettniveau bei etwa (0,86 ± 0,03) eV lokalisiert ist.

119 citations


Journal ArticleDOI
TL;DR: In this paper, the lifetime of excitons bound to the neutral donors Li, P, and As and neutral acceptors B, Al, Ga, and In in silicon are determined by time-resolved photoluminescence measurements at 4.2 K and a strong dependence on the binding energy of the donor or acceptor is found.
Abstract: The lifetimes of excitons bound to the neutral donors Li, P, and As and neutral acceptors B, Al, Ga, and In in silicon are determined by time-resolved photoluminescence measurements at 4.2 K and a strong dependence on the binding energy of the donor or acceptor is found. This dependence can be understood assuming a localized phononless Auger-process to be the main recombination mechanism. A theoretical calculation using approximate wavefunctions is presented and leads to a very good agreement with the experimental results. Die Lebensdauern gebundener Exzitonen an den neutralen Donatoren Li, P und As sowie den Akzeptoren B, Al, Ga und In in Silizium werden bei 4,2 K mit zeitaufgeloster Photolumineszenzspektroskopie gemessen. Es ergibt sich eine starke Abhangigkeit von der Bindungsenergie der entsprechenden Storstelle. Man kann diese Abhangigkeit verstehen, wenn man einen lokalisierten, phononenfreien Auger-Prozes als wesentlichen Rekombinationsmechanismus annimmt. Eine theoretische Berechnung der Lebensdauer unter Verwendung angenaherter Wellenfunktionen ergibt eine sehr gute Ubereinstimmung mit den experimentellen Ergebnissen.

104 citations


Journal ArticleDOI
TL;DR: Extended Huckel theory calculations are carried out for interstitial hydrogen atoms in silicon model crystals without and with vacancies as discussed by the authors, and the vibrational frequencies for all defect types considered are in very close agreement with infrared bands observed after proton irradiation of silicon.
Abstract: Extended Huckel theory calculations are carried out for interstitial hydrogen atoms in silicon model crystals without and with vacancies. The energetically stable positions for the hydrogens appear to be the tetrahedral interstitial site in crystals without vacancies; in the case of vacancies the hydrogens favor positions in the dangling bonds of the vacancies 0.35 bond lengths away from the vacancy nearest neighbors. The vibrational frequencies for all defect types considered are in very close agreement with infrared bands observed after proton irradiation of silicon. The frequencies increase with the number of hydrogens in a vacancy. The hydrogen-related impurity levels are very close to the valence band edge, both above or below. Rechnungen nach der erweiterten Huckel-Theorie werden fur Wasserstoff-Zwischengitteratome in Silizium-Modellkristallen ohne und mit Leerstellen ausgefuhrt. Die energetisch stabilen Positionen fur die Wasserstoffatome erweisen sich als tetraedrische Zwischengitterplatze in Kristallen ohne Leerstellen. Im Falle von Leerstellen bevorzugen die Wasserstoffatome Positionen in den freien Bindungen der Leerstellen, 0,35 Bindungslangen von den nachsten Nachbaratomen der Leerstelle entfernt. Die Schwingungsfrequenzen fur alle betrachteten Defektarten liegen sehr nahe bei denen von Infrarotbanden, die nach Protonenbestrahlung von Silizium beobachtet wurden. Die Frequenzen nehmen mit der Anzahl von Wasserstoffatomen in einer Leerstelle zu. Die Defektniveaus, die von den Wasserstoffatomen herruhren, liegen sehr dicht ober- oder unterhalb der Valenzbandkante.

95 citations




Journal ArticleDOI
M. Röslee1, R. Zimmeemann1
TL;DR: In this paper, the phase diagram of electron-hole drop formation in excited direct band gap semiconductors including the coupling to LO phonons is calculated, and critical temperatures as high as 64 K are obtained.
Abstract: The phase diagram of electron-hole drop formation in excited direct band gap semiconductors is calculated including the coupling to LO phonons. Results are given for CdS, CdSe, ZnS, GaAs, and CdTe. Critical temperatures as high as 64 K. (CdS) are obtained. In the self-energy calculation the single-plasmon pole approximation with the full RPA treatment is compared critically. Das Phasendiagramm fur die Bildung von Elektron-Loch-Tropfen in angeregten Halbleitern mit direkter Energielucke wird unter Einschlus der Kopplung an LO-Phononen berechnet. Ergeb-nisse werden fur CdS, CdSe, ZnS, GaAs und CdTe angegeben. Die kritische Temperatur fur CdS ergibt sich zu 64 K. Bei der Berechnung der Selbstenergie wird die Plasmon-Pol-Naherung kri-tisch mit der vollen RPA-Rechnung verglichen.

74 citations


Journal ArticleDOI
TL;DR: In this article, the CNDO parametrization of solids was applied to first time for three-dimensional crystals (diamond and lithium fluoride) and the results obtained were compared with those of band structure calculations using the LCAO approximation.
Abstract: Equations are obtained describing in the CNDO approximation the electronic states of solids in the framework of the large unit cell approach. The CNDO approximation is applied to first timefor three-dimensional crystals (diamond and lithium fluoride). The applicability of the CNDO parametrization suggested for molecules for the calculation of electronic states of solids is discussed. The results obtained are compared with those of band structure calculations using the LCAO approximation. [Russian Text Ignored].

Journal ArticleDOI
TL;DR: In this paper, the rate equations for the exciton-exciton (ex-ex), excitonelectron (exe), and excitonhole (exh) recombination processes are derived by taking into account polariton effects.
Abstract: The rate equations for the exciton-exciton (ex-ex), exciton-electron (ex-e) and exciton-hole (ex-h) recombination processes are derived by taking into account polariton effects. The solutions of the stationary rate equations yield the spectra of the spontaneous emission and of the gain. Their temperature-dependent shifts are calculated by taking into account self-energy corrections which improve the agreement with experiment. Furthermore, the various threshold pump rates are calculated. Due to these results it is expected that the laser action should start at low temperatures for the ex-ex process, at intermediate temperatures for the ex-LO phonon process (which has been treated previously), and at high temperatures for the ex-e process. The temperature ranges in which the nonlinear recombination processes (ex-ex, ex-e) have the lowest threshold increase with decreasing resonator quality. Numerical results arc given for example for CdS. Die Bilanzgleichungen fur die Exziton-Exziton (ex-ex)-, Exziton-Elektron (ex-e)- und Exziton-Loch (ex-h)-Rekombinationsprozesse werden unter Berucksichtigung von Polariton-Effekten her-geleitet. Die Losungen der stationaren Bilanzgleichungen liefern die Spektren der spontanen Emission und der Verstarkungsfunktion. Fur die Berechnung der temperaturabhangigen Verschiebungen dieser Spektren werden die Selbstenergiekorrekturen berucksichtigt. Dadurch wird eine gute Ubereinstimmung mit experimentellen Ergebnissen erreicht. Auserdem werden die Laserschwellen der verschiedenen Prozesse bestimmt. Auf Grund dieser Ergebnisse wird erwartet, das die Laser-tatigkeit bei tiefen Temperaturen im ex-ex-Band einsetzt, und ferner, das im mittleren Temperaturbereich die stimulierte Emission zuerst im LO-Phonon-Band und bei hohen Temperaturen zuerst im ex-Band auftritt. Die Temperaturbereiche, in denen die nichtlinearen Rekombinations-prozesse (ex-ex, ex-e) die niederste Schwelle haben, werden groser mit abnehmender Resonator-qualitat. Numerische Ergebnisse werden fur das Beispiel von CdS angegehen.

Journal ArticleDOI
TL;DR: In this paper, a quantum theory of spontaneous γ-quantum radiation by relativistic channelled particles is developed, and the effect of potential unharmonism on spectral distribution is estimated.
Abstract: A quantum theory of spontaneous γ-quantum radiation by relativistic channelled particles is developed Planar channelling of positrons and axial channelling of electrons are considered The calculation results are in a good agreement with classical estimates Population of the levels is studied and the conditions of spontaneous radiation are analyzed in detail It is shown that, when the transitions between the lower levels are considered, one may limit oneself to the solution of the problem for a single potential well since in this case the neighbouring wells fail practically to affect the calculation results The effect of the potential unharmonism on spectral distribution is estimated [Russian Text Ignored]

Journal ArticleDOI
TL;DR: In this paper, the Fourier transform of Compton profiles of Si and Li has been shown to be invariant to the translation invariance of the lattice and the density of Bloch k-states (Fermi surface).
Abstract: Theorems on the one-dimensional Fourier transform of directional Compton profiles are given within the frame of the one-electron approximation. The theorems relate the one-dimensional Fourier transform of Compton profiles with the three-dimensional Fourier transform of the momentum density, with the off-diagonal elements of the first-order density matrix, with the translation invariance of the lattice, and with the density of Bloch k-states (Fermi surface) respectively. Possible applications of these theorems are discussed and demonstrated by means of the Fourier transform of experimental Compton profiles of Si and Li. Theoreme uber die eindimensionale Fouriertransformierte von richtungsabhangigen Compton-Profilen werden im Rahmen der Einelektronennaherung angegeben. Sie betreffen die Beziehirng der eindimensionalen Fouriertransformierten von Compton-Profilen zu der dreidimensionalen Fouriertransformierten der Impulsdichte, den Nichtdiagonalelementen der Dichte matrix erstor Ordnung, der Translationsinvarianz des Kristallgitters und zu der Dichte der Bloehschen k-Zu-stande (Fermi-Flachen). Mogliche Anwendungen dieser Theoreme werden diskutiert und an der Fouriertransformierten experimenteller Comptonprofile des Si und Li aufgezeigt.


Journal ArticleDOI
TL;DR: In this article, the authors applied submillimeter resonance spectroscopy and interband magneto-absorption to the investigation of the Hg1−xCdx Te alloys system in the range of composition x 120 meV.
Abstract: Submillimeter resonance spectroscopy and interband magneto-absorption are applied to the investigation of the Hg1−xCdx Te alloys system in the range of composition x 120 meV), on identical unoriented samples, in the Faraday and Voigt geometries. Magnetooptical data are analyzed using the virtual crystal approximation. All interband and intraband magnetooptical transitions are interpreted in terms of Γ6 and Γ8 Landau levels described by the Pidgeon and Brown model. The Kane matrix element, the interaction gap, and the Luttinger parameters are determined for each alloy composition from the comparison between theory and experiments. Magnetooptics also provide information on the evolution of the resonant acceptor states with the composition.

Journal ArticleDOI
TL;DR: A detailed survey of the dielectric properties of a wide range of solids shows that their response functions in frequency or in time depart strongly from the Debye response and fall into a remarkably common or "universal" pattern as mentioned in this paper.
Abstract: A detailed survey of the dielectric properties of a wide range of solids shows that their response functions in frequency or in time depart strongly from the Debye response and fall into a remarkably common or ‘universal’ pattern. The frequency response is similar for systems with permanent dipoles and with hopping charge carriers of electronic or ionic nature. It is also largely independent of the type of physical structure and chemical bonding in the materials. The existing approaches to the interpretation of this behaviour are shown to suffer from two basic drawbacks: they have to make rather arbitrary assumptions and they are unable to explain the essential similarity of the behaviour of many very different systems. Eine ausfuhrliche Untersuchung der dielektrischen Eigenschaften einer grosen Reihe von Festkorpern zeigt, das ihre Frequenzresponse oder Zeitresponse stark von derDebyeresponse abweichen und in ein auffallend gemeinsames oder „universelles” Muster passen. Die Frequenzresponse ist fur Systeme mit permanenten Dipolen und mit Hopping-Ladungstragern elektronischer oder ionischer Natur ahnlich. Sie ist auch weitgehend unabhangig vom physikalischen Strukturtyp und der chemischen Bindung des Materials. Die existierenden Methoden zur Interpretation dieses Verhaltens zeigen zwei Nachteile: sie mussen ziemlich willkurliche Annahmen machen, und sie sind nieht in der Lage, die wesentliche Ahnlichkeit im Verhalten vieler sehr unterschiedlicher Systeme zu erklaren.

Journal ArticleDOI
TL;DR: In this paper, the temperature dependence of the three bands, of which the total luminescence spectrum consists, could be determined seperately, and it was found that all three of them decrease at high temperature with approximately the same activation energy of 0.13 eV.
Abstract: Photoluminescence of amorphous silicon is measured in the range from 77 K to room temperature. The temperature dependence of the three bands, of which the total luminescence spectrum consists, could be determined seperately. It is found that all three of them decrease at high temperature with approximately the same activation energy of 0.13 eV. This decrease sets in at different temperatures for the different bands. The three bands are interpreted as transitions within electron-hole pairs consisting of more or less deeply trapped carriers. The activated decrease at high temperature is explained by thermally activated dissociation of these pairs. The electron-hole pair concept also explains why photoconductivity decreases about twice as fast as luminescence when the substrate temperature is lowered. Die Photolumineszenz von amorphem Silizium wird zwischen 77 K und Zimmertemperatur gemessen. Die Temperaturabhangigkeit der drei Banden, aus denen das gesamte Lumineszenz-spektrum besteht, kann dabei getrennt bestimmt werden. Alle drei Banden nehmen bei hoher Temperatur mit ungefahr der gleichen Aktivierungsenergie von 0,13 eV ab. Dieser Abfall setzt fur die verschiedenen Banden bei verschiedenen Temperaturen ein. Die drei Banden werden als Ubergange innerhalb von Elektron-Loch-Paaren gedeutet, wobei die Elektronen oder Locher in verschieden tiefen Haftstellen sitzen. Der aktivierte Abfall der Lumineszenz bei hoher Temperatur wird durch thermisch aktivierte Dissoziation dieser Paare erklart. Dieses Konzept erklart auch, warum die Photoleitung doppelt so schnell abnimmt wie die Lumineszenz, wenn die Substrat-temperatur erniedrigt wird.

Journal ArticleDOI
TL;DR: In this article, a theory of spontaneous radiation of γ-quanta in channeling relativistic particles was developed, which is different from the presently known types of radiation sources.
Abstract: The theory of a new effect is developed — spontaneous radiation of γ-quanta in channeling relativistic particles. The radiation characteristics are different from the presently known types of radiation sources. At energies of the order of 1 GeV the radiation is characterized by wavelength ⪅ 10−3 A. The radiation intensity is about 6 to 9 orders of magnitude higher than obtained from modern synchrotrons. Its monochromaticity is considerably better than bremsstrahlung or synchrotron radiation. The radiation is fairly well polarized. In the quantum treatment, the radiation is caused by transitions between levels, which are formed in channeling in the fields of atomic planes and rows. A classical and quantum calculation of the radiation intensity is presented. At a current of about 100 μA and a target thickness of ≈ 1000 μm, about 1018 to 1019 quanta/s are radiated. The spectral density of the radiation is considerably higher than that of any known kind of radiation. It is suggested that the radiation might be used to influence selectively nuclear transitions and to produce a γ-laser. This radiation can be used to study the crystal lattice potentials, measure the particle energy, and so on. Dispersion is studied. The possibility of enhancing the induced radiation is shown. A number of studies on light channeled particles are analysed. [Russian Text Ignored].

Journal ArticleDOI
TL;DR: In this paper, the Hartree-Fock-SCF-LCAO formulae for the electronic band structure of systems with screw symmetry were developed using the smallest screw displacement as elementary operation.
Abstract: The electronic band structure of systems with screw symmetry is developed using the smallest screw displacement as elementary operation. For atomic and molecular helical systems the resulting Hartree-Fock SCF-LCAO formulae are presented. Results for ferroelectric HC1 and HP are reported, obtained with the MUNICH-CHAIN programme, in which the new formalism is implemented. The connection to the translational symmetry and the numerical results are discussed. Die elektronische Bandstruktur von Systemen mit Schraubensymmetrie wird abgeleitet, wobei die kleinste Sehraubung als Elementaroperation zugrunde gelegt ist. Die Hartree-Fock-SCF-LCAO-Formeln fur helikale Atom- und Molekulsysteme werden angegeben. Es werden Ergebnisse fur ferroelektrisches HCl und HF mitgeteilt, die mit dem MUNICH-CHAIN-Programm erhalten wurden, in dem der neue Formalismus implementiert ist. Der Zusammenhang zur Translations-symmetrie und die numerischen Resultate werden diskutiert.

Journal ArticleDOI
TL;DR: In this paper, the third order elastic (TOE) constants of ionic solids, crystallizing in the NaCl structure, derived earlier from the Lundqvist potential by Puri and Verma are modified to take account of the second neighbour short range repulsive interactions.
Abstract: Expressions for the third order elastic (TOE) constants of ionic solids, crystallizing in the NaCl structure, derived earlier from the Lundqvist potential by Puri and Verma are modified to take account of the second neighbour short range repulsive interactions. These expressions are used to evaluate the TOE constants and the pressure derivatives of the second order elastic (SOE) constants of alkaline earth oxides and those alkali halides which crystallize in the NaCl structure. The calculated values give fairly good agreement with available experimental results and in this respect are better than the results reported by other theoretical workers and those obtained in earlier calculations where short range repulsion was limited to nearest neighbours only. #Es wird ein Ausdruck fur die elastischen Konstanten dritter Ordnung (TOE) von Ionenkristallen, die in der NaCl-Struktur kristallisieren, aus dem von Puri und Verma bereits fruher abgeleiteten Lundqvistpotential modifiziert und schliest nun kurzreichweitige abstosende Wechselwirkungen der zweiten Nachbarn ein. Diese Ausdrucke werden benutzt, um die TOE-Konstanten und die Druckableitungen der elastischen Konstanten zweiter Ordnung (SOE) von Erdalkalioxiden und solchen Alkalihalogeniden, die in der NaCl-Struktur kristallisieren, zu berechnen. Die berechneten Werte ergeben ziemlich gute Ubereinstimmung mit erhaltlichen experimentellen Ergebnissen und sind in dieser Hinsicht besser als die Ergebnisse fruherer Berechnungen und anderer theoretischer Arbeiten, wo kurzreichweitige Abstosung auf nur nachste Nachbarn begrenzt ist.

Journal ArticleDOI
TL;DR: In this paper, the two-photon absorption (TPA) of the biexciton in CuCl by using two different light sources has been investigated, and the ground-state energy and its symmetry has been verified experimentally.
Abstract: In studying the two-photon absorption (TPA) of the biexciton in CuCl by using two different light sources, interesting information is obtained. The biexciton ground-state energy is determined accurately; its symmetry is experimentally verified; a value for the TPA coefficient is deduced and compared with a theoretical evaluation; a lineshape analysis enables us to discuss the damping constants of the exciton and biexciton states involved. L'absorption simultanee de deux photons (TPA) du biexciton est mesuree dans CuCl a l'aide de deux sources lumineuses distinctes. Cette technique experimentale fournit d'interessantes possibilites. Ainsi, l'energie et la symetrie du niveau fondamental du biexciton sont determinees avec precision. Le coefficient d'absorption est mesure et compare a une estimation theorique. La forme spectrale de la raie d'absorption est etudiee. Les temps de relaxation de l'exciton et du biexciton sont evalues.


Journal ArticleDOI
TL;DR: In this article, the results of non-vertical interband transitions of two-dimensional band structures were discussed in terms of electron energy loss measurements, and the results were shown to be similar to those in this paper.
Abstract: Wave-vector (q)-dependent energy loss functions, Im [−ϵ⟂(ω, q⟂)]−1, and dielectric functions, ϵ2⟂(ω, q⟂), of hexagonal boron nitride and graphite up to q⟂-values of almost one third of the Brillouin zone and up to energies of 40 eV were derived from electron energy loss measurements. The results are discussed in terms of non-vertical interband transitions of two-dimensional band structures. Aus Elektron-Energieverlustmessungen wurden die vom Wellenvektor abhangigen Energieverlustfunktionen Im [−ϵ⟂(ω, q⟂)]−1 und dielektrischen Funktionen ϵ2⟂(ω, q⟂) von hexagonalem Bornitrid und Graphit bis hin zu q⟂ -Werten von ungefahr einem Drittel der Brillouinzone und bis hin zu Energieverlusten von 40 eV bestimmt. Die Ergebnisse werden in der Form nichtsenkrechter Interbandubergange fur zweidimensionale Bandstrukturen diskutiert.

Journal ArticleDOI
W. Rehm1, R. Fischer1, J. Stuke1, H. Wagner1
TL;DR: The photo and dark conductivity of boron and phosphorus-doped amorphous silicon is measured in the temperature range from 100 to 400 K, for various doping levels as discussed by the authors.
Abstract: The photo and dark conductivity of boron- and phosphorus-doped amorphous silicon is measured in the temperature range from 100 to 400 K, for various doping levels. Increasing doping generally decreases the activation energy of dark conductivity, down to 0.2 eV, and also decreases the σ0-value (extrapolation of dark conductivity for T ∞). This lowering of σ0 is explained by a temperature shift of the Fermi level plus a change in the conduction mechanism. The activation energy of photoconductivity is also lowered, at least by phosphorus doping, which is understood by an influence of doping on the tailing of the bands. Die Dunkel- und Photoleitung von Bor- und Phosphor-dotiertem amorphem Silizium wird fur verschiedene Dotierungen zwischen 100 und 400 K gemessen. Bei wachsender Dotierung sinkt die Aktivierungsenergie der Dunkelleitfahigkeit bis herab zu 0,2 eV: der σ0-Wert (die Extrapolation der Dunkelleitfahigkeit fur T ∞) nimmt jedoch ebenfalls ab. Diese Abnahme wird durch Verschiebung des Ferminiveaus erklart, verbunden mit einer Anderung des Leitungsmechanismus. Die Aktivierungsenergie der Photoleitung wird ebenfalls gesenkt, zumindest im Fall der Phosphor-Dotierung, was mit einer Beeinflussung der Bandauslaufer durch die Dotierung erklart wird.

Journal ArticleDOI
TL;DR: In this paper, a "screened hopping" model involving many-body interactions is proposed which has the requied generality and which should account for the commonly observed behaviour of most solids.
Abstract: On the basis of the experimental data previously presented, the case is made for a unifying approach to the interpretation of the common dielectrie response of most solids. This approach starts from the unique property of this response tht the ratio to the energy lost per cycle to the energy stored in the system is independent of frequency. A “screened hopping” model involving many-body interactions is proposed which has the requied generality and which should account for the commonly observed behaviour. The physical nature of the loss peaks is also interpreted in terms ofthe new model as the result of sequential interplay of the different types of decay processes in the time domain. The relation of the new model to the classical Debye picture is briefly discussed. Auf der Grundlage von fruher veroffentlichten experimentellen Werten wird der Versuch einer einheitlichen Behandlung beid er Interpretation des ublichen dielektrischen Response der meisten Festkorper gemacht. Diese Behandlung geht aus von der besonderen eigenschaft dieses Response. das das Verhaltnis des Energieverlustes pro Zyklus zur im System gespeicherten Energie frequenzunabhangig ist. Es wird ein Vieklorperwechselwirkungen enthaltendes „screened hopping”-Modell vorgeschlagen, das die geforderte Allgemeinheit besitzt und das gewohnlich beobachtete Verhalten erklaren soll. Die physikalische Natur der Verlustmaxima wird ebenfalls mit dem neuen Modell als Ergebnis eines zusammenspiels von Zwei unterschiedlichen Abklingprozessen in der Zeitdomane erklart. Die Beziehung des neuen Modells zum klassischen Debyebild wird kurz diskutiert.

Journal ArticleDOI
TL;DR: In this paper, the magnetoabsorption spectra of semimetallic Hg1−kMnkTe alloys (k ≦ 2%) provide evidence of striking modifications in the spin states of the T8 Landau levels, in particular a drastic increase of the electronic Lande factor is observed.
Abstract: T6 T8, magnetoabsorption spectra of semimetallic Hg1−kMnkTe alloys (k ≦ 2%) provide evidence of striking modifications in the “spin” states of the T8 Landau levels, in particular a drastic increase of the electronic Lande factor is observed. These anomalous spin effects are interpreted as the manifestation of the exchange interactions between the mobile electrons and the d electrons localized on the Mn atoms. The exchange integral for T8 levels is estimated. L′etude de la magnetoabsorption interbande T6 T8, effectuee sur des alliages semimetalliques Hg1_kMnkTe(k ≦ 2%), a permis de mettreen evidence des modifications importantes dans les sous niveaux de “spin” de la bande T8, en particulier un accroissement considerable du facteur de Lande des electrons est observe. Ces effets de spin anormaux sont interpretes comme provenant des interactions d′echange entre les electrons de conduction et les electrons d localises sur les atomes de manganese. L′integrale d′echange pour les niveaux T8 est evaluee.

Journal ArticleDOI
TL;DR: In this article, a theory for the temperature dependence of the ESR linewidth in amorphous germanium and silicon was outlined for the lifetime broadening with the motion of the spins.
Abstract: A theory is outlined for the temperature dependence of the ESR linewidth in amorphous germanium and silicon. By connecting the lifetime broadening with the motion of the spins, and assuming a distribution of spin relaxation times, the experimental results may be explained, in particular the observed relationship between temperature dependent linewidth and dc conductivity. Es wird eine Theorie fur die Temperaturabhangigkeit der ESR-Linienbreite in amorphem Germanium und Silizium entwickelt. Die experimentellen Ergebnisse lassen sich durch Verknupfung der Lebensdauerverbreiterung mit der Bewegung der Spins und unter Berucksichtigung einer Verteilung der Spin-Relaxationszeiten erklaren. Insbesondere kann die beobachtete Beziehung zwischen der temperaturabhangigen Linienbreite und der Gleichstromleitfahigkeit erklart werden.

Journal ArticleDOI
TL;DR: In this paper, the effect of penetration of an electric field into the metal, electrolyte, solution, or other plasmalike medium (PLM) on the image-potential energy in a dielectric adjacent to such a PLM is studied.
Abstract: The effect of penetration of an electric field into the metal, electrolyte, solution, or other plasmalike medium (PLM) on the image-potential energy in a dielectric adjacent to such a PLM is studied. The asymptotics of classical attraction of a test charge to an “impenetrable metal surface” at large distances and of effective interaction with “dielectric-dielectric interface” at small distances are found. The latter results in a repulsion of a charge from the boundary, when the dielectric constant of the background medium, in which plasma particles are dissolved, is smaller than the permittivity of the dielectric. A minimum of the image-potential curve is situated between the “repulsive” and “attractive” limiting branches. Thus an adsorption minimum is predicted within the scope of purely electrostatic considerations, the value of the “desorption energy” being estimated. [Russian Text Ignored].