Using far-infrared laser pulses, electron-spin resonance has been excited in ${\mathrm{Cd}}_{\mathit{x}}$${\mathrm{Mn}}_{1\mathrm{-}\mathit{x}}$Te in high magnetic fields up to 22 T at liquid-helium temperature. Electron-spin-resonance line shapes have been observed by monitoring the transmitted intensity. Simultaneously, the dynamic of the longitudinal magnetization was recorded with a pick-up coil showing, contrary to the transmission, a single line. The discrepancies were due to the geometrical interferences.

We introduce a simple model to calculate the Stark shift in multiple quantum wells consisting of highly anisotropic and optically nonlinear molecular-crystalline layers. This model is used to calculate the exciton absorption peak in quantum-well structures consisting of the archetype planar molecular compounds; 3,4,9,10-perylenetetracarboxylic dianhydride, 3,4,7,8-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole, and copper phthalocyanine. We find that the exciton absorption peak shifts by 60 to 70 meV in an electric field of <${10}^6$ V/cm. We also find that both redshifts and blueshifts are achieved for asymmetrical quantum-well structures.

The early stages of Sb films deposited at room temperature on Si(100)2×1 surfaces have been investigated by angle-integrated and angle-resolved Auger spectroscopy. A comparison between the experimental results and the predictions of simple deposition models indicates that the growth of the Sb film proceeds by island formation. Without any annealing, a uniform overlayer never develops up to films 4 nm thick.

Raman and resonance Raman spectroscopic techniques have been utilized to study the phenomenon of spontaneous ordering in epitaxial ${\mathrm{Ga}}_{0.52}$${\mathrm{In}}_{0.48}$P grown on (001) GaAs substrates at different temperatures. Raman selection rules suggest larger deviations from cubic zinc-blende symmetry for samples exhibiting a greater degree of ordering. Raman excitation profiles show a redshift and broadening of the resonance peak as the samples become more ordered. In addition, the anisotropy of the absorption coefficients along the [110] and [11¯0] crystallographic directions in the rhombohedral phase of the ordered material enables us to estimate the crystal-field splitting. Our results support the recently proposed microstructural model for ordering in these alloys.

The X-band ESR of thin diamond films deposited from a mixture of 99.5% ${\mathrm{H}}_2$ and 0.5% ${\mathrm{CH}}_4$ is compared to those of films similarly prepared from ${\mathrm{D}}_2$-${\mathrm{CD}}_4$ and ${\mathrm{H}}_2$${\mathrm{-}}^{13}$${\mathrm{CH}}_4$ mixtures. The main line and the satellites at ±7.2 G are unaffected by annealing at T≤1100 °C, but their intensity is reduced upon annealing at ∼1500 °C. Since the satellites are absent from the deuterated films, they are attributed to newly identified dangling-bond H centers, possibly on internal surfaces, but more plausibly embedded in the bulk. This is consistent with the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ relaxation rate, which indicates a uniform distribution of paramagnetic centers.

We analyze the photoluminescence and photoluminescence-excitation spectra of a 10-nm-thick (311)-oriented GaAs/${\mathrm{Al}}_{0.33}$${\mathrm{Ga}}_{0.67}$As single quantum well of state-of-the-art optical quality. The ground-state (1S) heavy-hole exciton transition is coincident in emission and absorption and has a linewidth of 0.86 meV. We observe the first excited state (2S) of the heavy-hole as well as of the light-hole exciton, allowing accurate determination of their binding energies. Having determined, in addition, both the quantum-well width and the barrier composition by independent means, we can thus deduce from the experimental transition energies the heavy-hole and light-hole masses along the [311] direction. The measured values of 0.460 and 0.092 for the heavy-hole and light-hole masses, respectively, are consistent with results derived from refined sets of Luttinger parameters proposed recently.

We investigate the growth kinetics on vicinal GaAs(001) surfaces by making detailed comparisons between reflection high-energy electron-diffraction specular intensity measured near in-phase diffraction conditions and the surface step density obtained from simulations of a solid-on-solid model. Only by including a barrier to interlayer transport and a short-range incorporation process of freshly deposited atoms can the simulations be brought into agreement with the measurements both during growth and during post-growth equilibration of the surface.

We present a self-consistent pseudopotential calculation of the valence-band offset at the GaAs/InAs (001) strained interface which is chosen as an example of isovalent, common-anion, lattice-mismatched heterojunctions. Our results show that the valence-band offset can be tuned by about 0.5 eV going from GaAs to InAs substrates, mainly due to the different effect of strain on the topmost valence-band state of the two bulk materials.

A high-precision low-energy electron-diffraction (LEED) structure analysis for an eight-monolayer ultrathin fcc Fe film epitaxially grown on Cu(100) is presented. The film is free of strain, i.e., its lattice coincides with that of equilibrium fcc iron rather than with that given by the Cu substrate. The top layer is reconstructed and its distance to the second layer is expanded. Similar features hold also for films in the range 5–11 monolayers. The theory-experiment fit is the best ever achieved in a LEED structure determination with a Pendry R factor of 0.09.

Neutral fullerene ${\mathrm{C}}_{60}$ is studied by the electron-lattice-coupling tight-binding model. When one or two electrons are excited from the highest occupied molecular orbital to the lowest unoccupied molecular orbital of a ${\mathrm{C}}_{60}$ molecule, the lattice relaxes and the lowest-energy state of ${\mathrm{C}}_{60}$ is discovered to be a ring-bipolaron exciton which is qualitatively consistent with the self-trapped polaron exciton observed in the luminescence experiment of neutral ${\mathrm{C}}_{60}$. The symmetry of optical excitation ${\mathrm{C}}_{60}$ is reduced from ${\mathit{I}}_{\mathit{h}}$ to ${\mathit{D}}_{5\mathit{d}}$ and it is proposed that four NMR lines would be observed in this material.

Single-crystal x-ray diffraction has been used to study the evolution of the molecular orientational ordering in the low-temperature simple-cubic phase of ${\mathrm{C}}_{60}$. It is found that the saturation of the intensity of characteristic reflections at the glass transition, ${\mathit{T}}_{\mathit{g}}$∼85 K, is more abrupt on heating than on cooling the sample. Furthermore ${\mathit{T}}_{\mathit{g}}$ is shown to increase with the rate of temperature variation, in excellent agreement with previous dilatometry measurements. We also confirm the existence of an anomaly (inflection) in the growth of the orientational order parameter near 165 K, indicating a structural change.

The quasiparticle electronic band structure of ${\mathrm{C}}_3$${\mathrm{N}}_4$ carbon nitride in the β-${\mathrm{Si}}_3$${\mathrm{N}}_4$ structure is calculated using the GW approximation. The indirect band gap is predicted to be 6.4±0.5 eV and the minimum direct gap is found to be at Γ with a value of 6.75 eV. A plane-wave local-density-approximation band structure is also presented.

An experimental study of the luminescence time decay in porous silicon as a function of temperature, excitation, and observation energies is reported. The decay line shape is well described by a stretched exponential for a variety of experimental conditions. A hierarchy of waiting times for carrier hopping, of intersite distances, and of site energies result from the analysis of our data.

Damage creation at GaAs/AlAs/GaAs interfaces during irradiation with MeV Kr and Ar ions was investigated by ion channeling experiments. The GaAs layers became amorphous while the AlAs layers showed unusual damage behavior. At one interface, AlAs on GaAs, an amorphous phase grows into the AlAs while at the opposite interface, GaAs on AlAs, the AlAs remains crystalline. The asymmetry is also observed in samples with five alternating layers; amorphization occurs at the two AlAs on GaAs interfaces but not at the GaAs on AlAs interfaces. The rate at which the amorphous layer grows does not depend on the deposited damage energy alone, but rather depends on the ratio of the ionization to damage energies, demonstrating the importance of ionization in the damage process. At large ratios of ionization to damage energies, the growth rate can be zero or even negative.

We propose a novel model for the nonlinear dynamics of spatiotemporal patterns in semiconductors with negative differential conductivity under the influence of a transverse magnetic field. Dielectric relaxation of both the applied electric field and the Hall field combined with the generation-recombination kinetics of the carriers obtained from a Monte Carlo simulation induces a transverse motion of the current filaments and complex sequences of nucleation, traveling, and destruction of filaments which result in chaotic current and voltage oscillations.

Radiative lifetimes and acoustic-phonon scattering times of near-band-gap excitons are calculated. With increasing spatial quantization, exciton relaxation by phonon emission decreases strongly in efficiency as compared to radiative recombination. A rate-equation analysis based on the calculated lifetimes indicates an increasing shift of the luminescence from the exciton ground state towards excited states. For typical parameters of dots fabricated from quantum wells the calculated total luminescence efficiency is not strongly reduced by the effect of a slowed relaxation. The luminescence from the ground state becomes weak for strong spatial quantization.

The time response of excited-state sodium desorption from NaF and NaCl has been investigated with synchrotron-radiation pulses. The decay curve of the Na D-line intensity from a desorbed excited-state sodium atom is found to consist of a fast component in the ns range and a slow component between 178 ns and 3 ms. This successful observation of the time response of excited-state alkali desorption suggests there are two types of desorption mechanism, a slow one originating from the thermal instability of surface defects and a fast one due to the lattice instability induced by an electronic transition in the surface layer.

Gallium clusters have been studied by near-threshold photoionization up to 2400 atoms. An electronic shell structure is clearly observed and may be interpreted by considering three electrons per atom. A quantum supershell corresponding to the interference between the contributions of triangular and square classical electronic orbits is obtained at about 2500 electrons. This number is considerably larger than expected from self-consistent homogeneous jellium calculations and is interpreted by introducing an inhomogeneous jellium approach.