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An analytical treatment of the Ruderman–Kittel–Kasuya–Yosida polarization in inhomogeneous media is possible for some simple models. This is exemplified with the half‐spaces and slabs in one and three dimensions, and with an especially chosen potential barrier in one dimension.

Since dissipation requires motion, the velocity‐independent friction of macroscopic systems must result from quick motions of some of its components. A model of coupled spins, some of which have irregular anisotropy directions, presents velocity independent loss. During a collective motion of the spin ensemble, an irregular spin can fall into its potential minimum, from which it is subsequently dragged out again. The effect is pronounced for a range of the ratio between the anisotropy and interatomic exchange coupling constants which is typical for rare‐earth ions.

For the coupling of two ferromagnets separated by a nonmagnetic layer, the Ruderman–Kittel [C. Kittel, Quantum Theory of Solids (Wiley, New York, 1963)] theory gives an expression which oscillates as a function of the thickness of the laser and asymptotically decreases as the reciprocal square of the thickness. The prefactor is independent of the electron density.

Polycrystalline films of ZnSe, pure and doped with Cu and Ga, have been deposited by a modified close‐spaced‐vapor‐transport method which requires low temperatures (500 °C) and no subsequent annealing. The resulting grains are of the order of 1 μm. The films were characterized by their photoluminescence emission in the temperature range 10–290 K. The undoped and Cu‐doped films display the usual Cu‐green and Cu‐red and near edge emission bands at low temperatures. In the Ga‐doped films only a mildly temperature dependent band centered at ∼620 nm appears at all temperatures. The films have very similar characteristics to those prepared by more sophisticated techniques.

The photoluminescence characteristics of undoped and TbCl3‐doped zinc oxide films deposited by the spray pyrolysis technique are reported. Undoped films present the characteristic blue‐green emission peak at ∼508 nm observed in single‐crystal and powder ZnO. The TbCl3‐doped films present a luminescence peak at ∼540 nm. The light emission of the doped films decreases with time of exposure of the sample to the excitation light. The phenomenon is interpreted in terms of a simple model in which a competitive process of hole trapping and phototrapping occurs at a radiative recombination center generated by the TbCl3.

InP epi‐layers heavily doped with Se exhibit very high carrier concentrations (N≳1020 cm−3) together with significant increases of the optical band‐gap energy. We show that in these epi‐layers (grown by liquid phase epitaxy) the Se concentration XSe varies with the depth. With increasing Se concentration, the optical band gap increases from 1.34 to ∼1.9 eV, where it remains fixed for Se concentrations larger than 1.5 at.%. This increase is very rapid at first owing to the filling of the low mass conduction band. Beyond XSe = 0.1 at.%, we enter the nonarapbolic bands regime and the electrons begin to overflow into the indirect minima. Because of the large density of states available, further increases in free carriers no longer affect the optical gap, which remains close to the indirect gap value (∼1.9 eV).

We show that cadmium telluride is a promising material for semiconductor‐electrolyte solar cells. Polycrystalline n‐type CdTe, in contact with an aqueous solution of SnCl2, forms a well‐defined Schottky barrier. The efficiency in sunlight is 4.8%. The cell shows a drift of characteristics with time that may be associated with a low rate of formation of hydroxide on the surface. However, operating stability is relatively good compared with other semiconductor‐electrolyte cells that have been reported in the past.

Coloration accompanied by an increase of several orders of magnitude in electrical conductivity can be induced at room temperature in rutile single crystals by contact with a Na amalgam. Sodium and hydrogen (which is present as an impurity of metallic sodium) diffuse during treatment. The crystals can be bleached by heating at temperatures T≳100 °C. The coloration process is highly anisotropic, being effective only along the c direction. Coloration is not observed in crystals previously irradiated with neutrons.

We report on the photoinduced discharge of sulfur single crystals using light in the range 400–580 nm, i.e., from strongly to weakly absorbed light. The results are interpreted in terms of a phenomenological model consistent in an equivalent RC circuit.

The model of the Schottky barrier is based on the presence of ionized donors within the barrier. The empty energy levels corresponding to these donors lie in the barrier. Thus, there can be resonant tunneling through these empty energy levels. This is an inherent effect associated with Schottky barriers. We show how resonant tunneling depends on the ionization energy of the donors and the conditions under which resonant tunneling prevails over common tunneling.

Cd vacancies are identified as responsible for both the 1.55‐eV narrow band and the 1.591‐eV bound exciton peak of the CdTe photoluminescence spectrum. The characteristic 1.44‐eV broadband does not seem to be related to luminescent centers involving those vacancies.

The temperature dependence of the high‐field conductivity of SiO2 films with a small atomic excess of Si content is interpreted in terms of a model previously proposed for granular metal films. We have found an excellent quantitative agreement between experimental data and the theory. This agreement clarifies the conduction mechanism in this material and strongly suggests that the Si particles have metallic characteristics. With this interpretation, we are able to determine the volume fraction of the excess Si x, the diameter of the Si grains d, and the interparticle distance s. In the case of samples with an excess of Si atoms of 1% to 3%, we found that x≂0.017, d≂9.5 A, and s≂20.5 A.

Experimental results where the resistance of samples of EuS single crystals prepared with two metallic contacts changes abruptly up to seven orders of magnitude, as a function of voltage, are presented. It is shown that this switching effect is associated with an insulating thin film that appears at the electrical contact between the metal and the semiconductor. The nature of the insulating film was studied by the SIMS technique.

Previous work has shown that while nCdTe‐electrolyte solar cells are low cost and efficient, their photocurrent decays after a few hours of operation. We ave systematically analyzed the changes that take place at the interface. Auger spectroscopy measurements have shown out‐diffusion of Cd2+ and the formation of a Te layer at the surface. Electroreflectance (ER) and electroluminescence measurements have further shown that this process results in the formation of a p‐type region. The evolution of the ER spectra as the p‐type region develops was followed and fully analyzed. This technique offers the advantage of easy control and optimization of the p‐n junction growth parameter. The influence of the Te layer on the cell performance was determined from spectral response measurements.