High-temperature diffusion of magnesium in dislocation-free silicon

The diffusion doping of dislocation-free single-crystal silicon with magnesium is studied in the temperature range 1000–1200°C. The conventional sandwich method is used as the doping method. It is found that the diffusion coefficient of magnesium is described by a universal Arrhenius curve in the extended temperature range 600–1200°C, with data earlier obtained for the range 600–800°C taken into consideration. The relatively low activation energy of diffusion transport (1.83 eV) is indicative of the interstitial mechanism of impurity diffusion.     

Fast photonic switches based on GaAs nanostructures

Fast photonic switches, in which light controls light, can be created based on high-voltage GaAs nanostructures with a thin (nanodimensional) surface dielectric layer. The switches offer a high operation speed that ensures optical data recording and transmission at a rate of 10⁴-10⁵ cps, possess a large modulation amplitude, and can operate at a relatively low optical control signal power (I<1 W/cm²). These devices can be used in systems of optical data processing, optical computation systems, all-optical communication lines with optical addressing of informative signals, etc.     

Analysis of the size-distribution function of metallic nanoclusters in a hydrogenated amorphous carbon host

A method for mathematical processing of TEM images of nanocomposites with a pronounced noise background is proposed. This method is based on the spline filtering of an image by using the values of average background intensity and is applied to TEM images of amorphous Cu-doped carbon. A size distribution function obtained for copper clusters is in good agreement with previous data. The dependence of the cluster-to-cluster distance on cluster size is determined. This dependence validates the hypothesis of the fluctuation nature of cluster generation at a lower metal content and of the coalescence of clusters at higher metal contents.     

Size distribution of cobalt nanoclusters in an amorphous carbon matrix

Results obtained in a study of electron micrographs of cobalt-doped amorphous hydrogenated carbon are presented. The micrographs were obtained by transmission electron microscopy, including high-resolution electron microscopy. Layers of amorphous carbon were grown by magnetron cosputtering of a graphite and a cobalt target in an atmosphere of argon-hydrogen plasma. It is shown that nanosize crystalline clusters are formed in the process. The influence exerted by 1-h thermal annealing at 800°C in an atmosphere of argon on the size distribution of nanoclusters was studied. It is shown that the distribution function is described by a Gaussian curve that is peaked at ～7 nm for as-grown samples and is strongly broadened upon annealing, with the peak position shifted to larger sizes and the curve exhibiting deviations from the Gaussian shape. A characteristic structure, attributed to nanosize carbon capsules that envelop the clusters, is seen at cluster boundaries in the high-resolution mode.     

Chemical Shift and Exchange Interaction Energy of the 1s States of Magnesium Donors in Silicon. The Possibility of Stimulated Emission

Semiconductors - The results of experiments aimed at the observation of split 1s states in Mg-doped Si are reported. From the results, it is possible to determine the chemical shift and exchange...     

Decomposition of a Solid Solution of Interstitial Magnesium in Silicon

Semiconductors - The decomposition of a solid solution of interstitial magnesium Mgi in silicon is studied. Float-Zone dislocation-free single-crystal n-Si with a resistivity of ~8 × 103...     

Gas discharge in thin gaps filled with argon and nitrogen at cryogenic temperatures

It is established that the cooling of argon-or nitrogen-filled microdischarge devices to cryogenic temperatures significantly affects the threshold potential of discharge initiation. For a discharge in the nitrogenfilled gap with a brass cathode, this effect can be explained by a decrease in the secondary electron emission coefficient, while the influence of cooling on the argon-filled gap has a more complicated nature. The results are of importance for the development of cryogenic microdischarge devices.     

Scanning tunneling spectroscopy of amorphous carbon: Tunneling model

An analysis is made of a model of tunnel current flow through amorphous diamond-like carbon. It is shown that single-electron phenomena may occur in this medium which result in the appearance of specific features on the current-voltage characteristics of thin amorphous carbon films. The model is used to explain the tunnel spectra of diamond-like carbon and the size of a graphite-like cluster is estimated. Pis’ma Zh. Tekh. Fiz. 25, 66–71 (December 26, 1999)     

Diffusion of interstitial magnesium in dislocation-free silicon

The diffusion of magnesium impurity in the temperature range T = 600–800°C in dislocation-free single-crystal silicon wafers of p-type conductivity is studied. The surface layer of the wafer doped with magnesium by the ion implantation technique serves as the diffusion source. Implantation is carried out at an ion energy of 150 keV at doses of 5 × 10¹⁴ and 2 × 10¹⁵ cm^–2. The diffusion coefficient of interstitial magnesium donor centers (D _i ) is determined by measuring the depth of the p–n junction, which is formed in the sample due to annealing during the time t at a given T. As a result of the study, the dependence D _i (T) is found for the first time. The data show that the diffusion process occurs mainly by the interstitial mechanism.     

Silicon with an increased content of monoatomic sulfur centers: Sample fabrication and optical spectroscopy

The effect of the high-temperature heating (at 1340°C) of sulfur-doped silicon samples and their subsequent quenching is studied. The results of such a treatment are analyzed on the basis of Hall-effect data obtained in the temperature range T = 78–500 K. It is shown that the heating duration strongly affects the relative concentrations of different types of deep sulfur-related centers. At comparatively short heating durations of t = 2–10 min, the concentration of quasi-molecular S₂ centers and S _X complexes substantially decreases, whereas the density of monoatomic S₁ centers grows. At the same time, the heating of a sample is accompanied by a monotonic decrease in the total concentration of electrically active sulfur over time. The results obtained make it possible to give recommendations concerning the optimal conditions for the fabrication of samples with a high concentration of S₁ centers. The absorption spectra of the samples show that the method is promising for the observation of a number of quantum-optical effects involving deep S₁ donors in silicon.