The effect of photon energy and temperature on the persistent tunneling photoconductivity effect in Al/δ(Si)-GaAs structures

The phenomenon of persistent tunneling photoconductivity was studied using the tunneling spectroscopy technique at liquid-helium temperature: the separation between the unoccupied levels in a δ-doped layer at the GaAs surface decreased after illumination. This decrease was due to an increase in the width of the quantum well of the δ-doped layer. For photon energies hv exceeding the GaAs band gap E _g , this increase in the width of the quantum well was related to the accumulation of positive charge in the depth of GaAs induced by the generation of the electron-hole pairs and photoionization of deep centers. For hv < E _g (including the case of CO₂ laser), only photoionization is important. The experimental data agree with the self-consistent calculations. The critical temperature for the effect has been determined (T _c = 45 K); at higher temperatures, the effect disappears.     

Changes in Structure and Physicochemical Properties of Spark Coatings Based on TiN and TiB2 after Treatment with Concentrated Solar Radiation

Studies have been made on the structure and properties of spark coatings made of TiN and TiB₂ on steel U8 after treatment with concentrated solar radiation. It is found that the absorption capacity of the steel raised by a factor 2–3. The concentrated radiation reduces the coefficient of friction of the spark coatings made of TiN and TiB₂ by a factor 1.4, while the wear rate is reduced by a factor 1.6–2 by comparison with the untreated material. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 64–69, July–August, 2005.     

Constitution of the Al Corner in the Ternary Al–Ge–Mg Phase Diagram

Powder Metallurgy and Metal Ceramics - A fragment of the Al corner in the ternary Al–Ge–Mg phase diagram has been constructed. Experimental methods have shown that the tie-line of the L...     

Phase composition and microhardness of microcrystalline powders of high speed steels

Translated from Poroshkovaya Metallurgiya, No. 12(324), pp. 82–87, December, 1989.     

Response of tunnel schottky-barrier junctions to radiation pressure of fir laser radiation

The response of tunnel Schottky junctions due to plasma reflection of laser radiation has been investigated in the far infrared. The signal was found to be independent of the laser radiation frequency below the plasma edge. At high power levels a nonlinearity of the response was observed. It is assumed that this nonlinearity is caused by near-zone field effects which lead also to a substantial enhancement of the responsivity.     

Electric-spark alloying of VT22 alloy by chromium and tungsten electrode materials

We investigate the dependence of the erosion characteristics of Cr and W electrode materials during deposition of an electric-spark coating on VT22 titanium alloy. The interrelation between the phase composition, structure, and tribological properties of a coating obtained by electric-spark alloying is determined. It is shown that a coating obtained from tungsten has optimal tribological properties: a micro- hardness of 16 GPa and a wear resistance of 4.9 μm/km at a sliding velocity of 5 m/sec and a load of 0.5 MPa.