[en] A deep level transient capacitance spectroscopy (DLTS) system, modified for the measurement of transient conductance, has been used to observe gamma-ray induced defect centres in the gate junction of 2N4416 Si field effect transistors. The defect concentrations increased linearly wth gamma-dose in the range 50 kGy to 10 x 10³ kGy (5-1000 Mrad) for the common Esub(c) - 0.17 eV level, and in the range 500 kGy to 10 x 10³ kGy (50-1000 Mrad) for the levels Esub(c) - 0.22 eV and Esub(c) - 0.44 eV. Another common level, a hole trap at Esub(v) + 0.42 eV, was the only minority trap observed. The technique may be useful for measur-ing gamma-fluxes in situations inaccessible to standard dosemeters (e.g. flux-mapping)

[en] Deep level transient capacitance spectroscopy has been used to examine γ-ray induced defect centres in germanium crystals grown under widely varying conditions. A deep acceptor level at Esub(v) + 0.38 eV has been observed for the first time in all p-type samples; this was removed by annealing at 675 deg C for three hours. A new, deep donor level at Esub(c) - 0.42 eV observed in n-type material was not removed by this procedure

[en] Deep level transient spectroscopy (DLTS) has been applied to defect centres in γ-ray compensated germanium that has been subjected to long-term annealing at room temperature. Deep donor levels (Esub(c) - 0.36 eV, Esub(c) - 0.20 eV) have been observed for the first time; annealing at 675 deg C for 3 hours increased their concentration in proportion to the free carrier density, indicating stable defect-impurity complexes. Recently irradiated samples from the original material have not shown these levels. The results support Russian work on the compensation mechanism - the formation of electically inactive vacancy-donor complexes

[en] Deep level transient spectroscopy has been applied for the first time to the study of deep level defects in n-GaAs nuclear radiation detectors. Devices made from commercial bulk and epitaxial material with net donor impurity densities in the range 5 x 10¹³ - 3 x 10¹⁶ cm^-3 have been studied and several common levels observed. The Poole-Frenkel effect has been identified in three levels (Esub (v) + 0.19 eV, Esub(c) - 0.62 eV, Esub(c) - 0.73 eV) in the epitaxial GaAs. A value for the Poole-Frenkel constant of β 4.7 +- 1.4 x 10^-4 eV Vsup(-1/2) cmsup(1/2) was obtained, compared to the theoretical value for GaAs of 2.3 x 10^-4 eV Vsup(-1/2) cmsup(1/2)

[en] Recent developments to further improve the graphitisation reaction rate and efficiency for small samples are presented. We have investigated three different methods of activating the Fe catalyst: (1) 750 mb H₂ at 600 deg. C for 1 h, (2) 750 mb H₂ at 600 deg. C for 24 h, and (3) 500 mb O₂ at 450 deg. C for 0.5 h followed by 750 mb H₂ at 600 deg. C for 1 h. The results show that method 3 is the most suitable method for activating the Fe catalyst for the graphitisation of small-mass samples as it helps to improve both the reaction rate and efficiency. In addition, a simple approach is presented to determine the ¹⁴C content and mass of extraneous carbon that is incorporated during sample preparation. These data were then used to correct for two test series of reference materials (FIRI-H and IAEA-C7) containing less than 200 μg of carbon, using three different formulations of procedural background correction. The corrected values of test samples are mostly in agreement with their consensus values. This indicates a good accuracy of our ¹⁴C analysis of small-mass samples

[en] A Q-switched ruby laser pulse (lambda = 0.6943 μm, 25 ns fwhm) was used to melt vacuum-evaporated Li layers on high purity (p = (1-6) x 10¹⁰ cm^-3) Ge for nuclear radiation detectors. The resulting highly doped contacts were extremely thin (<= 0.1 μm), and stable at room temperature. Full width half maximum (fwhm) resolutions of 15.3 keV for 5.48 MeV²⁴¹ Am α-particles and 3.1 keV for 662 keV¹³⁷ Cs γ-rays were obtained and show these contacts may be suitable for many detector applications. (orig.)

[en] The dominant defect levels in γ-irradiated doped and high purity Ge have been studied by transient capacitance spectroscopy. All p-type samples displayed acceptors at Esub(v) + 0.23 eV and Esub(v) + 0.38 eV, whose capture cross-sections for holes were approximately 10^-14 cm². In n-type samples a deep donor (Esub(c) - 0.42 eV) with electron capture cross-section approximately 10^-14 cm² was observed in all but the highest purity material. Long-term room temperature annealing introduced two deep donors (Esub(c) - 0.36 eV, Esub(c) - 0.20 eV) into some n-type material; newly irradiated samples from the same crystals did not show these levels. In the n-type material, the loss of shallow donor states by electrically inactive complexing with vacancies was the compensation mechanism. (author)

No abstract available

[en] Pico hydro power is a renewable energy system which has the potential to provide millions of rural people world-wide with a cheap, sustainable source of electricity. The development of new, cost-reducing approaches, including local manufacture and implementation in developing countries, has increased the accessibility of this technology to large numbers of people. The new approaches are investigated and some of the present constraints to wider adoption of this technology are analysed. (Author)