Determination of Zn in high-purity GaAs with neutron activation analysis
Neutron activation analysis was used to analyse Zn concentrations in high-purity GaAs. A combination of chemical separation of the neutron-induced 65Zn from the GaAs-matrix with anion-exchange chromatography and ultra low-level gamma-ray spectrometry in an underground laboratory was applied. Zn concentration ranged from 2.1 to 51 ng g(-1), and detection limits from 0.018 to 0.059 ng g(-1) were obtained.
Optimal conditions for identifying 80Br and 128I in health food Angelica keiskei using rapid epithermal neutron activation analysis.
This study presents an optimal rapid epithermal neutron activation analysis (ENAA) technique, using a 1mm Cd filter in reactor neutron flux, to analyze 80Br and 128I in the roots, stems, and leaves of health food Angelica keiskei (AK). Various sample weights of lichen (IAEA-336) for each portion of AK, under various periods of irradiation and counting, were used to optimize the elemental analysis. Selecting the analytical conditions depends on the minimum detectable concentration (MDC), required sensitivities and the quantitative accuracy of Br and I elements. These findings imply that the MDCs of Br and I, measured under 10min activation and 5min counting followed by 10min decaying, using 350mg of lichen are ideal for elemental analysis. Moreover, each portions of AK were analyzed under optimal conditions. The elemental concentrations of Br, Cl, I, Mg, Mn and Na and their implications are discussed.
Survey analysis of impurities in gallium arsenide by instrumental neutron activation
Abstract The major advantages of activation analysis over almost all other analytical techniques are the avoidance of errors due to impurities in the chemical reagents employed in the procedure and high sensitivity in the determination of selective trace elements. A nondestructive investigation was made of six doped gallium arsenide crystals (Cr, O, Si, Ge) grown by the Bridgman, Czoehralski and eutectic epitaxy techniques. The detection in the parts per billion to parts per million range and identification of radioisotopes of impurity elements having relatively short (t 1 2 ⩽ 0.5 day ) and moderately long (t 1 2 ⩾ 2−250 days ) half-lives was considered. The specific resistivity range from 0.003 to 10 8 Ω cm was studied. No direct correlation was established between resistivity and spectrum intensity except for one heavily Si-doped crystal. All gallium arsenide crystals contained silicon at levels of 4·3 × 10 16 −4·7 × 10 17 atoms cm 3 . Other impurities detected were indium, gold, germanium and zinc at concentrations 16 atoms cm 3 ; none of these were consistent contaminants. Phosphorus and indium were identified in a Ge-epitaxy layer on a Si-doped GaAs substrate. Semi-insulating Cr-doped gallium arsenide cyrstals were analyzed for chromium and found to contain 9·8 × 10 17 −1·59 × 10 18 Cr cm 3 . The chromium activation analysis results do not appear to bear any relationship with the concentrations derived from the electrical measurements and suggest the existence of an inhomogeneous second phase. Improvements in the instrumental technique are discussed which can lead to the determination of additional elements for trace characterization of bulk and solution grown gallium arsenide.