The spectrometer system developed in this work consists of a Ge(Li) detector and a 4096-channel multichannel analyzer interfaced directly to a computer with 16,384 24-bit words. The restrictions imposed by a medium-sized core have been circumvented by performing the data reduction in successive steps which are called from a disk file while the data remain in core. Since the analyzer memory is not used to store data during reduction, new data can be acquired while data reduction is in progress.The disk file includes routines for energy calibration, efficiency calibration for each of the geometries used in counting, smoothing, and peak location and integration. The output options include linear or semilogarithmic plots of the spectra. Calibration in the energy region 40-1600 keV is done with a mixed source 57 Co, I37 Cs, and 60 Co. Since the samples are routinely irradiated under reproducible conditions in the same reactor, the flux can be derived from a single flux value obtained from a gold and cobalt monitor.Analysis of standard mixtures indicates an accuracy ranging from ±4.9 to ±7.5%, depending on the counting statistics. Silicon analyses using 125
A neutron activation analysis technique has been developed for the analysis of epitaxial silicon. The technique is described in detail along with a table of detection limits. Impurity and dopant concentrations have been profiled through epitaxial films on boron‐ and antimony‐doped substrates. These data along with experience in routine analyses show a factor of 10 to 40 higher impurity concentrations in the outer layer of silicon epitaxial films. Autoradiography combined with profiling has been shown to be a powerful tool for studying doping uniformity.
The composition of HgCdTe oxides obtained by anodization in a standard KOH/ethylene glycol solution has been determined by Rutherford backscattering spectroscopy for the first time. This technique is advantageous because it is not as surface sensitive as Auger or x-ray photoemission spectroscopy and it provides a nondestructive depth profile of the oxide which can be quantitatively modeled without relying on standards for comparison, as is necessary when using the electron microprobe. The measured composition (61% O, 23% Te, 11.8% Hg, 4.2% Cd for material with x=0.202) is within 0.4% of a stoichiometric mixture of 51.3% HgTeO3, 18.3% CdTeO3, and 30.4% TeO2. While the Hg content in the oxide relative to Te is reduced from the bulk value, it is substantially larger than what is normally reported by other techniques, which found much higher levels of Cd. This composition is consistent with oxide growth occurring primarily by oxygen ions moving into the substrate by a hopping mechanism, while metal ions simultaneously are hopping toward the oxide–solution interface where they can be dissolved into solution. This is the growth mechanism determined by comparing depth profiles after sequential growths in solutions containing KOH and H2O2, the latter solution producing a significant Hg and Cd depletion which can be easily observed by secondary ion mass spectroscopy and Auger electron spectroscopy.
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