Some results of up to 12 beam contrast calculations for systematic orientations have indicated that high order reflections at high voltages may provide improved dislocation resolution. For example the contrast profiles for dislocations show a decrease in image width for increasing order of reflection (i.e. increasing ḡ·), thus enabling improved resolution of narrow dislocation dissociations and closely spaced dipoles or superdislocations.This paper provides experimental confirmation that high order systematic reflections do indeed result in an improvement in bright field image resolution, e.g. image widths of dislocations can be reduced by a factor of ~3. The results have been obtained from [001] foils of GaAs semiconducting devices in which dislocations are associated with surface and interfacial defects. In each case the crystal is set at the exact Bragg condition for each reflection along the systematic row being used. The work was done on the Berkeley Hitachi microscope operated at 650 kV.
Measurements have been made to determine the effect of temperature and elevated-temperature preconditioning on the outgassing rate of double-aluminized mylar (DAM) and dacron net (DN), two materials used in multilayer insulation systems. The outgassing rate of DAM was measured at seven constant temperatures between 219 and 394 K, while that of DN was measured at six temperatures between 275.7 and 399 K for 7 days each. The isothermal DAM measurements permitted analytical expressions to be derived for the outgassing rate, from which diffusion coefficient and activation energies could be derived. The effect of elevated-temperature preconditioning on long-term outgassing rate at 298 K was determined in a series of tests on both DAM and DN, in which the samples were heated for 24 h in vacuum to various elevated temperatures between 298 and 423 K, then returned to 298 K, at which temperature their outgassing rate was measured for the next 6 days. It was found that there is an optimum preconditioning temperature for DAM in the region of 343 to 363 K. Preconditioning above this temperature actually increases the long-term outgassing rate at 298 K. For DN, raising the preconditioning temperature steadily lowers the long-term 298 K outgassing rate. In general, elevated temperature preconditioning is more effective for DN than DAM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.