Normal emission photoelectron diffraction studies at Stanford Synchrotron Radiation Laboratory. (USA)

Classified abstracts 47304736 energy distribution are in agreement lo within 5% with momentum analysis by a magnetic mass spectrometer. C F Burrell et al, Rer Sci Instrum. 51 (II), 1980, 1451-1462. 37. VACUUM

INSTRUMENTATION

FOR SURFACE STUDIES 37

4730. electron

Theoretical emission

efGciency of from aluminium.

back-scattered

electrons

in

secondary

(GB) The secondary electron yield S, due lo primary electrons, the yield cq due to back-scattered electrons. and the efficiency c of these last electrons, are estimated using the recently developed models for secondary electron emission and electron back-scattering, with appropriate assumptions and using the following relation 6=6, [l + (c/6,) ~1. The values of c/a,, obtained for aluminium with primary energy of the order of 1 keV seem lo agree in the low primary energy range with the more empirical calculations worked out so far. An analysis of the discrepancy which still remains between theoretical and experimental values suggests further modifications in order lo achieve better agreement and to extend the models in the region of several keV where scanning electron microscopes are usually operated. (France) R Biodi et al, J Phys D: Appl Phys, 13 (12). 1980.2351-2361 (in French) 37

(GB) A projectile which is scattered through an angle B by an atom with smaller mass can have two different energies after scattering. This phenomenon is treated and demonstrated by the scatfering of 9 keV 84Kr* ions from a stepped (410) copper surface. The measured energy and intensity distributions agree very well with theoretical expectations. (Netherlands) A J Algra et al, J Phys D: Appl Phys, 13 (12), 1980,2363-2368. 4731. The

two scattering

energies

in a single

collision.

room temperature. A method based on dechanneling theory was developed for the interpretation of CPIX results in terms of numbers of displaced atoms. The results agreed with those obtained with the Rutherford-backscattering-channeling (RBC) technique. The dependence of displacement damage on energy partition was evaluated by selection of ion species and incident energy (ZO keV, H, + ; 20 keV, He+ i 70 keV, N + and 500 keV. Xe”). Except for H, + imolantation. the net number of displaced atoms at damage’levels below saturation was found to depend almost entirely upon the energy deposited into atomic collision processes. For the hydrogen implantations the damage was approximately a factor of 4 higher for equal energy into atomic collisions. Comparison ofchanneling along the (0001) and (1120) directions revealed that aluminum atoms are displaced preferentially into sites along c-axis rows. Ionizationstimulated annealing was investigated with the CPIX technique. Exposure of ion-bombardment-damaged samples to ionizing radiation did not produce annealing measureable by CPIX. T F Luera, J Appl Phys. 51 (1 I), 1980, 5792-5796. 37 4734.

Normal emission Synchrotron Radiation

photoelectron Laboratory.

diffraction

studies

at

Stanford

(USA) A series of experiments designed to characterize the surface structural sensitivity of photoelectron diffraction (PhD) is described. The technique’s relation to low energy electron diffraction and to surface extended X-ray absorption fine structure (SEXAFS) is explored, and useful comparisons with the latter are pointed out. The application of normal emission photoelectron dilTraction to disordered overlayers is shown to be reasonably straightforward. Data on both 2-D and 3-D (multiple-site) disordered overlayers are presented. The localized atom-specific nature of PhD is shown to lend the technique real potential in the study of molecular adsorbate systems. S D Kevan, Appl Oprics. 19 (23). 1980. 39743977. 37

37 4732. Transmission

electron damage

microscopy structures

and Rutherford in P+ implanted

4735. The influence

backscattering

studies of different Si. (USA) Cross-sectional transmission electron microscopy (TEM) and MeV He+ channelling methods have been used to examine different damage structures present under the color bands visible at the surface of a highdose-rate P+ implanted (111) Si implanted to a dose of 7.5 x 10’s ions/cm’. TEM and channelling results obtained from individual coloured regions showed a good qualitative correlation in that discrete damage layers observed in the cross-sectional TEM micrographs appeared as discrete peaks in the channelled spectra. The mean depths of the damage layers obtained from these two methods were in agreement. However, the widths of the deeper lying damage layers calculated from the channelling measurements were always greater than the widths observed by TEM. An empirical method based on subtraction of dechannelling background in the channelling spectra gave damage layer widths that were in close agreement with the TEM results. D K Sadnna et al, J Appl Phys, 51 (11). 1980. 5718-5724.

37 4733. Chant&d-proton-induced

X-ray

measurements

of radiation

damage

in sapphire. (USA) Channeled-proton-induced X-rays (CPIX) were used to measure displacement damage produced in sapphire (a-Al,O,) by ion bombardment at

of surface properties in semiconductors.

on minority

carrier

lifetime

and

conductance (GB) Surface accumulation of carriers not only affects the conductance of a semiconductor sample, but is traditionally invoked as a means ofreducing the eNectsof surface recombination velocity on minority carrier lifetime. It is shown that circumstances can easily arise where the latter elTect is actually reversed, to the detriment of device performance. Simple expressions are derived for the effective surface recombination velocity, and the relationship between minority carrier lifetime and sheet conductance in truly surface dominated samples. A M White, J Phy D: Appl Phys, 14 (1). 1981, Ll-L3.

sheet

37

(GB) The K-absorption spectrum has been studied in vermiculite mica with a view to studying its Fe’+/Fe’+ ratio and Fe-O bond length before and tier subjecting it lo heat treatment at 800°C. The heat treatment is found IO lead to near total conversion of Fe*+ to Fe’+, but the value of the bond length does not seem to change significantly. The tihite line’ observed in its spectrum, ascribed to exciton levels, is found to broaden on heat treatment. The results are compared with those obtained on other trioctahedral micas in an earlier study. (India) D C Jain et al, J Phys D: Appl Phys, 14 (1) 1981, L5-L7. 4736. X-ray

absorption

study

of vermiculite

mica.

279