5220. Electron damage in ZnSe using transmission electron microscopy

Classified abstracts 5219-5228 and TiO2 have no intrinsic band-gap surface states, while nearly perfect MgO(100) surfaces exhibit a cation-derived empty surface state about 2 eV below the bulk conduction band edge. Defect surface states generally involve 0 vacancies, with attendant charge transfer to surface ca'tions that results in occupied states in the band-gap region. Victor E Henrich and Richard L Kurtz, J Vac Sci Tec/mol, 18 (2), 1981, 416-419. 37 5219. A study of secondary molecular ion formation in rare earth and rare earth oxides. (USA) Secondary atomic and molecular ion energy spectra have been obtained for several rare earth and rare earth oxide samples. The energy dependencies of the diatomic ions were found to be a product of the energy dependencies of the atomic ions. Qualitative agreement of this product rule is also found for larger clusters. A recombination mechanism for molecular formation is demonstrated to be consistent with these results. Several preliminary ion implant studies are presented to give further insight into the recombination model. D T Hodul et al, Rad EJJects, 55 11,'2), 1981, 57 66. 37

5220. Electron damage in ZnSe using transmission electron microscopy. (USA) Features having a similar appearance to those produced by irradiation damage have been observed in ZnSe after electron irradiation at subthreshold voltages in a transmission electron microscope. It has been suggested that these features are due to recombination enhanced point defect generation. This paper shows that the appearance of these features is related to the particular microscope employed and are not caused by the aggregation of point defects but are a surface defect layer of a second phase which is probably an oxide of zinc. (GB) A Nouruzi-Khorasani et al, Rad Effects, 55 (1/2), 1981, 79-84. 37

5221. Secondary ion emission from binary alloy systems. Part I: O f bombardment. (USA) We have studied the emission of positive atomic ions from five binary alloys: Cr-Ni, Fe-Ni, Cu-Ni, Pd-Ni, and Ag-Pd, all under O~ bombardment. Significant enhancement and suppression of ionization probabilities due to the presence of the second alloy component were observed. The alloying effect follows two general rules. The first rule states that for an alloy A-B, where A forms a stronger oxide bond than B, the presence of A enhances the emission of B*, while the presence of B suppresses the emission of A *. The second rule states that the presence of A sharpens the energy distribution of B ÷, while the presence of B broadens the energy distribution of A +. X-ray photoemission studies of the O~ bombarded alloy surfaces connect the general rules with the enhanced oxidation of B and the suppressed oxidation of A in the alloys. All the cases that deviate from the rules originate from insufficient oxygen for oxidation resulting from the self-limiting nature of oxidation by O~- bombardment. Ming L Yu and Wilhad Reuter, d Appl Phy.~, 52 (3), 1981, 1489- 1498. 37 5222. Secondary ion emission from binary alloy systems. Part I1: Ar ÷ bombardment with 0 2 absorption. (USA) The emission of positive atomic ions from Cu-Ni, Pd-Ni, and Ag-Pd alloys was studied under Ar ÷ bombardment with saturated 0 2 adsorption. In line with other published data on Cr-Fe, Cr-Ni, and Fe-Ni alloys, these studies all agree well with two general rules proposed previously for O~ bombardment. The first rule states that for an alloy A-B, where A forms a stronger oxide bond than B, the presence of A enhances the emission of B +, and the presence of B suppresses the emission of A +. The second rule states that the presence of A sharpens the energy distribution of B ÷ while the presence of B broadens the energy distribution of A*. The experimental data fit the rules with better consistency than for the case of O~- b o m b a r d m e n t except in cases of low oxygen sticking coefficients on the alloy surfaces. The success of the general rules is linked with the enhanced oxidation of B and the suppressed oxidation of A in the alloy. X-ray photoemission studies of the oxidized surfaces support this explanation. Further evidence of an energy-dependent ionization probability of Ni + from pure Ni provides a consistent explanation of the second general rule. Ming L Yu and Wilhad Reuter, d Appl Phys, 52 (3), 1981, 1489 1498 37

5223. Grain boundary potential determination in polycrystalline silicon by the scanning light spot technique. (USA) Local grain boundary potential has been determined by scanning light

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spot technique. Photocurrent peaks vary from boundary to boundary giving a strong peak for large-angle grain boundaries and becoming negligible for the smallest-angle grain boundaries observed. The largest potentials had typical values of around 0.3 eV and the corresponding interface state densities were in the 10 ~3 c m - 2 range. (Spain) J Martinez et al, J AppI Phys, 52 (3L 1981, 1301-1305. 37 5224. Determination of the multiplier gain of a photomultiplier. (GB) Two means for measuring multiplier gain are described. The determination of the total number of single electron pulses, N enters into both methods. Use of a muhichannel analyser of calibrated input sensitivity reveals that the error in determining (~/) arises mainly from an inability to assess whether all contributions from the low energy region of the pulse height distribution have been included in N. It is concluded that mean gain measurements with better than 10°,, accuracy are unlikely for most photomultipliers. This has serious implications for the absolute measurement of light intensities through the need to know F, the collection efficiency, the determination of which can be sensitive to the assumed values of (,q) and var (,q). A G Wright, d Phys E: Sci Instrum. 14 (7), 1981, 851-855. 37 5225. A goniometer head for an atom-probe field ion microscope. (GBt The goniometer head of a field ion microscope is described. An area of about 0.I nm 2 on the surface of a metallic sample can be selected and analysed by means of a time-of-flight mass spectrometer. The coaxial geometry of the head allows a voltage pulse to be transmitted with a rise time of I n s to the sample which can be cooled to about 20 K in a vacuum better than 0.13 pPa ( 10 9 Torrl. With a master clock of 200 M H z these features result in a mass accuracy of I part in 300. (France) J M Sarran et al, J Ph)'.~ E: Sci lnstrum, 14 (7), 1981. 800-802. 37

5226. Transmission electron microscope study of ion beam annealing effects of ion-implanted and evaporated amorphous silicon. (USA I High power ion beam annealing has been applied to ion-implanted and evaporated amorphous silicon samples. Microstructures induced by this novel technique have been investigated by transmission electron microscope. The analysis of diffraction patterns and direct images of ion beam annealed as well as thermally annealed specimens indicates that ion beam annealing is a promising technique to process ion-implanted and evaporated amorphous samples. It was found that several seconds of intense ion beam bombardment produced similar effects as did l-h 600 900:C thermal annealing. (Taiwan) L J Chen el al, d Appl Phys, 52 (51, 1981, 3304 3309. 37 5227. Novel charged particle analyser for momentum determination in the

multichanneling mode. Ii. Physical realization, performance tests, and sample spectra. (USAI Following a design described in a preceding paper, an energy dispersive analyser system has been constructed for the simultaneous determination of polar angle (01 distributions ofcharged particles originating on a solid surface in the range 0 _<0 < 90 . The analyser is a toroidal prism used in an unusual geometry, followed by a truncated cone lens. The starting polar angle is preserved in the spectrometer and translated into the arrival position on a position sensitive detector based on the charge division method. The dependence on azimuthal emission angles (6) is obtained by recording energy and polar angle dependent spectra after mechanical variation of the azimuth. Total N(E, 6, 01 spectra are accumulated with a minicomputer, using a multichannel analyser as buffer: the point-by-point subtraction of two spectra, e.g., to extract the spectral changes brought about by adsorption on a surface, is possible. Test procedures to check the performance (preservation of angles; energy and angular resolution; invariance of transmission with angle) are described. The analyser can be used for electron (LEED, AES, UPS, ELS, INS, etc.) and ion (ISS, ESD) spectroscopies of clean surfaces and adsorption layers: sample spectra for LEED, AES, UPS, and ISS are shown. (West Germany1 H A Engelhardt et al, Rec Sci Instrum, 52 (8), 1981, 1161-1173. 37

5228. Ultrahigh vacuum multipurpose offset manipulator for surface and thin film reaction studies. (USA) A novel ultrahigh vacuum (uhvl manipulator has been constructed which allows positioning of a sample on any point of an 11.5-cm radius main circle and provides two orthogonal off-axis rotations at the selected point. The motions are a 0-90 ~ tilt of the sample face and a + 180: rotation normal to the sample face. The main circle position may be varied by + 1 cm in X and Y directions and +0.7 cm in the Z direction, which is