A comparison of secondary ion and photon yields from ion bombarded CuNi alloys

A133 ~s found to stand upright on the surface as confirmed by symmetry selectmn rules and the study of the shape resonance of the 40 orbital upon changing the photon energy The ordering of the valence levels ts opposite to that of the gas phase The band dtspersmn of the 40 and compostte (50 + l~r) levels has been measured along the lugh-symmetry dtrecUons m the Brfllomn zone for the ordered c ( 4 x 2) structure Different poss~ble explanations for the fact that the dtsperston of both bands ~s about the same are discussed A feature ~s attributed to a shifted surface state of the P d ( l l l ) surface, rather than the 2~r* CO orbital

Surface Science 139 (1984) 443-452 North-Holland, Amsterdam KIKUCHI

PATTERNS

443

OF Mo( 100} AND

PRIMARY

ELECTRON

LOCALIZATION M V. G O M O Y U N O V A ,

I.I. P R O N I N

and I A

SHMULEVITCH

loffe Physwo-TechmcalInstztute, Academy of Sctences of the USSR, Lemngrad, USSR Recetved 2 February 1983, accepted for pubhcatton 6 December 1983 The Kakuchl patterns of Mo{100} obtained m the mctdent electron energy range 0 5 - 2 keV have been compared w~th the angular d~stnbuttons of electrons scattered quas~elastlcally from polycrystalhne molybdenum The principal maxima of electron emission from Mo(100} are shown to correspond to the outgoing electrons oriented along closely packed atomic rows For fixed polar angles 0, the electron em~ssmn intensity at the maxima may exceed by 3 - 4 t~mes that at the m m t m a The average contrast of the Kakuchl patterns (with exceptmn of the high symmetry o n e n t a u o n s ) vanes only shghtly over the 0 angle range studied, 20-80 ° The observed enhanced electron emtssmn from a single crystal compared with a polycrystaUme sample drops off with increasing polar angle A study of the effect of crystal temperature on the angular distributions of quas~elasttcally scattered electrons has shown an increase of temperature to reduce p n m a r y the emtssmn at the maxima The major results of the study are quahtatwely accounted for the effect of primary electron Iocahzatmn on the secondary dfffracuon of quaslelastlcally scattered electrons

Surface Science 139 (1984) 453-462 North-Holland, Amsterdam A COMPARISON ION C.M.

OF SECONDARY

BOMBARDED LOXTON

453 ION

AND

PHOTON

YIELDS

FROM

CuNi ALLOYS

* and I.S.T

TSONG

Department of Physws, Arizona State Umverstty, Tempe, Arizona 85287, USA Received 11 October 1984, accepted for pubhcaUon 13 December 1983 The secondary ton and photon yields produced by 7 keV Ar + ton bombardment of a series of polycrystalhne CuN~ alloys under ultrahigh vacuum cond~Uons have been compared By measuring the relatwe alloy sputtering rates and the ton and photon yields at steady state condmons, the matrix effects on both relauve m m z a t m n and exc~tauon p r o b a b d m c s have been mvesugated The N~ e×cttatmn and lomzatlon effic~enc~es decrease when Cu ~s alloyed w~th N~ On the other hand, the addlUon of NI to Cu initially depresses the Cu iomzation and excJtatmn efficlencles These efficienc~es are subsequently enhanced as the Nl content of the alloy is increased The rauo of both m n and photon enusslon probabdmes of Cu compared to Nl remains independent of alloy compos~tmn, ~ e yields are smularly enhanced from the same surface The tmtml decrease m yields from the low NI content alloys makes predlcttons about the nature of the enhancement m e c h a m s m difficult These results do not favour any simple surface electromc structure model