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Chemisorptive emission and luminescence
A245 Surface Science 129 (1983) 399-418 North-Holland Publishing Company CHEMISORPTIVE If. Electron and ion
EMISSION
399 AND LUMINESCENCE
emission from chlorine and bromine reactions with yttrium, titanium, zirconium and hafnium surfaces M . P . C O X *, J.S. F O O R D
** a n d R . M . L A M B E R T
Department of Physical Chemistry, University of Cambridge, Cambridge CB2 1EP, UK and R.H. PRINCE
Department of Physics, York University, Toronto, Canada M3J 1P3 Received 28 September 1982; accepted for publication 28 February 1983 Exoelectron and ion emission during chemisorption has been studied under UHV conditions for a variety of halogens (X = chlorine, bromine) and group I l i a (Y) and group IVA (Ti, Zr, Hf) surfaces, both clean and with alkali (M = Na, Rb) predosing. The experimental data include absolute yields and energy distribution functions, as well as the kinetics of the emission processes. The variation in electron yield over four orders of magnitude is acceptably described by a previous model invoking Auger relaxation, as are certain aspects of the energy distributions. Ionic species ejected during the reaction include M +, X - and MX~-, the latter exhibiting a kinetic behaviour strongly correlated to the formation of low work function "exopatches", believed to consist of a polar halide overlayer.
Surface Science 129 (1983) 419-431 North-Holland Publishing Company THE ASYMMETRIC CLUSTER
DIMER
419 O N Si(100): C O R R E L A T I O N
EFFECTS
IN
CALCULATIONS
W.S. VERWOERD
Department of Physics, University of South Africa, P.O. Box 392, Pretoria 0001, Rep. of South Africa Received 24 February 1983 In the light of recent objections against the reliability of the prediction of an asymmetric dimer on Si(100) by Hartree-Fock based calculations, we re-examine our earlier MINDO/3 cluster calculations. It is shown that MINDO/3 does include bond correlation effects to an extent comparable with GVB/CI, but nevertheless predicts the asymmetric dimer to have a lower energy than the double bonded symmetric state. The discrepancy is ascribed to a failure of the GVB method to include intra-atomic correlation.
EMISSION
399 AND LUMINESCENCE
emission from chlorine and bromine reactions with yttrium, titanium, zirconium and hafnium surfaces M . P . C O X *, J.S. F O O R D
** a n d R . M . L A M B E R T
Department of Physical Chemistry, University of Cambridge, Cambridge CB2 1EP, UK and R.H. PRINCE
Department of Physics, York University, Toronto, Canada M3J 1P3 Received 28 September 1982; accepted for publication 28 February 1983 Exoelectron and ion emission during chemisorption has been studied under UHV conditions for a variety of halogens (X = chlorine, bromine) and group I l i a (Y) and group IVA (Ti, Zr, Hf) surfaces, both clean and with alkali (M = Na, Rb) predosing. The experimental data include absolute yields and energy distribution functions, as well as the kinetics of the emission processes. The variation in electron yield over four orders of magnitude is acceptably described by a previous model invoking Auger relaxation, as are certain aspects of the energy distributions. Ionic species ejected during the reaction include M +, X - and MX~-, the latter exhibiting a kinetic behaviour strongly correlated to the formation of low work function "exopatches", believed to consist of a polar halide overlayer.
Surface Science 129 (1983) 419-431 North-Holland Publishing Company THE ASYMMETRIC CLUSTER
DIMER
419 O N Si(100): C O R R E L A T I O N
EFFECTS
IN
CALCULATIONS
W.S. VERWOERD
Department of Physics, University of South Africa, P.O. Box 392, Pretoria 0001, Rep. of South Africa Received 24 February 1983 In the light of recent objections against the reliability of the prediction of an asymmetric dimer on Si(100) by Hartree-Fock based calculations, we re-examine our earlier MINDO/3 cluster calculations. It is shown that MINDO/3 does include bond correlation effects to an extent comparable with GVB/CI, but nevertheless predicts the asymmetric dimer to have a lower energy than the double bonded symmetric state. The discrepancy is ascribed to a failure of the GVB method to include intra-atomic correlation.