A202

Surface Science 141 (1984) 409-416

North-Holland, Amsterdam 409

THE CHEMICAL SPUTTERING OF SILICA BY Ar + IONS AND XeF, M.A. LOUDIANA, A. SCHMID * and J.T. DICKINSON

Department o/ Phvsrcs, Washrngton Stare Unroersrtv. Pullman, Washrngton 99164 -2X14, USA

and

E.J. ASHLEY

Nuc~l Weapons Cenrer, Chtna Lake, Calrfornra 93555. USA

Received 11 January 1984; accepted for publication 5 March 1984

The physical sputtering yield of an SiO, thin film with 500 eV Ar ions was measured to be 100

AMU/ion. The presence of XeF, gas increased the sputtering yield to 355 AMU/ion. This SiO,.

XeF,, Ar ion system was studied using AES and quartz crystal microbalance techniques to

determine the mechanism responsible for this large enhancement in the sputter etch rate. In the

absence of an ion beam the SiO, surface adsorbs a monolayer of fluorine when exposed to XeF,.

Our measurements suggest that this adsorbed fluorine layer is responsible for the chemical

sputtering.

Surface Science 141 (1984) 4177454

North-Holland, Amsterdam 417

RECENT DEVELOPMENTS IN MODELING BINARY ALLOY SURFACE SEGREGATION: LOW INDEX PLANES, STEPS, KINKS, AND CHEMISORPTION

T.S. KING * and R.G. DONNELLY **

Department of Chemrcal Engineertng, Massachusetts Instrrure of TechnoloK)?, Massac~husetts 02139,

USA

Received 15 July 1983; accepted for publication 6 March 1984

This paper reports the application of a Monte Carlo method for the calculation of surface

segregation effects for binary alloy low index planes, steps and kink surfaces. The effect of

chemisorption is also modelled. The essential feature of this method is that metallic bond energies

are allowed to vary near the alloy surface. The coordination dependent bond energies are

determined from an empirical potential model. Composition profiles and surface ensemble size

distributions are reported for the (100). (110) and (111) surface of Ag-Au and Au-P1 binary

alloys. Surface composition probability maps are given for the more highly structured step and

kink surfaces of Ag-Au and CuNi alloys. The results of this work are compared with experimen-

tally determined surface compositions and the results of other models.