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AES study of room temperature oxygen interaction with near noble metal-silicon compound surfaces
A533 Surface Science 161 (1985) 1-11 North-Holland, Amsterdam AES STUDY OF ROOM
TEMPERATURE
WITH NEAR N O B L E M E T A L - S I L I C O N S. V A L E R I , U . D E L P E N N I N O ,
OXYGEN INTERACTION COMPOUND
P. L O M E L L I N I
SURFACES
a n d G. O T T A V I A N I
Dipartimento di Fisica, Universith di Modena, Via Campi 213//t, 1-41100 Modena, Italy Received 20 February 1985; accepted for publication 5 June 1985 We have carried out a comparative study of room temperature (RT) oxidation of near noble metal silicides similar in stoichiometry (M2Si) and electronic structure. Core-valence-valence (CVV) Auger line measurements on Ni2Si, Pd2Si and Pt2Si surfaces before and after exposure to 104 L of oxygen were performed. We compare the results with those for the oxidation of pure Si. In general oxygen interacts with Si atoms only. In Ni2Si, however, features ascribed to the onset of oxidation of Ni atoms appear in the Ni(MW) line. In the Ni2Si and PdzSi case, the Si reaction rate is increased with respect to that of pure Si, the strongest oxidation enhancement being obtained in Ni2Si. However, Si cannot be oxidized to SiO2 in these conditions; a SiOx (x < 2) phase is formed. The Pt2Si oxidation behaviour is close to that of pure Si. The different catalytic effect of Ni, Pd and Pt on Si oxidation has been discussed. We conclude that the main effect of metal is to by-pass the kinetic bottleneck of pure Si oxidation, i.e. the dissociation of the 02 molecule at the silicide/gas interface. The effect of different exposure procedures was also underlined.
12 RHEED
Surface Science 161 (1985) 12-24 North-Holland, Amsterdam FROM
INTENSITY
STEPPED
SURFACES
OSCILLATIONS
AND ITS RELATION
OBSERVED
DURING
TO RHEED
MBE
T. K A W A M U R A
Department of Physics, Yamanashi University, Kofu, Yamanashi 400, Japan and P.A. MAKSYM
Department of Physics, University of Leicester, Leicester LE1 7RH, UK Received 4 May 1985; accepted for publication 24 May 1985 Multiple scattering theory is used to calculate the intensities of reflection high energy electron diffraction from periodic arrays of surface steps. The intensities are found to depend strongly on the direction of the incident beam azimuth. When the incident beam azimuth is parallel to the step edges, both the specular and diffracted beam intensities are diminished with respect to the intensities from a flat surface. When the incident beam azimuth is perpendicular to the edges, the intensities of all the beams are of the same order of magnitude as for a flat surface but some of the peak heights are oscillatory functions of the number of atoms in the topmost layer. These peak intensity oscillations are very similar to the intensity oscillations observed during molecular beam epitaxial film growth.
TEMPERATURE
WITH NEAR N O B L E M E T A L - S I L I C O N S. V A L E R I , U . D E L P E N N I N O ,
OXYGEN INTERACTION COMPOUND
P. L O M E L L I N I
SURFACES
a n d G. O T T A V I A N I
Dipartimento di Fisica, Universith di Modena, Via Campi 213//t, 1-41100 Modena, Italy Received 20 February 1985; accepted for publication 5 June 1985 We have carried out a comparative study of room temperature (RT) oxidation of near noble metal silicides similar in stoichiometry (M2Si) and electronic structure. Core-valence-valence (CVV) Auger line measurements on Ni2Si, Pd2Si and Pt2Si surfaces before and after exposure to 104 L of oxygen were performed. We compare the results with those for the oxidation of pure Si. In general oxygen interacts with Si atoms only. In Ni2Si, however, features ascribed to the onset of oxidation of Ni atoms appear in the Ni(MW) line. In the Ni2Si and PdzSi case, the Si reaction rate is increased with respect to that of pure Si, the strongest oxidation enhancement being obtained in Ni2Si. However, Si cannot be oxidized to SiO2 in these conditions; a SiOx (x < 2) phase is formed. The Pt2Si oxidation behaviour is close to that of pure Si. The different catalytic effect of Ni, Pd and Pt on Si oxidation has been discussed. We conclude that the main effect of metal is to by-pass the kinetic bottleneck of pure Si oxidation, i.e. the dissociation of the 02 molecule at the silicide/gas interface. The effect of different exposure procedures was also underlined.
12 RHEED
Surface Science 161 (1985) 12-24 North-Holland, Amsterdam FROM
INTENSITY
STEPPED
SURFACES
OSCILLATIONS
AND ITS RELATION
OBSERVED
DURING
TO RHEED
MBE
T. K A W A M U R A
Department of Physics, Yamanashi University, Kofu, Yamanashi 400, Japan and P.A. MAKSYM
Department of Physics, University of Leicester, Leicester LE1 7RH, UK Received 4 May 1985; accepted for publication 24 May 1985 Multiple scattering theory is used to calculate the intensities of reflection high energy electron diffraction from periodic arrays of surface steps. The intensities are found to depend strongly on the direction of the incident beam azimuth. When the incident beam azimuth is parallel to the step edges, both the specular and diffracted beam intensities are diminished with respect to the intensities from a flat surface. When the incident beam azimuth is perpendicular to the edges, the intensities of all the beams are of the same order of magnitude as for a flat surface but some of the peak heights are oscillatory functions of the number of atoms in the topmost layer. These peak intensity oscillations are very similar to the intensity oscillations observed during molecular beam epitaxial film growth.