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Observation of acoustic and optical surface phonons in LiF(001) by inelastic He scattering
A433 684
Surface Science 189/190 (1987) 684-688 North-Holland, Amsterdam
OBSERVATION OF ACOUSTIC AND OPTICAL IN LiF(001) BY INELASTIC He SCATfERING G. BRACCO, M. D'AVANZO, a n d F. T O M M A S I N 1
SURFACE
C. S A L V O , R. T A T A R E K
PHONONS
*, S. T E R R E N I
Dipartimento di Fisica dell'Universit& via Dodecaneso 33, 16146 Genova, Italy Received 7 April 1987; accepted for publication 19 May 1987
The vibrational spectrum of the LiF(00I) surface measured by inelastic He scattering with time-of-flight detection along the {110~ and ~100~ crystal directions is reported. The acoustic and optical modes are described in the whole surface Brillouin zone up to energies of 50 meV.
Surface Science 189/190 (1987) 689-694 North-Holland, Amsterdam
689
HIGH RESOLUTION ELECTRON ENERGY LOSS INVESTIGATION OF THE AZIMUTHAL DEPENDENCE O F T H E S i ( l l l ) ( 2 × 1) SURFACE EXCITATIONS U. D E L P E N N I N O ,
M.G. BETH,
C. M A R I A N I
Dipartimento di Fisica, Universit~ di Modena, 1-41100 Modena, Italy
C.M. BERTONI Dipartimento di Fisica, UniversittJ di Roma "'Tor Vergata", 1-00173 Roma, ltal)'
S. N A N N A R O N E Dipartimento di Fisica, Universit~ di Roma "'La Sapienza", 1-00185 Roma, Italy
I. A B B A T I , L, B R A I C O V I C H
a n d A. R I Z Z I
Dipartimento di Fisica, Politeenico di Milano, 1-20133 Milano, Italr
Received 13 April 1987; accepted for publication 15 April 1987 Electron energy loss spectroscopy has been used, with low energy of the primary beam and azimuthal resolution, to study the anisotropy of the surface vibrational and electronic properties of the cleavage surface of silicon. The analysis of the loss function has been performed through the subtraction of the kinematic prefactor accounting for the finite angular acceptance of the spectrometer. The angular dependence of the phonon excitation, even at very low primary energies, is not so high as expected in previous works. The loss features associated with the transition between surface electronic bands is discussed in terms of a theoretical model of the surface dielectric function.
Surface Science 189/190 (1987) 684-688 North-Holland, Amsterdam
OBSERVATION OF ACOUSTIC AND OPTICAL IN LiF(001) BY INELASTIC He SCATfERING G. BRACCO, M. D'AVANZO, a n d F. T O M M A S I N 1
SURFACE
C. S A L V O , R. T A T A R E K
PHONONS
*, S. T E R R E N I
Dipartimento di Fisica dell'Universit& via Dodecaneso 33, 16146 Genova, Italy Received 7 April 1987; accepted for publication 19 May 1987
The vibrational spectrum of the LiF(00I) surface measured by inelastic He scattering with time-of-flight detection along the {110~ and ~100~ crystal directions is reported. The acoustic and optical modes are described in the whole surface Brillouin zone up to energies of 50 meV.
Surface Science 189/190 (1987) 689-694 North-Holland, Amsterdam
689
HIGH RESOLUTION ELECTRON ENERGY LOSS INVESTIGATION OF THE AZIMUTHAL DEPENDENCE O F T H E S i ( l l l ) ( 2 × 1) SURFACE EXCITATIONS U. D E L P E N N I N O ,
M.G. BETH,
C. M A R I A N I
Dipartimento di Fisica, Universit~ di Modena, 1-41100 Modena, Italy
C.M. BERTONI Dipartimento di Fisica, UniversittJ di Roma "'Tor Vergata", 1-00173 Roma, ltal)'
S. N A N N A R O N E Dipartimento di Fisica, Universit~ di Roma "'La Sapienza", 1-00185 Roma, Italy
I. A B B A T I , L, B R A I C O V I C H
a n d A. R I Z Z I
Dipartimento di Fisica, Politeenico di Milano, 1-20133 Milano, Italr
Received 13 April 1987; accepted for publication 15 April 1987 Electron energy loss spectroscopy has been used, with low energy of the primary beam and azimuthal resolution, to study the anisotropy of the surface vibrational and electronic properties of the cleavage surface of silicon. The analysis of the loss function has been performed through the subtraction of the kinematic prefactor accounting for the finite angular acceptance of the spectrometer. The angular dependence of the phonon excitation, even at very low primary energies, is not so high as expected in previous works. The loss features associated with the transition between surface electronic bands is discussed in terms of a theoretical model of the surface dielectric function.