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New features in the low energy Auger spectra of the nitrides of titanium and vanadium
A267 Surface Science 249 (1991) 223-232 North-Holland
223
New features in the low energy Auger spectra of the nitrides of titanium and vanadium P.T. Dawson and K.K. Tzatzov Department of Chemistry and Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada LSS 4M1 Received 14 August 1990; accepted for publication 27 December 1990 For Ti and V nitrides, two Auger features assigned to the M(3P)M(3d)M(3d) and M(3p)N(2p)M(3d) transitions have been previously observed in the energy range 20-40 eV. For the stoichiometric nitrides the total intensity of these features approaches zero, and this has led to a search for additional transitions responsible for the decay of the M(3p) hole. We have discovered two new features below 20 eV, and describe background subtraction procedures necessary to extract these features from the rapidly changing background. The new features appear at approximately the same energies in both the titanium and vanadium nitrides, with peaks in the N ( E ) spectrum near 5 and 15 eV. Both features are thought to involve the N(2s) level, the 5 eV feature has been assigned to a N(2s)N(2p)M(3d) transition and that at 15 eV could arise from a M(3p)N(2s)M(3d) transition. The disappearance of the previously observed M(3p) transitions in the stoichiometric nitride can be ascribed to a greater probability fol: the M(3p)N(2s)M(3d) transition.
Surface Science 249 (1991) 233-236 North-Holland
233
Step roughness on vicinal A g ( l l l ) J.F. Wolf, B. Vicenzi and H. Ibach lnstitut jear Grenzfliichenforschung und Vakuumphysik, Forschungszentrum Jiilich, Postfach 1913, W-5170 Jiilich, Germany Received 29 October 1990; accepted for publication 15 January 1991 The roughness of steps on Ag(111) has been investigated using the tunnel microscope. At 300 K monatomic steps are rough with a roughness of the order of one atom diameter, while submonolayer steps caused by stacking faults or screw dislocations are always smooth. Monatomic steps become smooth when the temperature is lowered to 27 K. It is suggested that the observed roughness is caused by kink diffusion.
Surface Science 249 (1991) 237-247 North-Holland
237
Molecular dynamics study of diffusion in a molten surface X.J. Chen, F. Ercolessi, A.C. Levi and E. Tosatti International School for Advanced Studies, Strada Costiera 11, 34014 Trieste, Italy Received 20 November 1990; accepted for publication 31 December 1990 Using molecular dynamics simulations, we have studied atomic diffusion in a molten Lennard-Jones fcc (110) surface, at temperatures where the thickness of the quasi-liquid layer (QLL) is small. Both short-time (displacement) and long-time (diffusion) dynamics have been found to have anisotropy effects in the plane (between the [110] and [001] directions) due to the underlying anisotropy of the crystalline periodic potential. The dynamics in the [001] direction is found to be faster in the short-time regime, but slower in the long-time regime. The amount of anisotropy, and the cross-over time are found to decrease as the temperature is increased. Atoms in the QLL are found to diffuse via both single and double jumps along [110], and mainly via single jumps along [001]. Another, more obvious, anisotropy between the in-plane and vertical motions is found to be very strong when the QLL is thin, and to vanish gradually in the centre of the QLL when the QLL becomes thick. This kind of anisotropy persists up to the triple point close to both the solid-QLL and the QLL-vapour interface.
223
New features in the low energy Auger spectra of the nitrides of titanium and vanadium P.T. Dawson and K.K. Tzatzov Department of Chemistry and Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada LSS 4M1 Received 14 August 1990; accepted for publication 27 December 1990 For Ti and V nitrides, two Auger features assigned to the M(3P)M(3d)M(3d) and M(3p)N(2p)M(3d) transitions have been previously observed in the energy range 20-40 eV. For the stoichiometric nitrides the total intensity of these features approaches zero, and this has led to a search for additional transitions responsible for the decay of the M(3p) hole. We have discovered two new features below 20 eV, and describe background subtraction procedures necessary to extract these features from the rapidly changing background. The new features appear at approximately the same energies in both the titanium and vanadium nitrides, with peaks in the N ( E ) spectrum near 5 and 15 eV. Both features are thought to involve the N(2s) level, the 5 eV feature has been assigned to a N(2s)N(2p)M(3d) transition and that at 15 eV could arise from a M(3p)N(2s)M(3d) transition. The disappearance of the previously observed M(3p) transitions in the stoichiometric nitride can be ascribed to a greater probability fol: the M(3p)N(2s)M(3d) transition.
Surface Science 249 (1991) 233-236 North-Holland
233
Step roughness on vicinal A g ( l l l ) J.F. Wolf, B. Vicenzi and H. Ibach lnstitut jear Grenzfliichenforschung und Vakuumphysik, Forschungszentrum Jiilich, Postfach 1913, W-5170 Jiilich, Germany Received 29 October 1990; accepted for publication 15 January 1991 The roughness of steps on Ag(111) has been investigated using the tunnel microscope. At 300 K monatomic steps are rough with a roughness of the order of one atom diameter, while submonolayer steps caused by stacking faults or screw dislocations are always smooth. Monatomic steps become smooth when the temperature is lowered to 27 K. It is suggested that the observed roughness is caused by kink diffusion.
Surface Science 249 (1991) 237-247 North-Holland
237
Molecular dynamics study of diffusion in a molten surface X.J. Chen, F. Ercolessi, A.C. Levi and E. Tosatti International School for Advanced Studies, Strada Costiera 11, 34014 Trieste, Italy Received 20 November 1990; accepted for publication 31 December 1990 Using molecular dynamics simulations, we have studied atomic diffusion in a molten Lennard-Jones fcc (110) surface, at temperatures where the thickness of the quasi-liquid layer (QLL) is small. Both short-time (displacement) and long-time (diffusion) dynamics have been found to have anisotropy effects in the plane (between the [110] and [001] directions) due to the underlying anisotropy of the crystalline periodic potential. The dynamics in the [001] direction is found to be faster in the short-time regime, but slower in the long-time regime. The amount of anisotropy, and the cross-over time are found to decrease as the temperature is increased. Atoms in the QLL are found to diffuse via both single and double jumps along [110], and mainly via single jumps along [001]. Another, more obvious, anisotropy between the in-plane and vertical motions is found to be very strong when the QLL is thin, and to vanish gradually in the centre of the QLL when the QLL becomes thick. This kind of anisotropy persists up to the triple point close to both the solid-QLL and the QLL-vapour interface.