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Elastic analysis of the energy and relaxation of stepped surfaces
A506 Surface Science 255 (1991) 111-119 North-Holland
I 1t
Elastic analysis of the energy and relaxation of stepped surfaces D.J. Srolovitz a and J.P. Hirth b " Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136, USA
h Department of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164.2920, USA Received 27 September 1990; accepted for publication 29 January 1991 We present an analytical, elastic analysis for the energy and relaxation of stepped surfaces. The analysis is based upon the observation that the most prominent feature of the non-reconstructive surface relaxation consists of the atoms at the top of the ledges relaxing inwards toward the bulk. This is modeled by replacing the true atomic structure with a continuum elastic half space subjected to a periodic array of line forces (with the periodicity of the steps) directed normal to the free surface. This model is then employed to determine the stress, strain and displacement fields and elastic energy associated with the surface relaxation. We find that the stress and strain fields decay quickly into the bulk as Y e - r, where Y is the distance from the surface normalized by the interledge spacing. The surface energy is largely controlled by the terrace energy and the ledge energy, while the ledge interaction energy decays as the inverse square of the ledge spacing. The elastic model provides an accurate description of the wavelength, phase and decay rate of the surface relaxations compared with atomistic simulation results for metals.
120
Surface Science 255 (1991) 120-126 North-Holland
Computer simulation of the surface composition change of a Cu-Ni alloy under ion bombardment at different sample temperatures Akira Kurokawa a, Hee Jae Kang b and Ryuichi Shimizu
a
"Department of Applied Physics, Osaka University, Suita, Osaka 565, Japan b Department of Physics, Chungbuk National University, Cheongju 360- 763, Korea Received 14 September 1990; accepted for publication 21 March 1991 The Monte Carlo simulation reported in a previous paper was verified by simulating the surface composition changes of a Cu-Ni alloy during ion bombardment. This simulation includes both the effects of radiation-enhanced diffusion and radiation-induced surface segregation as well as preferential sputtering processes. The best fit value of the parameter of the radiation induced surface segregation, K b, was determined by comparing with the experimental results published so far. The results show that the present simulation describes the dynamic changes of the composition profile in a Cu-Ni alloy at room temperature with considerable success.
Surface Science 255 (1991) 127-134 North-Holland
127
Two-target-atom model for calculating cross sections of direct recoils Shiladitya Chaudhury Department of Physics and Solid State Science Center, UCLA, Los Angeles, CA 90024-1547, USA
and R. Stanley Williams Department of Chemistry and Biochemistry and Solid State Science Center, UCLA, Los Angeles, CA 90024-1569, USA Received 22 January 1991; accepted for publication 21 March 1991 A new two-target-atom m o d e l for calculating the intensity of particles that have been directly recoiled from a surface has been developed to examine the effects of shadowing and blocking on the recoils. This model is similar to one that was recently introduced for calculating the intensity of the primary particles scattered back from a surface. Important surface structure information can be obtained by comparing calculated recoil intensities as a function of incident ion identity and kinetic energy, target ~ t a t i o n , and recoil angle and energy to experimentally measured quantities.
I 1t
Elastic analysis of the energy and relaxation of stepped surfaces D.J. Srolovitz a and J.P. Hirth b " Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136, USA
h Department of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164.2920, USA Received 27 September 1990; accepted for publication 29 January 1991 We present an analytical, elastic analysis for the energy and relaxation of stepped surfaces. The analysis is based upon the observation that the most prominent feature of the non-reconstructive surface relaxation consists of the atoms at the top of the ledges relaxing inwards toward the bulk. This is modeled by replacing the true atomic structure with a continuum elastic half space subjected to a periodic array of line forces (with the periodicity of the steps) directed normal to the free surface. This model is then employed to determine the stress, strain and displacement fields and elastic energy associated with the surface relaxation. We find that the stress and strain fields decay quickly into the bulk as Y e - r, where Y is the distance from the surface normalized by the interledge spacing. The surface energy is largely controlled by the terrace energy and the ledge energy, while the ledge interaction energy decays as the inverse square of the ledge spacing. The elastic model provides an accurate description of the wavelength, phase and decay rate of the surface relaxations compared with atomistic simulation results for metals.
120
Surface Science 255 (1991) 120-126 North-Holland
Computer simulation of the surface composition change of a Cu-Ni alloy under ion bombardment at different sample temperatures Akira Kurokawa a, Hee Jae Kang b and Ryuichi Shimizu
a
"Department of Applied Physics, Osaka University, Suita, Osaka 565, Japan b Department of Physics, Chungbuk National University, Cheongju 360- 763, Korea Received 14 September 1990; accepted for publication 21 March 1991 The Monte Carlo simulation reported in a previous paper was verified by simulating the surface composition changes of a Cu-Ni alloy during ion bombardment. This simulation includes both the effects of radiation-enhanced diffusion and radiation-induced surface segregation as well as preferential sputtering processes. The best fit value of the parameter of the radiation induced surface segregation, K b, was determined by comparing with the experimental results published so far. The results show that the present simulation describes the dynamic changes of the composition profile in a Cu-Ni alloy at room temperature with considerable success.
Surface Science 255 (1991) 127-134 North-Holland
127
Two-target-atom model for calculating cross sections of direct recoils Shiladitya Chaudhury Department of Physics and Solid State Science Center, UCLA, Los Angeles, CA 90024-1547, USA
and R. Stanley Williams Department of Chemistry and Biochemistry and Solid State Science Center, UCLA, Los Angeles, CA 90024-1569, USA Received 22 January 1991; accepted for publication 21 March 1991 A new two-target-atom m o d e l for calculating the intensity of particles that have been directly recoiled from a surface has been developed to examine the effects of shadowing and blocking on the recoils. This model is similar to one that was recently introduced for calculating the intensity of the primary particles scattered back from a surface. Important surface structure information can be obtained by comparing calculated recoil intensities as a function of incident ion identity and kinetic energy, target ~ t a t i o n , and recoil angle and energy to experimentally measured quantities.