Surface Diffusion of Antimony on Germanium(111) Investigated by Second Harmonic Microscopy

Schultz, Kurt Alan

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Description

Title

Surface Diffusion of Antimony on Germanium(111) Investigated by Second Harmonic Microscopy

Author(s)

Schultz, Kurt Alan

Issue Date

1992

Doctoral Committee Chair(s)

Seebauer, Edmund G.

Department of Study

Chemical Engineering

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemistry, Physical
• Physics, Condensed Matter
• Physics, Optics

Abstract

Surface diffusion of Sb on Ge(111) has been measured with the newly-developed technique of second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by second harmonic generation with 5 $\mu$m spatial resolution. A Boltzmann-Matano analysis of the concentration profiles yields the coverage dependence of the diffusivity D without parameterization. Experiments were performed at roughly 70% of the bulk melting temperature T$\sb{\rm m}.$ In the coverage range of $0<\theta<0.6,$ the activation energy E$\sb{\rm diff}$ remains constant at 47.5 $\pm$ 1.5 kcal/mol. The corresponding pre-exponential factor decreases from 8.7 $\times$ 10$\sp{3\pm0.4}$ to 1.6 $\times$ 10$\sp{2\pm0.4}$ cm$\sp2$/sec. The results are explained in terms of a new vacancy model for surface diffusion at high-temperatures. The model accounts semiquantitatively for the large values of E$\sb{\rm diff}$ and D$\sb{\rm o},$ and suggest that these quantities may be manipulated by bulk doping levels and photon illumination of the surface.

Graduation Semester

1992

Type of Resource

text

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