Surface diffusion of Sb on Ge(111) monitored quantitatively with optical second harmonic microscopy

Journal Article · Sun Nov 01 04:00:00 EST 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463657· OSTI ID:7048501

Schultz, K A; Seebauer, E G ^[1]

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1. Department of Chemical Engineering, University of Illinois, Urbana, Illinois 61801 (United States)

Surface diffusion of Sb on Ge(111) has been measured with the newly developed technique of optical second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by surface second harmonic generation with 5 {mu} spatial resolution. A Boltzmann--Matano analysis yields the coverage dependence of the diffusivity {ital D} without parametrization. Experiments were performed at roughly 70% of the bulk melting temperature {ital T}{sub {ital m}}. In the coverage range 0{le}{theta}{le}0.6, the activation energy {ital E}{sub diff} remains constant at 47.5{plus minus}1.5 kcal/mol, but the pre-exponential factor {ital D}{sub 0} decreases from 8.7{times}10{sup 3{plus minus}0.4} to 1.6{times}10{sup 2{plus minus}0.4} cm{sup 2}/s. Both {ital E}{sub diff} and {ital D}{sub 0} are quite large, which is consistent with high-temperature measurements in other systems. The inadequacies of current theories for high-temperature surface diffusion are outlined, and a new vacancy model is proposed for low-coverage diffusion. The model accounts semiquantitatively for the large values of {ital E}{sub diff} and {ital D}{sub 0}, and suggests that these quantities may be manipulated using doping levels and photon illumination. An islanding mechanism is proposed to explain the decrease in {ital D}{sub 0} with {theta}.

• DOE Contract Number: FG02-91ER45439
• OSTI ID: 7048501
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 97:9; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
360606* -- Other Materials-- Physical Properties-- (1992-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ANTIMONY
CRYSTAL DEFECTS
CRYSTAL DOPING
CRYSTAL STRUCTURE
DIFFUSION
ELEMENTS
FREQUENCY MIXING
GERMANIUM
HARMONIC GENERATION
LIGHT TRANSMISSION
MATHEMATICAL MODELS
METALS
MICROSCOPY
OPTICAL MICROSCOPY
POINT DEFECTS
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
VACANCIES