Condensation on (002) graphite of liquid bismuth far below its bulk melting point
- Physical Electronics Research Institute, Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)
Condensation of thermally evaporated Bi on (002) graphite, at temperatures of 300-523 K, was studied using in situ reflection high-energy electron diffraction (RHEED) and room temperature ex situ atomic force microscopy (AFM). For deposition at temperatures below 415{+-}5 K, transmission RHEED patterns of Bi appeared at an average thickness of {approx}0.5 monolayer (ML). AFM images showed that the film consisted of crystallites in the shape of triangular step pyramids with step heights corresponding to single and double Bi layers in the [111] direction. This morphology indicates crystallization from the vapor. For deposition at higher temperatures, diffuse RHEED patterns appeared independent of the deposited thickness. When these films were cooled, clear transmission patterns of crystalline Bi appeared. After cooling to near room temperature, the melting and solidification behaviors of these films were investigated with RHEED. Upon subsequent heating, the topmost layers of the probed Bi crystallites started to lose long-range order at {approx}10-15 K below the Bi bulk melting point, T{sub 0}=544.52 K. When crystallized from the melt, supercooling by {approx}125 K below T{sub 0} was observed. These results indicate that Bi condensed on graphite in the form of supercooled liquid droplets when the graphite temperature was above 419 K (T{sub 0}-125). Below that temperature, Bi condensed in the solid phase. Bi films crystallized by cooling the liquid had crystal morphologies that depended on the degree of liquid supercooling.
- OSTI ID:
- 20719844
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 72, Issue 20; Other Information: DOI: 10.1103/PhysRevB.72.205426; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC FORCE MICROSCOPY
BISMUTH
CRYSTALLIZATION
CRYSTALS
DEPOSITION
DROPLETS
ELECTRON DIFFRACTION
EVAPORATION
FILMS
GRAPHITE
HEATING
LAYERS
LIQUIDS
MELTING
MELTING POINTS
MORPHOLOGY
REFLECTION
SOLIDIFICATION
TEMPERATURE DEPENDENCE
VAPORS