Dynamics of surface melting

Technical Report · Sat Jun 01 04:00:00 EDT 1991

OSTI ID:5519488

Elsayed-Ali, H E

The objective of this program is to study the phenomenon of surface disordering surface melting'' of single crystals of metals at temperatures below that of bulk melting. We use conventional static electron diffraction techniques as well as dynamic ultrafast reflection high-energy electron diffraction (RHEED) to study the temperature dependent surface structural behavior. Static RHEED experiments on surface disordering of Pb(110) crystal were conclusive on the existence of surface disordering at temperatures {approximately}50 K below the bulk melting temperature. A large set of time-resolved RHEED experiments was conducted to study the thermal response of Pb(110) to {approximately}150-ps pulsed laser heating. The surface Debye-Waller effect was used to time resolve the evolution of surface temperature. This provided a picosecond time-resolved surface lattice structure and temperature probe. Results for laser fluences below the surface disordering temperature show agreement with a heat diffusion model. For laser fluences above the surface disordering temperature, surface disorder upon heating and regrowth of crystalline order were observed to be completely reversible within {approximately}150 ps. An extensive study of the temperature dependent surface disordering of Pb(100) using angle-resolved photoemission was conducted. Results show that the onset of surface disorder occurs at 586{plus minus}5 K. The number of disordered layers grow logarithmically to {approximately}4--5 monolayers at 599 K. Slight anisotropy, which favors disordering along the (011) azimuth compared to that along the (001) azimuth, was observed. 22 refs., 6 figs.

• Research Organization: Rochester Univ., NY (United States). Lab. for Laser Energetics
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-88ER45376
• OSTI ID: 5519488
• Report Number(s): DOE/ER/45376-3; ON: DE91016344
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
COHERENT SCATTERING
CRYSTALS
DIFFRACTION
DOCUMENT TYPES
ELECTROMAGNETIC RADIATION
ELECTRON DIFFRACTION
ELEMENTS
LASER RADIATION
LEAD
MELTING
METALS
PHASE TRANSFORMATIONS
PROGRESS REPORT
RADIATIONS
SCATTERING
SURFACES
TEMPERATURE DEPENDENCE