TIME-RESOLVED STRUCTURAL STUDIES OF THE LOW-INDEX FACES OF LEAD

Reflection high-energy electron diffraction with 200-ps time resolutio n is used to study the structural behavior of the three low-index face s of Pb. The surfaces are subjected to heating and cooling rates on th e order of 10(11) K/s. The open Pb(110) surface is seen to reversibly disorder below the bulk melting temperature, T(m). In contrast to Pb(1 10), the close-packed Pb(111) surface sustains superheating to T(m) 120 K. Pb(100), a surface with atomic packing intermediate to that of Pb(110) and Pb(111), shows evidence of residual order at a temperature above the bulk melting point.