ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The energetics of Pb film grown at 300 K on two well-defined oxides [a MgO(100) thin film and a p(2×1)-oxide on Mo(100)] have been measured using single-crystal adsorption microcalorimetry. The evolution of the film morphology was followed using Auger electron spectroscopy (AES). An initial heat of adsorption of 103 kJ/mol is observed for the Pb/MgO(100) system. Auger results indicate that this is due to the formation of an ∼20 atom Pb island in the first pulse of Pb gas incident on the MgO(100) surface. This allows the extraction of a Pb–MgO(100) bond energy of ∼32±2 kJ/mol in the small two-dimensional particles formed in the first pulse. As more Pb is deposited onto the MgO(100) surface, the Pb forms three-dimensional islands. The integral of the heats of adsorption up to high coverage indicates an adhesion energy of 76.5±∼20 μJ/cm2 for large 3D Pb particles to the MgO(100) substrate. This indicates a Pb–MgO(100) bond energy of 49±13 kJ/mol at the 3D interface. Similar analyses of the Pb/p(2×1)-oxide on Mo(100) surface give an initial heat of adsorption of 146.2 kJ/mol and an adhesion energy of 82.5±20 μJ/cm2 for thick Pb films. This indicates a bond energy of 52±12 kJ/mol for a Pb atom to this surface at the interface of a thick Pb film. The metal's sticking probabilities as a function of coverage and the coverage-dependent changes in optical reflectivity were measured. For the Pb/MgO(100) system, an initial sticking probability of 0.70 at 300 K was observed, whereas for the Pb/p(2×1)-oxide on Mo(100) surface unit sticking probability was observed. The relationship between these quantities and the adsorption energetics is discussed. © 2001 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1337097
