Coverage and temperature dependence of the morphology of strained metal overlayers: Deposition of Pd on a bcc(110) substrate

The structure of Pd thin films deposited on a bcc(110) substrate has been investigated for coverages ranging from 0.25 to 3.50 bcc equivalent monolayers (ML) and temperatures from 75 to 500 K using molecular-dynamics and Monte Carlo simulation techniques. A pseudomorphic Pd bcc thin film is found to be metastable at low temperatures for all coverages studied. At high temperature, the Pd thin film is only pseudomorphic for coverages below 1.0 ML and rapidly undergoes a phase transition to an incommensurate fcc film above 1.0 ML. Low-energy electron-diffraction (LEED) patterns are calculated from the simulated configurations and compared to experimental results to demonstrate that two-dimensional wavelike structures in the Pd adlayer may be responsible for observed LEED patterns in Pd/Nb(110), Pd/Ta(110), and Co/Mo(110) systems. The energetics for Pd diffusion, island formation, and second to first adlayer atom incorporation are investigated.