Concept for improved vacuum pressure measuring device

To measure vacuum pressures in the range of 5 times 10 to the minus 7 to 5 times 10 to the minus 16, a semiconductor resistor composed of sintered zinc oxide is used. Through the effect of surface absorbed gases on the resistance of the semiconductor material, very low pressures are measured

Collective surface diffusion near a first-order phase transition

For a large class of lattice models we study the thermodynamic factor, $\Phi$, of the collective surface diffusion coefficient near a first-order phase transition between two phases at low temperatures. In a two-phase regime its dependence on the coverage, \te, is \Phi \approx \te/[(\te-\te_-)(\te_+ - \te)N], where $N$ is the number of adsorption sites and \te_\pm are the single-phase coverages at the transition. In the crossover between the two-phase and single-phase regimes \Phi(\te) is shown to have a more complex behavior. The results are applied to a simple 2D lattice model.Comment: 9 pages, 4 figure