Surface Barrier Model Research Articles

The sticking coefficient of hydrogen on niobium

We present an expression for the sticking coefficient of H on Nb based on a surface-barrier model for hydrogen uptake. This expression explains some of the hitherto unexplained features of previous measurements of the sticking coefficient of H on Nb. The expression can be generalized to other metal-gas systems in which solution plays a major role.

The sticking coefficient of hydrogen on niobium

We present an expression for the sticking coefficient of H on Nb based on a surface-barrier model for hydrogen uptake. This expression explains some of the hitherto unexplained features of previous measurements of the sticking coefficient of H on Nb. The expression can be generalized to other metal-gas systems in which solution plays a major role.

Linear response function of a bounded jellium metal in the RPA

The integral equation describing the dielectric response of a surface system cannot in general by solved analytically because quantum effects introduce a nonseparable kernel. An approximate separable kernel is proposed with which the static response problem (for the infinite surface barrier model) is readily solved in exact analytic form. The method, when tested for several physical problems, proves rather accurate and is then used to calculate the real self-energy of a test charge at arbitrary positions relative to the surface. Dynamical response are briefly discussed in the context of the dispersion of long-wave surface plasmons, for which an alternative iterative method is also proposed.

Flux motion and moving dislocations in type II superconductors

Abstract The interaction of mobile dislocations with Abrikosov vortices is described and shown to be reversible with the motion of dislocations, the dislocations sweeping flux into the specimen. In addition the flux change varies linearly with the strain rate. This interaction is observed to be independent of temperature, between 0·2 and 0·6 Tc, which rules out a surface barrier model. A model, which relates the change in flux to the mobile dislocation density, is presented and compared with the observations.

On the choice of surface barrier models for LEED intensity calculations

The significance of surface barrier scattering in LEED is assessed. The scattering properties of various model barriers are compared. Modifications and improvements are suggested for the simpler barrier models. A computational test for Cu(001) shows that a step barrier is satisfactory for LEED intensity calculations except where details of the surface barrier resonance are desired.

The effect of different surface barrier models on the Nottingham energy exchange process

TF emission current densities, total energy distributions and Nottingham inversion temperatures are calculated for three different models of the surface potential barrier. The models studied were: (i) Classical image potential, (ii) Quantum-modified image potential, (iii) Seitz-Van Oostrom modification of the image potential. The modified potential produced the expected lowering of the electron energy distribution and correspondingly reduced emission current densities. The third model potential also produced measurable changes for all quantities calculated. However, neither of the modified potentials yielded agreement with recent experimental values of inversion temperatures. Current work examining sources of this discrepancy are discussed.