ISSN:0022-5355    

DOI:10.1116/1.1316349

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1316352

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

The inelastic-collision model of LEED using isotropics-wave scatterers (phase shift π/2 and damping parameter 8 Å) describes the qualitative features of experimental intensity profiles from clean surfaces. For energies above ca. 100 eV, theoretical and experimental profiles give strong scattering near the kinematical positions. From this result, the crystal structure and exposed face can be determined using the kinematical model. For a(2×2)chemisorbed monolayer, calculated intensity profiles of the extra beams show considerable, substrate-dependent, structure. However, the integrals of these profiles over a wide voltage range are in excellent agreement with the predictions of the kinematical model for the absorbate layer alone. This result is independent of the substrate, the phase shifts used to describe the adsorbate, and the position of the adsorbate normal to the substrate. Consequently, extensive structural information can be extracted from LEED using the kinematical model without making a dynamical calculation.

ISSN:0022-5355    

DOI:10.1116/1.1316356

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1316374

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

The isotropic-scatterer, inelastic-collision model is used to analyze experimental elastic intensity profiles characteristic of electrons in the energy range10≤E≤120 eVscattered from Al(100). Using the double-diffraction approximation a satisfactory description of these profiles is achieved for a variety of incident beam angles, θ≤25°. The temperature dependence of these profiles due to both thermal expansion and lattice vibrations is examined. Using the inelastic-collision-model description of the elastic scattering, the RPA plasmon dispersion relations and lifetimes, and the sharp-junction, “uniform” electron fluid electron-plasmon interaction vertices, the inelastic energy and angular profiles for the two-step excitation of bulk and surface plasmons are predicted using a double-diffraction analysis of this process. Observation of these profiles and their correlation with such an analysis constitutes a critical test of existing models of inelastic diffraction.

ISSN:0022-5355    

DOI:10.1116/1.1316257

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1316266

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1316275

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

Flash filament techniques and mass spectrometry have been used to make sputtering measurements for nitrogen which is chemisorbed on a tungsten surface and bombarded withAr+ions. The sputtering rate for a given energy between 20 eV and 300 eV is described by the equationdN/dt=−S(N/)N0)ni,whereNis the surface coverage,N0the saturation surface coverage,nithe ion flux, andSthe sputtering ratio measured at saturation. The sputtering ratio for nitrogen was found to be ∼0.02 at 17 eV, indicating a low threshold energy for sputtering of the strongly bound nitrogen atom. This result suggests that the well-known experimental relationship between sublimation energy (∼7 eV/nitrogen atom) and threshold energy may not hold for chemisorbed gases. For all energies between 100 and 300 eV the measured sputtering ratio for nitrogen was approximately twice that found for tungsten from atomically clean tungsten. This is particularly surprising when one considers that nitrogen covers less than 20% of the geometrical surface area. This result may, indicate a large sputtering ratio even for gases with large binding energies.

ISSN:0022-5355    

DOI:10.1116/1.1316280

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

When a Cu surface is sputtered by ion bombardment under the condition that Mo atoms arrive at the Cu surface during sputtering an unexpected phenomenon can arise: the surface of the Cu target becomes covered with microscopic cones. The cone density increases with increasing flux density of arriving Mo atoms. When the cones are closely spaced they give the target a velvet-like black appearance. The result of dense cone coverage are a lower sputtering yield and a more oblique ejection of sputtered material. The cone tops seem to consist of Mo nuclei which are constantly replenished via surface migration and protect the underlying Cu from being sputtered.

ISSN:0022-5355    

DOI:10.1116/1.1316290

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1316294

出版商:American Vacuum Society    

年代:1971

数据来源: AIP