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Adlayer-induced LEED beams near order-disorder transitions
Classified
abstracts
45834591
36 4583. Relationship of optical degradation changes in solar absorbers. (USA)
to
The physical basis for high-temperature electro-deposited black chrome coatings scanning electron microscopy and Auger coupled with inert gas depth profiling. metallic chromium in the coatings has believed to result in shape changes of the film thereby decreasing their near-infra-red for air heat-treated coatings.
G Zajac
and A Ignatiev,
surface
optical degradation been investigated electron spectroscopy Severe oxidation of been observed and it particles comprising absorbance as is observed
has
J Vuc Sci Techttol,
16 (2), 1979,
4588. (USA)
morphology of via the is the
233-235.
36 4584.
Analysis
of ELEED
intensities
from
ZnTe(ll0).
(USA) Elastic low-energy electron diffraction (ELEED) intensities were measured from ZnTe(l10) surfaces at 300 and 125 K. The (Ol), (Oi), (lo), (11) and (Ii) beams for normally incident electrons were and dynamic methods. Surface analysed using both kinematic structures corresponding to covalent rotations and ionic contractions of the top three surface layers, as well as two minimum-energy structures were examined. The best description of the measured ELEED intensities achieved to date is associated with a model of the reconstructed surface in which the tellurium sublattice is found IO be undistorted, while the top layer zinc sinks 0.4 A and the second layer zinc rises 0.2 A. Third layer distortions do not improve correspondence between the calculations and the data.
C B Duke
et al, J Vat SC; Techtrol,
16 (2),
1979, 647-650. 36
4585.
LEED
analysis
of the reconstructed
Au(ll0)
surface.
(USA) The LEED I-Y profiles for six inequivalent non-specular diffraction beams from an Au(1 IO)-( I / 2) surface have been measured, with the incident beam at normal incidence, and compared with model calculations. The experimental curves are compared with theoretical calculations for a model in which every other close-packed, (1 IO’type row is removed, i.e., the ‘missing row’ model. The analysis provides little agreement between measured profiles and the calculations for this particular model; e.g., the R factor as deiined by Zannazzi and Jona is always greater than 0.6 for changes of bo\h structural and non-structuraf model parameters.
J R Noonan
and H L Davis,
J Voc Sri Tdttrol,
4586. Semidynamical RFS technique application to GaAs(ll0). (USA)
for
16 (2), 1979, 587-289.
LEED
analysis,
with
36 an
Realistic dynamical calculations using Pendry’s renormalized forward scattering (RFS) scheme are almost impossible to perform at energies E 2 IO0 eV for the structure of GaAs(I IO) reported by Kahn c’t nl., which includes subsurface atomic displacements, because of the time needed to compute layer reflection and transmission matrices. The technique presented is based on the RFS scheme, using kinematically computed layer matrices, which reduces computation times by almost two orders of magnitude. Curves computed thus are in good agreement with dynamically computed curves over an energy interval where the latter calculation is feasible. The kinematical RFS curves are also compared with experimental data taken at normal and off-normal angles of incidence. (Mexico) C Cisneros, J Vat Sci Techtto/, 16 (2). 1979, 584-586.
4587. Angular-dependent ultra-violet photoemission spectroscopy polycrystalline films: a probe of surface electronic structure. (USA)
36 of
Angle-resolved ultra-violet photoemission (ARUPS) studies of polycrystalline noble metal are reported. In polycrystalline films. the electron exit angle with respect to the crystalline axes is averaged over, thus variation of the electron polar (exit) angle should result in variation of surface sensitivity. This work represents the first application of ARUPS with low-exit-angle geometries for the investigation of surface electronic structure. The main results are that Cu exhibits considerable (- 17%) d-band narrowing at the bottom of the&band at the surface, while the effects in Ag and Au appear to be much smaller. (Germany)
S P Kowalctyk, 354
J Vuc Sci Teclurol,
16 (2). 1979, 520-522.
Adlayer-induced
LEED
beams
near
order-disorder
transitions.
36
We present a Monte Carlo study of the adlayer-induced LEED beams in a representative order-disorder transition. Calculations of the widths of fractional order beams indicate that, as seen in recent experimental work on the O/Ni(ll I) system, these widths rise sharply and suddenly above T,. Furthermore the slope of this rise provides a sensitive probe of the adatom-adatom interactions. The increase in the width results From the existence of ordered domains above T,.. _, and has not been previously discussed since prior calculations have concentrated on beam intensities. We further derive a functional relation between the window approach used in simulations of orderdisorder transitions and the instrument response function approach of the experimentalist, to detail the effect of the LEED apparatus on the profile of the extra beams.
L D Roelofs
et al, J Vuc Sci Techol,
16 (2), 1979, 478-482.
4589. Simultaneous RHEED-AES-QMS growth on Si(lll) and sapphire (1102) vapor deposition. (USA)
study surfaces
on epitaxial by partially
36 Si film ionized
The role of simultaneous measurements of the chemical composition of a surface by AES. surface crystalline structure by RHEED, and released species by QMS are presented. A molecular beam of Si is effused from a partially ionized vapour deposition (PIVD) source consisting of a Kundsen cell and an electron-impact-type ionization chamber. The 7 >( 7 structure of a Si(lll) substrate at 1100 K changes into a broad I s 1 structure after vacuum deposition (VD) of 15 nm of Si while the epitaxial temperature can be lowered to 620 K (PIVD) in a OS:< ionized atomic vapour with a typical deposition rate and acceleration energy of 0.3 nm min’ and 100 eV, respectively. Epitaxial growth of Si on sapphire (lT02) can be observed at 850 (VD) and at 700 K(PIVD). with a I”< ionized atomic vapour. The Auger spectra during deposition at 870 K remarkably shows that 0 and Al are reacted with Si on the film. (Japan)
T Narusawa
et al, J VW Sci Twhtto/,
16 (2), 1979, 366-368. 36
4590.
Copper-polyvinyl
alcohol
interface:
A study
with XPS.
(USA) It has been known for some time that oxygen treatment of a polymer surface can lead to enhanced adhesion with metals. This has prompted us to investigate the metal-polymer interface of an oxygen-containing polymer, polyvinyl alcohol. We have vapour-deposited copper on the clean polymer surface and examined the interface with X-ray photoemission spectroscopy (XPS). At very low copper coverages, about 0.005 monolayer, the copper 2~~” core level binding energy is I.2 eV larger than the bulk copper value. As the copper coverage increases, this core level shift decreases: at a coverage of one monolayer this shift is sometimes as large as 0.2 eV. AI a cooper coveraee of two monolayers. the 2p”* core-binding energy is the same as it% in bulk copper, 932.85 eV. In addition to these chances. the carbon Is and oxygen Is core levels are observed to change wzh ;he addition of copper. The intensity of the C 1.9 level at 286.6 eV, associated with a C-O group, is observed to decrease faster than that at 285.0 eV which is associated with a CHL group. At the same time a new peak in the 0 Is spectrum is formed at 530.6 eV, 2.4 eV less than the original level. These changes indicate the formation of a coppercarbon complex at the interface.
J M Burkstrand,
J Vat Sci Techttol,
4591.
of two-phase
16 (2). 1979, 363-365. 36
Sputtering
polycrystalline
metals.
(USA) Polycrystalline niobium and its alloys with oxygen have been sputtered with a 15 keV argon ion beam. Yield measurements and scanning electron microscope topographic observations have been made for both singleand two-phase (Nb + NbO) targets which were also characterized by use of a scanning Auger microprobe. Results indicate that the relative yields of different phases, as well as of different grains, are critically dependent on the direction of the argon beam with respect to the individual grain orientations. Oxygen in solid solution and oxygen-containing atmospheres were important factors which influenced the target topography. The observed differential erosion of grains and the presence of surface relief inside individual grains are discussed with reference to the use of sputtering for depth profiling in surface analysis.
P F Tortorelli 804-807.
and C J Altstetter,
J Vuc Sci Techttol,
16 (2).
1979,
abstracts
45834591
36 4583. Relationship of optical degradation changes in solar absorbers. (USA)
to
The physical basis for high-temperature electro-deposited black chrome coatings scanning electron microscopy and Auger coupled with inert gas depth profiling. metallic chromium in the coatings has believed to result in shape changes of the film thereby decreasing their near-infra-red for air heat-treated coatings.
G Zajac
and A Ignatiev,
surface
optical degradation been investigated electron spectroscopy Severe oxidation of been observed and it particles comprising absorbance as is observed
has
J Vuc Sci Techttol,
16 (2), 1979,
4588. (USA)
morphology of via the is the
233-235.
36 4584.
Analysis
of ELEED
intensities
from
ZnTe(ll0).
(USA) Elastic low-energy electron diffraction (ELEED) intensities were measured from ZnTe(l10) surfaces at 300 and 125 K. The (Ol), (Oi), (lo), (11) and (Ii) beams for normally incident electrons were and dynamic methods. Surface analysed using both kinematic structures corresponding to covalent rotations and ionic contractions of the top three surface layers, as well as two minimum-energy structures were examined. The best description of the measured ELEED intensities achieved to date is associated with a model of the reconstructed surface in which the tellurium sublattice is found IO be undistorted, while the top layer zinc sinks 0.4 A and the second layer zinc rises 0.2 A. Third layer distortions do not improve correspondence between the calculations and the data.
C B Duke
et al, J Vat SC; Techtrol,
16 (2),
1979, 647-650. 36
4585.
LEED
analysis
of the reconstructed
Au(ll0)
surface.
(USA) The LEED I-Y profiles for six inequivalent non-specular diffraction beams from an Au(1 IO)-( I / 2) surface have been measured, with the incident beam at normal incidence, and compared with model calculations. The experimental curves are compared with theoretical calculations for a model in which every other close-packed, (1 IO’type row is removed, i.e., the ‘missing row’ model. The analysis provides little agreement between measured profiles and the calculations for this particular model; e.g., the R factor as deiined by Zannazzi and Jona is always greater than 0.6 for changes of bo\h structural and non-structuraf model parameters.
J R Noonan
and H L Davis,
J Voc Sri Tdttrol,
4586. Semidynamical RFS technique application to GaAs(ll0). (USA)
for
16 (2), 1979, 587-289.
LEED
analysis,
with
36 an
Realistic dynamical calculations using Pendry’s renormalized forward scattering (RFS) scheme are almost impossible to perform at energies E 2 IO0 eV for the structure of GaAs(I IO) reported by Kahn c’t nl., which includes subsurface atomic displacements, because of the time needed to compute layer reflection and transmission matrices. The technique presented is based on the RFS scheme, using kinematically computed layer matrices, which reduces computation times by almost two orders of magnitude. Curves computed thus are in good agreement with dynamically computed curves over an energy interval where the latter calculation is feasible. The kinematical RFS curves are also compared with experimental data taken at normal and off-normal angles of incidence. (Mexico) C Cisneros, J Vat Sci Techtto/, 16 (2). 1979, 584-586.
4587. Angular-dependent ultra-violet photoemission spectroscopy polycrystalline films: a probe of surface electronic structure. (USA)
36 of
Angle-resolved ultra-violet photoemission (ARUPS) studies of polycrystalline noble metal are reported. In polycrystalline films. the electron exit angle with respect to the crystalline axes is averaged over, thus variation of the electron polar (exit) angle should result in variation of surface sensitivity. This work represents the first application of ARUPS with low-exit-angle geometries for the investigation of surface electronic structure. The main results are that Cu exhibits considerable (- 17%) d-band narrowing at the bottom of the&band at the surface, while the effects in Ag and Au appear to be much smaller. (Germany)
S P Kowalctyk, 354
J Vuc Sci Teclurol,
16 (2). 1979, 520-522.
Adlayer-induced
LEED
beams
near
order-disorder
transitions.
36
We present a Monte Carlo study of the adlayer-induced LEED beams in a representative order-disorder transition. Calculations of the widths of fractional order beams indicate that, as seen in recent experimental work on the O/Ni(ll I) system, these widths rise sharply and suddenly above T,. Furthermore the slope of this rise provides a sensitive probe of the adatom-adatom interactions. The increase in the width results From the existence of ordered domains above T,.. _, and has not been previously discussed since prior calculations have concentrated on beam intensities. We further derive a functional relation between the window approach used in simulations of orderdisorder transitions and the instrument response function approach of the experimentalist, to detail the effect of the LEED apparatus on the profile of the extra beams.
L D Roelofs
et al, J Vuc Sci Techol,
16 (2), 1979, 478-482.
4589. Simultaneous RHEED-AES-QMS growth on Si(lll) and sapphire (1102) vapor deposition. (USA)
study surfaces
on epitaxial by partially
36 Si film ionized
The role of simultaneous measurements of the chemical composition of a surface by AES. surface crystalline structure by RHEED, and released species by QMS are presented. A molecular beam of Si is effused from a partially ionized vapour deposition (PIVD) source consisting of a Kundsen cell and an electron-impact-type ionization chamber. The 7 >( 7 structure of a Si(lll) substrate at 1100 K changes into a broad I s 1 structure after vacuum deposition (VD) of 15 nm of Si while the epitaxial temperature can be lowered to 620 K (PIVD) in a OS:< ionized atomic vapour with a typical deposition rate and acceleration energy of 0.3 nm min’ and 100 eV, respectively. Epitaxial growth of Si on sapphire (lT02) can be observed at 850 (VD) and at 700 K(PIVD). with a I”< ionized atomic vapour. The Auger spectra during deposition at 870 K remarkably shows that 0 and Al are reacted with Si on the film. (Japan)
T Narusawa
et al, J VW Sci Twhtto/,
16 (2), 1979, 366-368. 36
4590.
Copper-polyvinyl
alcohol
interface:
A study
with XPS.
(USA) It has been known for some time that oxygen treatment of a polymer surface can lead to enhanced adhesion with metals. This has prompted us to investigate the metal-polymer interface of an oxygen-containing polymer, polyvinyl alcohol. We have vapour-deposited copper on the clean polymer surface and examined the interface with X-ray photoemission spectroscopy (XPS). At very low copper coverages, about 0.005 monolayer, the copper 2~~” core level binding energy is I.2 eV larger than the bulk copper value. As the copper coverage increases, this core level shift decreases: at a coverage of one monolayer this shift is sometimes as large as 0.2 eV. AI a cooper coveraee of two monolayers. the 2p”* core-binding energy is the same as it% in bulk copper, 932.85 eV. In addition to these chances. the carbon Is and oxygen Is core levels are observed to change wzh ;he addition of copper. The intensity of the C 1.9 level at 286.6 eV, associated with a C-O group, is observed to decrease faster than that at 285.0 eV which is associated with a CHL group. At the same time a new peak in the 0 Is spectrum is formed at 530.6 eV, 2.4 eV less than the original level. These changes indicate the formation of a coppercarbon complex at the interface.
J M Burkstrand,
J Vat Sci Techttol,
4591.
of two-phase
16 (2). 1979, 363-365. 36
Sputtering
polycrystalline
metals.
(USA) Polycrystalline niobium and its alloys with oxygen have been sputtered with a 15 keV argon ion beam. Yield measurements and scanning electron microscope topographic observations have been made for both singleand two-phase (Nb + NbO) targets which were also characterized by use of a scanning Auger microprobe. Results indicate that the relative yields of different phases, as well as of different grains, are critically dependent on the direction of the argon beam with respect to the individual grain orientations. Oxygen in solid solution and oxygen-containing atmospheres were important factors which influenced the target topography. The observed differential erosion of grains and the presence of surface relief inside individual grains are discussed with reference to the use of sputtering for depth profiling in surface analysis.
P F Tortorelli 804-807.
and C J Altstetter,
J Vuc Sci Techttol,
16 (2).
1979,