| 1. |
- Janin, E, et al.
(author)
-
Hydrogen adsorption on the Pt(111)(root 3x root 5)R30 degrees-Sn surface alloy studied by high resolution core level photoelectron spectroscopy
- 1996
-
In: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 99:4, s. 371-378
-
Journal article (peer-reviewed)abstract
- Investigation of the clean and atomic hydrogen covered Pt(111)(root 3 x root 3)R30 degrees-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy, The Pt 4(7/2) spectrum recorded from the clean surface alloy shows a single surface peak shifted - 0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4(7/2) spectrum. These results are discussed in the light of the thermodynamical calculations, H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.
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| 2. |
- Bjorkqvist, M, et al.
(author)
-
NH3 on Si(111)7x7 : Dissociation and surface reactions
- 1998
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 57:4, s. 2327-2333
-
Journal article (peer-reviewed)abstract
- Core-level and valence-band photoelectron spectroscopy on the dissociative adsorption of ammonia on Si(111) 7 X 7 is presented. Adsorption at room temperature produces three nitrogen 1s components, of which two are assigned to NH2 and one to NH, with an initial tendency for double dissociation. These doubly dissociated species can be connected to the development of silicon atoms coordinated with two nitrogen atoms, necessitating silicon-silicon bonds to be broken. The dominating picture evolving is thus adatoms saturated by NH2 with a NH group inserted into one backbond, and hydrogen preferentially capping restatoms. The dissociation proces is hence much more complex than generally proposed before. This is further accentuated by the fact that not all adatoms appear reacted. When annealed above 600 K the dissociation process progresses and atomic nitrogen appears at 700 K, to be the only remaining specie at 850 K. At 1200 K, further changes in the N 1s core level indicates true silicon nitride formation.
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| 3. |
- Gothelid, M, et al.
(author)
-
Etching and a disordered overlayer on the Ge(100)-S surface
- 1997
-
In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 115:1, s. 87-95
-
Journal article (peer-reviewed)abstract
- High resolution core level photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) have been used to study the adsorption and desorption of S on and off the Ge(100) surface. The previously proposed bridge adsorption site of S is consistent with our results at low coverage. At saturation the substrate contains several GeSx species, with x = 0.5 to 4. Both photoemission and STM reveals a non-ideal surface, with a saturation coverage above one monolayer. Furthermore, S is found to etch the substrate. The reaction products forms a disordered overlayer on top of the interface. This overlayer is transparent in the filled state STM images.
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| 4. |
- Gothelid, M, et al.
(author)
-
Ge/(111)3x1:K/Sn; On the influence of tin substitution in a metal induced 3x1 reconstruction
- 1996
-
In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 113-117
-
Journal article (peer-reviewed)abstract
- Go-adsorption of tin and potassium is found to induce a 3x1 reconstruction on the Ge(lll) surface. A very small amount of tin influences the Ge 3d core level spectra substantially compared to the Ge(111)3x1:K reconstruction. This is interpreted as resulting from a relaxation of the strain in the rows Ge atoms running along the surface, as proposed for this structure.
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| 5. |
- GOTHELID, M, et al.
(author)
-
GEOMETRY OF THE GE(111)-AU(ROOT-3X-ROOT-3)R 30-DEGREES RECONSTRUCTION
- 1994
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:7, s. 4470-4475
-
Journal article (peer-reviewed)abstract
- A structure model for the Ge(111)-Au(root 3X root 3)R30 degrees surface reconstruction is proposed based on scanning tunneling microscopy (STM) and photoelectron spectroscopy on the Ge 3d and Au 4f core lines. The basic unit is a Au3Ge molecule binding in one-third of the T-1 substrate sites with a gold trimer pointing out of the surface. This leaves two-thirds of a monolayer of unoccupied T-1 sites which make up a hexagonal honeycomb pattern. Two types of STM images have been obtained which are explained within this model, where either the trimers or the substrate Ge atoms are probed depending on the specific tip conditions in combination with the sample bias voltage. Furthermore, small insets of a metallic (1X1) structure are found at low gold coverage together with a distorted (2X2) surface structure.
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| 6. |
- Le Lay, G., et al.
(author)
-
STM and synchrotron radiation studies of "prototypical" metal{plus 45 degree rule}semiconductor systems
- 1994
-
In: Surface Science. - 0039-6028. ; 307-309:PART A, s. 280-294
-
Journal article (peer-reviewed)abstract
- Since the origin of surface science noble metal{plus 45 degree rule}elemental semiconductor couples have been considered as "prototypical" systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the extensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions. © 1994.
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| 7. |
- LELAY, G, et al.
(author)
-
STM AND SYNCHROTRON-RADIATION STUDIES OF PROTOTYPICAL METAL-SEMICONDUCTOR SYSTEMS
- 1994
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 280-294
-
Journal article (peer-reviewed)abstract
- Since the origin of surface science noble metal/elemental semiconductor couples have been considered as ''prototypical'' systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the ''tensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions.
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| 8. |
- TORNEVIK, C, et al.
(author)
-
ADSORPTION OF SN ON SI(111)7X7 - RECONSTRUCTIONS IN THE MONOLAYER REGIME
- 1994
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 314:2, s. 179-187
-
Journal article (peer-reviewed)abstract
- Different monolayer phases of Sn on Si(111)7 x 7 have been studied by means of scanning tunneling microscopy (STM), core-level photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). The STM results show that square-root 3 x square-root 3 reconstructions are obtained for room-temperature deposition of 1/3 ML of Sn followed by sample annealing in a broad temperature range. A T4 Sn adatom square-root 3 x square-root 3 phase is formed for temperatures between 500 and 800-degrees-C, with a concentration of defects that is strongly dependent on the temperature and which is as high as 25% for the lowest temperatures. Above 825-degrees-C a second square-root 3 x square-root 3 adatom reconstruction is formed, a mosaic-like phase with a 1: 1 mixture of Si and Sn atoms in T4 positions. The results from investigations of the higher coverage 2 square-root 3 x 2 square-root 3 reconstruction by XPS and RBS support the theory that this phase is a two-layer epitaxial Sn structure with all Si(111) dangling bonds saturated. The Sn coverage for this phase was determined to be between 1 and 1.2 ML.
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| 9. |
- Varekamp, P R, et al.
(author)
-
Reaction of I-2 with the (001) surfaces of GaAs, InAs, and InSb .1. Chemical interaction with the substrate
- 1996
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 54:3, s. 2101-2113
-
Journal article (peer-reviewed)abstract
- InAs(001)-c(8x2), InSb(001)-c(8x2), and several reconstructions of GaAs(001) are exposed at room temperature to iodine molecules (I-2). Low-energy electron diffraction (LEED) and synchrotron soft x-ray photoelectron spectroscopy (SXPS) are employed to study the surfaces as a function of I-2 dose and sample anneal. In the exposure range studied, GaAs and InAs become saturated with I-2, resulting in removal of the clean surface reconstruction and the formation of a very strong 1x1 LEED pattern. Iodine bonds primarily to the dominant elemental species present on the clean surface, whether it is a group-III or -V element. The InSb(001)-c(8x2) reconstruction is also removed by I-2 adsorption, and a strong 1x1 LEED pattern is formed. SXPS data, in conjunction with scanning tunneling microscopy images, however, reveal that InSb(001)-c(8x2) does not saturate at room temperature, but is instead etched with a preferential loss of In. Heating the iodine-covered group-III-rich InAs(001)-c(8x2) and InSb(001)-c(8x2) surfaces causes removal of the iodine overlayer and transformation to a group-V-rich reconstruction. When the iodine-covered As-rich GaAs(001)-c(2x8) surface is heated to remove iodine, however, the c(2x8) reconstruction is simply regenerated.
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| 10. |
- Varekamp, P R, et al.
(author)
-
Reaction of I-2 with the (001) surfaces of GaAs, InAs, and InSb .2. Ordering of the iodine overlayer
- 1996
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 54:3, s. 2114-2120
-
Journal article (peer-reviewed)abstract
- The overlayer formed by the reaction of molecular iodine (I-2) with GaAs(001), InAs(001), and InSb(001) is investigated with synchrotron soft x-ray photoelectron spectroscopy (SXPS) and scanning tunneling microscopy (STM). Two components, separated by about 0.5 eV, are present in all of the I 4d SXPS spectra. At very low iodine coverages, the high binding energy (BE) component dominates. When the iodine coverage saturates, however, the two components have equal intensities. In contrast to GaAs and InAs, exposure of InSb(001)-c(8x2) to additional I-2 results in a further increase of the relative intensity of the low-BE component. STM images of I-2 covered InSb(001)-c(8x2) directly reveal the ordering in the overlayer. Islands are visible for submonolayer coverages, suggesting that adsorption occurs via a mobile precursor state. STM images feature occupies a 1x1 unit cell with the same spacing as bulk-terminated InSb(001). The other feature has a coverage of similar to 1/3 ML and is arranged in pairs oriented along the [110] azimuth.
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| 11. |
- Bjorkqvist, M, et al.
(author)
-
Nitride formation and dangling-bond passivation on Si(111)-(7x7) with NH3
- 1997
-
In: Surface Science. - 0039-6028 .- 1879-2758. ; 394:1-3, s. L155-L161
-
Journal article (peer-reviewed)abstract
- Thermal nitridation of the Si(111)-(7 x 7) reconstructed surface with ammonia has been investigated using scanning tunneling microscopy (STM). True nitride formation in the form of ring-like structures as in stoichiometric silicon nitride (Si3N4) was observed at imperfections on the surface, which otherwise preserved the characteristics of the (7 x 7) reconstruction. However, the ratio of reacted adatoms in the reconstruction never exceeded similar to 50%, indicative of a frustrated saturation behavior for the adatom dangling bonds in the Si(111)-(7 x 7)-NH3 reaction system. (C) 1997 Elsevier Science B.V.
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| 12. |
- GOTHELID, M, et al.
(author)
-
ADSORPTION OF TIN ON THE GE(111)-C(2X8) SURFACE STUDIED WITH SCANNING-TUNNELING-MICROSCOPY AND PHOTOELECTRON-SPECTROSCOPY
- 1995
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 328:1-2, s. 80-94
-
Journal article (peer-reviewed)abstract
- The growth and epitaxy of Sn on Ge(111) have been investigated using scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and core level photoelectron spectroscopy for coverages ranging from 0.4 monolayers (ML) to above the critical coverage at 1.6 ML. At the lowest coverage a (root 3 X root 3)R30 degrees reconstruction is formed at an annealing temperature of 250-300 degrees C while an annealing above 500 degrees C creates a dimer-adatom-stacking fault (DAS) (7 X 7) structure. In the (7 X 7) structure we argue that Sn occupies both adatom and dimer sites. A previously suggested difference in the (root 3 X root 3)R30 degrees reconstruction at different coverages could not be revealed in our STM images and it seems likely that the structure is the same both at 0.4 and 0.7 ML Sn coverage. We also report the observation of a new superstructure, a (4 X root 7) reconstruction in the submonolayer regime, which appears as a minority structure in disordered regions adjacent to a (5 X 5) DAS structure, Finally in the post-monolayer region a (3 X 2 root 3) structure, surrounded by vast areas of an amorphous tin overlayer, has been imaged by STM. As the coverage was increased, the amorphous layer completely covered the ordered (3 X 2 root 3) phase, which still could be observed in LEED. Additional room temperature deposition of Sn deteriorated the fractional order LEED spots presumably due to indiffusion of Sn from the interface as the critical coverage was surpassed.
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| 13. |
- GOTHELID, M, et al.
(author)
-
FORMATION OF AN IODINE ZIGZAG CHAIN C(2X4) RECONSTRUCTION ON THE GE(111) SURFACE
- 1994
-
In: Microscopy Microanalysis Microstructures. - : EDP Sciences. - 1154-2799. ; 5:4-6, s. 277-282
-
Journal article (peer-reviewed)abstract
- Room temperature adsorption of I-2 on the Ge(lll) surface is found to break the initial c(2 x 8) adatom reconstruction as iodine preferentially occupies the on top substrate site, breaks the backbonds between the adatom and the substrate and thus removes the Ge adatoms. As this process continues a c(2 x 4), and modifications thereof, reconstruction is formed consisting of chains of I-2 molecules bound in almost T-1 sites with a I-I bond length of 3.6 Angstrom.
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| 14. |
- Gothelid, M, et al.
(author)
-
Iodine reaction and passivation of the Ge(111) surface
- 1997
-
In: Surface Science. - 0039-6028 .- 1879-2758. ; 371:2-3, s. 264-276
-
Journal article (peer-reviewed)abstract
- The Ge(111)-I surface has been studied at different I coverages ranging from 0.05 hit up to saturation, and different annealing temperatures, using photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM). At saturation the surface is covered with I in the top site and Gel, species in the bridge site, coexisting with small islands/clusters comprising GeI2, giving a total coverage of I in GeIx species of 1.15 ML. The chemically induced shifts in the Ge 3d core level are 0.39 eV per attached I atom. The coverage determined from the I 4d core level is higher than 1.15 ML, which we explain by the presence of I not bound to Ge. Annealing at 200 degrees C decreases the iodine coverage, whereas the I 4d and Ge 3d line profiles are practically unchanged. Further heating desorbs the iodide species and restores the virgin c(2 x 8) structure.
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| 15. |
- GOTHELID, M, et al.
(author)
-
METAL-SEMICONDUCTOR FLUCTUATION IN THE SN ADATOMS IN THE SI(111)-SN AND GE(111)-SN (ROOT-3X-ROOT-3)R30-DEGREES RECONSTRUCTIONS
- 1995
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:20, s. 14352-14355
-
Journal article (peer-reviewed)abstract
- The two components of the Sn 4d core level in the Si(111)-Sn and Ge(111)-Sn. (root 3 X root 3)R30 degrees structures are proposed to arise from semiconductor-metal fluctuations in the Sn adatom layer. Adsorption of potassium on the Si(111)-Sn (root 3 X root 3)R30 degrees surface suppresses the metallic component and shifts the tin into a purely semiconducting phase with a filled dangling bond state.
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| 16. |
- GOTHELID, M, et al.
(author)
-
SN-INDUCED SURFACE RECONSTRUCTIONS ON THE GE(111) SURFACE STUDIED WITH SCANNING TUNNELING MICROSCOPY
- 1992
-
In: Surface Science. - 0039-6028 .- 1879-2758. ; 271:3, s. L357-L361
-
Journal article (peer-reviewed)abstract
- Scanning tunneling microscopy (STM) has been used to study different Sn induced reconstructions on the Ge(111) surface; namely the (7 x 7), (5 x 5) and (square-root 3 x square-root 3)R30-degrees structures. The first two have been confirmed to be of the dimer adatom stacking fault (DAS) type with adatoms mainly being Sn. The (square-root 3 x square-root 3)R30-degrees superstructure was found at different Sn depositions. At 0.4 monolayer (ML) Sn coverage a homogeneous Sn adatom layer is adsorbed on the (1 x 1) surface in threefold sites directly over second-layer atoms (T4), while at low coverage, 0.1 ML, the top layer is a mixture of Sn and Ge atoms. We also propose the chemical identities of the different atoms seen in the STM images as related to their apparent height.
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| 17. |
- GOTHELID, M, et al.
(author)
-
STRUCTURAL AND ELECTRONIC EVOLUTION ON THE GE(111)-AG SURFACE
- 1995
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:19, s. 14104-14110
-
Journal article (peer-reviewed)abstract
- High-resolution core-level photoelectron spectroscopy has been used to study three different silver induced surface reconstructions on the Ge(111) surface. At the lowest coverage a (4 X 4) structure is formed, which displays a similar Ge 3d core-level line shape as the clean c(2 X 8) surface. Details in the spectra are discussed with respect to possible models. The Ge(111)-Ag (root 3 X root 3)R30 degrees structure Ge 3d spectrum is dominated by a very strong contribution assigned to the two topmost Ge layers in a missing top layer structure, similar to the Si(111)-Ag (root 3 X root 3)R30 degrees surface. A weak bulk peak is present on the high-binding-energy side of the spectrum, while a third contribution assigned to Ge in phase boundaries is included in the fit on the lower-binding-energy side. A comparison with results obtained from the Ge(111)-Au root 3 structure points to substantial differences between the two noble-metal-induced root 3 reconstructions on the Ge(111) surface. Finally, after further deposition of silver at room temperature, the root 3 geometry is locally broken creating a (6 X 6) structure and a new surface-related peak emerges on the low-binding-energy side of the Ge 3d spectrum, which was interpreted as being due to Ge atoms floating on top of the outermost surface layer. The valence band also revealed the existence of small metallic silver islands.
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| 18. |
- Landälv, Ludvig, 1982-, et al.
(author)
-
Structural evolution in reactive RF magnetron sputtered (Cr,Zr)2O3 coatings during annealing
- 2017
-
In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 131, s. 543-552
-
Journal article (peer-reviewed)abstract
- Reactive RF-magnetron sputtering is used to grow Cr0.28Zr0.10O0.61 coatings at 500 degrees C. Coatings are annealed at 750 degrees C, 810 degrees C, and 870 degrees C. The microstructure evolution of the pseudobinary oxide compound is characterized through high resolution state of the art HRSTEM and HREDX-maps, revealing the segregation of Cr and Zr on the nm scale. The as-deposited coating comprises cc-(Cr,Zr)(2)O-3 solid solution with a Zr-rich (Zr,Cr)O-x. amorphous phase. After annealing to 750 degrees C tetragonal ZrO2 nucleates and grows from the amorphous phase. The ZrO2 phase is stabilized in its tetragonal structure at these fairly low annealing temperatures, possibly due to the small grain size (below 30 nm). Correlated with the nucleation and growth of the tetragonal-ZrO2 phase is an increase in hardness, with a maximum hardness after annealing to 750 degrees C, followed by a decrease in hardness upon coarsening, bcc metallic Cr phase formation and loss of oxygen, during annealing to 870 degrees C. The observed phase segregation opens up future design routes for pseudobinary oxides with tunable microstructural and mechanical properties. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 19. |
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| 20. |
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| 21. |
- Varekamp, P R, et al.
(author)
-
Observation of true c(8x2) symmetry in scanning tunnelling microscopy images of the clean InSb(001) surface
- 1996
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 350:1-3, s. L221-L226
-
Journal article (peer-reviewed)abstract
- Filled and empty state scanning tunnelling microscopy images of the sputtered and annealed InSb(001) surface are presented. The sputter-anneal preparation generates a surface with two distinct phases. The dominant phase possesses a unit cell with true c(8 x 2) symmetry, whereas the other phase is attributed to an asymmetric 1 x 3 reconstruction. The presence of a c(8 x 2) unit cell in filled state images is in contrast to previous reports, which identified only a 4 x 1 unit cell. The true c(8 x 2) symmetry further indicates, if the available structural model is used as a guide, that the current interpretation of features in filled state images is incorrect. This result may necessitate a reevaluation of the structural model for the InSb(001)-c(8 x 2) surface.
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| 22. |
- Brena, Barbara, et al.
(author)
-
Valence-band electronic structure of iron phthalocyanine : An experimental and theoretical photoelectron spectroscopy study
- 2011
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:7, s. 074312-
-
Journal article (peer-reviewed)abstract
- The electronic structure of iron phthalocyanine (FePc) in the valence region was examined within a joint theoretical-experimental collaboration. Particular emphasis was placed on the determination of the energy position of the Fe 3d levels in proximity of the highest occupied molecular orbital (HOMO). Photoelectron spectroscopy (PES) measurements were performed on FePc in gas phase at several photon energies in the interval between 21 and 150 eV. Significant variations of the relative intensities were observed, indicating a different elemental and atomic orbital composition of the highest lying spectral features. The electronic structure of a single FePc molecule was first computed by quantum chemical calculations by means of density functional theory (DFT). The hybrid Becke 3-parameter, Lee, Yang and Parr (B3LYP) functional and the semilocal 1996 functional of Perdew, Burke and Ernzerhof (PBE) of the generalized gradient approximation (GGA-) type, exchange-correlation functionals were used. The DFT/B3LYP calculations find that the HOMO is a doubly occupied pi-type orbital formed by the carbon 2p electrons, and the HOMO-1 is a mixing of carbon 2p and iron 3d electrons. In contrast, the DFT/PBE calculations find an iron 3d contribution in the HOMO. The experimental photoelectron spectra of the valence band taken at different energies were simulated by means of the Gelius model, taking into account the atomic subshell photoionization cross sections. Moreover, calculations of the electronic structure of FePc using the GGA+U method were performed, where the strong correlations of the Fe 3d electronic states were incorporated through the Hubbard model. Through a comparison with our quantum chemical calculations we find that the best agreement with the experimental results is obtained for a U-eff value of 5 eV.
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| 23. |
- GREHK, TM, et al.
(author)
-
CLEAN AND CS-EXPOSED SI(111)ROOT-3X-ROOT-3-B SURFACE STUDIED WITH HIGH-RESOLUTION PHOTOEMISSION
- 1995
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 52:15, s. 11165-11171
-
Journal article (peer-reviewed)abstract
- Both the clean and Cs-exposed Si(111)root 3X root 3R30 degrees:B surfaces have been investigated by high-resolution photoemission. In the spectra from the Si 2p level, contributions were identified from the bulk, the adatoms plus the first layer, the second and 2/3 ML of the third-layer atoms not binding to the B atoms, and, finally, the 1/3 ML of third-layer atoms binding to the boron atoms. The interaction between the Cs atoms and the surface is found to be dependent on the coverage. At low coverages the geometric and electronic structure of the Si(111)root 3X root 3R30 degrees:B interface is only to a minor degree affected by the presence of Cs on the surface. At high coverage the Cs atoms react with the surface and alter the binding configuration of the Si adatoms.
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| 24. |
- Hirschauer, B, et al.
(author)
-
CeO2 on Si(111) 7 X 7 and Si(111)-H 1 X 1, an interface study by high-resolution photoelectron spectroscopy
- 1999
-
In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 148:3-4, s. 164-170
-
Journal article (peer-reviewed)abstract
- The formation of the CeO2-Si(111) interface was studied by high-resolution photoelectron spectroscopy. It is shown that CeO2 and Si(111) forms a highly reactive: interface with a strong interdiffusion of Si into the CeO2. A passive silicon surface formed by saturating the Si dangling bonds with hydrogen is considerably less reactive. Defects on the surface, however, act as nucleations centres for reactions of a Si:Ce:O matrix. Oxygen leaves the surface at about 800 degrees C and at 1000 degrees C a surface reconstruction of Si(111)-Ce 2 X 2/root 3 X root 3 is formed. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 25. |
- Hirschauer, B, et al.
(author)
-
Studies of highly oriented CeO2 films grown on Si(111) by pulsed laser deposition
- 1999
-
In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 348:1-2, s. 3-7
-
Journal article (peer-reviewed)abstract
- CeO2 is an interesting buffer layer material for the growth of YBa(2)Cu(3)O(7-)delta overlayers on Si in devices, with the aim of preventing heat-diffusion due to its excellent lattice matching with Si and YBa(2)Cu(3)O(7-)delta. Epitaxial CeO2-films have been synthesised on Si(lll) by pulsed laser deposition. Stoichiometric changes of the CexOy-film depending on the ambient oxygen pressure during the deposition were studied by X-ray photoelectron spectroscopy. A method is presented for growing a sharp interface between CeO2 and Si(111). The dependence of the inplane orientation of the CeO2 film on the substrate temperature was investigated by X-ray diffraction. The best films, grown at 700 degrees C, showed full width at half maximum of the rocking curve close to 0.1 degrees, but already at room temperature very highly oriented films with less than 0.2 degrees were synthesised. (C) 1999 Elsevier Science S,A. All rights reserved.
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| 26. |
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| 27. |
- Zhirkov, Igor, 1980-, et al.
(author)
-
Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen
- 2017
-
In: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:8
-
Journal article (peer-reviewed)abstract
- Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O-2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.
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