| 1. |
- Gothelid, M, et al.
(författare)
-
Etching and a disordered overlayer on the Ge(100)-S surface
- 1997
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 115:1, s. 87-95
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Gothelid, M, et al.
(författare)
-
Ge/(111)3x1:K/Sn; On the influence of tin substitution in a metal induced 3x1 reconstruction
- 1996
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 113-117
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 3. |
- GOTHELID, M, et al.
(författare)
-
GEOMETRY OF THE GE(111)-AU(ROOT-3X-ROOT-3)R 30-DEGREES RECONSTRUCTION
- 1994
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:7, s. 4470-4475
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Gothelid, M, et al.
(författare)
-
Iodine reaction and passivation of the Ge(111) surface
- 1997
-
Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 371:2-3, s. 264-276
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- GOTHELID, M, et al.
(författare)
-
METAL-SEMICONDUCTOR FLUCTUATION IN THE SN ADATOMS IN THE SI(111)-SN AND GE(111)-SN (ROOT-3X-ROOT-3)R30-DEGREES RECONSTRUCTIONS
- 1995
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:20, s. 14352-14355
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- GOTHELID, M, et al.
(författare)
-
STRUCTURAL AND ELECTRONIC EVOLUTION ON THE GE(111)-AG SURFACE
- 1995
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:19, s. 14104-14110
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- LELAY, G, et al.
(författare)
-
CORE-LEVEL SPECTROSCOPY STUDY OF THE INITIAL FORMATION OF TIN GERMANIUM INTERFACES
- 1992
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 56-8, s. 178-184
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the initial stages of the Schottky barrier formation at Sn/Ge(100) interfaces, in comparison with Sn/Ge(111) ones, with high resolution core-level spectroscopy measurements (Ge 3d and Sn 4d shallow core levels) using synchrotron radiation. A detailed, stringent decomposition of the core lines reveals three different components for both Ge and Sn on the two surfaces. The three components of the Sn 4d line on the Ge(100)2 x 1-Sn surface are interpreted as due to three different adsorption sites simultaneously occupied, while the persistence of the surface components in the Ge 3d core lines suggests that the building block of the reconstruction remains an asymmetric Ge dimer.
|
|
| 8. |
- LELAY, G, et al.
(författare)
-
ELECTRONIC-PROPERTIES OF CLEAVED(110) AND MBE-GROWN(100) INAS SURFACES, CLEAN AND COVERED WITH AN ULTRA-THIN AG ADLAYER
- 1993
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 70-1, s. 502-506
-
Tidskriftsartikel (refereegranskat)abstract
- The initial electronic structure of the pseudomorphic InAs/GaAs(100) heterostructure as well as that of the Ag/InAs(110) interface at 20 K have been studied by synchrotron radiation photoelectron spectroscopy. In the first case we find that the valence band spectra show no evidence for the formation of bulk-like energy bands. In the second case we prove for the first time that upon deposition of minute amounts of Ag at low temperature onto cleaved InAs(110) substrates one induces a giant movement of the Fermi level well into the conduction band thus creating a strong two-dimensional electron channel at the surface.
|
|
| 9. |
- LELAY, G, et al.
(författare)
-
STM AND SYNCHROTRON-RADIATION STUDIES OF PROTOTYPICAL METAL-SEMICONDUCTOR SYSTEMS
- 1994
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 280-294
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 10. |
|
|
| 11. |
- LELAY, G, et al.
(författare)
-
SURFACE CORE-LEVEL SHIFTS ON GE(100) - C(4X2) TO 2X1 AND 1X1 PHASE-TRANSITIONS
- 1992
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 45:12, s. 6692-6699
-
Tidskriftsartikel (refereegranskat)abstract
- By comparing, under identical experimental conditions, high-resolution synchrotron-radiation core-level photoemission spectra taken from both Ge(111) and Ge(100) samples, we establish that the decomposition of the Ge 3d lines from the clean Ge(100) 2 x 1 surface at room temperature requires two surface components shifted by -0.23 and -0.60 eV relative to the bulk one. This deconvolution is fully consistent with the asymmetric-dimer reconstruction model of this surface. We further study the reversible phase transitions that occur on this surface: 2 x 1 <--> c(4 x 2) at low temperature; 2 x 1 <--> 1 x 1 at high temperature. We show from both core-level and valence-band studies that the number of dimer bonds is essentially conserved in these transitions. We also suggest, by comparing a dimer with an Ising spin, that these transitions correspond, respectively, to an antiferromagnetic ordering at low temperatures and to a paramagnetic disordering at high temperatures.
|
|
