Surface Reactions During the Deposition of Ge from Chemical Sources on Ge(100)-(2×1)

1996 ◽  
Vol 448 ◽  
Author(s):  
C. Michael Greenlief ◽  
Jihong Chen
Keyword(s):  
Room Temperature ◽  
Isotopic Labeling ◽  
Low Energy ◽  
Surface Processes ◽  
Elimination Reaction ◽  
Reaction Step ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Hydride Elimination

AbstractThe adsorption and decomposition of diethylgermane, triethylgermane, and digermane on the Ge(100) surface are investigated with the intent of elucidating the surface processes leading to the deposition of epitaxial Ge films. Room temperature adsorption of diethylgermane or triethylgermane leads to the formation of surface germanium hydrides and ethyl groups. The ethyl groups decompose at higher temperatures and form ethylene via a β-hydride elimination reaction. Isotopic labeling experiments are used to confirm this reaction step. This is in contrast to the Si(100) surface where both α- and β-hydride elimination is observed for the decomposition of surface ethyl groups. The adsorption and reaction of digermane with the Ge surface is also determined to help provide a comparison with the ethylgermanes. Low energy electron diffraction is used to evaluate the quality of the deposited germanium films.

Growth of Epitaxial Co Layers on Sb-Passivated GaAs(110) Substrates

1998 ◽  
Vol 05 (01) ◽  
pp. 279-283 ◽  
Author(s):  
C. M. Teodorescu ◽  
J. Chrost ◽  
H. Ascolani ◽  
J. Avila ◽  
F. Soria ◽  
...  
Keyword(s):  
Polar Angle ◽  
Low Energy ◽  
Photoelectron Diffraction ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
A Minor ◽  
Bcc Phase ◽  
Crystallographic Axes

The role of Sb in the formation of the Co/GaAs(110) interfaces has been investigated by angular photoelectron diffraction (PD), synchrotron-radiation (SR) core-level photoemission and low-energy electron diffraction. We find that Co forms a metastable bcc phase on GaAs(110), with its principal crystallographic axes parallel to the substrate. From polar-angle-scanned PD, we determine an outward expansion of up to 14% of the lattice constant perpendicular to the surface, for epitaxial Co films grown on nontreated substrates. By Sb passivation of the GaAs(110) surface prior to the Co deposition, the epitaxial quality of the metallic overlayer is improved. The resulting Co phase is found to grow in a perfect bcc (110) orientation with a minor disruption of the substrate underneath and a reduced intralayer spacing outward expansion of less than 1%.

Studies on surfaces of Zr(0001) that contain oxygen and show (2 × 2)-type low-energy electron diffraction patterns

1987 ◽  
Vol 65 (5) ◽  
pp. 464-467 ◽  
Author(s):  
P. C. Wong ◽  
K. A. R. Mitchell
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Low Energy ◽  
Energy Electron ◽  
Leed Pattern ◽  
Low Energy Electron Diffraction ◽  
Adsorption Sites ◽  
Low Energy Electron ◽  
Low Exposure ◽  
Diffraction Patterns

Oxygen chemisorption on the Zr(0001) surface has been studied in the low-exposure regime with Auger electron spectroscopy and measurements of the width of a half-order low-energy electron diffraction (LEED) beam. The new observations and conclusions are as follows. (i) The diffusion of O atoms to the bulk effectively starts at around 236 °C. (ii) Oxygen adsorbs in a disordered state at room temperature and orders sufficiently to show a (2 × 2)-type LEED pattern on heating to 220 °C. (iii) With increasing O exposure, 1/4, 1/2, and 3/4 of the available adsorption sites can be systematically filled, while showing the apparent (2 × 2)-LEED pattern, prior to the establishment of an ordered (1 × 1)-O surface. (iv) The process in (iii) can be reversed by starting with the (1 × 1)-O surface and heating above 236 °C.

ORDERED AND DISORDERED RIPPLING IN THE CoAl(110)-(1×1) SURFACE

1996 ◽  
Vol 03 (03) ◽  
pp. 1409-1415 ◽  
Author(s):  
V. BLUM ◽  
C. RATH ◽  
G.R. CASTRO ◽  
M. KOTTCKE ◽  
L. HAMMER ◽  
...  
Keyword(s):  
Average Distance ◽  
Low Energy ◽  
Chemical Order ◽  
Low Energy Electron Diffraction ◽  
R Factor ◽  
Preferential Sputtering ◽  
Topmost Layer ◽  
Low Energy Electron ◽  
The Ideal

A quantitative structural analysis of CoAl(110)-(1×1) by low energy electron diffraction shows that the topmost layer of the surface is rippled by an amplitude of 0.18 Å, with aluminum atoms pulled out of the surface and the average distance to the second layer only slightly expanded. In contrast to the perfect stoichiometry found for the top layer and the chemical order in the bulk, about 20% of the second layer Al atoms are substituted by Co. This is probably due to preferential sputtering during the course of sample preparation and incomplete subsequent reordering. A new version of Tensor LEED allows the detection of some disordered rippling induced by the substitutional disorder in this layer, with substitutional cobalt being 0.05 Å above the ideal aluminum position. The quality of the theory–experiment fit is mirrored by a Pendry R factor value of R=0.10.

AN ORDERED MIXED STRUCTURE FORMED BY RESTRUCTURING TYPE COADSORPTION OF Na AND K ON Ag(001)

2001 ◽  
Vol 08 (06) ◽  
pp. 653-659 ◽  
Author(s):  
SEIGI MIZUNO ◽  
MASAO IMAKI ◽  
HIROSHI TOCHIHARA
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Low Energy ◽  
Energy Electron ◽  
Mixed Structure ◽  
Leed Pattern ◽  
Low Energy Electron Diffraction ◽  
Site Selectivity ◽  
Low Energy Electron

Coadsorption of Na and K on Ag(001) at room temperature has been studied by low energy electron diffraction (LEED). A 3 × 3 LEED pattern was observed irrespective of the order of adsorption. For this formation, it is necessary to deposit Na and K atoms with appropriate coverage. We have determined the 3 × 3 structure by a tensor LEED analysis. It is a restructured surface and is very similar to the previously determined 3 × 3 structure formed on Ag(001) by pure Na adsorption. In the coadsorption, Na and K atoms occupy preferable sites selectively, and construct an ordered mixed structure on Ag(001). That is, small Na atoms are located in the missing row sites, while large K atoms sit on the hollow sites of four-Ag-atom islands. The reason for the site selectivity of Na and K atoms in the mixed 3 × 3 structures is discussed.

Adsorbed Structures of Ba on Si(110) Surfaces Studied by LEED and STM

2003 ◽  
Vol 10 (02n03) ◽  
pp. 467-472 ◽  
Author(s):  
Y. Sakamoto ◽  
Y. Fukui ◽  
J. Takeuchi ◽  
S. Hongo ◽  
T. Urano ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Periodic Structures ◽  
Low Energy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Low Energy Electron Diffraction ◽  
Annealing Temperatures ◽  
Unit Structure ◽  
Low Energy Electron

Adsorbed structures of barium on Si(110) surfaces have been studied by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Several structures of "10 × 1," "12 × 2," 11 × 6 and streaky 4 × n were observed by LEED at annealing temperatures of about 775°C, 800°C, 900°C and 1100°C, respectively, after a-few-monolayer deposition of Ba at room temperature. In the STM experiment periodic structures of "10 × 6" and 11 × 6, and a rearrangement of pentagon pairs which is the unit structure seen on the terrace for the clean Si(110) "16 × 2" surface, were observed.

THE SURFACE STRUCTURES OF Pd(100)-(1×1) AND c(2×2)-K

1996 ◽  
Vol 03 (03) ◽  
pp. 1339-1343 ◽  
Author(s):  
J. BURCHHARDT ◽  
E. LUNDGREN ◽  
M.M. NIELSEN ◽  
J.N. ANDERSEN ◽  
D.L. ADAMS
Keyword(s):  
Quantitative Analysis ◽  
Electron Diffraction ◽  
Hard Sphere ◽  
Room Temperature ◽  
Interlayer Spacing ◽  
Low Energy ◽  
Surface Structures ◽  
Low Energy Electron Diffraction ◽  
Sphere Radius ◽  
Low Energy Electron

The surface structure of the Pd (100)- c (2×2)-K phase formed by adsorption of K at room temperature has been determined by quantitative analysis of low-energy electron-diffraction (LEED) intensity-energy measurements. K atoms occupy four-fold hollow sites on a slightly perturbed substrate. The vertical distance between the K layer and the first Pd layer is determined to be 2.13±0.06 Å, which corresponds to an effective hard-sphere radius of 1.83 Å for the adsorbed K atoms. The second Pd layer is rumpled with a splitting of 0.04 Å between two bilayers. An analysis of LEED intensities measured for the clean Pd(100) surface confirms previous reports of an expansion of the first interlayer spacing. Adsorption of K in the c (2×2) structure results in a reduction of this expansion from 5% to 1%.

HUGE MAGNETOVOLUME EFFECT IN AN INVERTED Mn LAYER ON Ag(001) STUDIED BY LEED

2002 ◽  
Vol 09 (03n04) ◽  
pp. 1431-1436 ◽  
Author(s):  
P. SCHIEFFER ◽  
C. KREMBEL ◽  
M.-C. HANF ◽  
G. GEWINNER ◽  
Y. GAUTHIER
Keyword(s):  
Room Temperature ◽  
High Spin State ◽  
Low Energy ◽  
Dimensional Structure ◽  
Low Energy Electron Diffraction ◽  
Magnetovolume Effect ◽  
Small Contraction ◽  
Low Energy Electron ◽  
Atomic Radii ◽  
The Ideal

The surface structure obtained by deposition of a Ag monolayer on the ideal c(2 × 2) antiferromagnetic Mn monolayer on Ag(001) at 100 K and subsequent annealing at room temperature is determined by low energy electron diffraction. It is established that this system is actually a good realization of an inverted monolayer, i.e. a pseudomorphic Ag/Mn/Ag(001) structure that corresponds to a reversed composition of the two topmost layers with respect to the Mn overlayer. The Ag–Mn and Mn–Ag interlayer distances, d12 = 1.97 ± 0.015 Å and d23 = 1.97 ± 0.02 Å respectively, indicate only a fairly small contraction of ~ 3.5% (~ 1.5%) with respect to the ideal Ag bulk lattice (Mn monolayer on top) as compared to ~ 10% expected from atomic radii in bulk Mn and Ag. This clearly reveals a spectacular magnetovolume effect related to the high spin state of Mn in this two-dimensional structure.

Photoemission Study of the Si, Ge Epitaxial Growth Process Using Surfactants

1992 ◽  
Vol 259 ◽  
Author(s):  
Xiaoyu Yang ◽  
Renyu Cao ◽  
Jeff Terry ◽  
Piero Pianetia
Keyword(s):  
Free Energy ◽  
Growth Process ◽  
Room Temperature ◽  
Energy Deposition ◽  
Low Energy ◽  
Heteroepitaxial Growth ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Photoemission Study

ABSTRACTHeteroepitaxial growth of Ge on Si(100) and Si on Ge(100) surfaces with Sb as a surfactant has been investigated by in situ high resolution photoemission and low energy electron diffraction (LEED). Our results show that an ordered monolayer of Sb atoms saturate the surface dangling bonds and consequently lower the surface free energy. Deposition of Ge or Si on the Sb/Si(100) or Sb/Ge(100) surfaces either at room temperature, followed by mild annealing or deposition at elevated temperature, result in an epitaxial layer of Ge or Si on the substrate, respectively. We provide clear experimental evidence that the deposited Ge or Si atoms changes position with the surface Sb atoms in this process. Ge or Si atoms occupy the epitaxial sites previously occupied by the Sb atoms. The Sb atoms in turn segregate to the surface and form a new ordered layer. The Bi-assisted growth process is also discussed.

STRUCTURE OF A SINGLE-ATOMIC LAYER OF COBALT ON THE Pt(111) SURFACE: A STUDY BY QUANTITATIVE LOW-ENERGY ELECTRON DIFFRACTION

1995 ◽  
Vol 02 (03) ◽  
pp. 279-283 ◽  
Author(s):  
ANDREA ATREI ◽  
MONICA GALEOTTI ◽  
UGO BARDI ◽  
MARCO TORRINI ◽  
ERMANNO ZANAZZI ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Atomic Structure ◽  
Room Temperature ◽  
Atomic Layer ◽  
Crystallographic Analysis ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

The atomic structure of the surface formed by depositing a single-atomic layer of cobalt on Pt (111) has been investigated using low-energy electron diffraction (LEED) crystallographic analysis. Cobalt grows at room temperature on the Pt (111) surface forming islands a single-atomic layer thick. The layer is ordered and it forms a 1×1 epitaxial phase where cobalt atoms are in an fcc registry with respect to the substrate.

EFFECT OF Cu DEPOSITION AND ANNEALING UPON A GaSe/Si(111) HETEROJUNCTION

1999 ◽  
Vol 06 (06) ◽  
pp. 1173-1178 ◽  
Author(s):  
B. ABIDRI ◽  
J.-P. LACHARME ◽  
M. GHAMNIA ◽  
C. A. SÉBENNE ◽  
M. EDDRIEF ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Low Energy ◽  
Layered Semiconductor ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Temperature Interaction

Single crystal substrates of GaSe, a layered semiconductor with a 2 eV band gap, were epitaxially grown by MBE onto a Si(111)(1×1)–H substrate, forming a perfectly abrupt heterojunction. Controlled amounts of Cu were sequentially deposited onto the clean passive surface of GaSe from a few tenths to several hundred monolayers (1 ML refers to the GaSe surface: 8 × 1014 at/cm 2). After given Cu depositions, the effect of UHV annealings at increasing temperatures was studied, until GaSe removal. The system was characterized as a function of either Cu deposit or annealing temperature using low energy electron diffraction, Auger electron spectroscopy and photoemission yield spectroscopy. The room temperature interaction starts as an apparent intercalation process until Cu islands begin to form, beyond about 50 ML. Upon annealings as low as 250°C, several ML of Cu disappear into the bulk of an apparently recovered GaSe, towards the GaSe/Si interface.

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