Growth Morphology and Electronic Structure of Ultra-Thin TaOx Films on Ag(100)

2000 ◽  
Vol 623 ◽  
Author(s):  
M. M. Howard ◽  
C. A. Ventrice ◽  
H. Geisler ◽  
D. A. Hite ◽  
P. T. Sprunger
Keyword(s):  
Electronic Structure ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Valence Band Maximum ◽  
Low Energy ◽  
Growth Morphology ◽  
Band Maximum ◽  
Low Energy Electron Diffraction ◽  
Level Shifts ◽  
Low Energy Electron

AbstractA study of the growth morphology and electronic structure of TaOx films on the Ag(100) substrate has been performed to determine the properties of ultra-thin TaOx films without the influence of a mixed interfacial oxide (i.e., a disordered SiO2/TaOx interface for growth on Si). The TaO, films were grown by thermal evaporation of Ta in an oxygen atmosphere of 1 × 101−6 Torr. Growth on a Ag(100) surface held at room temperature results in an amorphous TaOx overlayer, as determined by low energy electron diffraction. The onset of ordering of these films occurs for a post-anneal at ∼500°C. A diffraction pattern that corresponds to a multi-domain overlayer structure is observed for anneals at ∼550°C. Deposition of Ta without oxygen results in the formation of Ta islands. These results indicate that there is a very weak adsorbatesubstrate interaction. Photoemission measurements of the TaOx films show the formation of a band gap with the valence band maximum residing at 3.5 eV below the Fermi level. Core level shifts of ∼3.5 eV are observed for the Ta with no indication of metallic Ta at the surface.

The Growth Of Thin Ti Films on Si(111)-(7×7) Surfaces

1995 ◽  
Vol 402 ◽  
Author(s):  
Adli A. Saleh ◽  
D. Peterson
Keyword(s):  
Room Temperature ◽  
Growth Morphology ◽  
Continuous Film ◽  
Temperature Growth ◽  
Low Energy Electron Diffraction ◽  
Auger Signal ◽  
Low Energy Electron ◽  
Atomically Flat ◽  
Signal Time ◽  
Ti Films

AbstractA study of the room-temperature growth of ultrathin Ti films (up to 7 ML) on clean and atomically flat Si(111)- (7×7) surfaces using Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) is presented. The variations in the Auger signal due to Si L2.3VV with binding energy of 92 eV are used to model the growth morphology of this system. These measurements indicate the growth of an initial disordered and continuous Ti film of up to 1.6 ML in thickness, where the LEED pattern completely disappears and the Si Auger signal is strongly attenuated. As more Ti is deposited, this is followed by the disintegration of the continuous film and the formation of an intermixed Ti/Si film. This is evidenced by a change in the slope of the Auger signal time (AST) plot, and the reappearance of the LEED pattern. The modification in the overlayer composition for films thicker than 1.6 ML is confirmed by a change in the Si L2.3VV Auger peak that resembles the peak shape due to TiSi2.

Surface Band Structure Studies of Si Rich Reconstructions on 4H-SiC(1-100)

2005 ◽  
Vol 483-485 ◽  
pp. 547-550 ◽  
Author(s):  
Konstantin V. Emtsev ◽  
Thomas Seyller ◽  
Lothar Ley ◽  
A. Tadich ◽  
L. Broekman ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Electron Diffraction ◽  
Photoelectron Spectroscopy ◽  
Low Energy ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Surface Band ◽  
X Ray ◽  
Low Energy Electron Diffraction ◽  
Different Temperatures ◽  
Low Energy Electron

We have investigated Si-rich reconstructions of 4H-SiC( 00 1 1 ) surfaces by means of low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and angleresolved ultraviolet photoelectron spectroscopy (ARUPS). The reconstructions of 4H-SiC( 00 1 1 ) were prepared by annealing the sample at different temperatures in a flux of Si. Depending on the temperature different reconstructions were observed: c(2×2) at T=800°C, c(2×4) at T=840°C. Both reconstructions show strong similarities in the electronic structure.

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.

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.

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%.

SYNCHROTRON RADIATION AND LOW ENERGY ELECTRON DIFFRACTION STUDIES OF ULTRATHIN C60 FILMS DEPOSITED ON Cu(100), Cu(111) AND Cu(110)

1992 ◽  
Vol 06 (23n24) ◽  
pp. 3909-3913 ◽  
Author(s):  
J.E. Rowe ◽  
P. Rudolf ◽  
L.H. Tjeng ◽  
R.A. Malic ◽  
G. Meigs ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Chemical Properties ◽  
Level Line ◽  
Core Level ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
Level Shifts ◽  
Low Energy Electron ◽  
X Ray Absorption

High resolution K-edge photoemission and X-ray absorption spectroscopies have been used to study the chemical properties of the interface formed with C 60 and Cu . We find that for very thin (0.24–1 monolayers) C 60 films, deposited in ultrahigh vacuum, the Cu substrate plays a role similar to that of K in K 3 C 60 films. Thus Cu donates charge to partially fill the π* LUMO band, and the C (1s) core level shifts due to charge transfer. For monolayer coverage the C (1s) core-level line shape is broad. Low energy electron diffraction studies of C 60 on Cu (100), Cu (111) and Cu (110) show that well ordered overlayers of thickness >2 monolayers can be formed on all three Cu surfaces, but single-domain epitaxy is achieved only on Cu (111). The substrate temperature during C 60 deposition is critical for the ordering of the film.

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.

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