Effects of low-energy electron and ion irradiation on CO/Cu(100): In-situ production and coadsorbate-induced adsorption of CO above room temperature

1997 ◽  
Vol 15 (5) ◽  
pp. 2653-2660 ◽  
Author(s):  
H. Yu ◽  
D. Q. Hu ◽  
K. T. Leung
Keyword(s):  
Room Temperature ◽  
Ion Irradiation ◽  
Low Energy ◽  
Energy Electron ◽  
Adsorption Of Co ◽  
Low Energy Electron ◽  
In Situ Production ◽  
Induced Adsorption

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.

In Situ Nitride Growth Studies by Low Energy Electron Microscopy (LEEM) and Low Energy Electron Diffraction (LEED)

1997 ◽  
Vol 3 (S2) ◽  
pp. 611-612
Author(s):  
E. Bauer ◽  
A. Pavlovska ◽  
I.S.T. Tsong
Keyword(s):  
Low Energy ◽  
Energy Electron ◽  
Ex Situ ◽  
Electron Microscopic ◽  
Insulating Layer ◽  
Light Emitting ◽  
Surface Sensitivity ◽  
Microscopic Studies ◽  
Low Energy Electron

Nitride films play an increasing role in modern electronics, for example silicon nitride as insulating layer in Si-based devices or GaN in blue light emitting diodes and lasers. For this reason they have been the subject of many ex situ electron microscopic studies. A much deeper understanding of the growth of these important materials can be obtained by in situ studies. Although these could be done by SEM, LEEM combined with LEED is much better suited because of its excellent surface sensitivity and diffraction contrast. We have in the past studied the high temperture nitridation of Si(l11) by ammonia (NH3)and the growth of GaN and A1N films on Si(l11) and 6H-SiC(0001) by depositing Ga and Al in the presence of NH3 and will report some of the results of this work for comparison with more recent work using atomic nitrogen instead of NH3.

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.

IN SITU STUDIES WITH LOW-ENERGY ELECTRON MICROSCOPY

1995 ◽  
Vol 02 (01) ◽  
pp. 103-107
Author(s):  
RUUD M. TROMP
Keyword(s):  
Electron Microscopy ◽  
Low Energy ◽  
Energy Electron ◽  
Misfit Dislocations ◽  
Dynamical Processes ◽  
In Situ Studies ◽  
Kinetic Instability ◽  
In Situ Observations ◽  
Low Energy Electron

This paper gives a brief review of low-energy electron microscopy (LEEM) as used for in situ studies of surface dynamical processes. The capabilities of LEEM are illustrated with two examples. One is a kinetic instability observed during growth of the first layer of CaF 2 on Si (111). The second concerns the nucleation of misfit dislocations during the growth of thicker, epitaxial CaF 2 films on Si (111), as the critical thickness is exceeded. Both examples highlight the importance of real time, in situ observations of surface dynamical processes.

scholarly journals Electron interactions with the heteronuclear carbonyl precursor H2FeRu3(CO)13 and comparison with HFeCo3(CO)12: from fundamental gas phase and surface science studies to focused electron beam induced deposition

2018 ◽  
Vol 9 ◽  
pp. 555-579 ◽  
Author(s):  
Ragesh Kumar T P ◽  
Paul Weirich ◽  
Lukas Hrachowina ◽  
Marc Hanefeld ◽  
Ragnar Bjornsson ◽  
...  
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Surface Science ◽  
Metal Content ◽  
Room Temperature ◽  
Science Studies ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron ◽  
Surface Science Studies

In the current contribution we present a comprehensive study on the heteronuclear carbonyl complex H2FeRu3(CO)13 covering its low energy electron induced fragmentation in the gas phase through dissociative electron attachment (DEA) and dissociative ionization (DI), its decomposition when adsorbed on a surface under controlled ultrahigh vacuum (UHV) conditions and exposed to irradiation with 500 eV electrons, and its performance in focused electron beam induced deposition (FEBID) at room temperature under HV conditions. The performance of this precursor in FEBID is poor, resulting in maximum metal content of 26 atom % under optimized conditions. Furthermore, the Ru/Fe ratio in the FEBID deposit (≈3.5) is higher than the 3:1 ratio predicted. This is somewhat surprising as in recent FEBID studies on a structurally similar bimetallic precursor, HFeCo3(CO)12, metal contents of about 80 atom % is achievable on a routine basis and the deposits are found to maintain the initial Co/Fe ratio. Low temperature (≈213 K) surface science studies on thin films of H2FeRu3(CO)13 demonstrate that electron stimulated decomposition leads to significant CO desorption (average of 8–9 CO groups per molecule) to form partially decarbonylated intermediates. However, once formed these intermediates are largely unaffected by either further electron irradiation or annealing to room temperature, with a predicted metal content similar to what is observed in FEBID. Furthermore, gas phase experiments indicate formation of Fe(CO)4 from H2FeRu3(CO)13 upon low energy electron interaction. This fragment could desorb at room temperature under high vacuum conditions, which may explain the slight increase in the Ru/Fe ratio of deposits in FEBID. With the combination of gas phase experiments, surface science studies and actual FEBID experiments, we can offer new insights into the low energy electron induced decomposition of this precursor and how this is reflected in the relatively poor performance of H2FeRu3(CO)13 as compared to the structurally similar HFeCo3(CO)12.

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.

scholarly journals Surface Structural Analysis of the Layered Perovskite Ca1.9Sr0.1RuO4 by Low Energy Electron Diffraction I-V

2018 ◽  
Vol 7 (1) ◽  
pp. 56-62
Author(s):  
Ismail Ismail ◽  
Rongying Jin ◽  
David Mandrus ◽  
Earl Ward Plummer
Keyword(s):  
Electron Diffraction ◽  
Bond Length ◽  
Atomic Structure ◽  
Room Temperature ◽  
Low Energy ◽  
Energy Electron ◽  
Layered Perovskite ◽  
Plane Rotation ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

Abstract – The atomic structure at surface of the layered perovskite Ca1.9Sr0.1RuO4 has been studied by Low Energy Electron Diffraction (LEED) I-V. The perovskite Ca1.9Sr0.1RuO4 of single crystal was cleaved in ultra high vacuum chamber (the pressure in the chamber was about 1x10-10 Torr). The experiments were conducted at room temperature (T=300 K). The sharp LEED pattern was observed which indicates that the surface of Ca1.9Sr0.1RuO4 is flat and it is a well ordered crystal. LEED I-V data, nine equivalent beams of the layered perovskite Ca1.9Sr0.1RuO4 were recorded at room temperature. LEED I-V calculation was performed to fit experimental data to obtain the surface atomic structure. The LEED I-V analysis reveals that in the surface of the layered perovskite Ca1.9Sr0.1RuO4 the RuO6 octahedra are rotated (in-plane rotation) alternating clockwise and counterclockwise. The in-plane rotation at the surface is 11 degree which is smaller than that in the bulk (13 degree). The Ru – O(1) bond-length at the surface is found to be 1.936 Å which is about the same as in the bulk (1.939 Å). The Ru – O(2) bond length at the surface is 1.863 Å which is much shorter than that in the bulk (2.040 Å). The volume of octahedral Ru-O6 at the surface is reduced by 9% with respect to the bulk. This finding shows that the atomic structure at surface of the layered perovskite Ca1.9Sr0.1RuO4is significantly different than that in the bulk. These lattice distortions strongly influence its electronic properties.   Key words: Transition Metal Oxide; Perovskite; Surface Atomic Structure; LEED I-V

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