In-Situ Transmission Elecron Microscopy (TEM) Study of the Nitridation of Basal Plane Sapphire by Reactive Molecular Beam Epitaxy (RMBE)

1997 ◽  
Vol 3 (S2) ◽  
pp. 475-476
Author(s):  
M. Yeadon ◽  
M.T. Marshall ◽  
J.M. Gibson
Keyword(s):  
Buffer Layer ◽  
Lattice Mismatch ◽  
High Vacuum ◽  
High Energy ◽  
Substantial Improvement ◽  
Ultra High Vacuum ◽  
Sapphire Surface ◽  
Group Iii ◽  
Flat Surfaces

Group III-nitride thin films are currently of great interest for use in wide-bandgap semiconductor applications including UV lasers and light emitting diodes (LEDs). Sapphire (a-Al2O3) is currently the substrate of choice for the growth of GaN despite a large lattice mismatch. Growth of high quality GaN epilayers typically involves the deposition of a buffer layer of either AIN or GaN at a temperature well below that used for the growth of the active GaN layer. It has been found empirically that nitridation of the sapphire surface with nascent nitrogen prior to growth of the buffer layer results in a substantial improvement in film quality. Using a novel ultra-high vacuum (UHV) in-situ TEM with in-situ RMBE, we have studied the nitridation of the (0001) sapphire surface using transmission and reflection electron microscopy (REM), reflection high energy electron diffraction (RHEED) and Auger electron spectroscopy (AES).An electron-transparent sapphire TEM sample was annealed at 1400°C for 12 hours in flowing oxygen, to form atomically flat surfaces for our investigation.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

Modifications of a JEOL 2000EX TEM for insSitu surface studies

1993 ◽  
Vol 51 ◽  
pp. 640-641
Author(s):  
Michael T. Marshall ◽  
Xianghong Tong ◽  
J. Murray Gibson
Keyword(s):  
Electron Diffraction ◽  
Surface Science ◽  
Film Growth ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Transmission Electron ◽  
Fundamental Insight

We have modified a JEOL 2000EX Transmission Electron Microscope (TEM) to allow in-situ ultra-high vacuum (UHV) surface science experiments as well as transmission electron diffraction and imaging. Our goal is to support research in the areas of in-situ film growth, oxidation, and etching on semiconducter surfaces and, hence, gain fundamental insight of the structural components involved with these processes. The large volume chamber needed for such experiments limits the resolution to about 30 Å, primarily due to electron optics. Figure 1 shows the standard JEOL 2000EX TEM. The UHV chamber in figure 2 replaces the specimen area of the TEM, as shown in figure 3. The chamber is outfitted with Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Residual Gas Analyzer (RGA), gas dosing, and evaporation sources. Reflection Electron Microscopy (REM) is also possible. This instrument is referred to as SHEBA (Surface High-energy Electron Beam Apparatus).The UHV chamber measures 800 mm in diameter and 400 mm in height. JEOL provided adapter flanges for the column.

A Mechanism of Sliding on the Nanometer-Thick Ag Layers

2005 ◽  
Author(s):  
F. Honda ◽  
M. Goto
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
High Vacuum ◽  
High Energy ◽  
Thin Layers ◽  
Ultra High Vacuum ◽  
Wear And Friction ◽  
Thickness Measurements

Tribological performance of sub-nano to nanometer-thick Ag layers deposited on Si(111) have been examined to understand the role of surface thin layers to the wear and friction characteristics. The slider was made of diamond sphere of 3 mm in radius. Sliding tests were carried out in an ultra-high vacuum environment (lower than 4 × 10−8 Pa) and analyzed in-situ by Auger electron spectroscopy (AES) for the quantitative thickness-measurements, by reflection high-energy electron diffraction (RHEED) to clarify the substrate cleanliness and crystallography of the Ag films, and by scanning probe microscopy (SPM) for the morphology of the deposited/slid film surfaces. As the results, a minimum of the friction coefficient 0.007 was observed from the film thickness range of 1.5–10 nm, and exactly no worn particles were found after 100 cycles of reciprocal sliding. Results have directly indicated that solid Ag(111) sliding planes allowed to reduce the friction coefficient very low without any detectable wear particles, and Ag nanocrystallites in Ag polycrystalline layers increase the size to 20–40 nm order, during sliding. The friction coefficient was slightly dependent to the normal load. Results were discussed on the role of the surface atoms to the friction, and a mechanism of sliding on Ag thin layers.

In situ quantitative analysis of GeXSi1-X alloys during growth by reflection EELS

1991 ◽  
Vol 49 ◽  
pp. 878-879
Author(s):  
Shouleh Nikzad ◽  
Channing C. Ahn ◽  
Harry A. Atwater
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Film Growth ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Mbe Growth ◽  
Electron Microscopes ◽  
Electron Energy Loss

The universality of reflection high energy electron diffraction (RHEED) as a structural tool during film growth by molecular beam epitaxy (MBE) brings with it the possibility for in situ surface chemical analysis via spectroscopy of the accompanying inelastically scattered electrons. We have modified a serial electron energy loss spectrometer typically used on an electron microscope to work with a 30 keV RHEED-equipped MBE growth chamber in order to determine the composition of GexSi1-x alloys by reflection electron energy loss (REELS) experiments. Similar work done in transmission electron microscopes has emphasized the surface sensitivity of this technique even though these experiments have never been done under ultra-high vacuum conditions. In this work, we are primarily concerned with the accuracy with which core losses can be used to determine composition during MBE growth.

Epitaxial NiO-Co exchange-biased bilayers grown on MgO single crystals Influence of the substrate orientation on the film morphology, the Co structure and the magnetic behavior

2001 ◽  
Vol 672 ◽  
Author(s):  
B. Warot ◽  
E. Snoeck ◽  
J.C. Ousset ◽  
M.J. Casanove ◽  
S. Dubourg ◽  
...  
Keyword(s):  
Layer Structure ◽  
High Vacuum ◽  
Magnetic Behavior ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Diffraction Reflection ◽  
Face Centered Cubic ◽  
Substrate Orientation ◽  
Flat Surfaces ◽  
Hexagonal Close Packed Structure

ABSTRACTCo/NiO bilayers have been grown on MgO(001), MgO(110) and MgO(111) substrates in an ultra high vacuum sputtering chamber. Growth mode and surface morphology are investigated by X-ray diffraction, Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM) and High Resolution Transmission Electron Microscopy (HRTEM). NiO layers grow epitaxially whatever the substrate orientation. Flat surfaces are observed on NiO/MgO(001) whereas on MgO(110) the NiO surface exhibits a roof-like morphology consisting in (100) and (010) facets elongated along the [001] direction. On MgO(111), the NiO surface presents pyramids with {100} facets. A temperature dependence of the cobalt layer structure is observed: on NiO(001) at room temperature it grows in its high temperature face-centered cubic structure (fcc), whereas it has the hexagonal close-packed structure (hcp) when deposited at slightly higher temperatures.

Si NWs Conversion to Si-SiC Core-Shell NWs by MBE

2015 ◽  
Vol 821-823 ◽  
pp. 965-969
Author(s):  
Fernando Lloret ◽  
D. Araujo ◽  
M.P. Villar ◽  
L. Liu ◽  
Konstantinos Zekentes
Keyword(s):  
Electron Microscopy ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Si Nanowires ◽  
Transmission Electron ◽  
Set Up

Si nanowires (NWs) samples have been converted to silicon carbide (SiC) NWs at different conditions of substrate temperature in an ultra-high vacuum using a molecular beam epitaxy (MBE) set-up. Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) have been in-situ carried out to control the growth process. Scanning electron microscopy (SEM) and conventional transmission electron microscopy (CTEM) have been used to characterize the resulting nanostructures. In addition, the samples have been prepared by focused ion beam (FIB) in order to have electron-transparently lamellas for TEM with the interface nanowire-substrate. SiC/Si shell/core NWs free of planar defects have been obtained for conversion tmpratures lower than 800oC.

Chemical Bonding, Structure, and Morphology of Mg/∝-Al2O3 and MGO / ∝-Al2O3 Interfaces

1994 ◽  
Vol 357 ◽  
Author(s):  
Yan Yu ◽  
R.J. Lad
Keyword(s):  
Photoelectron Spectroscopy ◽  
Spinel Phase ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
High Energy Electron ◽  
Sapphire Surface ◽  
X Ray ◽  
Bonding Structure ◽  
Oxygen Anions

AbstractUltra-thin films of Mg and MgO were grown on ∝-Al2O3 (1012) surfaces (r-cut sapphire) and studied using reflection high energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS). When Mg is deposited at 30°C in ultra-high vacuum (UHV), the first monolayer of Mg atoms chemically bonds to the oxygen anions of the sapphire surface. At Mg coverages above a monolayer, a polycrystalline metallic Mg overlayer is formed. Annealing above 250°C in UHV causes the metallic Mg to desorb from the surface. However, annealing above 250°C in 10−6 torr O2 produces a polycrystalline MgO film. This MgO film recrystallizes after annealing in O2 at 900°C for 60 minutes and exhibits a crystallographic orientation of MgO (100) // ∝-Al2O3 (1012). RHEED indicates that the recrystallized MgO layer dewets the sapphire surface and forms islands. When Mg is deposited at 30°C in 10−6 torr O2, a polycrystalline MgO layer is created. This layer also becomes recrystallized and dewets the sapphire surface after extended annealing in O2 at 900°C. No evidence for a MgAl2O4 spinel phase was observed.

Enhanced Nucleation and Decreased Growth Rates of Cu2O in Cu0.5Au0.5 (001) Thin Films During in situ Oxidation

2005 ◽  
Vol 20 (7) ◽  
pp. 1902-1909 ◽  
Author(s):  
Liang Wang ◽  
Judith C. Yang
Keyword(s):  
Lattice Mismatch ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Oxide Growth ◽  
Inert Component ◽  
Initial Oxidation ◽  
In Situ Oxidation ◽  
Transmission Electron ◽  
Oxidation Behaviors

The initial oxidation behaviors of Cu–50 at.% Au (001) single-crystal thin film were studied by in situ ultra-high-vacuum transmission electron microscopy to model nano-oxidation of alloys with one oxidizing component and one inert component. The oxidation behaviors such as incubation time, oxide nucleation rate, oxide growth kinetics as well as nucleation activation energy were greatly changed by the addition of nonoxidizing Au. The reasons for these changes, such as Au segregation to the top surface, a decrease in Cu activity, and reduced lattice mismatch due to the addition of Au, were discussed, and a qualitative analysis of nucleation energetics was given.

Silicon Homoepitaxy at 300°C Using ArF Excimer Laser Photolysis of Disilane

1990 ◽  
Vol 201 ◽  
Author(s):  
B. Fowler ◽  
T. Lian ◽  
D. Bullock ◽  
S. Banerjee
Keyword(s):  
Electron Diffraction ◽  
Excimer Laser ◽  
Growth Rates ◽  
Defect Density ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Arf Excimer Laser

AbstractPhotolysis of Si2H6 by an ArF excimer laser has been used to deposit Si homoepitaxial layers at temperatures as low as 300°C. The chemical vapor deposition process at growth rates from 0.5-4 Å/minute is performed in an ultra-high vacuum chamber which, along with an ex situ HF dip and a novel in situ hydrogen clean using laser excitation, results in minimization of oxygen and carbon contamination which inhibits Si epitaxy. The growth involves photolytic decomposition of Si2H6 and the generation and adsorption of SiH2 precursors on the hydrogenated Si surface, which is the rate limiting step. Growth rates are observed to vary proportionally with laser power. Very low defect density films in terms of stacking faults and dislocation loops (less than 105 cm−2), and excellent crystallinity have been deposited as confirmed by Schimmel etching and Nomarski microscopy, transmission electron microscopy, electron diffraction and in situ reflection high energy electron diffraction.

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