Shock Synthesis of Nanocrystalline High -Pressure Phases in Semiconductors by High-Velocity Thermal Spray

2000 ◽  
Vol 638 ◽  
Author(s):  
R. Goswami ◽  
J. Parise ◽  
H. Herman ◽  
S. Sampath ◽  
R. Gambino ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
Thermal Spray ◽  
High Velocity ◽  
Metastable Phase ◽  
High Energy ◽  
Metastable Phases ◽  
Transmission Electron ◽  
Average Size

AbstractShock synthesis of nanocrystalline Si, Ge and CdTe was accomplished using high- velocity thermal spray. Si or Ge powders were injected into a high energy flame, created by a thermal spray gun, where the particles melt and accelerate to impact on a substrate. The shock wave generated by the sudden impact of the droplets propagated through the underlying deposits, which induces a phase transition to a high pressure form. The decompression of the high-pressure phase results in the formation of several metastable phases, as evidenced by transmission electron microscopy and x-ray diffraction studies. The peak pressure is estimated to be ≈23GPa with a pulse duration of 1-5 ns. Transmission electron microscopy revealed that the metastable phases of Si with a size range of 2 to 5 nm were dispersed within Si-I. In Ge, a metastable phase, ST-12, was observed. This is a decompression product of Ge-II which possesses the β-Sn type of structure. In the case of CdTe, a fine dispersion of hexagonal CdTe particles, embedded in cubic-CdTe with an average size of 2 nm was obtained.

Effects of High-Energy Ions on Synthetic Quartz

1972 ◽  
Vol 30 ◽  
pp. 544-545
Author(s):  
Joseph J. Comer ◽  
Charles Bergeron ◽  
Lester F. Lowe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Energy ◽  
Transmission Electron ◽  
Kikuchi Lines ◽  
High Energy Ions ◽  
Diffraction Patterns ◽  
Dauphiné Twinning ◽  
Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

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.

Transmission Electron Microscopy characterization of epitaxial III-V semiconductor thin films grown on Si(100) by ion-assisted deposition

1990 ◽  
Vol 48 (4) ◽  
pp. 686-687
Author(s):  
L. Hultman ◽  
C.-H. Choi ◽  
R. Kaspi ◽  
R. Ai ◽  
S.A. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
High Energy ◽  
Nucleation Mechanism ◽  
Layer By Layer ◽  
Extended Defect ◽  
Island Formation ◽  
Si Substrates ◽  
Transmission Electron

III-V semiconductor films nucleate by the Stranski-Krastanov (SK) mechanism on Si substrates. Many of the extended defects present in the films are believed to result from the island formation and coalescence stage of SK growth. We have recently shown that low (-30 eV) energy, high flux (4 ions per deposited atom), Ar ion irradiation during nucleation of III-V semiconductors on Si substrates prolongs the 1ayer-by-layer stage of SK nucleation, leading to a decrease in extended defect densities. Furthermore, the epitaxial temperature was reduced by >100°C due to ion irradiation. The effect of ion bombardment on the nucleation mechanism was explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.For the case of InAs grown at 380°C on Si(100) (11% lattice mismatch), where island formation is expected after ≤ 1 monolayer (ML) during molecular beam epitaxy (MBE), in-situ reflection high-energy electron diffraction (RHEED) showed that 28 eV Ar ion irradiation prolonged the layer-by-layer stage of SK nucleation up to 10 ML. Otherion energies maintained layer-by-layer growth to lesser thicknesses. The ion-induced change in nucleation mechanism resulted in smoother surfaces and improved the crystalline perfection of thicker films as shown by transmission electron microscopy and X-ray rocking curve studies.

Structural and Chemical Properties of MBE Grown Niobium Overlayers on (110) Rutile

1996 ◽  
Vol 441 ◽  
Author(s):  
J. Marien ◽  
T. Wagner ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Chemical Properties ◽  
High Energy ◽  
Initial Growth ◽  
High Energy Electron ◽  
Transmission Electron ◽  
Different Temperatures ◽  
And Chemical Properties

AbstractThin Nb films were grown by MBE in a UHV chamber at two different temperatures (50°C and 950°C) on the (110) surface of TiO2 (rutile).At a growth temperature of 50°C, reflection high energy electron diffraction (RHEED) revealed epitaxial growth of Nb on rutile: (110)[001] TiO2 ¦¦ (100)[001] Nb. In addition, investigations with Auger electron spectroscopy (AES) revealed that a chemical reaction took place between the Nb overlayer and the TiO2 substrate at the initial growth stage. A 2 nm thick reaction layer at the Nb/TiO2 interface has been identified by means of conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM).At a substrate temperature of 950°C, during growth, the Nb film was oxidized completely, and NbO2 grew epitaxially on TiO2. The structure and the chemical composition of the overlayers have been investigated by RHEED, AES, CTEM and HRTEM. Furthermore, it was determined that the reaction of Nb with TiO2 is governed by the defect structure of the TiO2 and the relative oxygen affinities of Nb and TiO2.

The Creation and Annealing of Heavy Ion Damage in Silicon

1987 ◽  
Vol 93 ◽  
Author(s):  
L. M. Howe ◽  
M. H. Rainville
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spatial Distribution ◽  
High Resolution ◽  
Heavy Ion ◽  
High Energy ◽  
Transmission Electron ◽  
Ion Damage ◽  
Deposited Energy ◽  
Microscopy Techniques

ABSTRACTHigh resolution transmission electron microscopy techniques have been used to obtain information on the contrast, spatial distribution, size and annealing behaviour of the damaged regions produced within individual collision cascades by heavy ion (As, Sb and Bi) bombardment (10–120 KeV) of silicon with 1.0 × 1011 – 6.0 × 1011 ions cm−2. The fraction of the theoretical cascade volume occupied by a heavily damaged region steadily increased as the average deposited energy density within the cascade increased. At high energy densities, the visible damage produced in the main cascade consisted of a single, isolated damaged region. With decreasing values of (i.e. increasing ion implant energies), there was an increasing tendency for multiple damaged regions to be produced within the main cascade.

Crystal structures of high-pressure phases formed in Si by laser irradiation

Microscopy ◽  
2018 ◽  
Vol 67 (1) ◽  
pp. 30-36
Author(s):  
Hiroyuki Iwata ◽  
Daisuke Kawaguchi ◽  
Hiroyasu Saka
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
Laser Beam ◽  
Crystal Structures ◽  
Laser Irradiation ◽  
Pulse Laser ◽  
Transmission Electron ◽  
Micro Cracks ◽  
Pressure Phase

Abstract Internal modification induced in Si by a permeable pulse laser was investigated by transmission electron microscopy. A laser induced modified volume (LIMV) was a cylindrical rod along the track of a laser beam with the head at the focus of the laser beam. In the LIMV, beside voids, dislocations, micro-cracks and what had been supposed to be an unidentified high-pressure phase (hpp) of Si were observed in LIMV. The so-called ‘hpp’ was identified mostly as diamond Si.

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