scholarly journals Sputtering Induced Changes in Defect Morphology and Dopant Diffusion for Si Implanted GaAs: Influence of Ion Energy and Implant Temperature

1994 ◽  
Vol 354 ◽  
Author(s):  
H.G. Robinson ◽  
C.C. Lee ◽  
T.E. Haynes ◽  
E.L. Allen ◽  
M.D. Deal ◽  
...  
Keyword(s):  
Defect Density ◽  
Vacancy Concentration ◽  
High Energy ◽  
Amorphous Semiconductors ◽  
Yield Enhancement ◽  
Excess Vacancy ◽  
Dopant Diffusion ◽  
Extended Defect ◽  
Ion Energy ◽  
Sputter Yield

AbstractExperimental observations of dopant diffusion and defect formation are reported as a function of ion energy and implant temperature in Si implanted GaAs. In higher energy implants (>100 keV), little or no diffusion occurs, while at energies less than 100 keV, the amount of dopant redistribution is inversely proportional to energy. The extended defect density shows the opposite trend, increasing with increasing ion energy. Similarly, the diffusion of Si during post implant annealing decreases by a factor of 2.5 as the implant temperature increases from -2 to 40°C. In this same temperature range, the maximum depth and density of extrinsic dislocation loops increases by factors of 3 and 4, respectively. Rutherford Backscattering (RBS) channeling measurements indicate that Si implanted GaAs undergoes an amorphous to crystalline transition at Si implant temperatures between -51 and 40°C. A unified explanation of the effects of ion energy and implant temperature on both diffusion and dislocation formation is proposed based on the known differences in sputter yields between low and high energy ions and crystalline and amorphous semiconductors. The model assumes that the sputter yield is enhanced at low implant energies and by amorphization, thus increasing the excess vacancy concentration. Estimates of excess vacancy concentration are obtained by simulations of the diffusion profiles and are quantitatively consistent with a realistic sputter yield enhancement. Removal of the vacancy rich surface by etching prior to annealing completely suppresses the Si diffusion and increases the dislocation density, lending further experimental support to the model.

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.

scholarly journals Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 17
Author(s):  
Eldred Lee ◽  
Kaitlin M. Anagnost ◽  
Zhehui Wang ◽  
Michael R. James ◽  
Eric R. Fossum ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Quantum Yield ◽  
Photon Energy ◽  
High Efficiency ◽  
High Energy ◽  
Yield Enhancement ◽  
X Ray ◽  
Simulation Results ◽  
Conversion Efficiencies

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.

scholarly journals Mechanisms of Enhanced Ionic Conduction at Interfaces in Ceramics

1994 ◽  
Vol 357 ◽  
Author(s):  
D. Lubben ◽  
F. A. Modine
Keyword(s):  
Film Thickness ◽  
Ionic Conduction ◽  
Defect Density ◽  
Ionic Conductivities ◽  
Dislocation Motion ◽  
Extended Defects ◽  
Epitaxial Relationship ◽  
Extended Defect ◽  
Charge Layer ◽  
Fine Grained

AbstractA large enhancement in the ionic conductivity of certain compounds occurs when the compound is produced as a composite material containing a finely-dispersed non-conductor such as SiO2 or Al2O3 This effect has been reported on for more than 20 years, and it is well established that the enhancement is associated with the presence of interfaces. The popular explanation has been based on a model which contends that the enhancement is due to a space-charge layer which forms to compensate a net charge layer at an interface. A different model proposes that extended defects such as dislocations and grain boundaries, either resulting from or stabilized by the interface, are responsible for the enhancement. This paper describes recent experiments which strongly support the latter model. The ionic conductivities of LiI and CaF2 thin films grown on sapphire(0001) substrates were monitored in-situ during deposition as a function of film thickness and deposition conditions. LiI films grown at 27°C exhibited a region of enhanced conduction within 100 nm of the substrate and a lesser enhancement as the film thickness was increased further. This conduction enhancement was not stable but annealed out with a characteristic log(time) dependence. The observed annealing behavior was fit with a model based on dislocation motion which implies that the increase in conduction near the interface is due to extended defects generated during the growth process. LiI films grown at higher temperatures (100°C) in order to reduce the grown-in defects showed no interfacial conduction enhancement. X-ray diffraction measurements suggest that these high-temperature LiI films nucleate as faceted epitaxial islands with a stable misfit dislocation density defined by the epitaxial relationship between the substrate and film. CaF2 films grown at 200°C showed a behavior similar to the 27°C LiI films, with a region of thermally unstable enhanced conduction that occurs within 10 nm of the substrate. Amorphous Al2O3 films deposited over the CaF2 layers created no additional enhancement but did increase the stability of the conduction, consistent with an extended defect model. Simultaneous deposition of CaF2 and Al2O3 produced films consisting of very-fine-grained CaF2 and particles of amorphous Al2O23 (5-10 nm grain and particle size) and a high defect density which was stable even well above the growth temperature. Measured conduction in the composite at 200°C was approximately 360 times that of bulk CaF2.

Bulk Gan Crystal With Low Defect Density Grown By Hydride Vapor Phase Epitaxy

1997 ◽  
Vol 482 ◽  
Author(s):  
A. Usui
Keyword(s):  
Vapor Phase ◽  
Flat Surface ◽  
Defect Density ◽  
Vapor Phase Epitaxy ◽  
Hydride Vapor Phase Epitaxy ◽  
Extended Defect ◽  
New Approach ◽  
Bulk Gan ◽  
Gan Crystal ◽  
Reflectance Measurements

AbstractA new approach to grow thick GaN layers by hydride vapor phase epitaxy (HVPE) is described. Selective growth is carried out at the beginning of growth. The coalescence of selectively grown facet structures makes it possible to achieve a flat surface over the entire substrate. As a result, crack-free GaN films with mirror-like surfaces are successfully grown even to a thickness of about 100 μm on a 2-inch-diameter sapphire substrate. The extended defect density is as low as 6×107 cm−2. The reduction mechanism for dislocation is discussed based on TEM observation. The high optical properties of FIELO GaN are confirmed by 5 K photoluminescence and reflectance measurements.

Point and extended defect interaction in low – high energy phosphorus implantation sequences

2018 ◽  
Vol 5 (6) ◽  
pp. 14778-14784 ◽  
Author(s):  
I. Mica ◽  
M.L. Polignano ◽  
P. Bacciaglia ◽  
D. Brazzelli ◽  
D. Cseh ◽  
...  
Keyword(s):  
High Energy ◽  
Extended Defect ◽  
Defect Interaction

Spectroscopic Study of Hydrogen Induced Defect in a-Ge:H

1990 ◽  
Vol 209 ◽  
Author(s):  
Shu Jin ◽  
Lothar Ley
Keyword(s):  
Electronic Structure ◽  
Spectroscopic Study ◽  
Density Gradient ◽  
Growth Condition ◽  
Photoelectron Spectroscopy ◽  
Defect Density ◽  
Total Yield ◽  
Structure Change ◽  
Amorphous Semiconductors ◽  
Hydrogenated Amorphous

ABSTRACTTotal yield photoelectron spectroscopy has been used to study the electronic structure change of UHV evaporated a-Ge subjected to posthydrogenation and various annealing cycles. We identify in R.T. hydrogenated a-Ge:H a new hydrogen induced defect at about Ev + 0.45eV, which can be healed upon 300°C annealing. This new defect accounts for the defect density gradient of hydrogenated amorphous semiconductors, spanning the range from ∼ 1018 cm−3 at the growing surface to 1018−1015 cm−3 in the bulk, depending on growth condition and time. The origin of this new defect is discussed.

Synthesis and Characterization of Nanostructured Mechanical Cu-Fe-Co Alloy

2018 ◽  
Vol 941 ◽  
pp. 1232-1237
Author(s):  
Alisiya Biserova-Tahchieva ◽  
Isabel López-Jiménez ◽  
Núria Llorca-Isern
Keyword(s):  
Defect Density ◽  
Nanocrystalline Structure ◽  
High Energy ◽  
Magnetic Behaviour ◽  
X Ray Diffraction ◽  
X Ray ◽  
Soft Ferromagnetic ◽  
Hours Of Work ◽  
And Diffusion

Nanocrystalline structure of CuFeCo (50:25:25 wt%) alloy has been obtained by high energy mechanical milling from elemental metal powder mixture during large hours of work. Phase transformations and diffusion in the system subjected to heat treatment are discussed. Thermal stability at high temperatures is analysed and considered of importance for several applications. The nanostructure was studied by employing X-Ray diffraction and electron microscopy. It has been determined the reduction in crystallite size and the induced microstrain by the milling time. The solid solution achievement through the increment of defect density was confirmed by Mössbauer analysis. Magnetic behaviour was analysed through magnetization technique entailing their soft ferromagnetic behaviour related to the microstructural changes.

scholarly journals Effects of oblique incidence and colliding pulses on laser-driven proton acceleration from relativistically transparent ultrathin targets

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
J. Ferri ◽  
E. Siminos ◽  
L. Gremillet ◽  
T. Fülöp
Keyword(s):  
Oblique Incidence ◽  
Laser Pulses ◽  
High Energy ◽  
Femtosecond Laser Pulses ◽  
Reference Case ◽  
Proton Acceleration ◽  
Ion Energy ◽  
High Energies ◽  
Proton Charge ◽  
Induced Transparency

The use of ultrathin solid foils offers optimal conditions for accelerating protons to high energies from laser–matter interactions. When the target is thin enough that relativistic self-induced transparency sets in, all of the target electrons get heated to high energies by the laser, which maximizes the accelerating electric field and therefore the final ion energy. In this work, we first investigate how ion acceleration by ultraintense femtosecond laser pulses in transparent CH $_2$ solid foils is modified when turning from normal to oblique ( $45^\circ$ ) incidence. Due to stronger electron heating, we find that higher proton energies can be obtained at oblique incidence but in thinner optimum targets. We then show that proton acceleration can be further improved by splitting the laser pulse into two half-pulses focused at opposite incidence angles. An increase by ${\sim }30\,\%$ in the maximum proton energy and by a factor of ${\sim }4$ in the high-energy proton charge is reported compared to the reference case of a single normally incident pulse.

scholarly journals Effect of excess vacancy concentration on As and Sb doping in Si

2009 ◽  
Vol 42 (16) ◽  
pp. 165106
Author(s):  
M Dalponte ◽  
M C Adam ◽  
H I Boudinov ◽  
L V Goncharova ◽  
T Feng ◽  
...  
Keyword(s):  
Vacancy Concentration ◽  
Excess Vacancy ◽  
Sb Doping

Electrical properties of zinc oxide thin films deposited using high-energy H2O generated from a catalytic reaction on platinum nanoparticles

2013 ◽  
Vol 1494 ◽  
pp. 127-132
Author(s):  
Kanji Yasui ◽  
Naoya Yamaguchi ◽  
Eichi Nagatomi ◽  
Souichi Satomoto ◽  
Takahiro Kato
Keyword(s):  
Zinc Oxide ◽  
Electrical Properties ◽  
Film Thickness ◽  
Electron Mobility ◽  
Lattice Mismatch ◽  
Defect Density ◽  
Chemical Vapor ◽  
High Energy ◽  
Chemical Vapor Deposition Method ◽  
Zno Films

ABSTRACTZinc oxide (ZnO) with excellent crystallinity and large electron mobility was grown on aplane (11-20) sapphire (a-Al2O3) substrates by a new chemical vapor deposition method via the reaction between dimethylzinc (DMZn) and high-energy H2O produced by a Pt-catalyzed H2-O2 reaction. The electron mobility at room temperature increased from 30 cm2/Vs to 189 cm2/Vs with increasing film thickness from 0.1 μm to approximately 3 μm. Electron mobility increased significantly with decreasing temperature to approximately 110 – 150 K, but decreased at temperatures less than 100 K for films greater than 500 nm in thickness. On the other hand, the mobility hardly changed with temperature for films lesser than 500 nm in thickness. Based on the dependence of the electrical properties on the film thickness, the ZnO films grown on a-Al2O3 substrates are considered to consist of an interfacial layer with a high defect density (degenerate layer) generated due to a large lattice mismatch between ZnO and Al2O3 substrates and an upper layer with a low defect density.

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