scholarly journals Influence of a thin amorphous surface layer on de-channeling during aluminum implantation at different temperatures into 4H-SiC

2019 ◽  
Vol 125 (12) ◽  
Author(s):  
M. K. Linnarsson ◽  
A. Hallén ◽  
L. Vines
Keyword(s):  
Surface Layer ◽  
Elevated Temperatures ◽  
Secondary Ion Mass Spectrometry ◽  
Decisive Role ◽  
Native Oxide ◽  
Atomic Displacements ◽  
Aluminum Ions ◽  
Aluminum Implantation ◽  
Different Temperatures ◽  
Amorphous Surface

AbstractIon implantation is an important technique in semiconductor processing and has become a key technology for 4H-SiC devices. Today, aluminum (Al) implantations are routinely used for p-type contacts, p+-emitters, terminations and many other applications. However, in all crystalline materials, quite a few ions find a path along a crystal channel, so-called channeling, and these ions travel deep into the crystal. This paper reports on the channeling phenomenon during Al implantation into 4H-SiC, and in particular, the influence of a thin native oxide will be discussed in detail. The effects of thermal lattice vibrations for implantations performed at elevated temperatures will also be elucidated. 100 keV Al ions have been implanted along the [000-1] direction employing samples with 4° miscut. Before implantation, the samples have been aligned using the blocking pattern of backscattered protons. Secondary ion mass spectrometry has been used to record the Al depth distribution. To predict implantation profiles and improve understanding of the role of crystal structure, simulations were performed using the Monte-Carlo binary collision approximation code SIIMPL. Our results show that a thin surface layer of native oxide, less than 1 nm, has a decisive role for de-channeling of aligned implantations. Further, as expected, for implantations at elevated temperatures, a larger degree of de-channeling from major axes is present due to increased thermal vibrations and the penetration depth of channeled aluminum ions is reduced. The values for the mean-square atomic displacements at elevated temperatures have been extracted from experimental depth profiles in combination with simulations.

Channeled Implantations of p-Type Dopants into 4H-SiC at Different Temperatures

2019 ◽  
Vol 963 ◽  
pp. 382-385 ◽  
Author(s):  
Margareta K. Linnarsson ◽  
Anders Hallén ◽  
Lasse Vines ◽  
Bengt G. Svensson
Keyword(s):  
Room Temperature ◽  
Depth Distribution ◽  
Elevated Temperatures ◽  
Secondary Ion Mass Spectrometry ◽  
Lattice Vibrations ◽  
Simulation Code ◽  
Different Temperatures ◽  
P Type ◽  
Secondary Ion ◽  
Collision Approximation

Channeling of B and Al ions in 4H-SiC(0001), has been investigated by secondary ion mass spectrometry (SIMS). Ion implantations have been performed between room temperature (RT) and 600 °C at various fluences. Before implantation, the major crystal axes were determined and the sample was aligned using the blocking pattern of backscattered protons. As expected, the depth distribution of the implanted ions along a crystal direction penetrates much deeper compared to non-channeling directions. At elevated temperatures, the channeling depth for 100 keV Al-ions is decreased due to lattice vibrations. For 50 keV B-ions, the temperature effect is minor, indicating a smaller interaction between target atoms and B. Simulations has been performed using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation, to predict experimental data and get a deeper insight in the channeling process.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Microstructure of sputter deposited Ni-Sb ohmic contacts on GaAs

1989 ◽  
Vol 47 ◽  
pp. 450-451
Author(s):  
S. Yegnasubramanian ◽  
V.C. Kannan ◽  
R. Dutto ◽  
P.J. Sakach
Keyword(s):  
High Performance ◽  
Ohmic Contacts ◽  
Surface Defects ◽  
Pure Metal ◽  
Device Fabrication ◽  
Native Oxide ◽  
Metal Thin Films ◽  
Recent Developments ◽  
Different Temperatures ◽  
Sputter Deposited

Recent developments in the fabrication of high performance GaAs devices impose crucial requirements of low resistance ohmic contacts with excellent contact properties such as, thermal stability, contact resistivity, contact depth, Schottky barrier height etc. The nature of the interface plays an important role in the stability of the contacts due to problems associated with interdiffusion and compound formation at the interface during device fabrication. Contacts of pure metal thin films on GaAs are not desirable due to the presence of the native oxide and surface defects at the interface. Nickel has been used as a contact metal on GaAs and has been found to be reactive at low temperatures. Formation Of Ni2 GaAs at 200 - 350C is reported and is found to grow epitaxially on (001) and on (111) GaAs, but is shown to be unstable at 450C. This paper reports the investigations carried out to understand the microstructure, nature of the interface and composition of sputter deposited and annealed (at different temperatures) Ni-Sb ohmic contacts on GaAs by TEM. Attempts were made to correlate the electrical properties of the films such as the sheet resistance and contact resistance, with the microstructure. The observations are corroborated by Scanning Auger Microprobe (SAM) investigations.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Facing extremes: archaeal surface-layer (glyco)proteins

Microbiology ◽  
2003 ◽  
Vol 149 (12) ◽  
pp. 3347-3351 ◽  
Author(s):  
Jerry Eichler
Keyword(s):  
Surface Layer ◽  
Structural Integrity ◽  
Elevated Temperatures ◽  
Protein Biosynthesis ◽  
Extreme Environments ◽  
Archaeal Protein ◽  
The Face ◽  
Micro Organisms ◽  
Physical Challenges ◽  
Insight Into

Archaea are best known in their capacities as extremophiles, i.e. micro-organisms able to thrive in some of the most drastic environments on Earth. The protein-based surface layer that envelopes many archaeal strains must thus correctly assemble and maintain its structural integrity in the face of the physical challenges associated with, for instance, life in high salinity, at elevated temperatures or in acidic surroundings. Study of archaeal surface-layer (glyco)proteins has thus offered insight into the strategies employed by these proteins to survive direct contact with extreme environments, yet has also served to elucidate other aspects of archaeal protein biosynthesis, including glycosylation, lipid modification and protein export. In this mini-review, recent advances in the study of archaeal surface-layer (glyco)proteins are discussed.

Tensile Properties of Low Nickel Austenitic Stainless Steel at Elevated Temperatures

2012 ◽  
Vol 159 ◽  
pp. 346-350
Author(s):  
Shu Min Liu ◽  
Jian Bin Zhang
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Elevated Temperatures ◽  
Peak Stress ◽  
Temperature Curve ◽  
Delta Ferrite ◽  
Cross Sectional ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Reduction Percentage

The elevated temperature short-time tensile test with the sample of casting low nickel stainless steel was conducted on SHIMADZU AG-10 at ten temperatures 300, 500, 600, 700, 800, 950, 1000, 1050, 1100, and 1250°C, respectively. The stress-strain curves with the thermal deformation at the different temperatures, the peak stress intensity-temperature curve, and the reduction percentage of cross sectional area-temperature curve were obtained. Metallographic test samples were prepared and the morphology of deforming zone was observed by optical microscopy. The experimental results show that the tensile strength of the test samples decreases with increasing temperature. From 300 to 800°C, the work harding occurred and the tensile strength increases with increasing strain. The work softening occurred and the tensile strength decreases with increasing strain at temperatures of 800 to 1250°C. The minimum value of reduction percentage was measured at 800 °C. The austenite and delta-ferrite are the main phase in the tested samples. When the tensile temperatures are increased to 1200°C, the delta-ferrite became thinner and broke down to be spheroidized.

scholarly journals Thermal Stability of Residual Stresses in Differently Deep Rolled Surface Layers of Steel SAE 1045

2021 ◽  
Author(s):  
Stephanie Saalfeld ◽  
Thomas Wegener ◽  
Berthold Scholtes ◽  
Thomas Niendorf
Keyword(s):  
Thermal Stability ◽  
Elevated Temperature ◽  
Residual Stresses ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Decisive Role ◽  
Deep Rolling ◽  
Material Conditions ◽  
The Stability ◽  
Thermal Stability Of

AbstractThe stability of compressive residual stresses generated by deep rolling plays a decisive role on the fatigue behavior of specimens and components, respectively. In this regard, deep rolling at elevated temperature has proven to be very effective in stabilizing residual stresses when fatigue analysis is conducted at ambient temperature. However, since residual stresses can be affected not only by plastic deformation but also when thermal energy is provided, it is necessary to analyze the influence of temperature and time on the relaxation behavior of residual stresses at elevated temperature. To evaluate the effect of deep rolling at elevated temperatures on stability limits under thermal as well as combined thermo-mechanical loads, the present work introduces and discusses the results of investigations on the thermal stability of residual stresses in differently deep rolled material conditions of the steel SAE 1045.

Mechanical Property and Oxidation Behavior of LPS-SiC Materials

2006 ◽  
Vol 321-323 ◽  
pp. 913-916
Author(s):  
Sang Ll Lee ◽  
Yun Seok Shin ◽  
Jin Kyung Lee ◽  
Jong Baek Lee ◽  
Jun Young Park
Keyword(s):  
Mechanical Property ◽  
Fracture Toughness ◽  
Oxidation Behavior ◽  
Elevated Temperatures ◽  
Indentation Test ◽  
Bending Test ◽  
Secondary Phases ◽  
Three Point Bending ◽  
Different Temperatures

The microstructure and the mechanical property of liquid phase sintered (LPS) SiC materials with oxide secondary phases have been investigated. The strength variation of LPS-SiC materials exposed at the elevated temperatures has been also examined. LPS-SiC materials were sintered at the different temperatures using two types of Al2O3/Y2O3 compositional ratio. The characterization of LPS-SiC materials was investigated by means of SEM with EDS, three point bending test and indentation test. The LPS-SiC material with a density of about 3.2 Mg/m3 represented a flexural strength of about 800 MPa and a fracture toughness of about 9.0 MPa⋅√m.

scholarly journals Hardening of Nickel Alloys by Ion Implantation of Titanium and Carbon

1996 ◽  
Vol 444 ◽  
Author(s):  
S. M. Myers ◽  
D. M. Follstaedt ◽  
J. A. Knapp ◽  
T. R. Christenson
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Surface Layer ◽  
Ion Implantation ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Nickel Alloys ◽  
Element Modeling ◽  
Order Of Magnitude ◽  
Amorphous Surface

AbstractDual ion implantation of titanium and carbon was shown to produce an amorphous surface layer in annealed bulk nickel, in electroformed Ni, and in electroformed Ni7 5Fe 2 5. Diamond-tip nanoindentation coupled with finite-element modeling quantified the elastic and plastic mechanical properties of the implanted region. The amorphized matrix, with a thickness of about 100 nm, has a yield stress of approximately 6 GP and an intrinsic hardness near 16 GPa, exceeding by an order of magnitude the corresponding values for annealed bulk Ni. Implications for micro-electromechanical systems are discussed.

scholarly journals Impact of ocean acidification and elevated temperatures on early juveniles of the polar shelled pteropod <i>Limacina helicina</i>: mortality, shell degradation, and shell growth

2010 ◽  
Vol 7 (6) ◽  
pp. 8177-8214 ◽  
Author(s):  
S. Lischka ◽  
J. Büdenbender ◽  
T. Boxhammer ◽  
U. Riebesell
Keyword(s):  
Ocean Acidification ◽  
Surface Waters ◽  
Elevated Temperatures ◽  
Shell Growth ◽  
Shell Diameter ◽  
Partial Pressures ◽  
Limacina Helicina ◽  
Different Temperatures ◽  
Arctic Surface

Abstract. Due to their aragonitic shell thecosome pteropods may be particularly vulnerable to ocean acidification driven by anthropogenic CO2 emissions. This applies specifically to species inhabiting Arctic surface waters that are projected to become locally undersaturated with respect to aragonite as early as 2016. This study investigated the effects of rising pCO2 partial pressures and elevated temperature on pre-winter juveniles of the polar pteropod Limacina helicina. After a 29 days experiment in September/October 2009 at three different temperatures and under pCO2 scenarios projected for this century, mortality, shell degradation, shell diameter and shell increment were investigated. Temperature and pCO2 had a significant effect on mortality, but temperature was the overriding factor. Shell diameter, shell increment and shell degradation were significantly impacted by pCO2 but not by temperature. Mortality was 46% higher at 8 °C compared to 3 °C (in situ), and 14% higher at 1100 μatm CO2 as compared to 230 μatm CO2. Shell diameter and increment were reduced by 10% and 12% at 1100 μatm CO2 as compared to 230 μatm CO2, respectively, and shell degradation was 41% higher at elevated compared to ambient pCO2 partial pressures. We conclude that pre-winter juveniles will be negatively affected by both rising temperature and pCO2 which may result in a possible abundance decline of the overwintering population, the basis for next year's reproduction.

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