Nitrogen Incorporation during Seeded Sublimation Growth of 4H-SiC and 6H-SiC

2015 ◽  
Vol 821-823 ◽  
pp. 60-63 ◽  
Author(s):  
Nikolaos Tsavdaris ◽  
Pawel Kwasnicki ◽  
Kanaparin Ariyawong ◽  
Nathalie Valle ◽  
Hervé Peyre ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Temperature Dependent ◽  
Bulk Crystal Growth ◽  
Bond Density ◽  
Nitrogen Incorporation ◽  
Nitrogen Desorption ◽  
Sublimation Method ◽  
The Difference ◽  
Sublimation Growth ◽  
Incorporated Nitrogen

We address the problem of nitrogen incorporation during bulk crystal growth of 4H-SiC and 6H-SiC by seeded sublimation method. The partial pressure of nitrogen and temperature dependence were considered in bulk SiC crystals. Free carrier concentration and incorporated nitrogen were determined using Raman spectroscopy and Secondary Ion Mass Spectrometry, respectively. The incorporated nitrogen at the (000-1) C-face of 4H-SiC and 6H-SiC is found to be independent of the polytype of the crystal. Higher desorption rate at Si-face compared to C-face is found, using a Langmuir equation, which is attributed to the difference in bond density between the two polar faces. The increased nitrogen desorption when growth temperature increases is believed to be the most contributing factor, based on the temperature dependent trends.

Dopant incorporation efficiencies of SiC crystals grown on {1100}-face

1996 ◽  
Vol 423 ◽  
Author(s):  
Naohiro Sugiyama ◽  
Atsuto Okamoto ◽  
Toshihiko Tani ◽  
Nobuo Kamiya
Keyword(s):  
Grown Crystal ◽  
Boron Concentration ◽  
Aluminum Concentration ◽  
Absorption Coefficients ◽  
Dopant Incorporation ◽  
Nitrogen Incorporation ◽  
Nitrogen Concentrations ◽  
Bulk Single Crystals ◽  
Sublimation Method ◽  
The Difference

AbstractThe dopant incorporation efficiencies of SiC bulk single crystals were investigated by the measurement of optical absorption coefficients and chemical analysis by Glow Discharge Mass Spectroscopy. The SiC crystals were grown on the seed with the {1100} face by a sublimation method. The grown ingot consisted of approximately three parts, which were the regions grown with the {1100} face (I), the {110n} face (II) and the {110n} face (III) as a growing front. The nitrogen concentrations in these parts were in the order of II>I>III. The wafers exhibited the color distributions in the c-plane due to the difference of the growing facet. The nitrogen incorporation efficiencies were discussed in terms of atomic structure on the surface. The aluminum concentration in the crystal grown on a {1100}-faced seed was in the medium between those in crystals grown on Si-face and C-face. On the other hand, the boron concentration was similar to that of Si-face grown crystal, and higher than that of C-face grown crystal.

Temperature-Dependent Logic Failure in a GaAs Power Amplifier-Duplexer Module Caused by a Subtle Parasitic Schottky Diode

2014 ◽  
Author(s):  
Rose Emergo ◽  
Steve Brockett ◽  
Pat Hamilton
Keyword(s):  
Power Amplifier ◽  
Schottky Diode ◽  
Production Test ◽  
Temperature Dependent ◽  
Cold Temperatures ◽  
Collector Junction ◽  
Power Mode ◽  
The Difference ◽  
Base Contact ◽  
Single Power

Abstract A single power amplifier-duplexer device was submitted by a customer for analysis. The device was initially considered passing when tested against the production test. However, further electrical testing suggested that the device was stuck in a single power mode for a particular frequency band at cold temperatures only. This paper outlines the systematic isolation of a parasitic Schottky diode formed by a base contactcollector punch through process defect that pulled down the input of a NOR gate leading to the incorrect logic state. Note that this parasitic Schottky diode is parallel to the basecollector junction. It was observed that the logic failure only manifested at colder temperatures because the base contact only slightly diffused into the collector layer. Since the difference in the turn-on voltages between the base-collector junction and the parasitic Schottky diode increases with decreasing temperature, the effect of the parasitic diode is only noticeable at lower temperatures.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

The interaction of bovine milk caseins with the detergent sodium dodecyl sulphate. II. The effect of detergent binding on spectral properties of caseins

1970 ◽  
Vol 37 (2) ◽  
pp. 259-267 ◽  
Author(s):  
G. C. Cheeseman ◽  
Dorothy J. Knight
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Bovine Milk ◽  
Difference Spectrum ◽  
Temperature Dependent ◽  
Difference Spectra ◽  
Negative Change ◽  
Tryptophan Residues ◽  
Hydrophobic Binding ◽  
The Difference

SummaryThe dissociation of casein aggregates by the detergent sodium dodecyl sulphate (SDS) gave rise to difference spectra and these spectra were characteristic for each of the different types of casein. Increase in absorption by the chromophore groups, tyrosine and tryptophan, when αs1- and β-casein aggregates were dissociated indicated binding of the detergent at regions of the molecule containing these residues. A decrease in absorption when κ-casein was dissociated indicated that the tyrosine and tryptophan residues were not in the region of the molecule to which the detergent was bound and that in the κ-casein aggregate these residues were in a more hydrophobic environment. Peaks on the difference spectra were obtained at 280 and 288 nm for αs1-casein and 284 and 291 nm for β-casein and troughs at 278 and 286 nm for κ-casein. The difference spectrum reached a maximum value when the αsl- and β-casein aggregates were dissociated and the further binding of SDS did not alter this value. The large negative change in the difference spectrum of κ-casein did not occur until after most of the aggregates were dissociated and did not reach a maximum until binding with SDS was complete. The value obtained for ΔOD was found to be temperature-dependent for β-casein-SDS interaction, but not for αs1- and κ-casein. Changes in spectra were also observed when αs1- and κ-casein interacted to form aggregates. The data obtained confirmed the importance of hydrophobic binding in casein aggregate formation and indicated the possible involvement of tyrosine and tryptophan residues in this binding.

Theory of ultrasonic attenuation in one and two dimensional metals

1976 ◽  
Vol 54 (14) ◽  
pp. 1454-1460 ◽  
Author(s):  
T. Tiedje ◽  
R. R. Haering
Keyword(s):  
Ultrasonic Attenuation ◽  
Three Dimensional ◽  
Electronic Systems ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
One Dimensional ◽  
The Difference

The theory of ultrasonic attenuation in metals is extended so that it applies to quasi one and two dimensional electronic systems. It is shown that the attenuation in such systems differs significantly from the well-known results for three dimensional systems. The difference is particularly marked for one dimensional systems, for which the attenuation is shown to be strongly temperature dependent.

The mechanism of work-hardening and slip-band formation

1957 ◽  
Vol 242 (1229) ◽  
pp. 147-159 ◽  
Keyword(s):  
Single Crystals ◽  
Slip Band ◽  
Work Hardening ◽  
Stage I ◽  
Polycrystalline Materials ◽  
Temperature Dependent ◽  
Band Formation ◽  
Slip Bands ◽  
Three Stages ◽  
The Difference

A summary is given of some present ideas on the mechanism of work-hardening of single crystals and polycrystalline materials. In particular, the difference is stressed between the three stages of hardening: stage I, or easy glide; stage II, the region of rapid hardening accompanied by short slip lines; and stage III, the region of slow or parabolic hardening which is temperature-dependent and in which long slip bands are formed.

Catecholamine elevation in iron deficiency

1979 ◽  
Vol 237 (5) ◽  
pp. R297-R300 ◽  
Author(s):  
E. Dillmann ◽  
D. G. Johnson ◽  
J. Martin ◽  
B. Mackler ◽  
C. Finch
Keyword(s):  
Body Temperature ◽  
Body Temperatures ◽  
Temperature Dependent ◽  
Urinary Catecholamines ◽  
Threefold Increase ◽  
Iron Deficient ◽  
Catecholamine Response ◽  
The Difference ◽  
And Control ◽  
Maintain Body Temperature

Iron-deficient rats have increased blood and urinary catecholamines regardless of whether anemia is or is not present. The catecholamine response in both iron-deficient and control animals is largely temperature dependent, showing little difference at the isothermic temperature of 30 degrees C but a two- to threefold increase in iron-deficient animals over controls at lower temperatures. The iron-deficient rat is unable to maintain body temperature at 4 degrees C and this is independent of anemia or of food intake. When animals are run on the treadmill for 4 h, body temperatures increase but the difference observed at 4 degrees C between iron-deficient and control animals persists. The underlying abnormality in temperature regulation and in catecholamine response disappeared after 6 days of iron therapy.

scholarly journals Comparison of Nitrogen Adsorption and Mercury Penetration Results: II. Pore size Distributions Calculated from Type IV Isotherm Data

1988 ◽  
Vol 5 (3) ◽  
pp. 168-190 ◽  
Author(s):  
Bruce D. Adkins ◽  
Burtron H. Davis
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Nitrogen Adsorption ◽  
Type Iv ◽  
Pore Size Distributions ◽  
Nitrogen Desorption ◽  
The Difference ◽  
Penetration Data ◽  
Packed Sphere

The pore distributions calculated from nitrogen desorption and from mercury penetration data are similar for the four materials utilized in this study. While there are small differences in the distributions calculated using different models (Cohan. Foster or Broekhoff-deBoer) with nitrogen adsorption or desorption isotherm data, all three show reasonable agreement with distributions calculated from mercury penetration data. Frequently practical catalysts have such a broad pore size distribution that neither method alone is adequate to measure the total pore size range. The present results suggest a direct comparison, without recourse to a scaling factor, is appropriate when comparing results from the two methods even though the pore size distribution maximum may vary by at least 50% depending upon the model chosen for the calculation. Better agreement may be obtained between the two experimental techniques by adjusting either the nitrogen adsorption data using a packed sphere model or the mercury penetration data by an earlier reported correction ratio. The difference between the two methods becomes less than 20% when a correction procedure is used; however, further studies are needed to define the range of material shaped that these procedures are applicable to.

THE CRYSTALLINE FORM OF 1,3,5,7-TETRANITRO-1,3,5,7-TETRAZACYCLOOCTANE (HMX)

1962 ◽  
Vol 40 (12) ◽  
pp. 2278-2299 ◽  
Author(s):  
M. Bedard ◽  
H. Huber ◽  
J. L. Myers ◽  
George F Wright
Keyword(s):  
Electrical Property ◽  
Absorption Spectra ◽  
Crystalline Form ◽  
Dielectric Constants ◽  
Temperature Dependent ◽  
Crystal Forms ◽  
The Difference ◽  
Absorption Frequencies

The absorption spectra and dielectric constants of three of the four polymorphs of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) have been examined. The difference in absorption frequencies shows that these crystal forms are more distinctive than are most polymorphs. Likewise the distortion polarizations of HMX-I, -II, and -III are markedly different whereas identical distortion polarizations have been found among typical polymorphic systems. The distortion polarizations of HMX-II and -III also are unique because they are appreciably temperature dependent, although this electrical property ought to be temperature independent. Because of these unique behaviors we have postulated that the so-called HMX polymorphs actually are lattice-caged conformational modifications.

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