Complete Characterization of AlxGa1-xN/InxGa1-xN/GaN Devices by Sims

1997 ◽  
Vol 468 ◽  
Author(s):  
C. Huang ◽  
S. Mitha ◽  
J. W. Erickson ◽  
R. Clark-Phelps ◽  
Jack Sheng ◽  
...  
Keyword(s):  
Growth Rate ◽  
Reverse Engineering ◽  
Failure Analysis ◽  
Concurrent Engineering ◽  
Alloy Composition ◽  
Electronic Devices ◽  
Complete Characterization ◽  
Sims Analysis

ABSTRACTSIMS analysis was applied to the characterization of GaN, AlGaN/GaN and InGaN/GaN grown by MOCVD. Such characterization enables the control of purity and doping, and the determination of growth rate and alloy composition. The analysis can be performed on finished optoelectronic and electronic devices and this makes SIMS technique a powerful tool for failure analysis, reverse engineering, and concurrent engineering.

Photoluminescence Excitation Spectroscopy of Carbon-Doped Gallium Nitride

1998 ◽  
Vol 537 ◽  
Author(s):  
E. E. Reuter ◽  
R. Zhang ◽  
T. F. Kuech ◽  
S. G. Bishop
Keyword(s):  
Complete Characterization ◽  
Photoluminescence Excitation ◽  
Yellow Luminescence ◽  
Broad Excitation Band ◽  
Carbon Doped ◽  
Sapphire Substrates ◽  
Red Luminescence ◽  
Unusual Shape

AbstractWe have done a comparative study of carbon-doped GaN and undoped GaN utilizing photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies in order to investigate deep levels involved in yellow luminescence (YL) and red luminescence (RL). When the GaN was excited by above-bandgap light, red luminescence (RL) centered at 1.82 eV was the dominant below-gap PL from undoped GaN, but carbon-doped GaN below-gap PL was dominated by yellow luminescence (YL) centered at 2.2 eV. When exciting PL below the band-gap with 2.4 eV light, undoped GaN had a RL peak centered at 1.5 eV and carbon-doped GaN had a RL peak centered at 1.65 eV. PLE spectra of carbon-doped GaN, detecting at 1.56 eV, exhibited a strong, broad excitation band extending from about 2.1 to 2.8 eV with an unusual shape that may be due to two or more overlapping excitation bands. This RL PLE band was not observed in undoped GaN. We also demonstrate that PL spectra excited by below gap light in GaN films on sapphire substrates are readily contaminated by 1.6-1.8 eV and 2.1-2.5 eV chromium-related emission from the substrate. A complete characterization of the Cr emission and excitation bands for sapphire substrates enables the determination of the excitation and detection wavelengths required to obtain GaN PL and PLE spectra that are free of contributions from substrate emission.

Sensor Placement for Angular Velocity Determination

2005 ◽  
Vol 128 (3) ◽  
pp. 543-547 ◽  
Author(s):  
Guy M. Genin ◽  
Joseph Genin
Keyword(s):  
Angular Velocity ◽  
Rigid Body ◽  
Velocity Vector ◽  
Constraint Equation ◽  
Complete Characterization ◽  
Angular Velocity Vector ◽  
Algebraic Constraint ◽  
Transducer Placement

Velocity transducer placement to uniquely determine the angular velocity of a rigid body is investigated. The angular velocity of a rigid body can be determined with no fewer than five properly placed velocity transducers, if no other types of sensors are present and no algebraic constraint equation involving the angular velocity vector can be written. Complete characterization of the velocity of a rigid body requires six transducers. Choice of transducer placement and orientation requires care, as suboptimal transducer placement can result in data from which the determination of a unique angular velocity vector is impossible. Conditions for successful transducer placement are established, and two examples of adequate transducer placement are presented: an Earth-penetrating projectile, and a bioengineering device for the measurement of head motion.

scholarly journals Isometric and Closed-Range Composition Operators between Bloch-Type Spaces

2011 ◽  
Vol 2011 ◽  
pp. 1-15
Author(s):  
Nina Zorboska
Keyword(s):  
Holomorphic Function ◽  
Composition Operators ◽  
Function Spaces ◽  
Complete Characterization ◽  
Closed Range ◽  
Different Types ◽  
Type Spaces ◽  
Range Determination

We present an overview of the known results describing the isometric and closed-range composition operators on different types of holomorphic function spaces. We add new results and give a complete characterization of the isometric univalently induced composition operators acting between Bloch-type spaces. We also add few results on the closed-range determination of composition operators on Bloch-type spaces and present the problems that are still open.

Simultaneous Determination of E, G and ν of Soft Hydrogels Using Theory of Elasticity

2009 ◽  
Author(s):  
Uday Chippada ◽  
Xue Jiang ◽  
Lulu Li ◽  
Rene Schloss ◽  
Bernard Yurke ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Theory Of Elasticity ◽  
Complete Characterization ◽  
Poisson's Ratio ◽  
Force Microscopy ◽  
Cellular Processes ◽  
Atomic Force ◽  
Significant Research

Hydrogels have been used as substrates by many researchers in the study of cellular processes. The mechanical properties of these gels play a significant role in the growth of the cells. Significant research using several methods like compression, indentation, atomic force microscopy and manipulation of beads has been performed in the past to characterize the stiffness of these substrates. However, most of the methods employed assume the gel to be incompressible, with a Poisson’s ratio of 0.5. However, Poisson’s ratio can differ from 0.5. Hence, a more complete characterization of the elastic properties of hydrogels requires that one experimentally obtain the value of at least two of the three quantities: Poisson’s ratio, shear modulus, and elastic modulus.

scholarly journals Quantitative Analysis of Portland Cement Clinker with Rietveld Refinement: Implications of the Amorphous Matter

2021 ◽  
Vol 5 (1) ◽  
pp. 75
Author(s):  
Georgios E. Christidis ◽  
Maria Dimitriadi ◽  
George Triantafyllou ◽  
Christos Tsoumeleas
Keyword(s):  
Portland Cement ◽  
Rietveld Method ◽  
Internal Standard ◽  
Complete Characterization ◽  
Cement Clinker ◽  
White Cement ◽  
Portland Cement Clinker ◽  
Amorphous Matter

Six ordinary Portland cement (OPC) clinkers and one white cement clinker were analyzed with the Rietveld method, using ZnO internal standard (IC), to determine the presence of amorphous matter (AM). All clinkers contain abundant AM and have lower silicate phase contents when compared with the same clinkers analyzed without IC, whereas the abundances of the aluminate and ferrate phases were not affected by AM. The white cement clinker had the highest AM content. Determination of AM is important for complete characterization of the OPC clinker and might contribute to a better understanding of the mechanical properties of the clinker.

Reflection electron microscopy of triangular quantum wells

1993 ◽  
Vol 51 ◽  
pp. 828-829
Author(s):  
M. Gajdardziska-Josifovska
Keyword(s):  
Electron Microscopy ◽  
Quantum Wells ◽  
Alloy Composition ◽  
Electronic Devices ◽  
Thin Layers ◽  
Compositional Gradient ◽  
Digital Alloy ◽  
Nominal Thickness ◽  
Reflection Electron Microscopy

Asymmetric triangular quantum wells (ATQW) have recently been developed to improve the absorption and emission characteristics of opto-electronic devices. A triangular compositional gradient is produced during epitaxial growth of AlxGa1-xAs on GaAs by either continuous variation of x or by alternate deposition of thin layers of the two compounds where the ratio of the layer thickness produces an average alloy composition. The knowledge of the compositional profile of the actual ATQW, as derived from HREM, has proven essential for the description of the photo-emission properties of the device. Recently, the technique of reflection electron microscopy has also been applied to multiple rectangular quantum wells of GaAs/AlxGa1-xAs with the encouraging result that layers with 1% Al can be distinguished from the GaAs layers. In this work we investigate the applicability of REM to characterization of ATQW.Triangular quantum wells were grown by MBE, employing the digital alloy method. Fig. 1 shows a schematic representation of the nominal thickness and composition of the studied ATQW.

scholarly journals Theory and experiments of liquid phase epitaxial growth Part 1

2018 ◽  
Vol 39 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Nikolay S. Peev
Keyword(s):  
Growth Rate ◽  
Liquid Phase ◽  
Epitaxial Growth ◽  
Normal Growth ◽  
Initial Growth ◽  
Liquid Phase Epitaxial ◽  
Liquid Phase Epitaxial Growth ◽  
Theory And Experiments

Abstract Characterization of the liquid phase epitaxial growth is in the scope of the present paper. The determination of the main parameters of the process such as the stationary growth rate, the time constant, the stationary supercooling, the kinetic coefficient, the initial growth rate, the crystallization mechanism are under consideration. Pursuing this aim a differential equation has been obtained which allows obtaining the dependences of the supersaturation, the growth rate and the growth layer thickness on the duration of growth. These dependences allow the determination of the above mentioned process parameters. Two mechanisms of crystallization are considered - the normal growth and the growth assisted by the screw dislocations. The two dimensional nuclei growth has not been considered because an analytical solution of the equation was not possible. Some of the theoretical contentions are confirmed by the experiments. Using the obtained values of the parameters dependences are defined. Good agreement between theory and experimental results is observed.

scholarly journals Polyphenols content of selected medical plants and food supplements present at Bulgarian market

Pharmacia ◽  
2021 ◽  
Vol 68 (4) ◽  
pp. 819-826
Author(s):  
Petya Koleva ◽  
Silvia Tsanova-Savova ◽  
Slaveyka Paneva ◽  
Stefan Velikov ◽  
Zaharina Savova
Keyword(s):  
Medicinal Plants ◽  
Hplc Method ◽  
Complete Characterization ◽  
Food Supplements ◽  
Mentha Piperita ◽  
Total Phenolic ◽  
Polyphenolic Composition ◽  
Medical Plants

Background: Medicinal plants are a rich source of antioxidant polyphenols and in particular flavonoids. Materials and methods: In the present study 5 Bulgarian medical plants and 5 food supplements, present at the Bulgarian market, are analyzed for their Total phenolic, Total flavonoids and selected individual flavonoids content. A HPLC method was developed and validated for simultaneous determination of (+)-catechin, (-)-epicatechin and rutin in plant and supplements, using PDA detection. Results: The results show that polyphenols in the selected food supplements are lower than those of the medical plants analyzed. Mentha piperita and Melissa officinalis have the highest polyphenols content (67.38 and 65.17 mg GAE/g; 54.59 and 57.76 mg RE/g respectively). Rutin was detected in all samples analyzed, reaching highest levels in Mentha piperita (7332.5 µg/g), followed by fruits of Sambucus nigra (2818.7 µg/g). Conclusion: The results of the study are a practical contribution to a more complete characterization of the polyphenolic composition in Bulgarian medicinal plants.

scholarly journals Elastic Properties of a Polyimide Film Determined by Brillouin Scattering and Mechanical Techniques

1993 ◽  
Vol 308 ◽  
Author(s):  
R. Sai Kumar ◽  
Ivan K. Schuller ◽  
Sudha S. Kumar ◽  
A. Fartash ◽  
M. Grimsditch
Keyword(s):  
Elastic Properties ◽  
Brillouin Scattering ◽  
Direct Determination ◽  
Polyimide Film ◽  
Complete Characterization ◽  
Elastic Behavior ◽  
Complete Determination ◽  
Vibrating Membrane

ABSTRACTWe discuss here the complete determination of the elastic properties of a polyimide film using two experimental techniques. One technique employs the polymer film as a vibrating membrane and allows a direct determination of the ’macroscopic’ biaxial modulus. Brillouin scattering, which measures the elastic properties on a ∼ 100 μ scale, allows for a complete characterization of the elastic behavior. The results obtained by the two techniques are in agreement within the reported error bars.

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