209 research outputs found
Perlin to lecture on history of wood
No full textJohn Perlin, author of "A Forest Journey: The Role of Wood in the Development of Civilization," will lecture on "The Role of Wood in World History," March 15 at 3 p.m., in the Fralin Biotechnology Center Auditorium at Virginia Tech's Blacksburg Campus
Defect-related degradation in InGaN laser diodes
No full textThe paper describes an extensive analysis of the degradation of InGaN-based laser diodes submitted to constant stress at room temperature. The analysis is based on electrical and optical characterizations, deep level transient spectroscopy (DLTS) and capacitance measurement as function of temperature. The results obtained during the stress demonstrate: (i) the presence of a diffusion process in the first hours of stress; (ii) an increase in the junction capacitance, and so of the free charge, with the aging of the device; (iii) the presence of shallow traps, in particular an acceptor like trap, associated with line defects
Defect generation during constant current stress of InGaN laser diodes
No full textWe analyzed a group of InGaN-based laser diodes, with a peak wavelength around 418 nm, carrying out stress at a fixed current and room temperature. Electrical and optical characteristics were continuously monitored during the stress, and capacitance measurements and DLTS analysis were carried out in order to investigate the possible presence of defects within or around the active region. We observed the presence of a diffusion process in the first hours of stress. Capacitance-temperature measurements and DLTS allow us to identify shallow traps generated during the stress, in particular the presence of an acceptor-like trap, associated with line defects
John Perlin, renowned expert on the role of wood in civilization, to present here Dec. 6
No full textJohn Perlin, author of the highly acclaimed A Forest Journey: The Role of Wood in the Development of Civilization, will make his second visit to Virginia Tech to present a College of Natural Resources seminar titled"A Forest Journey: The Story of Wood and Civilization," on Wednesday, Dec. 6 at 2 p.m. in Fralin Auditorium
Metodologie etymologii
No full textPod pojęciem etymologii, czyli pochodzenia wyrazu, rozumie się albo historyczną ciągłość między jego końcową dla nas postacią a jej najbliższym zaświadczonym historycznym poprzednikiem, albo relację między końcową postacią wyrazu a jej prehistoryczną zrekonstruowaną formą lub kolejnymi formami z następujących po sobie faz rozwoju języka. W każdym wypadku poprzednik badanego wyrazu może być określony nazwą etymonu. Autor rozważa różne metodologie związane z przejściem od etymonu do wyrazu badanego posługując się licznymi przykładami.Udostępnienie publikacji Wydawnictwa Uniwersytetu Łódzkiego finansowane w ramach projektu „Doskonałość naukowa kluczem do doskonałości kształcenia”. Projekt realizowany jest ze środków Europejskiego Funduszu Społecznego w ramach Programu Operacyjnego Wiedza Edukacja Rozwój; nr umowy: POWER.03.05.00-00-Z092/17-00
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Advanced introduction to mental health law /
No full text"Elgar Advanced Introductions are stimulating and thoughtful introductions to major fields in the social sciences, business and law, expertly written by the world's leading scholars. Designed to be accessible yet rigorous, they offer concise and lucid surveys of the substantive and policy issues associated with discrete subject areas. Written by esteemed legal scholar Michael L. Perlin, this indispensable Advanced Introduction examines the long-standing but ever-dynamic relationship between law and mental health. The author discusses and contextualises how the law, primarily in the United States but also in other countries, treats mental health, intellectual disabilities, and mental incapacity, giving examples of how issues such as the rights of patients, the death penalty and the insanity defense permeate constitutional, civil, and criminal matters, and indeed the general practice of law. Key features include: unpacks key US Supreme Court decisions to focus on the issues that have been most significant in the development of the field; explains the distortion of this area of law by biased and stereotypical social attitudes including sanism; examines lesser-known cases that illuminate judicial attitudes, helping readers to better understand likely future developments in mental health law. Offering an insightful introduction to this field, the Advanced Introduction to Mental Health Law is an invaluable resource for students and newly qualified lawyers, and will appeal not only to those looking to understand the law in the United States, but how this contributes to the development of the field as a whole"-
Polarization - Doped InGaN LEDs and Laser Diodes for Broad Temperature Range Operation
No full textThis work reports on the possibility of sustaining a stable operation of polarization-doped InGaN light emitters over a particularly broad temperature range. We obtained efficient emission from InGaN light-emitting diodes between 20 K and 295 K and from laser diodes between 77 K and 295 K under continuous wave operation. The main part of the p-type layers was fabricated from composition-graded AlGaN. To optimize injection efficiency and improve contact resistance, we introduced thin Mg-doped layers of GaN (subcontact) and AlGaN (electron blocking layer in the case of laser diodes). In the case of LEDs, the optical emission efficiency at low temperatures seems to be limited by electron overshooting through the quantum wells. For laser diodes, a limiting factor is the freeze-out of the magnesium-doped electron blocking layer for temperatures below 160 K. The GaN:Mg subcontact layer works satisfyingly even at the lowest operating temperature (20 K).The names of the individual files correspond to the numbering of the figures in the paper Muhammed Aktas ,Szymon Grzanka, Łucja Marona, Jakub Goss, Grzegorz Staszczak, Anna Kafar and Piotr Perlin; Polarization-Doped InGaN LEDs and Laser Diodes for Broad Temperature Range Operation - https://doi.org/10.3390/ma17184502Files included in this collection:Figure 1. Structure of LED (a) and laser (b) with polarization-doped p-cladding layer.Figure 2. Energy - band diagram (@ 3.5 V) and refractive index of the laser structure (a) zoomed at an active area (b) and EBL area (c). The regions corresponding to (b,c) are marked by green dashed rectangles in the picture (a). Vertical axes are identical for all graphs.Figure 3. Polarization doped LED’s I–V measurement (a); EL measurement at 100 mA (b).Figure 4. Polarization-doped laser structure’s L-I-V measurement in pulse mode (a). Threshold currents and slope efficiencies in pulse mode (b).Figure 5. Temperature dependence pulse mode EL spectra of polarization-doped laser structure at low current (a), high currents (b), and their peak wavelength (c).Figure 6. L-I-V measurement in CW mode of the polarization-doped laser structure (a). Threshold currents and slope efficiencies in CW mode (b), with pulse mode results for reference.Figure 7. Temperature dependence EL spectra of polarization-doped laser structure at 1 mA (a), above the threshold current (b), and their peak wavelength (c) in CW mode.Figure 8. Thermal resistance of polarization doping laser structure.</p
Palladium-Based Contacts on p-GaN and Their Application in Laser Diodes
No full textPalladium-Based Contacts on p-GaN and Their Application in Laser Diodes. Iryna Levchenko, Serhii Kryvyi, Eliana Kamińska, Szymon Grzanka, Ewa Grzanka, Łucja Marona and Piotr Perlin. Materials 2023, 16(19), 6568; https://doi.org/10.3390/ma16196568In this paper, we investigate the effect of Pd thickness and heat treatment on Pd/Ni/Au/p-GaN metal contacts. The as-deposited samples exhibit a smooth morphology and non-linear I–V characteristics. Heat treatment in a N2 atmosphere leads to degradation of the contact microstructure, resulting in diffusion of Ga, void formation on the interface and mixing of metals. Annealing in a mixture of N2 and O2 improves adhesion and reduces contact resistance. However, this process also induces GaN decomposition and species mixing. The mixing of metal–Ga and metal–metal remains unaffected by the method of thermal treatment but depends on gas composition for thin Pd contacts. To achieve low-resistance contacts (≈1 × 10−4 Ω cm2), we found that increasing the Pd thickness and using N2 + O2 as the annealing environment are effective measures. Nevertheless, the degradation effect of the annealed contact microstructure in the form of the void generation becomes evident as the thickness of Pd increases. Laser diodes (LDs) with optimized palladium-based contacts operate at a voltage of 4.1 V and a current density of 3.3 kA/cm².The names of files correspond to the nnumbering of the figures in the paper. It includes:Figure 1. SEM image of the surface of as-deposited Pd/Ni/Au (10/10/30 nm) metallization on p-GaN. The provided layer thicknesses correspond to the settings used for evaporation.Figure 2. XRD profile for investigated Pd/Ni/Au (10/10/30 nm) as-grown sample. The powder diffraction patterns with corresponding reference numbers in PDF-2 and ICSD databases are shown.Figure 3. HR-STEM image (a) of as-deposited Pd/Ni/Au (10/10/30 nm) together with the interplanar distance for the indicated lattice planes (b) determined from measurements by FFT. ZA—zone axis.Figure 4. Crystallographic orientation of GaN (a) and metal layers (b,c).Figure 5. I−V plots for the as-deposited and annealed contacts.Figure 6. SEM (a) and STEM (b) images of Pd/Ni/Au (10/10/30 nm) annealed in RTA in N2 flow at 530 °C.Figure 7. EDX elemental mapping data for p-GaN/Pd/Ni/Au (10/10/30 nm) contact annealed in N2 (a–f). Schematic view of the contact composition (g).Figure 8. XRD profiles for investigated as-grown sample and after annealing in N2.Figure 9. SEM data of Pd/Ni/Au (10/10/30 nm) annealed in RTA in N2 + O2 flow at 530 °C.Figure 10. EDX elemental mapping data (a–f) and schematic view (g) of Pd/Ni/Au (10/10/30 nm) annealed in RTA in N2 + O2 flow at 530 °C.Figure 11. XRD profiles for investigated as-grown sample after annealing by RTA in N2 + O2 flow.Figure 12. SEM data of Pd/Ni/Au (90/10/30 nm) after annealing by (a) oven in N2 + O2 + H2O and (b) RTA in N2 + O2.Figure 13. EDX maps of Pd/Ni/Au (90/10/30 nm) after annealing by oven in N2 + O2 + H2O (a–f) and scheme of Pd/Ni/Au (90/10/30 nm) composition (g).Figure 14. XRD profiles for investigated as-grown sample and after annealing.</p
Pros and Cons of (NH4)2S Solution Treatment of p-GaN/Metallization Interface: Perspectives for Laser Diode
No full textThe impact of wet treatment using an (NH4)2S-alcohol solution on the interface state of the p-GaN/Ni/Au/Pt contact system and laser diode processing was investigated. Sulfur wet cleaning resulted in reduced surface roughness and contact resistivity. The lowest specific contact resistance (ρc < 1 × 10−4 Ω·cm2) was achieved with samples treated with an (NH4)2S-isopropanol solution, whereas the highest resistivity (ρc = 3.3 × 10−4 Ω·cm2) and surface roughness (Ra = 16 nm) were observed in samples prepared by standard methods. Annealing the contact system in an N2 + O2 + H2O atmosphere caused degradation through species inter-diffusion and metal-metal solid solution formation, irrespective of the preparation method. Standard prepared substrates developed a thin GaN-Au intermediate layer at the interface after heat treatment. Enhanced adhesion and the absence of GaN decomposition were observed in samples additionally cleaned with the (NH4)2S-solvent solution. Complete oxidation of nickel to NiO was observed in samples that underwent additional sulfur solution treatment. The intensity of metal species mixing and nickel oxidation was influenced by the metal diffusion rate and was affected by the initial state of the GaN substrate obtained through different wet treatment methods.The names of files corespond to the numbering of the figures in the paper Iryna Levchenko,Serhii Kryvyi,Eliana Kamińska,Julita Smalc-Koziorowska,Szymon Grzanka,Jacek Kacperski,Grzegorz Nowak,Sławomir Kret,Łucja Marona and Piotr Perlin. Pros and Cons of (NH4)2S Solution Treatment of p-GaN/Metallization Interface: Perspectives for Laser Diode. https://doi.org/10.3390/ma17184520.Files include next collection:Figure 1. AFM overview scan of p-GaN surface after (a) standard cleaning and (b) standard and (NH4)2S-t-(CH3)3COH treatment.Figure 2. AFM maps (a–d) and SEM images (e–h) of the surface of annealed p-GaN/Ni/Au/Pt contact system.Figure 3. c-AFM current maps (a–d) and AFM images (e–h) of annealed p-GaN/Ni/Au/Pt.Figure 4. STEM image of annealed p-GaN/Ni/Au/Pt, after standard preparation (a) and with additional treatment by (NH4)2S solution (b).Figure 5. STEM image (a) and EDX maps of the element propagation (b–f) for the annealed p-GaN/Ni/Au/Pt system with treatment in (NH4)2S-based solution.Figure 6. Schematic view on evolution of the annealed p-GaN/Ni/Au/Pt system with treatment in (NH4)2S-based solution (grey circles represent the voids).Figure 7. STEM image (a) and EDX maps of the element dispersion (b–f) for the annealed p-GaN/Ni/Au/Pt system after standard cleaning.Figure 8. Schematic view on evolution of the annealed p-GaN/Ni/Au/Pt system after standard cleaning.</p
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