Scanning electron microscopy cathodoluminescence studies of piezoelectric fields in an InGaN∕GaN quantum-well light-emitting diode

2005 ◽  
Vol 86 (8) ◽  
pp. 082108 ◽  
Author(s):  
K. L. Bunker ◽  
R. Garcia ◽  
P. E. Russell
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Quantum Well ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
Piezoelectric Fields ◽  
Scanning Electron

Scanning Electron Microscopy Cathodoluminescence Studies of Piezoelectric Fields in an InGaN Multiple Quantum Well Light Emitting Diode

2004 ◽  
Vol 831 ◽  
Author(s):  
Kristin L. Bunker ◽  
Roberto Garcia ◽  
Phillip E. Russell
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Quantum Well ◽  
Light Emitting Diode ◽  
Multiple Quantum Well ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Piezoelectric Field ◽  
Piezoelectric Fields ◽  
Scanning Electron

ABSTRACTScanning Electron Microscopy (SEM)-based Cathodoluminescence (CL) experiments were used to study the influence of piezoelectric fields on the optical and electrical properties of a commercial InGaN-based Multiple Quantum Well (MQW) Light Emitting Diode (LED). The existence and direction of a piezoelectric field in the InGaN-based LED was determined with voltage dependent SEM-CL experiments. The CL emission peak showed a blueshift followed by a redshift with increasing reverse bias due to the full compensation of the piezoelectric field. It was determined that the piezoelectric field points in the [000–1] direction and the magnitude was estimated to be approximately 1.0±0.2 MV/cm. SEM-CL carrier generation density variation and electroluminescence experiments were used to confirm the existence of a piezoelectric field in the InGaN-based MQW LED.

Physical–mechanical evaluation of a microhybrid and a nanofilled composite light activated by quartz-halogen tungsten and light-emitting diode

2018 ◽  
Vol 53 (7) ◽  
pp. 981-990
Author(s):  
Fernanda P Ritto ◽  
Eduardo Moreira da Silva ◽  
Hélio Rodrigues Sampaio-Filho ◽  
Raimundo A Lacerda ◽  
Márcio AP Borges ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Nuclear Magnetic Resonance ◽  
Light Emitting Diode ◽  
Degree Of Conversion ◽  
Dental Composite ◽  
Polymerization Shrinkage ◽  
Light Emitting ◽  
Scanning Electron

The aim of this study was to characterize organic and disperse phase of a microhybrid (Mh – Filtek Z250) and a nanofilled (Nf – Filtek Z350) dental composite and analyze the influence of two LCUs (QHT-quartz-halogen tungsten and LED – light-emitting diode) on its physical–mechanical properties (degree of conversion, polymerization shrinkage, Vickers hardness and diametral tensile strength). Surface morphology was studied by scanning electron microscopy. The disperse phase content was measured using thermogravimetric analysis (TGA) and the organic fractions were qualitatively analyzed by nuclear magnetic resonance spectroscopy. Physical–mechanical properties were analyzed varying dental composite and LCU: Mh-QHT, Nf-QHT, Mh-LED and Nf-LED. The degree of conversion was evaluated using Raman spectrophotometry and polymerization shrinkage was measured by water picnometry. Mechanical behavior was analyzed by Vickers microhardness and diametral tensile testing. Scanning electron microscopy analysis showed similar microstructure of the materials mainly composed with different-sized particles dispersed within methacrylate matrix. Thermogravimetric analysis shows 80.13% of inorganic fraction for microhybrid composite and 75.29% for nanofilled. Nuclear magnetic resonance analysis showed similar organic structure for composites and did not show the presence of the monomer TEGDMA. Different light sources did not influence the tested properties, but considering different composites, nanofilled showed the highest degree of conversion (Gr 2:77%, Gr 4: 79.4%). The study shows that when the optimum radiant exposure (24 J/cm2) was used for polymerization of composites, regardless of the polymerization source, the properties of these resin materials showed satisfactory and similar results in relation to the conversion of polymers, polymerization shrinkage and mechanical behavior.

scholarly journals Blue-emission tuning of perovskite light-emitting diodes with a simple TPBi surface treatment

2021 ◽  
Author(s):  
Xiaokun Huang ◽  
Rainer Bäuerle ◽  
Jean-Nicolas Tisserant ◽  
Wolfgang Kowalsky ◽  
Robert Lovrinčić ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Treatment ◽  
Light Emitting Diodes ◽  
Blue Emission ◽  
Visible Spectrum ◽  
Simple Approach ◽  
Perovskite Layer ◽  
Light Emitting ◽  
Scanning Electron

AbstractWe demonstrate a simple approach for blue-emission tuning of quasi-2D perovskite light-emitting diodes through a surface treatment of 2,2′,2″-(1,3,5-benzinetriyl)tris(1-phenyl-1H-benzimidazole) (TPBi). By increasing the TPBi concentration, we achieved tunable electroluminescence of the perovskite layer with wavelength shifted from the blue-green (506 nm) to blue (481 nm) regions of the visible spectrum. Fourier-transform infrared spectroscopy, scanning electron microscopy, and UV–Vis absorption spectroscopy were conducted to study the morphological and optoelectronic properties of the films. Our results suggest that the TPBi molecules accumulated on the surface and grain boundaries of the perovskite layer changed the perovskite electronic structure causing the observed blue shifts. Graphic abstract

Fine Structure of Visible Light Emitting Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
Kiyokazu Nakagawa ◽  
Akio Nishida ◽  
Toshikazu Shimada
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Optical Microscopy ◽  
Three Dimensional ◽  
Photoluminescence Spectroscopy ◽  
Porous Si ◽  
Light Emitting ◽  
Si Films ◽  
Scanning Electron

ABSTRACTPorous Si formed by anodization is studied by means of high-resolution scanning electron microscopy, optical microscopy, micro-photoluminescence spectroscopy, high-resolution transmisson electron microscopy, and micro-Raman spectroscopy. Surface morphologies of porous Si films are varied by changing the anodization conditions. High-resolution scanning electron microscopy measurements show that in all these films, porous Si fine structures of visible photoluminescent regions, which are confirmed with optical microscopy and micro-photoluminescence spectroscopy, are composed of particlelike structure of various sizes from several nm to several tens of nm. Transmission electron microscopy shows that these particles are composed of single-crystal Si spheres covered with an oxide layer. The peak of the Raman spectrum from the particlelike structure is shifted to lower energy and is wider than that for bulk Si, possibly due to lattice expansion around large surface fractions. These results suggest that the effective photoluminescence of porous Si is due to three-dimensional carrier confinement in quantum boxes.

Microstructures of Strontium Aluminates and Polystyrene Phosphorescent Composite Films

2010 ◽  
Vol 428-429 ◽  
pp. 544-547 ◽  
Author(s):  
Ye Tang Guo ◽  
Yuan Ming Huang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Composite Films ◽  
Green Light ◽  
Inorganic Materials ◽  
Moisture Resistance ◽  
Information Display ◽  
Light Emitting ◽  
Scanning Electron

Strontium-aluminates-based phosphorescent composite films were prepared by homogeneously distributing the green light emitting phosphors within polystyrene hosts. The composite films have the unique properties of flexibility of the polymers and the long-lasting phosphorescence of the strontium-aluminates-based phosphors. The microstructures of the flexible composite films were characterized with scanning electron microscopy. The results indicated that the organic and inorganic materials can be combined with each other better, and the composite films can be easily rolled but will not generate cracks. Therefore, this composite technology can effectively enhance the moisture resistance of the phosphors and the films can be used in the filed of information display.

Pathogenesis of Human Hair Defects

1974 ◽  
Vol 32 ◽  
pp. 12-13
Author(s):  
P.S. Porter ◽  
T. Aoyagi ◽  
R. Matta
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Human Hair ◽  
Standard Techniques ◽  
Scanning Electron

Using standard techniques of scanning electron microscopy (SEM), over 1000 human hair defects have been studied. In several of the defects, the pathogenesis of the abnormality has been clarified using these techniques. It is the purpose of this paper to present several distinct morphologic abnormalities of hair and to discuss their pathogenesis as elucidated through techniques of scanning electron microscopy.

Ultrastructural Analysis of the Salivary Glands of Gromphadorhina Portentosa (Schaum)

1977 ◽  
Vol 35 ◽  
pp. 638-639
Author(s):  
P.J. Dailey
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Salivary Glands ◽  
Secretory Vesicles ◽  
The Past ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Gromphadorhina Portentosa ◽  
Scanning Electron ◽  
Topographical Relief

The structure of insect salivary glands has been extensively investigated during the past decade; however, none have attempted scanning electron microscopy (SEM) in ultrastructural examinations of these secretory organs. This study correlates fine structure by means of SEM cryofractography with that of thin-sectioned epoxy embedded material observed by means of transmission electron microscopy (TEM).Salivary glands of Gromphadorhina portentosa were excised and immediately submerged in cold (4°C) paraformaldehyde-glutaraldehyde fixative1 for 2 hr, washed and post-fixed in 1 per cent 0s04 in phosphosphate buffer (4°C for 2 hr). After ethanolic dehydration half of the samples were embedded in Epon 812 for TEM and half cryofractured and subsequently critical point dried for SEM. Dried specimens were mounted on aluminum stubs and coated with approximately 150 Å of gold in a cold sputtering apparatus.Figure 1 shows a cryofractured plane through a salivary acinus revealing topographical relief of secretory vesicles.

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