Night Vision Coming Soon To Cell Phones, Eyeglasses

Adapting technology found in flat screen television sets, scientists have created a thin film that converts infrared light into visible light. The technology could give cell phones, eyeglasses and car windshields cheap, lightweight night vision.

"This device can convert any infrared image into a visible image and would weigh no more than a pair of eyeglasses," said Franky So, a scientist at the University of Florida who describes his new night vision technology in a recent article in the journal Advanced Materials that was funded in part by advanced technology powerhouse DARPA.

Most night vision devices today use massive amounts of electricity -- often several thousand volts, according to So -- and heavy, glass lenses that maintain a vacuum to make the night come alive. So's device takes a radically different turn, replacing glass with thin plastic, eliminating the vacuum and using energy-efficient, organic LEDs.

So does this by using technology borrowed from flat screen TVs. Infrared light enters the film and is detected by the first of seven separate layers, which generates a slight electrical charge. Additional electrical energy -- about three to five volts -- amplifies that signal, which is then converted back into visible light.

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://news.discovery.com/tech/night-vision-cell-phone-eyeglasses.html
Leer: [Jn 17:3]

Engineering researchers simplify process to make world's tiniest wires

Clumps of extremely tiny nanowires in this image are captured with the aid of an electron microscope. The clumping pattern, which occurs as a result of surface tension during the manufacturing process, limits the usefulness of the wires, which are viewed as a likely core element of more powerful microelectronics, solar cells, batteries and medical tools.

-- Surface tension isn't a very powerful force, but it matters for small things — water bugs, paint, and, it turns out, nanowires.
Tests of microscope-slide-sized surfaces, each containing trillions of nanowires, showed that the procedure effectively prevents clumping, Ziegler said.

In this image captured with the aid of an electron microscope, nanowires stand straight up as a result of a new process developed by University of Florida chemical engineering researchers. The engineers apply an electrical charge to the nanostructure during the manufacturing process, charging each wire and making it repel its neighbor, counteracting the opposite force induced by the surface tension. The researchers say the process is inexpensive and simple, a step toward making the nanowires a more common constituent of electronics, medical devices and solar cells.
Nanowires have not found wide commercial applications to date, but Ziegler said that as engineers learn how to make and manipulate them, they could underpin far more efficient solar cells and batteries because they provide more surface area and better electrical properties.

"Being able to pack in a higher density of nanowires gives you a much higher surface area, so you start to generate higher energy density," he said.

Ziegler said that biomedical engineers are also interested in using the wires to help deliver drugs to individual cells, or to hinder or encourage individual cell growth. The University of Florida has applied for a patent on the process, he added.

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://www.physorg.com/news198929565.html
Leer: [Jn7:38]

From ZnO colloidal nanostructures to functional nanomaterials

Fabien Grasset
The transparency and versatile chemistry of nanocolloids can be exploited to fabricate novel thin films.
15 August 2007, SPIE Newsroom. DOI: 10.1117/2.1200708.0805

Thin films are material layers ranging from fractions of a nanometer to several micrometers in thickness. They can be deposited onto metal, ceramic, glass, or semiconductor bases. Among the numerous coating techniques available, chemical or physical vapor deposition and sol-gel methods are the most commonly used in industry. Thin films are mainly used for optical coating and electronic device applications. However, the preparation of low cost functional thin films with high transparency and modulated optical properties remains a challenge for laser, photocatalytic, or display panel applications.

For example, for photocatalysis—which is increasingly used in chemical waste degradation—photostable light-harvesting nanoarchitectures are required: these are nanostructures that can be used to absorb light to facilitate chemical reactions, but are nevertheless robust to the radiation. Were they available, and provided that appropriate semiconductor catalysts were selected, charge carriers could be generated by UV or visible radiation to initiate reduction and oxidation reactions with adsorbed reactants, leading to the destruction of pollutants. However, most photocatalysts consist of metal oxides that are only functional in the UV region. The result is a lack of suitable materials with the appropriate band gap for visible absorption and the required stability for practical applications.

A second example is provided by Y2O3:Eu3+, the most widely used red phosphor for field emission display applications. Much attention has been paid to the synthesis and luminescent properties of Eu3+-doped rare-earth orthoborates (REBO3) thin films. This is due to their desirable properties as ideal vacuum UV phosphors, key materials for the development of plasma display panels. For such phosphors, both luminescence efficiency and color purity are required. Unfortunately, as a red phosphor, the intensity of the red emission of REBO3:Eu3+ is often lower than that of the orange, leading to poor chromaticity.

One of the largest application areas of sol-gel chemistry is thin-film preparation. Using this approach, we started to synthesize ZnO colloidal solutions for the preparation of functional thin films. Zinc oxide is a non-toxic semiconductor with a wide bandgap (3.37eV) and a large exciton binding energy. In bulk or nanosized form, it can be used in a wide range of applications such as UV light emitters, spin functional devices, gas sensors, transparent electronics or surface acoustic wave devices. Using high concentrations of the different polymeric nanocolloids shown in Figure 1(a), we were able to prepare various functional nanomaterials: these include the gels shown in Figure 1(c); the nanosized powders shown in Figure 1(f); the functional thin films (oxynitrides or oxides) produced as plates shown in Figure 1(b) and 1(e); and the fibers shown in Figure 1(d). Recently, red-luminescent Eu,Ti-functionalized ZnO or versatile ZnTiON colored thin films were also developed.

Eu,Ti-functionalized ZnO thin films
As part of these studies, we proposed a chemical alternative to rare-earth (RE) oxides using a very simple and efficient route to prepare highly red-luminescent RE-doped thin films: see Figure 1(b) and (e).1 Using a simple doping process, trivalent europium can easily be introduced in the solution and a Ti-functionalized ZnO can then be used as a nanohost. As shown in Figure 1(b), the red fluorescence of this nanomaterial at room temperature is easily observed under illumination from a compact 4W-UV lamp operating at 254nm. We showed that it was possible to activate RE fluorescence in a highly transparent Ti-functionalized ZnO thin film with simple annealing at 400°C for 15 minutes. The five characteristic emission peaks assigned to the 5D0→7FJ transition of Eu3+ (where J = 0, 1, 2, 3, and 4) are observed, with the strongest emission (J =2) at 613nm (Figure 2, insert).

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://spie.org/x15807.xml?ArticleID=x15807
Leer: [Jn6:63]

Stressed Nanomaterials Display Unexpected Movement- Science News

ScienceDaily (Feb. 24, 2010) — Johns Hopkins researchers have discovered that, under the right conditions, newly developed nanocrystalline materials exhibit surprising activity in the tiny spaces between the geometric clusters of atoms called nanocrystals from which they are made.

This finding, detailed recently in the journal Science, is important because these nanomaterials are becoming more ubiquitous in the fabrication of microdevices and integrated circuits. Movement in the atomic realm can affect the mechanical properties of these futuristic materials -- making them more flexible and less brittle -- and may alter the material's lifespan.

"As we make smaller and smaller devices, we've been using more nanocrystalline materials that have much smaller crystallites -- what materials scientists call grains -- and are believed to be much stronger," said Kevin Hemker, professor and chair of Mechanical Engineering in Johns Hopkins' Whiting School of Engineering and senior author of the Science article. "But we have to understand more about how these new types of metal and ceramic components behave, compared to traditional materials. How do we predict their reliability? How might these materials deform when they are subjected to stress?"

The experiments conducted by a former undergraduate research assistant and supervised by Hemker focused on what happens in regions called grain boundaries. A grain or crystallite is a tiny cluster of atoms arranged in an orderly three-dimensional pattern. The irregular space or interface between two grains with different geometric orientations is called the grain boundary. Grain boundaries can contribute to a material's strength and help it resist plastic deformation, a permanent change of shape. Nanomaterials are believed to be stronger than traditional metals and ceramics because they possess smaller grains and, as a result, have more grain boundaries.

Most scientists have been taught that these grain boundaries do not move, a characteristic that helps the material resist deformation. But when Hemker and his colleagues performed experiments on nanocrystalline aluminum thin films, applying a type of force called shear stress, they found an unexpected result. "We saw that the grains had grown bigger, which can only occur if the boundaries move," he said, "and the most surprising part of our observation was that it was shear stress that had caused the boundaries to move."

"The original view," Hemker said, "was that these boundaries were like the walls inside of a house. The walls and the rooms they create don't change size; the only activity is by people moving around inside the room. But our experiments showed that in these nanomaterials, when you apply a particular type of force, the rooms do change size because the walls actually move."

The discovery has implications for those who use thin films and other nanomaterials to make integrated circuits and microelectromechanical systems, commonly called MEMS. The boundary movement shown by Hemker and his colleagues means that the nanomaterials used in these products likely possess more plasticity, higher reliability and less brittleness, but also reduced strength.

"As we move toward making things at much smaller sizes, we need to take into account how activity at the atomic level affects the mechanical properties of the material," Hemker said. "This knowledge can help the microdevice makers decide on the proper size for their components and can lead to better predictions about how long their products will last."

The journal article describing this discovery was inspired by a Johns Hopkins master's thesis produced by Tim Rupert, then a combined bachelor's/master's degree student in mechanical engineering. Rupert, who is now a doctoral student at MIT, is lead author of the Science piece. Along with Hemker, the co-authors are Daniel Gianola, a former doctoral student and postdoctoral fellow in Hemker's lab who is now an assistant professor of materials science and engineering at the University of Pennsylvania; and Y. Gan of the Karlsruhe Institute of Technology in Germany.

Funding for the research was provided by the U.S. Department of Energy and the National Science Foundation.

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://www.sciencedaily.com/releases/2010/02/100223132019.htm
Leer: [Jn3:16-17]

Electronic Materials Research Lab.

Sputter deposition chamberWelcome to the website for the Electronic Materials Research Lab at Longwood University. In our lab, we fabricate and characterize semiconducting thin-films, bulk materials and nanowires. We conduct research in some pretty exciting areas of materials science that directly contributes to the advancement of technologies such as Blu-Ray, liquid crystal displays, bright-light LEDs, UV detectors, gas sensors and much more.

Students working in the lab gain hands on experience that will carry over seamlessly into the workforce, whether pursuing a career in research, teaching or industry. Specifically, our students work on ultra-high-vacuum systems, atomic force microscopes, electrical characterization tools, thin-film deposition techniques and much more. We fabricate nanowires up to 10,000 times smaller in diameter than a human hair. We measure currents over 1 trillion times smaller than the currents found in your toaster. We have even been known to play around in the machine shop from time to time, fabricating our own parts.

Our two main projects are currently the following: (1) we are investigating the role of the surface in the electrical properties of the wide band-gap semiconductors ZnO and GaN; and (2) we are fabricating and characterizing ZnO nanowires to study I-V behavior and charge transport properties for this quasi-quantum-confined system. We also have a few smaller projects such as the construction of a scanning tunneling microscope that can image surfaces at the atomic level, incorporating our research into the physics curriculum, and physics education research projects..

To learn more about our research, the people involved and the equipment we have available, click on the links at the top of the page, or as follows:

People :: Learn more about the people involved in the lab
Research :: Learn more about our research
Equipment :: Learn more about the types of equipment available in our lab

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://www.longwood.edu/staff/moorejc/
Leer: [Jn3:3]

Thin Film and Nanostructured Materials Physics Group

Welcome to the web site for the Thin Film and Nanostructured Materials Physics Group, Condensed Matter Sciences Division at Oak Ridge National Laboratory. Our research currently addresses two broad scientific challenges, as described below. For detailed examples of our work please see the Research and Personnel pages.

Research on Nanomaterials: Controlled Synthesis and Properties
This research addresses the central challenge of nanoscale science: the need for fundamental understanding of how nanomaterials grow and for control of the growth environment, in order to synthesize materials with new or greatly enhanced properties at attractive rates. The materials focus currently is on carbon nanotubes/nanofibers and on mesoscale oxide films/multilayers for greatly improved ionic conductivity. Part of the research addresses a grand challenge of nanomaterials synthesis: the growth of macroscopic single wall carbon nanotube (SWNT) crystals, and is carried out in collaboration with Rice University. The program’s strength is its integration of three key capabilities: advanced synthesis; time-resolved, in situ diagnostics during growth; and an arsenal of nanomaterials properties measurement and functionalization methods. For synthesis, energetic-beam methods of pulsed laser deposition (PLD), laser vaporization (LV), supersonic chemical beams, and plasma-enhanced chemical vapor deposition (PECVD) are used, together with thermal CVD. A complete suite of time-resolved, in situ diagnostic methods is used to obtain information about the precursor species, temperatures, products, and dynamics of growth in these environments. For ex situ characterization, the program particularly exploits unique ORNL Z-STEM/EELS transmission electron microscopy and spectroscopy to determine structure and composition, now with atomic resolution through aberration correction. This research also involves strong multidisciplinary collaborations with other ORNL and university investigators.

Research on the Emergence of Nanoscale Cooperative Phenomena
This research addresses one of the most important scientific themes of our time, the fundamental and practical importance of understanding complex, self-organizing behavior. Its materials focus is on transition metal oxides (TMOs) and ferroelectric oxides, with special interest in electronically highly correlated materials that exhibit spontaneous electronic phase separation on the meso- to nano-scale. Their astonishing range of properties is believed to result from a variety of possible ground states that lie close together in energy, so that small changes can create new phenomena. The objective is to understand and control such effects in order to design artificially structured TMOs with new combinations of properties. This group's effort is part of a larger ORNL program that integrates three key capabilities: advanced synthesis, detailed characterization (nanoscale to bulk), and theoretical modeling and simulation. For synthesis we have assembled the tools and skills needed to study nanoscale interactions between different electronic phases in 3D (thick or coupled films), 2D (isolated thin layers and superlattices), and quasi-1D (quantum nanowires). For characterization an arsenal of ORNL scanning probe, electronic, magnetic, and transport properties measurements is used, together with Z-contrast scanning transmission electron microscopy (Z-STEM) and electron energy loss spectroscopy (EELS). Aberration-corrected Z-STEM/EELS now permits “seeing” how electronic properties vary, locally and quantitatively, across compositional interfaces, with atomic resolution. For theory, the high-performance computing facilities of ORNL’s Center for Computational Sciences (CCS) are employed together with collaborations between in-house and external theorists, to develop computational approaches suitable for nanoscale highly correlated electronic systems.

Research Impact
The impact of understanding self-organizing behavior, and of finding ways to further direct assembly to make exotic nanoscale properties useful at the macroscale, clearly will be enormous. There undoubtedly are general rules of controlled synthesis and directed assembly to be discovered, and the systematic application of these will result in the addition of many different nanostructured materials to our toolbox. Each success in directed assembly of nanomaterials will make available a new subset of engineering materials, and we know from centuries of experience that the discovery and development of advanced materials always have been the source of new technology.

Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente: http://www.tnmp.ornl.gov/
Leer: [Ap22:14]

Characterization of Pentacene-Based Thin Film Transistors using the MM-16 Spectroscopic Ellipsometer.

Céline Eypert - Application Scientist - Thin Film Division

The performance of organic thin-film transistors (OTFTs) using small molecules has considerably improved during recent years. Organic materials have the key advantage of potentially simple and low-temperature thin film processing, using techniques as spin coating, inkjet printing or stamping. This fact suggests that OTFTs could be useful for applications requiring large-area coverage, low temperature processing and low cost.

Organic Thin Film Transistor Structure
Thin film transistors (TFTs) using organic semiconductors as the active material are of interest for a number of applications. Used as pixel-access devices in active-matrix displays, organic TFTs could complement liquid-crystal valves or organic light emitting diodes to allow inexpensive display fabrication on flexible, lightweight polymeric substrates.

Moreover, among the OTFTs with organic semiconductor as the active chanel, those fabricated with pentacene allowed the highest performance. Its high hole mobility approaches or even surpasses the mobility values found in amorphous Si. The most usual gate dielectric in these pentacene devices is thermally grown silicon dioxide on crystalline silicon. The effects of pentacene channel thickness influence the field-effect mobility of the material, and spectroscopic ellipsometry is an ideal, non-destructive tool for its characterization.
Pentacene (C22H14) is a polycyclic aromatic hydrocarbon that contains five benzene rings. There are two types of geometry of organic field effect transistor, below you can see two representations of these structures:

Results
The ellipsometric data were measured using the HORIBA Jobin Yvon MM-16 spectroscopic ellipsometer which is based on liquid crystals modulators. The experimental data were acquired at an angle of 70°across the spectral range 450-850nm. The analysis is made in two steps, firstly the characterization of silicon oxide followed by characterization of the pentacene layer.

Characterization of Silicon Dioxide
A single layer model has been used. The optical properties of the SiO2 are taken from the standard DeltaPsi2 optical library.

Pentacene characterization
The oxide thickness has been fixed in the sample structure of OTFT.
First the model was fitted using the spectral range 600-850nm. The optical constants of the pentacene were determined using a four oscillator dispersion formula. The optical properties were then extended near the lower energies using an advanced function of DeltaPsi2 software: the NK fit.
This NK fit function makes a direct inversion of ellipsometric data to n and k, and allows us to extend a dispersion formula and to characterise features of the refractive index curve that are not possible using a dispersion formula. This function is not based on the Kramers-Kroning relation and must be used with care. For this characterization we believe that this approach provides a valid description of the material’s optical properties.

The model fits the sample perfectly. There is an excellent agreement between the experimental data and the model. Furthermore, the ellipsometry results show a sharp and strong peak in the extinction coefficient k at 654nm, with additional absorption peaks at 630nm, 580nm and 540nm.












Conclusión
Spectroscopic Ellipsometry based on the liquid crystal devices is an excellent technique for the highly accurate characterization of organic semiconductor in OTFTs device in the visible range.


Nombre y Apellido: Juan J. Núñez C.
Asignatura: CRF
Sección: 01
Fuente:http://www.horiba.com/fileadmin/uploads/Scientific/Documents/TFilm/lcmse-02.pdf
Leer: [Salm 100]