ICMUV

Burjassot, Spain
Burjassot, Spain

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Santamaria-Perez D.,Complutense University of Madrid | Kumar R.S.,University of Nevada, Las Vegas | Dos Santos-Garcia A.J.,Complutense University of Madrid | Errandonea D.,ICMUV | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

A recent high-pressure study on barium chromate BaCrO 4 reported a phase transition but the structure of the high-pressure phase structure could not be identified. This high-pressure phase was suggested to have a monoclinic structure different from other high-pressure forms of ABO 4-type compounds. In this work, we have carried out x-ray diffraction measurements up to 46 GPa using He as the quasihydrostatic pressure medium and density-functional theory calculations. Our studies allow us to identify the high-pressure phase as the P2 12 12 1 post-barite-type phase, recently reported for BaSO 4. The equations of state of both, the low- and the high-pressure phases have been determined. Elastic constants of the initial barite-type phase were calculated and the shear and Young moduli, and the Poisson coefficient deduced from them. Finally Raman and infrared-active modes are also calculated, discussed, and compared with experiments when possible. As a first approximation, the vibrations can be separated in internal vibrations of the CrO 4 tetrahedra and vibrations where the tetrahedral units behave as rigid units. Pressure coefficients of the different modes are reported being two soft modes found for the high-pressure phase. © 2012 American Physical Society.


Errandonea D.,ICMUV | Ferrer-Roca Ch.,ICMUV | Martinez-Garcia D.,ICMUV | Segura A.,ICMUV | And 6 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We have studied by means of high-pressure x-ray diffraction the structural stability of Ni2Mo3N, Co3Mo3N, and Fe3Mo3N. We also report ab initio computing modeling of the high-pressure properties of these compounds, Pd2Mo3N and Pt2Mo3N. We have found that the nitrides remain stable in the ambient-pressure cubic structure at least up to 50 GPa and determined their equation of state. All of them have a bulk modulus larger than 300 GPa. Single-crystal elastic constants have been calculated in order to quantify the stiffness of the investigated nitrides. We found that they should have a Vickers hardness similar to that of cubic spinel nitrides such as γ -Si 3N4. © 2010 The American Physical Society.


News Article | December 29, 2015
Site: www.nanotech-now.com

Home > Press > Simultaneous detection of the polarities of hundreds of semiconducting nanowires Abstract: Researchers at the University of Valencia have developed a technique to determine the individual polarities of hundreds of semiconducting nanowires in a single, time-saving process. Led by Ana Cros, director of the Universitat de València’s (UV) Materials Science Institute (ICMUV), the study constitutes a major step forward in both our understanding and application of these structures, since their polarity defines the properties of devices made from. Semiconducting nanowires are structures just tens of nanometres in diameter with a typical length-to-width ratio of around 1000 – like a human hair, only a thousand times smaller. So much so that they are often referred to as one-dimensional materials, and indeed they have many interesting properties not seen in larger 3D materials. Semiconducting nanowires are currently among the most-studied nanometric structures and are the basic building blocks for a range of optoelectronic devices that source, detect and control light, such as light detectors, emittors and nanosensors. Until now, determining their polarities required the nanowires to be analysed one-by-one as part of a complex and time-consuming process. This new technique uses an atomic-strength microscope and a Kelvin probe to detect minuscule forces and measure the electrical characteristics of the sample’s surface. When combined with advanced data analysis, these measurements reveal the polarities of hundreds of nanowires at the same time. Ana Cros offers us an analogy: “Our microscope explores the surface of the sample in the same way that a blind person explores their surroundings: it uses a probe as a cane, getting an idea as to surface properties based on changes in vibrations. The difference between the microscope and the cane is that its point is extremely sharp. If we then add the electrical charge, we are able to measure the electrical characteristics of the surface of very small objects without even needing to touch them.” Known as Kelvin probe force microscopy (KPFM), this technique has made it possible to determine the individual polarities of over 100 nanowires at the same time. Núria Garro, researcher at the ICMUV, explains: “What used to take days -having to select the nanowires one-by-one and ultimately destroying the sample- now takes a matter of hours, without incurring any damage whatsoever to the sample”. The study was published in the journal Nano Letters and was carried out jointly with the University of Murcia, the University of Grenoble and the French Atomic Energy Commission. It constitutes one of the primary findings from a new line of researched opened at ICMUV for the study of optoelectronic processes in advanced materials and surfaces. It was carried out as part of the European project NANOWIRING (FP7-People) and was led in Valencia by Núria Garro. Full bibliographic information A. Minj, A. Cros, N. Garro, J. Colchero, T. Auzelle, B. Daudin Assessment of Polarity in GaN Self-Assembled Nanowires by Electrical Force Microscopy Nano Letters 15, 6770 (2015); September 18, 2015; DOI: 10.1021/acs.nanolett.5b02607 For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Semiconducting nanowires are structures just tens of nanometres in diameter with a typical length-to-width ratio of around 1000 – like a human hair, only a thousand times smaller. So much so that they are often referred to as one-dimensional materials, and indeed they have many interesting properties not seen in larger 3D materials. Semiconducting nanowires are currently among the most-studied nanometric structures and are the basic building blocks for a range of optoelectronic devices that source, detect and control light, such as light detectors, emitters and nanosensors. Until now, determining their polarities required the nanowires to be analysed one-by-one as part of a complex and time-consuming process. This new technique uses an atomic-strength microscope and a Kelvin probe to detect minuscule forces and measure the electrical characteristics of the sample's surface. When combined with advanced data analysis, these measurements reveal the polarities of hundreds of nanowires at the same time. Ana Cros offers us an analogy: "Our microscope explores the surface of the sample in the same way that a blind person explores their surroundings: it uses a probe as a cane, getting an idea as to surface properties based on changes in vibrations. The difference between the microscope and the cane is that its point is extremely sharp. If we then add the electrical charge, we are able to measure the electrical characteristics of the surface of very small objects without even needing to touch them." Known as Kelvin probe force microscopy (KPFM), this technique has made it possible to determine the individual polarities of over 100 nanowires at the same time. Núria Garro, researcher at the ICMUV, explains: "What used to take days -having to select the nanowires one-by-one and ultimately destroying the sample- now takes a matter of hours, without incurring any damage whatsoever to the sample". The study was published in the journal Nano Letters and was carried out jointly with the University of Murcia, the University of Grenoble and the French Atomic Energy Commission. It constitutes one of the primary findings from a new line of researched opened at ICMUV for the study of optoelectronic processes in advanced materials and surfaces. It was carried out as part of the European project NANOWIRING (FP7-People) and was led in Valencia by Núria Garro. More information: A. Minj et al. Assessment of Polarity in GaN Self-Assembled Nanowires by Electrical Force Microscopy, Nano Letters (2015). DOI: 10.1021/acs.nanolett.5b02607

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