Structural and magnetic properties of E-Fe_{1-x}Co_xSi thin films deposited via pulsed laser deposition

We report pulsed laser deposition synthesis and characterization of polycrystalline Fe1-xCox Si thin films on Si (111). X-ray diffraction, transmission electron, and atomic force microscopies reveal films to be dense, very smooth, and single phase with a cubic B20 crystal structure. Ferromagnetism with significant magnetic hysteresis is found for all films including nominally pure FeSi films in contrast to the very weak paramagnetism of bulk FeSi. For Fe1-xCoxSi this signifies a change from helimagnetism in bulk, to ferromagnetism in thin films. These ferromagnetic thin films are promising as a magnetic-silicide/silicon system for polarized current production, manipulation, and detection.Comment: 12 pages, 4 figures accepted in the Applied Physics Letter

Structural and magnetic properties of ε -Fe1-x Cox Si thin films deposited via pulsed laser deposition

We report pulsed laser deposition synthesis and characterization of polycrystalline Fe1-x Cox Si thin films on Si (111). X-ray diffraction, transmission electron, and atomic force microscopies reveal films to be dense, very smooth, and single phase with a cubic B20 crystal structure. Ferromagnetism with significant magnetic hysteresis is found for all films including nominally pure FeSi films in contrast to the very weak paramagnetism of bulk FeSi. For Fe1-x Cox Si this signifies a change from helimagnetism in bulk, to ferromagnetism in thin films. These ferromagnetic thin films are promising as a magnetic-silicide/silicon system for polarized current production, manipulation, and detection. © 2009 American Institute of Physics

Simonkolleite nano-platelets : synthesis and temperature effect on hydrogen gas sensing properties

Please read abstract in article.The African Laser Centre “ALC”-Pretoria, the Abdus Salam ICTP-Trieste, the Nanosciences African Network “NANOAFNET”-Cape Town, iThemba LABS-National Research Foundation of South Africa and the French-South Africa as well as the Japan-South Africa bilateral cooperation programmes.http://www.elsevier.com/locate/apsuscnf201

Low-field microwave absorption in pulse laser deposited FeSi thin film

Low field microwave absorption (LFMA) measurements at 9.4 GHz (X-band), were carried out on pulse laser deposited (PLD) polycrystalline B20 cubic structure FeSi thin film grown on Si (111) substrate. The LFMA properties of the films were investigated as a function of DC field, temperature, microwave power and the orientation of DC field with respect to the film surface. The LFMA signal is very strong when the DC field is parallel to the film surface and vanishes at higher angles. The LFMA signal strength increases as the microwave power is increased. The LFMA signal disappears around 340 K, which can be attributed to the disappearance of ferromagnetic state well above room temperature in these films. We believe that domain structure evolution in low fields, which in turn modifies the low field permeability as well as the anisotropy, could be the origin of the LFMA observed in these films. The observation of LFMA opens the possibility of the FeSi films to be used as low magnetic field sensors in the microwave and rf frequency regions.University of Pretoria research development program and NRF/Ithemba LABS.http://www.elsevier.com/locate/jmmmnf201

Competitive growth texture of pulse laser deposited VO2 nanostructures on a glass substrate

We report on the crystal structure and morphology of vanadium dioxide (VO2) nanostructures synthesized by pulsed laser deposition on soda-lime glass substrates. The VO2 nanostructures exhibit sharp a-axis diffraction peaks, characteristic of the VO2 monoclinic phase, which implies that highly a-axis textured VO2 was formed. A detailed description of the growth mechanisms and the substrate–film interaction is given, and the characteristics of the electronic transition and hysteresis of the phase transition are described in terms of the morphology and grain boundary structure. The sharpness of the transition and the hysteresis upon heating and cooling are found to be strong functions of the crystal structure and microstructure (grain size and shape).UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, INRS (Canada), the ICTP-Trieste and the NANOAFNET.http://www.elsevier.com/locate/actamathb2014ai201

A study of porous carbon structures derived from composite of cross-linked polymers and reduced graphene oxide for supercapacitor applications

Please read abstract in the article.The South African Research Chairs Initiative of the Department of Science and Technology, the National Research Foundation of South Africa, the Organization for Women in Science for the Developing World (OWSD) and the University of Pretoria.https://www.elsevier.com/locate/esthj2023Physic

Effect of substrate temperature on the structure and the metal insulator transition in pulsed laser deposed V02\ films on soda lime glass

In this paper, we report the effect of soda lime substrate deposition temperature (Ts) on the crystal structure and the metal insulator transition of VO2 thin films. Samples were deposited at substrate deposition temperature ranging from 450 to 600 0C by pulsed-laser deposition and characterized by x-ray diffraction and UV-VIS spectrophotometer. At a substrate temperature of 550°C, the VO2 (100) reflection dominate the spectrum showing a change in crystalline grains orientation. The highest transition temperatures of 74 oC with the lowest hysteresis width of 11 oC were obtained on the same sample grown at a substrate deposition temperature of 500 oC and also corresponding to the largest grains size of a value of 350 nm.http://link.springer.com/journal/125962016-03-31hb201

Tungsten oxide thin film for room temperature nitrogen dioxide gas sensing

Tungsten oxide (WO3) thin films for gas sensing have been successfully deposited using reactive direct current (DC) magnetron sputtering at different deposition temperatures (300 °C, 400 °C and 500 °C). The structural, morphological properties, thickness and composition have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering spectrometry (RBS) techniques. To investigate the effect of deposition temperature on the gas sensing properties of deposited thin films on alumina substrates, was conducted using the Kenosistec gas sensing unit. WO3 thin film deposited at 500 °C exhibited a higher response when sensing Nitrogen dioxide (NO2) at room temperature as compared to the thin films prepared at 300 °C and 400 °C, respectively. However, as deposited WO3 thin films exhibited low sensitivity when sensing reducing gases such as hydrogen (H2) and ammonia (NH3), which was an indication of good selectivity properties of WO3 related sensors

Temperature-dependent growth mode of W-doped ZnO nanostructures

We report on the effects of glass substrate temperature on the crystal structure and morphology of tungsten (W)-doped ZnO nanostructures synthesized by pulsed-laser deposition. X-ray diffraction analysis data shows that the W-doped ZnO thin films exhibit a strongly preferred orientation along a c-axis (000L) plane, while scanning electron and atomic force microscopes reveal that well-aligned W-doped ZnO nanorods with unique shape were directly and successfully synthesized at substrate temperature of 550 ◦C and 600 ◦C without any underlying catalyst or template. Possible growth mechanism of these nanorods is suggested and discussed.www.elsevier.com/locate/apsus