Lidia Ghimpu

Strong light scattering and broadband (UV to IR) photoabsorption in stretchable 3D hybrid architectures based on Aerographite decorated by ZnO nanocrystallites

In present work, the nano- and microscale tetrapods from zinc oxide were integrated on the surface of Aerographite material (as backbone) in carbon-metal oxide hybrid hierarchical network via a simple and single step magnetron sputtering process. The fabricated hybrid networks are characterized for morphology, microstructural and optical properties. The cathodoluminescence investigations revealed interesting luminescence features related to carbon impurities and inherent host defects in zinc oxide. Because of the wide bandgap of zinc oxide and its intrinsic defects, the hybrid network absorbs light in the UV and visible regions, however, this broadband photoabsorption behavior extends to the infrared (IR) region due to the dependence of the optical properties of ZnO architectures upon size and shape of constituent nanostructures and their doping by carbon impurities. Such a phenomenon of broadband photoabsorption ranging from UV to IR for zinc oxide based hybrid materials is novel. Additionally, the fabricated network exhibits strong visible light scattering behavior. The developed Aerographite/nanocrystalline ZnO hybrid network materials, equipped with broadband photoabsorption and strong light scattering, are very promising candidates for optoelectronic technologies.

Optical and sensory properties of ZnO nanofibrous layers grown by magnetron sputtering

This paper presents optical and sensory properties of ZnO nanofirous layers grown by a cost-effective and fast fabrication method based on magnetron sputtering. The as-prepared nanofibrous layers show good conductive properties which are of interest for gas sensing structures. Their application for hydrogen detection is demonstrated in premiere, and the developed H2 sensor structure exhibits good response / recovery behavior under ultraviolet (UV) light, and good sensitivity. This method is cost-effective and facile and has a great potential for various sensorial applications.

Ultra-lightweight pressure sensor based on graphene aerogel decorated with piezoelectric nanocrystalline films

In this paper, we report on a pressure sensor based on graphene aerogel functionalized with SnO2 or GaN thin films deposited by magnetron sputtering. Decoration by nanocrystalline SnO2 or GaN was found to enhance the piezoresistive response of the bare aerogel. The responsivity and pressure sensing range (from 1-5 atm) of the sensor are shown to be higher than those inherent in pressure sensors based on graphene membranes.

Thickness dependent properties of CdS/CdTe hetero-photo-elements

The analysis of the I-V characteristics of a CdS/CdTe heterojunction shows the strong influence of the time of deposition of CdTe on the photo-electrical parameters. The best parameters with no antireflection coating, J/sub sc/=24.8 mA/cm/sup 2/, V/sub oc/=0.82 V, FF=0.48, /spl eta/=9.76% are obtained in the case when time of deposition of CdTe is 3.5 min. The photoresponse decreases with increasing CdTe thickness. The photosensitivity covers the wavelength range from 0.50 /spl mu/m to 0.86 /spl mu/m for all cells. The most efficient carrier generation and collection is for the structure with the time of the CdTe layer deposition of 3.5 min.

Effect of Al Sn — Doping on properties of zinc oxide nanostructured films grown by magnetron sputtering

Metal doping in nanostructured zinc oxide is important for device applications. To obtain improved performances for practical applications, Aluminum (Al) and Tin (Sn)-doping in zinc oxide nanostructured layers were investigated. Samples were grown by magnetron sputtering and studied by X-ray diffraction (XRD), micro-Raman, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) techniques. It was observed that nanoparticles are interconnected and form porous network of individual nanoparticles. It is found clear evidence of changes of different properties after doping with aluminum or tin in zinc oxide nanostructured films grown by magnetron sputtering.

Nanofibrous zinc oxide films synthesized by magnetron sputtering

ZnO nanofibrous-based materials required for sensors and dye-solar cells have been grown on tin oxide/glass substrates by magnetron sputtering. Synthesis regimes have been identified that give nanoporous and nanofibrous morphologies of depositions as shown by SEM. The structural properties of the nanomaterial have been characterized by X-ray diffraction. Vibrational properties have been investigated by Micro-Raman spectroscopy. All experimental data are discussed in details and promising applications are suggested.

Synthesis and characterization of photosensible CH 3 NH 3 PbI 3 and CH 3 NH 3 PbI 3– x Cl x perovskite crystalline films

Methylammonium lead-halide perovskites are very promising for applications as solar light-harvesting materials. This paper presents a study on the methylammonium iodide and iodide-chloride perovskite films prepared by spin coating from a liquid precursor. The powder diffraction spectroscopy has detected 10 lattice plane reflections common to a perovskite of a tetragonal crystal structure. The calculated cell parameters are a = 8.85 Å and c = 12.60 Å. The preparation conditions and their impact on the crystallization process and film morphology are discussed. A red shift of photoluminescence bands at low temperatures was evidenced. A photoelectrical study of perovskite films has revealed their high sensibility to illumination, especially in the visible spectrum, which gives a hint on their applications in photovoltaics.

Photocatalytic Applications of Doped Zinc Oxide Porous Films Grown by Magnetron Sputtering

Undoped, Al-doped and Sn-doped ZnO was sputter-deposited on glass substrates and on trenched Si substrates and some properties of these samples were evaluated. It was shown that the photocatalytic performance of the thin layers is improved by doping with Sn and Al. The samples doped with Al-doping provided a more pronounced effect compared to the control sample, as well as compared to the greater volume of undoped ZnO deposited on Si substrates. Morphology of produced particles was studied using transmission electron microscopy. Electron diffraction patterns were taken to confirm lattice parameters of the materials. Size and shape variations were monitored for un-doped, Al-doped and Sn-doped ZnO. EDX spectroscopy was utilized to assay chemical composition for doped and un-doped samples.

Porous and RF sputtering InP for portable THz-TDS in pharmaceutical and medical applications

We developed a technology for deposition of metal contacts/wires upon nanoporous InP thin film structures and RF sputtered InP films. Indium phosphide (InP) films were deposited onto glass substrate using RF magnetron sputtering by varying the substrate temperature (50-100°C), under constant argon pressure (6.3·10-3 Bar) and RF power (40-100 W).

Design of titania nanotube structures by focused laser beam writing

Matrices of titania nanotubes (TiO2NTs) have been prepared by anodization of Ti foils in ethylene glycol based electrolyte. These matrices were subjected to annealing at various temperatures or exposed to a focused laser beam and were characterized by transmission electron microscopy (TEM), micro-cathodoluminescence (CL) and Raman scattering (RS) spectroscopy. The obtained data demonstrate possibilities to control the crystallographic structure of TiO2NTs by means of focused laser beam writing. These findings open novel prospects for the design and fabrication of titania nanotube structures.