39 research outputs found
Morphology-driven electrical and optical properties in graded hierarchical transparent conducting Al:ZnO
Graded Al-doped ZnO layers, constituted by a mesoporous forest like system
evolving into a compact transparent conductor, were synthesized by Pulsed Laser
Deposition with different morphology to study the correlation with functional
properties. Morphology was monitored by measuring the resulting surface
roughness and its effects on electrical conductivity (especially carrier
mobility, which significantly decreases with increasing roughness) allow to
discuss the limitations in conduction mechanisms. Significant changes in light
scattering capability due to variations in morphology are also investigated and
discussed to study the correlation between morphology and functional
properties.Comment: 11 pages, 4 figure
Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO
The structure-property relation of nanostructured Al-doped ZnO thin films has
been investigated in detail through a systematic variation of structure and
morphology, with particular emphasis on how they affect optical and electrical
properties. A variety of structures, ranging from compact polycristalline films
to mesoporous, hierarchically organized cluster assemblies, are grown by Pulsed
Laser Deposition at room temperature at different oxygen pressures. We
investigate the dependence of functional properties on structure and morphology
and show how the correlation between electrical and optical properties can be
studied to evaluate energy gap, conduction band effective mass and transport
mechanisms. Understanding these properties opens the way for specific
applications in photovoltaic devices, where optimized combinations of
conductivity, transparency and light scattering are required.Comment: 8 pages, 9 figure
Multi-wavelength Raman scattering of nanostructured Al-doped zinc oxide
In this work we present a detailed Raman scattering investigation of zinc
oxide and aluminum-doped zinc oxide (AZO) films characterized by a variety of
nanoscale structure and morphology and synthesized by pulsed laser deposition
(PLD) under different oxygen pressure conditions. The comparison of Raman data
for pure ZnO and AZO films with similar morphology at the nano/mesoscale allows
to investigate the relation between Raman features (peak or band positions,
width, relative intensity) and material properties such as local structural
order, stoichiometry and doping. Moreover Raman measurements with three
different excitation lines (532, 457 and 325 nm) point out a strong correlation
between vibrational and electronic properties. This observation confirms the
relevance of a multi-wavelength Raman investigation to obtain a complete
structural characterization of advanced doped oxide materials.Comment: 27 pages, 7 figures, submitted to the Journal of Applied Physic
Tuning of Electrical and Optical Properties of Highly Conducting and Transparent Ta-Doped TiO2 Polycrystalline Films
We present a detailed study on polycrystalline transparent conducting Ta-doped TiO2 films, obtained by room temperature pulsed laser deposition followed by an annealing treatment at 550°C in vacuum. The effect of Ta as a dopant element and of different synthesis conditions are explored in order to assess the relationship between material structure and functional properties, i.e. electrical conductivity and optical transparency. We show that for the doped samples it is possible to achieve low resistivity (of the order of 5×10-4 Ωcm) coupled with transmittance values exceeding 80% in the visible range, showing the potential of polycrystalline Ta:TiO2 for application as a transparent electrode in novel photovoltaic devices. The presence of trends in the structural (crystalline domain size, anatase cell parameters), electrical (resistivity, charge carrier density and mobility) and optical (transmittance, optical band gap, effective mass) properties as a function of the oxygen background pressures and laser fluence used during the deposition process and of the annealing atmosphere is discussed, and points towards a complex defect chemistry ruling the material behavior. The large mobility values obtained in this work for Ta:TiO2 polycrystalline films (up to 13 cm2V-1s-1) could represent a definitive advantage with respect to the more studied Nb-doped TiO2
Scoliosis in patients with Prader Willi Syndrome – comparisons of conservative and surgical treatment
In children with Prader Willi syndrome (PWS), besides growth hormone (GH) therapy, control of the food environment and regular exercise, surgical treatment of scoliosis deformities seems the treatment of choice, even though the risks of spinal surgery in this specific population is very high. Therefore the question arises as to whether the risks of spinal surgery outweigh the benefits in a condition, which bears significant risks per se. The purpose of this systematic review of the Pub Med literature was to find mid or long-term results of spinal fusion surgery in patients with PWS, and to present the conservative treatment in a case study of nine patients with this condition
Prader-Willi syndrome: A primer for clinicians
The advent of sensitive genetic testing modalities for the diagnosis of Prader-Willi syndrome has helped to define not only the phenotypic features of the syndrome associated with the various genotypes but also to anticipate clinical and psychological problems that occur at each stage during the life span. With advances in hormone replacement therapy, particularly growth hormone children born in circumstances where therapy is available are expected to have an improved quality of life as compared to those born prior to growth hormone
Evaluation of noninvasive exercise cardiac output determination in chronic heart failure patients: a proposal of a new diagnostic and prognostic method
Peak oxygen consumption (VO 2) and various parameters of cardiopulmonary response to exercise are of important prognostic value in chronic heart failure patients. However, all the available parameters only indirectly reflect left-ventricular dysfunction and hemodynamic adaptation to an increased demand. Noninvasive assessment of cardiac output, especially during an incremental exercise test, would allow the direct measurement of cardiac reserve and may become the gold standard for prognostic evaluation of chronic heart failure patients
Tuning of Electrical and Optical Properties of Highly Conducting and Transparent Ta-Doped TiO2 Polycrystalline Films
We present a detailed study on polycrystalline transparent conducting Ta-doped TiO2 films, obtained by room temperature pulsed laser deposition followed by an annealing treatment at 550°C in vacuum. The effect of Ta as a dopant element and of different synthesis conditions are explored in order to assess the relationship between material structure and functional properties, i.e. electrical conductivity and optical transparency. We show that for the doped samples it is possible to achieve low resistivity (of the order of 5×10-4 Ωcm) coupled with transmittance values exceeding 80% in the visible range, showing the potential of polycrystalline Ta:TiO2 for application as a transparent electrode in novel photovoltaic devices. The presence of trends in the structural (crystalline domain size, anatase cell parameters), electrical (resistivity, charge carrier density and mobility) and optical (transmittance, optical band gap, effective mass) properties as a function of the oxygen background pressures and laser fluence used during the deposition process and of the annealing atmosphere is discussed, and points towards a complex defect chemistry ruling the material behavior. The large mobility values obtained in this work for Ta:TiO2 polycrystalline films (up to 13 cm2V-1s-1) could represent a definitive advantage with respect to the more studied Nb-doped TiO2
Tuning Hierarchical Cluster Assembly in Pulsed Laser Deposition of Al-doped ZnO
The synthesis of hierarchically assembled Al-doped ZnO layers by Pulsed Laser Deposition (PLD) at room temperature was investigated. PLD was performed in a background pressure of 100 Pa O2 to deposit clusters in a low energy regime and obtain nano- and mesostructures resulting from a hierarchical assembly of nanoclusters. We here analyzed the effects of varying the gas flow rate on mesoscale morphology, mass density and optical properties. The variation of the target-to-substrate distance was also investigated, identifying its effects on mass density and film morphology. The optimization of optical properties in terms of transparency and light scattering capability is of potential interest for photovoltaic applications