VIS-UV ZnCdO/ZnO multiple quantum well nanowires and the quantification of Cd diffusion.

We report on the growth and microstructure analysis of high Cd content ZnCdO/ZnO multiple quantum wells (MQW) within a nanowire. Heterostructures consisting of ten wells with widths from 0.7 to 10 nm are demonstrated, and show photoluminescence emissions ranging from 3.03 to 1.97 eV. The wells with thicknesses ≦̸2 nm have high radiative efficiencies compared to the thickest ones, consistent with the presence of quantum confinement. However, a nanometric analysis of the Cd profile along the heterostructures shows the presence of Cd diffusion from the ZnCdO well to the ZnO barrier. This phenomenon modifies the band structure and the optical properties of the heterostructure, and is considered in order to correctly identify quantum effects in the ZnCdO/ZnO MQWs.

Synthesis and characterization of ZnO nano and micro structures grown by low temperature spray pyrolysis and vapor transport.

In this work we present a systematic study of ZnO micro and nanostructures grown by spray pyrolysis (SP) and by physical vapour transport (PVT) on glass and c-sapphire substrates at low temperatures. Optimised growth conditions have allowed to obtain homogeneous ZnO nanolayers composed of quasi-spherical nanoparticles in the range 2 to 8 nm by spray pyrolysis, while by PVT the selected growth conditions allow to produce a wide variety of morphologies (tripods, grains, arrows and wires) of nano and microsize dimension. Grazing incidence X-ray diffraction, field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX) were used as characterization techniques in the investigation of structural, morphological and compositional nature of these nanostructures in relation with the growth method.

Surface band-gap narrowing in quantized electron accumulation layers.

An energy gap between the valence and the conduction band is the defining property of a semiconductor, and the gap size plays a crucial role in the design of semiconductor devices. We show that the presence of a two-dimensional electron gas near to the surface of a semiconductor can significantly alter the size of its band gap through many-body effects caused by its high electron density, resulting in a surface band gap that is much smaller than that in the bulk. Apart from reconciling a number of disparate previous experimental findings, the results suggest an entirely new route to spatially inhomogeneous band-gap engineering.

Anisotropic chemical etching of semipolar [1011]/[101+1] ZnO crystallographic planes: polarity versus dangling bonds.

ZnO thin films grown by metal-organic vapor phase epitaxy along the nonpolar [formula: see text] direction and exhibiting semipolar [formula: see text] facets have been chemically etched with HCl. In order to get an insight into the influence of the ZnO wurtzite structure in the chemical reactivity of the material, Kelvin probe microscopy and convergent beam electron diffraction have been employed to unambiguously determine the absolute polarity of the facets, showing that [formula: see text] facets are unstable upon etching in an HCl solution and transform into [formula: see text] planes. In contrast, [formula: see text] facets undergo homogeneous chemical etching perpendicular to the initial crystallographic plane. The observed etching behavior has been explained in terms of surface oxygen dangling bond density, suggesting that the macroscopic polarity plays a secondary role in the etching process.

Care needs among the dependent population in Spain: an empirical approach.

The objective of the present paper was to identify the profile and needs of social and healthcare users in Spain who required long-term care. To achieve this goal, an extensive empirical study was carried out in 2001 of a typical southern European region: the Valencia Autonomous Region in Spain. The method used was a questionnaire-based survey. The data collection instrument was a questionnaire comprising 119 questions grouped into seven sections: social and demographic data; clinical diagnosis and treatment; living environment; degree of dependence in activities of daily living (ADLs); cognitive state; social support; and the social, demographic and attendance data of the carer, if available. The sampling was carried out in two strata, i.e. social and healthcare: first, the authors randomly selected the centres and services as sampling points, and then they randomly selected the subjects. A total of 1265 people were interviewed. The results show different care profiles: users aged under 65 years were mostly mentally ill and/or drug users requiring short- and medium-term care from the health services, while those aged over 65 years had chronic illnesses for which they were actively receiving treatment, were functionally dependent for ADLs, and were normally receiving social care that basically provided company and resolved functional limitations.