Optical signatures of single ion tracks in ZnO.

The optical properties of single ion tracks have been studied in ZnO implanted with Ge by combining depth-resolved hyperspectral cathodoluminescence (CL) and photoluminescence (PL) spectroscopy techniques. The results indicate that ZnO is susceptible to implantation doses as low as 10 to 10 cm. We demonstrate that the intensity ratio of ionized and neutral donor bound exciton emissions [DX/DX] can be used as a tracer for a local band bending both at the surface as well as in the crystal bulk along the ion tracks.

Role of Nitrogen in Defect Evolution in Zinc Oxide: STEM-EELS Nanoscale Investigations.

Direct evidence of the formation of nitrogen molecules (N) after ion implantion of ZnO has been revealed by an atomically resolved scanning transmission electron microscopy (STEM)-electron energy-loss spectroscopy (EELS) investigation. Taking advantage of the possibility of using multiple detectors simultaneously in aberration-corrected STEM, we utilize the detailed correlation between the atomic structure and chemical identification to develop a model explaining the formation and evolution of different defect types and their interaction with N. In particular, the formation of zinc vacancy (V) clusters filled with N after heat treatment at 650 °C was observed, clearly indicating that N has not been stabilized in the O substitution site, thus limiting p-type doping.

Correlated annealing and formation of vacancy-hydrogen related complexes in silicon.

We report on a deep level transient spectroscopy study of annealing kinetics of a deep, vacancy-hydrogen related level, labeled E5, at 0.42 eV below the conduction band in hydrogen-implanted n-type silicon. The E5 annealing correlates with the formation of another commonly observed vacancy-hydrogen related level, labeled E5, at 0.

Structural and optical properties of individual ZnGeO particles embedded in ZnO.

Functionalizing transparent conducting oxides (TCOs) is an intriguing approach to expand the tunability and operation of optoelectronic devices. For example, forming nanoparticles that act as quantum wells or barriers in zinc oxide (ZnO), one of the main TCOs today, may expand its optical and electronic tunability. In this work, 800 keV Ge ions have been implanted at a dose of 1 × 10 cm into crystalline ZnO.

Metal Oxide Thin-Film Heterojunctions for Photovoltaic Applications.

Silicon-based tandem solar cells incorporating low-cost, abundant, and non-toxic metal oxide materials can increase the conversion efficiency of silicon solar cells beyond their conventional limitations with obvious economic and environmental benefits. In this work, the electrical characteristics of a metal oxide thin-film heterojunction solar cell based on a cuprous oxide (Cu₂O) absorber layer were investigated. Highly Al-doped n-type ZnO (AZO) and undoped p-type Cu₂O thin films were prepared on quartz substrates by magnetron sputter deposition.

Improving carrier transport in CuO thin films by rapid thermal annealing.

Cuprous oxide (CuO) is a promising material for large scale photovoltaic applications. The efficiencies of thin film structures are, however, currently lower than those for structures based on CuO sheets, possibly due to their poorer transport properties. This study shows that post-deposition rapid thermal annealing (RTA) of CuO films is an effective approach for improving carrier transport in films prepared by reactive magnetron sputtering.

Hydrogen motion in rutile TiO.

Uniaxial-stress experiments have been performed for the 3287- and 2445-cm local vibrational modes assigned to the positive charge state of interstitial hydrogen [Formula: see text] and deuterium [Formula: see text], respectively, occurring in mono-crystalline rutile TiO2. The onset of the defect alignment under the stress applied perpendicular to the [001] axis is detected at 165 K (185 K), which corresponds to the activation energy of 0.53 eV (0.

Interface phenomena in magnetron sputtered CuO/ZnO heterostructures.

The interface between ZnO and CuO has been predicted to be a good candidate for use in thin film solar cells. However, the high predicted conversion efficiency has yet to be fully realized experimentally. To explore the underlying causes of this we investigate the interface between ZnO and CuO in magnetron sputtered samples.

Electronic properties and morphology of copper oxide/n-type silicon heterostructures.

Silicon-based tandem heterojunction solar cells utilizing cuprous oxide (CuO) as the top absorber layer show promise for high-efficiency conversion and low production cost. In the present study, single phase CuO films have been realized on n-type Si substrates by reactive magnetron sputtering at 400 °C. The obtained CuO/Si heterostructures have subsequently been heat treated at temperatures in the 400-700 °C range in Ar flow and extensively characterized by x-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) imaging and electrical techniques.

TiO2-coated nanostructures for dye photo-degradation in water.

The photocatalytic efficiency of a thin-film TiO2-coated nanostructured template is studied by dye degradation in water. The nanostructured template was synthesized by metal-assisted wet etching of Si and used as substrate for the deposition of a thin film of TiO2 (10 nm thick) by atomic layer deposition. A complete structural characterization was made by scanning and transmission electron microscopies.

An enhanced photocatalytic response of nanometric TiO2 wrapping of Au nanoparticles for eco-friendly water applications.

We propose a ground-breaking approach by an upside-down vision of the Au/TiO2 nano-system in order to obtain an enhanced photocatalytic response. The system was synthesized by wrapping Au nanoparticles (∼8 nm mean diameter) with a thin layer of TiO2 (∼4 nm thick). The novel idea of embedding Au nanoparticles with titanium dioxide takes advantage of the presence of metal nanoparticles, in terms of electron trapping, without losing any of the TiO2 exposed surface, so as to favor the photocatalytic performance of titanium dioxide.

Hydrogen induced optically-active defects in silicon photonic nanocavities.

We demonstrate intense room temperature photoluminescence (PL) from optically active hydrogen- related defects incorporated into crystalline silicon. Hydrogen was incorporated into the device layer of a silicon on insulator (SOI) wafer by two methods: hydrogen plasma treatment and ion implantation. The room temperature PL spectra show two broad PL bands centered at 1300 and 1500 nm wavelengths: the first one relates to implanted defects while the other band mainly relates to the plasma treatment.

Impurity sublattice localization in ZnO revealed by Li marker diffusion.

Sublattice localization of impurities in compound semiconductors, e.g., ZnO, determines their electronic and optical action.

Intrinsic point-defect balance in self-ion-implanted ZnO.

The role of excess intrinsic atoms for residual point defect balance has been discriminated by implanting Zn or O ions into Li-containing ZnO and monitoring Li redistribution and electrical resistivity after postimplant anneals. Strongly Li-depleted regions were detected in the Zn-implanted samples at depths beyond the projected range (R(p)) upon annealing ≥ 600 °C, correlating with a resistivity decrease. In contrast, similar anneals of the O-implanted samples resulted in Li accumulation at R(p) and an increased resistivity.

Negative-U system of carbon vacancy in 4H-SiC.

Using electron paramagnetic resonance (EPR), energy levels of the carbon vacancy (V(C)) in 4H-SiC and its negative-U properties have been determined. Combining EPR and deep-level transient spectroscopy we show that the two most common defects in as-grown 4H-SiC--the Z(1/2) lifetime-limiting defect and the EH(7) deep defect--are related to the double acceptor (2-|0) and single donor (0|+) levels of V(C), respectively.

Formation of donor and acceptor states of the divacancy-oxygen centre in p-type Cz-silicon.

The formation of the divacancy-oxygen centre (V(2)O) in p-type Czochralski-grown silicon has been investigated by means of deep level transient spectroscopy (DLTS). The donor state (+/0) of V(2)O is located at ~E(v) + 0.23 eV (E(v) denotes the valence band edge) and emerges during heat treatment above 200 °C at the expense of the divacancy centre (V(2)).

Phase stability and pressure-induced structural transitions at zero temperature in ZnSiO(3) and Zn(2)SiO(4).

Using density functional total energy calculations the structural phase stability and pressure-induced structural transition in different polymorphs of ZnSiO(3) and Zn(2)SiO(4) have been studied. Among the considered monoclinic phase with space groups (P 2(1)/c) and (C 2/c), rhombohedral [Formula: see text] and orthorhombic (Pbca) modifications the monoclinic phase (P 2(1)/c) of ZnSiO(3) is found to be the most stable one. At high pressure monoclinic ZnSiO(3) (C 2/c) can co-exist with orthorhombic (Pbca) modification.

Polychlorinated dibenzo-p-dioxin and dibenzofuran levels and patterns in polyvinylchloride and chloralkali industry workers.

The production of chlorine and vinyl chloride (VCM) is associated with the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The objective of the present study was to determine whether the levels and congener patterns of PCDDs and PCDFs in the blood of workers involved in the production of such substances could be related to their occupational environment. PCDD and PCDF levels in blood plasma from VCM and chloralkali workers and in referents were determined by means of high-resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) techniques and the results were evaluated through principal component analysis (PCA).

Biomarkers of exposure, antibodies, and respiratory symptoms in workers heating polyurethane glue.

Objectives: The pathogenic basis of respiratory disorders associated with isocyanates are still obscure. One reason for this is the lack of good estimates of human exposure. In this study exposure was estimated by measurement of isocyanate metabolites in biological samples.

Cancer incidence and mortality of patients with suspected solvent-related disorders.

Objective: The aim of this study was to study the incidence of cancer and deaths from cancer and other diseases among patients referred to the 11 clinics of occupational medicine in Sweden between 1967 and 1987 for examination because of exposure to organic solvents.

Methods: The cohort comprised 5791 persons, 5283 men and 508 women. Information about cancer incidence and causes of death was collected from the Cancer Register of the National Board of Health and Welfare and the National Death Register of Statistics Sweden, respectively.

Fish consumption and exposure to persistent organochlorine compounds, mercury, selenium and methylamines among Swedish fishermen.

Objectives: This study assessed dietary habits and exposure to selenium, persistent organochlorine compounds, methylmercury, and methylamines among Swedish fishermen.

Methods: Two hundred and fifty randomly selected subjects from a cohort of 2896 fishermen from the Swedish east coast (Baltic Sea) and 8477 fishermen from the west coast (Skagerrak and Kattegatt) were interviewed along with 250 referents. Subgroups of fishermen and referents from different coastal areas were also selected for blood and urine sampling.

Mortality and cancer incidence among Swedish fishermen with a high dietary intake of persistent organochlorine compounds.

Objectives: The objective of this study was to determine mortality and cancer incidence in two cohorts of Swedish fishermen with different dietary intakes of persistent organochlorine compounds.

Methods: The following two cohorts of Swedish fishermen were established: a cohort of 2896 subjects from the Swedish east coast (on the Baltic Sea), and a cohort of 8477 subjects from the Swedish west coast. Mortality and cancer incidence were studied in these cohorts and comparisons were made both with the regional populations and between the cohorts.

Selenoprotein P and glutathione peroxidase (EC 1.11.1.9) in plasma as indices of selenium status in relation to the intake of fish.

In Sweden fish is considered to be an important source of dietary Se. Therefore Se status was assessed in forty-one middle-aged men with widely varying fish consumption. Glutathione peroxidase (EC 1.

Polychlorinated biphenyls, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE) in human plasma related to fish consumption.

Fatty fish species, e.g., salmon and herring, in the Baltic Sea have high levels of polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT), and its main metabolite: 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE).