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It is shown that a series sequence of transport involving grains and grain boundaries produces non-Drude THz conductivity in nanomaterials. The present model represents a different point of view than the well accepted Drude-Smith model. In this paper we review and describe how the complex conductivity is calculated and the real and imaginary parts of THz conductivity are obtained. We use two examples: nanoporous Si and nanogold (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The optical properties and X-ray luminescence of fluorochlorozirconate glasses and glass-ceramics with composition 53% ZrF4, 20% NaF, 3% AlF3, 3% LaF3, 1% SmF3, (20- x)% BaF2 and x% BaCl2 with x varying from 0% to 19% and doped by the addition of ErCl3 or SmF3 have been investigated. The glasses show absorption and emission bands typical for trivalent Er3+ and Sm3+ ions. The samples doped with Sm showed X-ray stimulated luminescence while those doped with Er gave no response. The annealing of samples at temperatures 250-290 °C increases the X-ray stimulated luminescence while there were no changes in optical absorption and photoluminescence. The observed effects are explained in terms of changes in the host glass and the enhancement of excitation transfer from the glass to embedded Sm3+ ions (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Microbeam Radiation Therapy (MRT) is a synchrotron based technique for cancer treatment. During MRT tumours are irradiated with micro-planar arrays of synchrotron-generated X-rays. The quality assurance of such a technique depends on the accurate measurement of very high dose levels (>1000 Gy) together with a precise measurement of the dose distribution over a scale of a few microns. For such applications we need to have a high dynamic range, high-dose detector with very high spatial resolution. As part of the work towards the development of such a detector we have examined the X-ray radiation induced conversion of rare-earth ions, especially Sm3+ to Sm2+, embedded in suitable media. We have exposed a variety of Sm3+ doped media, from single crystals to glass-ceramics, to a high dose radiation at the Canadian Light Source to examine whether we could convert the rare-earth ion valency. The irradiation was carried out at a bending magnet beamline using filtered white beam with a spectrum peaking at 50 keV. We have used the distinctly different signatures in the photoluminescence emission spectra of the two valency states to identify the rare-earth ions and whether a valency conversion has taken place. We report the results from these experiments, which show that the conversion of Sm3+ to Sm2+ is not universal and depends very much on the host material. We discuss possible reasons for the presence and lack of radiation induced valency conversion of Sm-ions, and identify the challenges that must be overcome to develop a high-resolution, high-dose detector. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Aging hydrogenated microcrystalline silicon in air is found to affect both the dark conductivity and the 1/f noise. For a sample with a crystalline volume fraction of 0.39, the conductivity decreased by three orders of magnitude at 20 °C after short-term (10–20 hrs) exposure to air. The conductivity recovered after annealing to 160 °C. Long-term exposure (2 years) resulted in a permanent decrease by a factor of 16 at 20 °C even after annealing. Long-term aging also increased the conductivity activation energy from 0.193 eV to 0.342 eV. After short-term aging and below the annealing temperature, the conductivity prefactor σ0 and the activation energy Eσ follow a Meyer-Neldel type of relation. Conductance fluctuations measured for annealed and aged states show all the expected characteristics of 1/f noise. The spectra fit a power law with slope -1; the slope is not affected by temperature or aging. The magnitude of the noise decreases with temperature after aging, but by much less after annealing. A simple analysis of the product of conductivity and noise magnitude can be used to estimate the free carrier mobility (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A lucky-drift (LD) model for impact ionization has been recently successfully used to account for avalanche phenomenon in amorphous semiconductors. This model however leads to the dependence of the impact ionization coefficient on the sample thickness. However such dependence has not been confirmed experimentally. Recently LD model has been improved taking into account the scattering and movement asymmetry of charge carriers in the applied electric field. As a result, the impact ionization coefficient was obtained independent on the sample thickness. We apply the improved LD model to study the field dependence of the impact ionization coefficient in a-Se, a-Si:H and Ge2Sb2Te5. We show that even in one-dimensional formulation of the improved LD model the agreement between theoretical results and experimental data evidenced in a-Se is better than that in the formulation with scattering and movement symmetry. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The phenomenon of photoinduced dichroism in chalcogenide glasses requires a structural rearrangement of atoms in the localized region where the photon is absorbed. The structural change is facilitated by the energy released during electron-hole recombination. The dichroism is induced because regions that preferentially absorb the incident polarization will be those that suffer the atomic rearrangements thus bleaching the material for that polarization. A strong electric field should break geminate pairs and transport the electron and hole away from the absorbing region which should quench the photoinduced dichroism. We have searched for such a field effect in glassy arsenic selenide at fields up to 10 V/μm. No decrease in the rate of induced dichroism is observed (the rate actually increases by about 10%) and no change is observed in the stretching parameter when the time dependence is fit to a stretched exponential. These results are consistent with those of other researchers who also failed to find a field effect. The implications of these results for the theory of photoinduced dichroism are discussed. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The photoluminescence (PL) emission band corresponding to 4F3/2 to 4I15/2 transition has been revealed using a double lock-in technique and quadrature frequency resolved spectroscopy (QFRS) at room temperature in Nd3+ in a GaLaS glass. The band is centred around 1840 nm and has a lifetime ~77µs, which seems to be the same for all four radiative transitions 4F3/2 to 4IJ (J = 9/2, 11/2, 13/2 and 15/2). The branching ratios beta J of the four above transitions have been estimated from the PL data and agree well with the results of Judd-Ofelt (JO) analysis. In addition to the 1840 nm band, we have observed another PL band appearing around 1580 nm and having a dominant lifetime ~3.8 µs. This band may be identified with the radiative transition from the doublet (4F5/2, 2H9/2) to the 4I15/2 manifold. The short lifetime ~3.8 µs may be caused by effective multiphonon relaxation from the doublet to the 4F3/2 manifold.

Commercially available flat panel, direct conversion, digital X-ray image detectors use a photoconductive layer of stabilized amorphous selenium (a-Se) sandwiched between two electrodes to convert incident X-ray radiation into stored electrical charge. These detectors use thin n -like and p -like blocking layers to trap charge carriers injected from the contacts and thus reduce the dark current by limiting the rate of carrier injection. The effect of each of these blocking layers is determined by measuring the dark current in 200 μm thick mammographic detector-like samples of a-Se with three different structures: a single intrinsic layer and n-i and i-p double layers. Dark current is measured as a function of time over 20,000 s and as a function of applied electric field over the range of −10 V/μm to +10 V/μm. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

ICOOPMA 2008 is the third in the ICOOPMA series, an International Conference on Optical, Optoelectronic and Photonic Materials and Applications (also known as The International Conference on Optical and Optoelectronic Properties of Materials and Applications), originally sponsored by Springer, that was held for the first time in Darwin, Australia, in July 2006. The ICOOPMA series arose from a need for such a conference for those researchers who sought a truly international conference that covered a wide range of materials and applications in optics, optoelectronics and photonics. One of the goals is to provide discussions between re-searchers working on different classes of materials that have similar applications; or have been character-ized by similar techniques. The conference has a large number of invited speakers to allow such cross-fertilization between researchers working on different classes of materials. The conference also seeks papers in interesting or novel applications, or papers that enhance material properties for applications. The In-ternational and Local Organizing Committees have the responsibility of ensuring an in-depth scientific coverage with invited and contributed papers from various countries and in various disciplines; and en-suring an enjoyable scientific program. The Second ICOOPMA was held in London, England, 29 July–3 August 2007, and had over 250 participants, and five plenary lectures. The Third ICOOPMA was held in Edmonton, Canada, 20–25 July 2008, and again had nearly 250 participants and had seven plenary talks. TRLabs in Edmonton was responsible for organizing and man-aging the conference and there were a number of ma-jor sponsors without whom this conference would not have had the success it deserves. We thank TRLabs for their organization, and our sponsors for their gra-cious contributions and commitment to the ICOOPMA. There were three parallel oral sessions from Monday to Thursday, and a poster session on Tuesday to cover all the 300 papers. The current Pro-ceedings represent a collection of papers that have been presented at the conference, and have been fully refereed for inclusion in the proceedings. With the agreement of the journal's Chief Editor and the authors, a selection of papers have been transferred to physica status solidi (a) 206(5) (May 2009). The papers in both issues cover not only topics on fundamental concepts, including various optical properties (luminescence being the most popular) of a wide class of materials, e.g. organics, glasses, semi-conductors, nanocrystals, quantum wells, wires and dots etc., but also a number of interesting applications from photonics modulators to X-ray detectors. There were four best poster prizes that were given during the conference to J. E. Cunningham and Edmund Lin-field et al. (University of Leeds, UK) on “Terahertz imaging and spectroscopy using on-chip systems”; Shabnam Homampour et al. (McMaster University, Canada) on “Thermal tuning of planar Bragg gratings in silicon-on-insulator rib waveguides”; Mamiko Kujiraoka et al. (National Institute of Information and Commu-nications Technology, Japan) on “Ensemble effect on Rabi oscillations of exciton in quantum dots”; Osamu Kojima et al. (Kobe University, Japan) on “Lengthening of photoluminescence decay time owing to expansion of electron envelope functions in stacked quantum dots”. Timely publication of conference papers in an easily accessible journal is one of the attractions in presenting one's latest work at conferences. It allows the work to appear relatively quickly after it has been discussed at the conference. The papers in the proceedings were therefore prepared in publica-tion-ready form. However, it is also important to en-sure that proper refereeing has been done before a paper has been accepted. We specifically allowed pa-per submissions to continue well after the conference date to ensure that the papers included discussions during the conference. We thank the many referees who have unselfishly dedicated their valuable time in reviewing some ninety-five manuscripts and, in many cases, reviewing the revised versions as well. We are grateful to the editorial team at Wiley-VCH, in par-ticular Stefan Hildebrandt in Berlin, for their help in getting the proceedings out as soon as possible once the refereeing of the papers were complete (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have studied the effects of adding small amounts of Mg on the electrical and thermal properties of a-Se films. The addition of Mg in the ppm range has resulted in significant changes in the charge transport and stability. The doped samples have shown to be excellent n -like layers which have electron ranges much greater than hole ranges, μeτe ≫ μhτh. The n -like layers block the injection of holes from the positive electrode which results in a lower dark current in a-Se based X-ray detectors. The Differential scanning calorimetry studies have shown that a-Se doped with lower concentrations of Mg is more stable than samples with higher concentrations. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)