The project ScinTAX developed novel thin scintillating films for the application in high performance X-ray imaging and subsequent introduced new X-ray detectors to the market. To achieve this aim lutetium orthosilicate (LSO) scintillators doped with different activators were grown successfully by liquid phase epitaxy. The high density of LSO (7.4 g/cm3), the effective atomic number (65.2) and the high light yield make this scintillator highly applicable for indirect X-ray detection in which the ionizing radiation is converted into visible light and then registered by a digital detector. A modular indirect detection system has been developed to fully exploit the potential of this thin film scintillator for radiographic and tomographic imaging. The system is compatible for high-resolution imaging with moderate dose as well as adaptable to intense high-dose applications where radiation hard microimaging detectors are required. This proceedings article shall review the achieved performances and technical details on this high-resolution detector system which is now available. A selected example application demonstrates the great potential of the optimized detector system for hard X-ray microimaging, i.e. either to improve image contrast due to the availability of efficient thin crystal films or to reduce the dose to the sample.

Within the framework of an FP6 project (SCINTAX)11The Project SCINTAX is funded by the European Community (STRP 033 427), 〈www.scintax.eu〉. we developed a new thin film single crystal scintillator for high resolution X-ray imaging based on a layer of modified LSO (Lu2SiO5) grown by liquid phase epitaxy (LPE) on a dedicated substrate. In this work we present the characterisation of the scintillating LSO films in terms of optical and scintillation properties as well as spatial resolution performances. The obtained results are discussed and compared with the performances of the thin scintillating films commonly used in synchrotron-based micro-imaging applications.

A radio-luminescence set-up was installed at the synchrotron light source ANKA to characterise scintillators under the high X-ray photon flux density of white beam synchrotron radiation. The system allows for investigating the radio-luminescence spectrum of the material under study as well as analysing in situ changes of its scintillation behaviour (e.g. under heat load and/or intensive ionising radiation). In this work we applied the radio-luminescence set-up for investigating the radiation damage effects on the luminescence properties of a new kind of thin single crystal scintillator for high resolution X-ray imaging based on a layer of modified Lu2SiO5 grown by liquid phase epitaxy on a dedicated substrate within the framework of an EC project (SCINTAX).1

We report on the epitaxial growth and spectroscopic study of highly doped Y2SiO5:Yb3+ (YSO:Yb) thin films on YSO substrates. The realization of Ge, La and Gd-codoped high quality thin films, with thickness up to 100μm, is demonstrated. YSO:Yb layers have their fluorescence and absorption spectra similar to the bulk ones, with a globally higher crystalline quality. The Yb3+ lifetime evolution exhibits a particularly slow decrease with Yb doping, proof of a low extrinsic quenching centers concentration. The refractive index increase with respect to dopants concentration is measured, and a phenomenological law is proposed. Such highly doped YSO:Yb layers could be an interesting alternative for active integrated optics or laser devices.

For production of highly effective photoconverters semiconductor materials with strictly determined parameters. are required. For thermophotovoltaic (TPV) GaSb cells. homogeneous Te-doping level of (2-7)-10(17) cm(-3) in the bulk semiconductor is required to produce high efficient PV cells by the Zn diffusion process [1-3]. In this paper we present data on investigation of the performance of the cells obtained on different GaSb:Te wafers of (100) and (211) orientation. Based on classical I/V measurements and external quantum efficiency (EQE) curves, we analyze cell performances in order to improve all fabrication stages like wafer surface preparation, p-type GaSb emitter elaboration by the zinc diffusion process, antireflection coating deposition and contact realization. Today good performances are obtained on both 3.5 x 3.5 mm(2) (211) and 10x10 mm(2) (100) GaSb cells. We obtained EQE of 70-76 % in the 800-1600 nm range for the first one and 80-88% in the same spectrum for the second one. Electrical characterization gives respectively, the fill factor (FF) from 67.8% down to 65.8% in the 1-2 A/cm(2) range and 63 % at 5 A/cm(2). The open circuit voltage Voc increases from 0.44 V (1 A/cm(2)) up to 0.49 V (5 A/cm(2)) for the small area cell.

Several CaF2 single crystals doped with trivalent rare-earth ions have been grown in the recent years in the form of bulk crystals by using the Bridgman method and in the form of thin films by using the MBE and LPE techniques. The spectroscopic, gain and laser properties of these crystals doped with Pr3+, on the one hand, and with Yb3+, Tm3+ or Er3+ ions, on the other hand, have been studied and are reviewed here for their laser potentials in the red and in the infrared spectral domains, respectively.

We report on relative gain measurements at 1.92μm in Tm:CaF2 films grown on pure CaF2 substrates by using Liquid Phase Epitaxy with CaCl2 as a solvent. Electron microscopy and X-ray diffraction measurements show that the Tm3+:CaF2 films are about 5μm thick and have a small lattice mismatch with the CaF2 substrate. Room temperature emission spectra of the Tm3+ ions around 1.9μm exhibit the same structure as in the bulk crystals and the lifetime of the 3F4 metastable level is found equal to about 12.8ms. The Tm:CaF2 films are guiding optical waves and exhibit a relative gain of 7% at 1.92μm when pumped at 0.765μm.

The fabrication by physical vapor deposition (PVD) of Er/Ce-doped fluoride glass channel waveguides using low cost silica on silicon (SiO2/Si) engraved cleavable substrates was demonstrated. The mean composition of the deposited glass was 38PbF2–19ZnF2–43GaF3 in mol% with Er and Ce concentrations fixed at 1mol%. The channel waveguides with cross-sectional dimensions 3×2μm2 were single-mode at 0.63μm. Propagation losses of less than 0.5dB/cm and loss reduction of 3.3dB/cm were measured at 1.535μm in a 3.2cm long waveguide with an absorbed power of about 3mW at 0.98μm.

In this paper, we have developed a new route to fabricate channel waveguides, by using ion implantation technique in buried epitaxial crystalline YAG:Nd,Tm layers. Excited state absorption and energy transfer upconversion mechanisms are discussed in view of a single beam pumped infrared to blue upconversion laser for integrated optics.

We have studied Er3+, Yb3+, and Ce3+ codoped microchannel waveguides that were developed by two methods: ionic exchange for heavy metal fluoride glasses [ZrF4-BaF2-AlF3-CeF3 (ZBAC)] and vapor phase deposition for transition metal fluoride glasses [PbF2-ZnF2-GaF3 (PZG)] by using a double-pass technique. For the first time to our knowledge, the measurement of propagation losses and amplification tests were carried out by use of the same experimental setup, leading to complete characterization of the waveguides. Net gains higher than 1 dB/cm were achieved in ZBAC Er/Ce single-mode fluoride glass waveguides.

The latest results on the preparation and characterization of Er3+-doped fluoride glass channel waveguides are presented. The waveguides are prepared by means of ion exchange between fluoride and chloride ions, through a silica mask, on ZBLA (ZrF4 - BaF2 - LaF3 - AlF3) fluoride glass substrate. Single mode propagation is demonstrated at 1.55 pin for a 10-mm long, 5-mum wide waveguide. Propagation losses are found to be not greater than 0.28 dB/cm. An "on/off" gain of 3.9 dB is measured at the output of a 1% Er3+ - 4% Ce3+ -doped fluoride waveguide, with about 240 mW incident pump power at 980 nm. Modelisation studies show that net gain could be achieved in (Er3+, Ce3+) doubly-doped and (Er3+, Ce3+, Yb3+) triply doped fluoride waveguides.

We report frequency modulation spectroscopy measurements performed on erbium doped fluoride glasses: PZG (39% PbF2, 19% ZnF2, 42% GaF3) and ZBAC (57% ZrF4, 34% BaF2, 5% CeF3, 4% AlF3). For the ZBAC glass, no changes of lifetime in channel waveguides versus bulk were observed as well as no pump power dependence from 1 to 100 mW. On the contrary, for the PZG glass, the lifetime of the 4I13/2 level was reduced from 7 ms in bulk to 2 ms into the waveguides. In this glass, upconversion effects appear very efficient at high incident pump power.

F/Cl ion-exchange technique is used to make planar waveguides in fluoride glass. The effects of temperature and time on the guide structure are described. The use of HF treatment to bury and chemically protect the guide, and reduce constraints on the glass surface is demonstrated. The impact of ion-exchange on the average roughness of the glass surface is shown.

Today, high crystal quality in sufficient size with high crystal growth yield appears to be a key point for a wide dissemination and use in ferroelectrics; applications. So, this paper is related to the growth of PZN-PT solid solution compound like (1-x)(PbZn1/3Nb2/3O3)-xPbTiO(3) and PMN-PT compound like (1-y)(PbMg1/3Nb2/3O3)yPbTiO(3). For these two rriaxor ferroelectric single crystals promising properties are obtained near the Morphotropic Phase Boundary (NUB) transition which occurred at values closed to x=0.09 for PZN-PT and y=0.34 for PMN-PT. The complex unit cell phase transition combined with an adequate applied electric field, oriented in the pseudo <001>(c) direction; confer to these single crystals some interesting piezoelectric properties. We present some crystal growth results obtained by the Vertical Gradient Freeze-Solution Growth method (VGF-SG) for PZN-PT and by a pseudo Kyropoulos method developed for PMN-PT. The obtained single crystals, up to 120 g for PZN-PT and 160 g for PMN-PT are then analysed in term of composition and structure. Both PMN-PT and PZN-PT perovskite crystals are rhombohedral (@RT), they show a good global homogeneity. Samples demonstrate ferroelectric behaviour, and after polarisation process, dielectric constants up to 48000 near the Curie temperature (Tc similar to174degreesC @ 1kHz) are obtained for PZN-PT and respectively 74000 for PMN-PT (Tc similar to142degreesC @ 100 Hz). The piezoelectric coefficient d(33) gives values up to similar to2200 pC/N (@RT 9 kV/cm) for PZN-PT and 1700 pC/N(@RT) for PMN-PT. A value up to 94 % is measured for the electromechanical coupling coefficient k(33).

The seed surface preparation for SiC sublimation growth has been investigated. Two methods have been developed to prepare and improve the seed surface contribution during the growth initiation:- An in-situ sublimation etching of the seed is performed.- The seed surface is prepared by ex-situ polishing and chemical and ozone cleaning.Both methods promote a better lateral growth mechanism, and then promote the prefered step now growth mechanism. This results in a better crystalline quality of the crystals in terms of mosaicity, polytype stability and micropipe density.

We report on purity improvement effects which recently have been observed when comparing different series of wafers produced in two separate, but basically similar, home-made physical vapor transport (PVT) reactors. Looking in detail for the origin of this phenomenon, we have found a strong influence of the residual purity of the graphite material used to manufacture the crucibles. After proper optimization, a second effect has been found. It manifests when the residual level of impurities in the seed material is high and provides evidence for in situ auto-doping. Finally, quantitative analyses of C(V) characteristics and Raman spectra have been done. In this way we follow the trend in residual carrier concentration and mobility.