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1

Influence of sol-gel matrices on the optical excitation of europium ions

Banski M., Podhorodecki A., Misiewicz J.

Materials Science Poland

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2010

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Vol. 28, No. 1

217--227

EN

Photoluminescence (PL), total photoluminescence excitation (TPLE), transmission and decay photoluminescence experiments were done to establish the most efficient excitation mechanism of the europium (Eu3+) ions in amorphous Al2O3 and Y3Al5O12 host matrices. Both matrices were fabricated using the sol-gel technique, doped with Eu3+ ions and sputtered on a flat quartz plate. Because of relatively low temperatures of annealing (200 °C), after this treatment the matrices should remain in an amorphous phase. In such a system, Eu3+ ions occupy the points having different site symmetries. However, based on characteristic features of the PL spectra, the effective site symmetry (ESS) parameter was defined to describe the PL properties of the Eu3+ ions in various matrices. Low intensive direct f-f transitions at 392, 465, 530 nm were observed in the TPLE spectra. The most intensive, wide excitation bands were centred at around 250-260 nm and the charge transfer process was found to be related to these excitation bands. Finally, a good correlation between photoluminescence lifetimes, the PL intensity and CT energy was observed.

2

Influence of the deposition parameters of nucleation layer on the properties of thick gallium nitride layers

Prażmowska J., Korbutowicz R., Paszkiewicz R., Szyszka A., Podhorodecki A., Misiewicz J., Tłaczała M.

Materials Science Poland

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2008

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Vol. 26, No. 1

79--85

EN

Gallium nitride layers were grown on sapphire (0001) substrates on low temperature (LT)-GaN layer deposited by the HVPE method. HCl flow rates and deposition times of the nucleation layer were varied in the range of 8-10 cm3/min and 5-9 min (with the step of 2 min), respectively. Morphologies of LTGaN buffer layers and subsequent high temperature (HT)-GaN layers were examined by scanning electron microscopy. Photoluminescence spectra of HT-GaN layers were recorded which allowed us to evaluate the optical quality of thick HVPE HT-GaN layers.

3

Optical emission from Eu, Tb, Nd luminescence centers in TiO2 prepared by magnetron sputtering

Kaczmarek D., Domaradzki J., Borkowska A., Podhorodecki A., Misiewicz J., Sieradzka K.

Optica Applicata

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2007

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Vol. 37, nr 4

433-438

EN

This work presents the results of optical emission from Eu3+, Tb3+ and Nd3+ luminescence centers in TiO2 thin films. Thin films were prepared by magnetron sputtering from metallic Ti-Eu, Ti-Tb, Ti-Nd targets, respectively. Optical properties were examined by means of photoluminescence and optical transmission measurements. The total content of dopants was analyzed using an energy disperse spectrometer. It has been shown that doping of TiO2 thin films using selected lanthanides results in the visible (Eu, Tb) and near-infrared (Nd) light emission, upon ultraviolet radiation. Additionally, transparency range and optical band gap of prepared thin films were determined, in comparison to pure TiO2.

4

Influence of the second shell layer (TOPO, HDA) on the optical properties of CdSe/ZnS nanocrystal powder

Zatryb G., Podhorodecki A., Misiewicz J., Nauka K.

Optica Applicata

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2007

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Vol. 37, nr 4

459-464

EN

CdSe/ZnS nanocrystal powder covered with an additional cap layer (II-shell) of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO) has been investigated by using photoluminescence (PL) and total photoluminescence excitation (TPLE) spectroscopy. Depending on II-shell composition, different emission properties of the system have been observed. Strong emission bands at 2.00 eV and 1.95 eV related to nanocrystalline CdSe core recombination have been observed for TOPO and HDA-CdSe/ZnS nanocrystals, respectively. In both cases, weak emission bands centered at 3.5 and 2.8 eV have also been found. Moreover, in the case of TOPO II-shell, emission band at 1.65 eV related to defect state recombination has been observed. In both cases, similar absorption properties have been found, indicating that II-shell composition does not change nanocrystal absorption properties in an efficient way.

5

Influence of post annealing on optical and structural properties of Eu and Pd-doped TiO2 thin films

Domaradzki J., Borkowska A., Kaczmarek D., Podhorodecki A., Misiewicz J.

Optica Applicata

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2007

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Vol. 37, nr 1-2

51-56

EN

This work presents optical and structural characterization of europium and palladium doped titanium dioxide thin films prepared by modified magnetron sputtering. The metallic Eu and Pd dopants have been co-sputtered from a base Ti target (mosaic target) and deposited on SiO2 substrates. After the deposition samples were additionally annealed in air ambient for 2 hours at the temperatures of 200 °C, 400 °C, 600 °C and 800 °C, respectively. Structural properties of TiO2:(Eu, Pd) thin films were examined using X-ray diffraction (XRD). XRD patterns recorded after thermal treatment showed the dominating TiO2-rutile phase, independently of the temperature of annealing. Optical properties were studied as defined by optical transmission. It has been shown, that doping shifts the fundamental absorption edge of TiO2 toward the longer wavelength range. As the samples were additionally annealed the band gap widening has been observed from 1.7 eV, for as deposited sample up to 2.31 eV for those annealed at 800 °C.

6

Optical properties of InGaAsP quantum well for infrared emission investigated by modulation spectroscopy

Podhorodecki A., Andrzejewski J., Motyka M., Kudrawiec R., Misiewicz J., Wójcik J., Robinson B. J.

Optica Applicata

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2005

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Vol. 35, nr 3

509-515

EN

Modulation spectroscopy, i.e., photoreflectance (PR) and contactless electroreflectance (CER) are very powerful techniques to investigate optical properties of nanostructures. These techniques together with photoluminescence spectroscopy were used for investigation of optical properties of InGaAsP quantum well with infrared emission at 1.55 um. Samples used in this study were grown by gas source molecular beam epitaxy (MBE) on n-doped (100) InP substrate. Based on the numerical calculations the origin of observed optical transitions has been explained and the energy structure of the investigated samples has been proposed.