Raman, electron microscopy and electrical transport studies of x-ray amorphous Zn-Ir-O thin lms deposited by reactive DC magnetron sputtering

M. Zubkins, R. Kalendarev, J. Gabrusenoks, K. Smits, K. Kundzins,
K. Vilnis, A. Azens, J. Purans

Abstract. Zn-Ir-O thin lms on glass and Ti substrates were deposited by reactive DC
magnetron sputtering at room temperature. Structural and electrical properties were
investigated as a function of iridium concentration in the lms. Raman spectrum of Zn-Ir-
O (61.5 at.% Ir) resembles the spectrum of rutile IrO2, without any distinct features of wurtzite
ZnO structure. SEM images indicated that morphology of the lms surface improves with
the iridium content. EDX spectroscopy and cross-section SEM images revealed that the lms
growing process is homogeneous. Crystallites with approximately 2 – 5 nm size were discovered
in the TEM images. Thermally activated conductivity related to the variable range hopping
changes to the non-thermally activated before iridium concentration reaches the 45 at.%.

IOP Conference Series: Materials Science and Engineering 77 (2015) 012035


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Luminescence of Er/Yb and Tm/Yb doped FAp nanoparticles and ceramics

L. Grigorjeva, K. Smits, D.Millers, Dz.Jankoviča

Abstract. The nanoparticles of hydroxiapatite and fluorapatite doped with
Er/Yb and Tm/Yb were synthesized and characterized by FTIR, XRD, SEM and
TEM methods. The results of up-conversion luminescence studies were
presented for the samples as prepared, annealed at 500°C and at 900-1000 °C.
At annealing above 800°C the ceramic state was formed. It is shown that
fluorapatite host is more appropriate than hydroxiapatite host for rare ions
luminescence and up-conversion processes. The post preparing annealing of
nanarticles significantly enhanced the luminescence intensity. The Tm/Yb
doped fluorapatite shows intense up-conversion luminescence in 790-800 nm
spectral region and is potentially useful for biomedical applications.

IOP Conference Series: Materials Science and Engineering 77 (2015) 012036


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TSL and fractional glow study of Ge-doped α-quartz.

A. Zolatarjovs, A.N. Trukhin, K. Smits, D. Millers

Abstract. Crystalline α-quartz doped with 0.1wt% and 0.9wt% germanium was studied using
TSL and FGT equipment. Sample was chosen because previously it is known that Ge in quartz
is efficient trap for electrons, therefore it could be used for detection of hypothetic self-trapped
hole in α-quartz. However previous investigations of ODMR and TSL shows that in α-quartz
the hole is still mobile and trapping occurs only on defect states. The activation energies for
both TSL peaks are found by fractional glow and Hoogenstraaten method. The TSL
distribution changes depending on Ge concentration and also on irradiation type. The TSL
peaks below 70K in quartz doped with Ge could belong to hole trapped on Ge.

IOP Conference Series: Materials Science and Engineering 49 (2013) 012056


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Characterization of hydroxyapatite by time-resolved luminescence and FTIR spectroscopy

L.Grigorjeva, D.Millers, K.Smits, Dz.Jankovica, L.Pukina

Abstract. Time-resolved luminescence and FTIR absorption spectra of undoped and Eu
and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were
studied. The luminescence band at 350-400 nm was detected and two decay times (11 ns
and 38 ns) was determinated for Ce doped samples. The luminescence spectra and decay
kinetics were analized for Eu doped nanopowders. The Eu3+ ion was incorporated in
different Ca sites. The process of energy transfer to Eu3+ excited state (5D0) was detected
from luminescence decay kinetics.

IOP Conference Series: Materials Science and Engineering 49 (2013) 012005


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Zirconia nanocrystals as submicron level biological label

K Smits, J Liepins, M Gavare, A Patmalnieks, A Gruduls and D Jankovica

Abstract. Inorganic nanocrystals are of increasing interest for their usage in biology and pharmacology research. Our interest was to justify ZrO2 nanocrystal usage as submicron level biological label in baker’s yeast Saccharomyces cerevisia culture. For the first time (to our knowledge) images with sub micro up-conversion luminescent particles in biologic media were made. A set of undoped as well as Er and Yb doped ZrO2 samples at different concentrations were prepared by sol-gel method. The up-conversion luminescence for free standing and for nanocrystals with baker’s yeast cells was studied and the differences in up-conversion luminescence spectra were analyzed. In vivo toxic effects of ZrO2 nanocrystals were tested by co-cultivation with baker’s yeast.

IOP Conference Series: Materials Science and Engineering 38 (2012) 012050


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The luminescent properties of persistent strontium aluminate phosphor prepared by solar induced solid state synthesis

V Liepina, K Smits, D Millers, L Grigorjeva, C Monty

Abstract. A novel method – solar induced solid state synthesis – for the synthesis of aluminate phosphor doped with Eu and Dy and the study of its luminescent properties are presented in this article. Two kinds of samples of persistent strontium aluminate phosphor have been prepared – ones via this new method and ones via conventional high temperature solid state reaction. Both kinds of samples were made using the same raw materials. The samples were tested for their chemical composition using X-Ray diffraction method. The luminescence properties and phase composition of the obtained samples have been compared. The behaviour of afterglow, thermally stimulated luminescence, excitation and emission spectra are presented.

IOP Conference Series: Materials Science and Engineering 38 (2012) 012045


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