Ilze Aulika - Academia.edu (original) (raw)
Papers by Ilze Aulika
... Latvia. Presentation: Poster at E-MRS Fall Meeting 2006, Symposium A, by Ilze Aulika See On-l... more ... Latvia. Presentation: Poster at E-MRS Fall Meeting 2006, Symposium A, by Ilze Aulika See On-line Journal of E-MRS Fall Meeting 2006 Submitted: 2006-05-15 11:50 Revised: 2009-06-07 00:44. Google, Web, science24.com. ...
Optics Express, 2009
The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigatio... more The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigation in oxide thin films and crystals are examined in this work, along with the use of various parameters calculated from ellipsometric data (band gap energy E g , refractive index n and surface roughness) together with the directly measured main ellipsometric angles ψ and ∆, for the detection of phase transitions. The efficiency of spectroscopic ellipsometry on "surface" phase transition and its sensitivity to surface defects are also demonstrated.
Optical Materials, 2008
Structural and optical properties of Ba 0.8 Sr 0.2 TiO 3 (BST) ferroelectric thin films, deposite... more Structural and optical properties of Ba 0.8 Sr 0.2 TiO 3 (BST) ferroelectric thin films, deposited by the pulsed laser ablation (PLD) technique on Si/SiO 2 /Ti/Pt, Si/SrRuO 3 and Si substrates, were performed by X-ray diffraction, micro Raman, atomic force microscopy (AFM), and optical reflectometry measurements. Temperature dependences of the Raman spectrum, and room temperature refractive and extinction indices, and surface roughness were evaluated.
Journal of Nano Research, 2012
The main topic of this paper is the study of polyisoprene-multi wall carbon nanotubes (PiMWCNT) c... more The main topic of this paper is the study of polyisoprene-multi wall carbon nanotubes (PiMWCNT) composite's electrical conductivity and volatile organic compound sensing properties with respect to type of multi wall carbon nanotubes used. Electrical percolation parameters like percolation threshold and critical exponent of produced composites are determined and analyzed. PiMWCNT composites exhibit a promising sensitivity to the presence of volatile organic compounds. Therefore the composite's sensing mechanism of volatile organic compounds are analyzed in more detail by applying an original measuring technique which enables simultaneous measurement of an electrical resistance, mass and length change measurement of the sample in the presence and subsequent absence of a vapour. Measurement results enabled the evaluation of both vapour diffusion behavior in the composite and electrical resistance change mechanism.
![Research paper thumbnail of Formation of Optical Gradient in Chemical Solution-Derived PbZr[sub 0.52]Ti[sub 0.48]O[sub 3] Thin Films: Spectroscopic Ellipsometry Investigation](https://attachments.academia-assets.com/44291774/thumbnails/1.jpg)
](Journal of The Electrochemical Society, 2009
Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample ... more Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample preparation conditions on sol-gel PbZr 0.52 Ti 0.48 O 3 ͑PZT 52/48͒ thin-film homogeneity that allows identification and further optimization of thin-film performance. Separate crystallization of the layers determined the optical gradient appearance, irrespective of the chemical solvents used in this work. A more refined analysis showed that a refractive index gradient was apparent in the samples in which lattice parameters strongly changed with thickness. For these films, energy-dispersive X-ray spectroscopy analysis showed significant variation in Pb and Zr. Additionally, complex dielectric functions for each PZT 52/48 thin film in the wide phonon energy ͑1.03-5.39 eV͒ range were evaluated.
Journal of The Electrochemical Society, 2010
Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are r... more Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are reported. The UV-visible optical spectra were analyzed with special attention paid to the direct optical bandgap. Atmospheric radio-frequency barrier torch discharge and pulsed hollow cathode sputtering techniques for the film fabrication were used. For the crystalline films, similar values of the direct optical bandgap were found independent of the growth method used. The analysis of the amorphous films and powders revealed a pronounced Urbach-like exponential absorption tail approaching the bandedge. For the powders, the bandgap energies were larger than those for the crystalline and amorphous films. A decrease in the powder particle size in the powders leads to an increased direct optical bandgap.
We report on the preparation of ferroelectric polymeric nanowires through hard-templating strateg... more We report on the preparation of ferroelectric polymeric nanowires through hard-templating strategy. Wet-impregnation of poly(vinylidene fluoride) (PVDF) and its copolymer poly(vinylidene fluoride-tri fluoro ethylene) [P(VDF TrFE)] was performed into commercially available porous Anodic Alumina Membrane (AAM). The polymeric nanowires show a diameter ranging from 144 to 166 nm, a length of tenth of micron and a high filling ratio of the alumina pores. X-ray diffraction pattern and infrared spectroscopy show the crystallization of both polymers into the ferroelectric β phase. In addition, Curie temperature (T c ) tests show an increase to higher T c for the PVDF-TrFE polymeric nanowires with respect to the bulk polymeric material, thus revealing the importance of confined crystallization into mono-dimensional structures. A piezoelectric behavior was also observed by a voltage generation upon mechanical pressure, without pre-poling or mechanically orienting the polymer. These crystalline piezoelectric nanowires distributed in a vertical array would potentially address applications like mechanical pressure sensors, e.g., in robotics.
... Latvia. Presentation: Poster at E-MRS Fall Meeting 2006, Symposium A, by Ilze Aulika See On-l... more ... Latvia. Presentation: Poster at E-MRS Fall Meeting 2006, Symposium A, by Ilze Aulika See On-line Journal of E-MRS Fall Meeting 2006 Submitted: 2006-05-15 11:50 Revised: 2009-06-07 00:44. Google, Web, science24.com. ...
Optics Express, 2009
The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigatio... more The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigation in oxide thin films and crystals are examined in this work, along with the use of various parameters calculated from ellipsometric data (band gap energy E g , refractive index n and surface roughness) together with the directly measured main ellipsometric angles ψ and ∆, for the detection of phase transitions. The efficiency of spectroscopic ellipsometry on "surface" phase transition and its sensitivity to surface defects are also demonstrated.
Optical Materials, 2008
Structural and optical properties of Ba 0.8 Sr 0.2 TiO 3 (BST) ferroelectric thin films, deposite... more Structural and optical properties of Ba 0.8 Sr 0.2 TiO 3 (BST) ferroelectric thin films, deposited by the pulsed laser ablation (PLD) technique on Si/SiO 2 /Ti/Pt, Si/SrRuO 3 and Si substrates, were performed by X-ray diffraction, micro Raman, atomic force microscopy (AFM), and optical reflectometry measurements. Temperature dependences of the Raman spectrum, and room temperature refractive and extinction indices, and surface roughness were evaluated.
Journal of Nano Research, 2012
The main topic of this paper is the study of polyisoprene-multi wall carbon nanotubes (PiMWCNT) c... more The main topic of this paper is the study of polyisoprene-multi wall carbon nanotubes (PiMWCNT) composite's electrical conductivity and volatile organic compound sensing properties with respect to type of multi wall carbon nanotubes used. Electrical percolation parameters like percolation threshold and critical exponent of produced composites are determined and analyzed. PiMWCNT composites exhibit a promising sensitivity to the presence of volatile organic compounds. Therefore the composite's sensing mechanism of volatile organic compounds are analyzed in more detail by applying an original measuring technique which enables simultaneous measurement of an electrical resistance, mass and length change measurement of the sample in the presence and subsequent absence of a vapour. Measurement results enabled the evaluation of both vapour diffusion behavior in the composite and electrical resistance change mechanism.
Journal of The Electrochemical Society, 2009
Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample ... more Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample preparation conditions on sol-gel PbZr 0.52 Ti 0.48 O 3 ͑PZT 52/48͒ thin-film homogeneity that allows identification and further optimization of thin-film performance. Separate crystallization of the layers determined the optical gradient appearance, irrespective of the chemical solvents used in this work. A more refined analysis showed that a refractive index gradient was apparent in the samples in which lattice parameters strongly changed with thickness. For these films, energy-dispersive X-ray spectroscopy analysis showed significant variation in Pb and Zr. Additionally, complex dielectric functions for each PZT 52/48 thin film in the wide phonon energy ͑1.03-5.39 eV͒ range were evaluated.
Journal of The Electrochemical Society, 2010
Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are r... more Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are reported. The UV-visible optical spectra were analyzed with special attention paid to the direct optical bandgap. Atmospheric radio-frequency barrier torch discharge and pulsed hollow cathode sputtering techniques for the film fabrication were used. For the crystalline films, similar values of the direct optical bandgap were found independent of the growth method used. The analysis of the amorphous films and powders revealed a pronounced Urbach-like exponential absorption tail approaching the bandedge. For the powders, the bandgap energies were larger than those for the crystalline and amorphous films. A decrease in the powder particle size in the powders leads to an increased direct optical bandgap.
We report on the preparation of ferroelectric polymeric nanowires through hard-templating strateg... more We report on the preparation of ferroelectric polymeric nanowires through hard-templating strategy. Wet-impregnation of poly(vinylidene fluoride) (PVDF) and its copolymer poly(vinylidene fluoride-tri fluoro ethylene) [P(VDF TrFE)] was performed into commercially available porous Anodic Alumina Membrane (AAM). The polymeric nanowires show a diameter ranging from 144 to 166 nm, a length of tenth of micron and a high filling ratio of the alumina pores. X-ray diffraction pattern and infrared spectroscopy show the crystallization of both polymers into the ferroelectric β phase. In addition, Curie temperature (T c ) tests show an increase to higher T c for the PVDF-TrFE polymeric nanowires with respect to the bulk polymeric material, thus revealing the importance of confined crystallization into mono-dimensional structures. A piezoelectric behavior was also observed by a voltage generation upon mechanical pressure, without pre-poling or mechanically orienting the polymer. These crystalline piezoelectric nanowires distributed in a vertical array would potentially address applications like mechanical pressure sensors, e.g., in robotics.