Martin Loncaric | Ruder Boskovic Institute (original) (raw)
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Papers by Martin Loncaric
Journal of Physics: Condensed Matter, 2003
Transport and low-frequency optical reflection measurements are reported for the quasi-three-dime... more Transport and low-frequency optical reflection measurements are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH 3 ) 2 -DCNQI) 0.70 (2,5(CD 3 ) 2 -DCNQI) 0.30 ] 2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott-Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.
Photodiagnosis and Photodynamic Therapy, 2007
Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, wit... more Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, with the ability to accumulate in tumour tissue, by the use of fluorescence imaging. Of particular importance is the application of δ-5-aminolaevulinic acid (ALA) that, through the process of biosynthesis causes formation of the protoporphyrin IX (PpIX). The PpIX has the ability of selective fluorescence after basal cell carcinoma (BCC) has been treated with ALA. Higher concentration of PpIX in tumour tissue compared to surrounding normal skin is the basis for PDD. Our contribution in this preliminary study is application of the independent component analysis (ICA) to extract the BCC spatial map, by processing fluorescent RGB image acquired under excitation with 405nm light. Comparative performance analysis with other two widely used image processing methods: ratio imaging and optimal threshold based imaging, reveals that ICA produces BCC spatial map that is most consistent in term of diagnostic quality by both visual assessment and calculation of the BCC demarcation line. We believe this represents a solid basis for the design of a compact and low-cost multi-spectral fluorescence imaging system, capable for real time calculation of the skin tumour demarcation.
Synthetic Metals, 2001
ABSTRACT Electric-field-dependent measurements are reported in the low-temperature state of the o... more ABSTRACT Electric-field-dependent measurements are reported in the low-temperature state of the organic conductors Cu[2,5(CD3)(2)-DCNQI](2) and Cu[(2,5(CH3)(2)-DCNQI)(0.70)(2,5(CD3)(2)-DCNQI)(0.30)](2) With N=3 commensurate CDW. We correlate observed features of the electric conduction below and above threshold field with the temperature evolution of the N=3 CDW order as detected by the low-frequency dielectric measurements.
The European Physical Journal B, 2000
We report a detailed characterization of an unique 3-fold commensurate insulating state in single... more We report a detailed characterization of an unique 3-fold commensurate insulating state in single crystals of the organic π -inorganic d hybrid Cu(DMe-DCNQI)2 systems with deuterated and partially deuterated DCNQI ring, by means of low-frequency dielectric spectroscopy. A broad relaxation mode of strength ∆ε ≈ 10 3 −10 4 centred at ν0 ≈ 1−10 kHz is observed in the hysteresis temperature region in which the insulating phase coexists with metallic islands. At lower temperatures, outside the nucleation range, the relaxation narrows, approaching a Debye-like form for an overdamped response of a system with a single degree of freedom. Both, the relaxation strength and the mean relaxation time (τ0 =1 /2πν0) are much larger than that expected for single-particle excitations. These features suggest the origin of the dielectric relaxation as an intrinsic property of the N = 3 charge density wave state.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2012
ABSTRACT
Metal island films show unique optical properties owing to the local surface plasmon resonance of... more Metal island films show unique optical properties owing to the local surface plasmon resonance of islands free electrons. In the present study, the electric field assisted dissolution of clusters in metal island films is reported. Island films of Au, Ag, and Cu are deposited under different conditions by thermal evaporation and coated with thin dielectric layers. The samples are treated with the simultaneous application of an intense electric field and temperature, leading to the sample partial or total bleaching due to the dissolution of metal clusters in the films. Owing the facility of production of metal island films and the inexpensive technical requirements of the dissolution process, this approach suggests a novel path for the production of low-cost photonic structures.
Thin Solid Films, 2011
Metal island films of noble metals are obtained by deposition on glass substrates during the firs... more Metal island films of noble metals are obtained by deposition on glass substrates during the first stage of evaporation process when supported metal nanoparticles are formed. These films show unique optical properties, owing to the localized surface plasmon resonance of free electrons in metal nanoparticles. In the present work we study the optical properties of gold metal island films deposited on glass substrates with different mass thicknesses at different substrate temperatures. The optical characterization is performed by spectroscopic ellipsometry at different angles of incidence and transmittance measurements at normal incidence in the same point of the sample. Fitting of the ellipsometric data allows determining the effective optical constants and thickness of the island film. A multiple oscillator approach was used to successfully represent the dispersion of the effective optical constants of the films.
Applied Physics A-materials Science & Processing, 2011
Bimetallic islands films consisting of composite Au-Ag nanoparticles are deposited on glass subst... more Bimetallic islands films consisting of composite Au-Ag nanoparticles are deposited on glass substrates by electron beam evaporation. Broad tuning of the surface-plasmon resonance (SPR) characteristics can be achieved by controlling film composition, deposition temperature and post-deposition thermal annealing. Optical and structural characterization of the samples enable one to establish the link between the SPR and the morphological and compositional characteristics of nanoparticles.
Applied Optics, 2011
We describe the optical properties of gold island films embedded between SiO 2 and/or TiO 2 layer... more We describe the optical properties of gold island films embedded between SiO 2 and/or TiO 2 layers. Plasmonic properties of gold films have been characterized using spectrometry and variable angle spectroscopic ellipsometry for various combinations of the embedding media. The obtained refractive indices of embedded gold island films have been used in the design of several types of multilayer reflectors.
Vacuum, 2009
Metal island films (MIFs) of Ag on glass substrates were fabricated by the e-beam evaporation tec... more Metal island films (MIFs) of Ag on glass substrates were fabricated by the e-beam evaporation technique. The dependence of the surface plasmon (SP) absorption properties on the deposition mass thickness and substrate temperature was quantified. The structural and optical characterization of the MIFs, obtained using spectrometry, grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) evidences the evolution of SP characteristics depending on the fabrication parameters: the red shift of the absorption peaks with the increase of deposition thickness accompanied by peak widening and the blue-shift of peaks with the increase of deposition temperature followed by the peak narrowing. These findings were explained by the differences in the concentration, shape and size of the obtained silver islands.
Vacuum
Polymer electrolytes as nanostructured materials are very attractive for components of batteries ... more Polymer electrolytes as nanostructured materials are very attractive for components of batteries and opto-electronic devices. (PEO) 8 ZnCl 2 polymer electrolytes and nanocomposites were prepared using PEO -irradiated to a selected dose of 529 kGy and with addition of 10% of TiO 2 nanograins. The influence of the added nanosize TiO 2 grains to the polymer electrolytes and the effect of -radiation from a Co-60 source were studied by smallangle X-ray scattering (SAXS) simultaneously recorded with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) at the synchrotron ELETTRA. Infrared (IR) and impedance spectroscopy (IS) were also performed [1]. It was shown by previous impedance spectroscopy (IS) that the room temperature conductivity of nanocomposite polymer electrolyte increased more than two times above 65°C, relative to pure composites of PEO and salts. We observed changes between 293 K and 373 K for treated and as prepared polymer electrolyte in SAXS, DSC and WAXD spectra and during the phase transition to the superionic phase at 335 K [2, 3]. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as to differences due to different heating and cooling rates. The crystal structure and temperatures of melting and crystallization of the nanosize grains was revealed by the simultaneous WAXD measurements.
Photodiagnosis and Photodynamic Therapy, 2007
Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, wit... more Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, with the ability to accumulate in tumour tissue, by the use of fluorescence imaging. Of particular importance is the application of ␦-5-aminolaevulinic acid (ALA) that, through the process of biosynthesis causes formation of the protoporphyrin IX (PpIX). The PpIX has the ability of selective fluorescence after basal cell carcinoma (BCC) has been treated with ALA. Higher concentration of PpIX in tumour tissue compared to surrounding normal skin is the basis for PDD. Our contribution in this preliminary study is application of the independent component analysis (ICA) to extract the BCC spatial map, by processing fluorescent RGB image acquired under excitation with 405 nm light. Comparative performance analysis with other two widely used image processing methods: ratio imaging and optimal threshold based imaging, reveals that ICA produces BCC spatial map that is most consistent in term of diagnostic quality by both visual assessment and calculation of the BCC demarcation line. We believe this represents a solid basis for the design of a compact and low-cost multi-spectral fluorescence imaging system, capable for real time calculation of the skin tumour demarcation.
European Physical Journal B, 2000
We report a detailed characterization of an unique 3-fold commensurate insulating state in single... more We report a detailed characterization of an unique 3-fold commensurate insulating state in single crystals of the organic π – inorganic d hybrid Cu(DMe-DCNQI)2 systems with deuterated and partially deuterated DCNQI ring, by means of low-frequency dielectric spectroscopy. A broad relaxation mode of strength ∆ε ≈ 103-104 centred at ν0 ≈ 1-10 kHz is observed in the hysteresis temperature region in which the insulating phase coexists with metallic islands. At lower temperatures, outside the nucleation range, the relaxation narrows, approaching a Debye-like form for an overdamped response of a system with a single degree of freedom. Both, the relaxation strength and the mean relaxation time (T0= 1/2πν0) are much larger than that expected for single-particle excitations. These features suggest the origin of the dielectric relaxation as an intrinsic property of the N = 3 charge density wave state.
Journal of Physics-condensed Matter, 2003
Transport and low-frequency optical reflection measurements (180-380 GHz) are reported for the qu... more Transport and low-frequency optical reflection measurements (180-380 GHz) are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH3)2-DCNQI)0.70(2,5(CD3)2-DCNQI)0.30]2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott-Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.
Journal of Physics: Condensed Matter, 2003
Transport and low-frequency optical reflection measurements are reported for the quasi-three-dime... more Transport and low-frequency optical reflection measurements are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH 3 ) 2 -DCNQI) 0.70 (2,5(CD 3 ) 2 -DCNQI) 0.30 ] 2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott-Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.
Photodiagnosis and Photodynamic Therapy, 2007
Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, wit... more Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, with the ability to accumulate in tumour tissue, by the use of fluorescence imaging. Of particular importance is the application of δ-5-aminolaevulinic acid (ALA) that, through the process of biosynthesis causes formation of the protoporphyrin IX (PpIX). The PpIX has the ability of selective fluorescence after basal cell carcinoma (BCC) has been treated with ALA. Higher concentration of PpIX in tumour tissue compared to surrounding normal skin is the basis for PDD. Our contribution in this preliminary study is application of the independent component analysis (ICA) to extract the BCC spatial map, by processing fluorescent RGB image acquired under excitation with 405nm light. Comparative performance analysis with other two widely used image processing methods: ratio imaging and optimal threshold based imaging, reveals that ICA produces BCC spatial map that is most consistent in term of diagnostic quality by both visual assessment and calculation of the BCC demarcation line. We believe this represents a solid basis for the design of a compact and low-cost multi-spectral fluorescence imaging system, capable for real time calculation of the skin tumour demarcation.
Synthetic Metals, 2001
ABSTRACT Electric-field-dependent measurements are reported in the low-temperature state of the o... more ABSTRACT Electric-field-dependent measurements are reported in the low-temperature state of the organic conductors Cu[2,5(CD3)(2)-DCNQI](2) and Cu[(2,5(CH3)(2)-DCNQI)(0.70)(2,5(CD3)(2)-DCNQI)(0.30)](2) With N=3 commensurate CDW. We correlate observed features of the electric conduction below and above threshold field with the temperature evolution of the N=3 CDW order as detected by the low-frequency dielectric measurements.
The European Physical Journal B, 2000
We report a detailed characterization of an unique 3-fold commensurate insulating state in single... more We report a detailed characterization of an unique 3-fold commensurate insulating state in single crystals of the organic π -inorganic d hybrid Cu(DMe-DCNQI)2 systems with deuterated and partially deuterated DCNQI ring, by means of low-frequency dielectric spectroscopy. A broad relaxation mode of strength ∆ε ≈ 10 3 −10 4 centred at ν0 ≈ 1−10 kHz is observed in the hysteresis temperature region in which the insulating phase coexists with metallic islands. At lower temperatures, outside the nucleation range, the relaxation narrows, approaching a Debye-like form for an overdamped response of a system with a single degree of freedom. Both, the relaxation strength and the mean relaxation time (τ0 =1 /2πν0) are much larger than that expected for single-particle excitations. These features suggest the origin of the dielectric relaxation as an intrinsic property of the N = 3 charge density wave state.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2012
ABSTRACT
Metal island films show unique optical properties owing to the local surface plasmon resonance of... more Metal island films show unique optical properties owing to the local surface plasmon resonance of islands free electrons. In the present study, the electric field assisted dissolution of clusters in metal island films is reported. Island films of Au, Ag, and Cu are deposited under different conditions by thermal evaporation and coated with thin dielectric layers. The samples are treated with the simultaneous application of an intense electric field and temperature, leading to the sample partial or total bleaching due to the dissolution of metal clusters in the films. Owing the facility of production of metal island films and the inexpensive technical requirements of the dissolution process, this approach suggests a novel path for the production of low-cost photonic structures.
Thin Solid Films, 2011
Metal island films of noble metals are obtained by deposition on glass substrates during the firs... more Metal island films of noble metals are obtained by deposition on glass substrates during the first stage of evaporation process when supported metal nanoparticles are formed. These films show unique optical properties, owing to the localized surface plasmon resonance of free electrons in metal nanoparticles. In the present work we study the optical properties of gold metal island films deposited on glass substrates with different mass thicknesses at different substrate temperatures. The optical characterization is performed by spectroscopic ellipsometry at different angles of incidence and transmittance measurements at normal incidence in the same point of the sample. Fitting of the ellipsometric data allows determining the effective optical constants and thickness of the island film. A multiple oscillator approach was used to successfully represent the dispersion of the effective optical constants of the films.
Applied Physics A-materials Science & Processing, 2011
Bimetallic islands films consisting of composite Au-Ag nanoparticles are deposited on glass subst... more Bimetallic islands films consisting of composite Au-Ag nanoparticles are deposited on glass substrates by electron beam evaporation. Broad tuning of the surface-plasmon resonance (SPR) characteristics can be achieved by controlling film composition, deposition temperature and post-deposition thermal annealing. Optical and structural characterization of the samples enable one to establish the link between the SPR and the morphological and compositional characteristics of nanoparticles.
Applied Optics, 2011
We describe the optical properties of gold island films embedded between SiO 2 and/or TiO 2 layer... more We describe the optical properties of gold island films embedded between SiO 2 and/or TiO 2 layers. Plasmonic properties of gold films have been characterized using spectrometry and variable angle spectroscopic ellipsometry for various combinations of the embedding media. The obtained refractive indices of embedded gold island films have been used in the design of several types of multilayer reflectors.
Vacuum, 2009
Metal island films (MIFs) of Ag on glass substrates were fabricated by the e-beam evaporation tec... more Metal island films (MIFs) of Ag on glass substrates were fabricated by the e-beam evaporation technique. The dependence of the surface plasmon (SP) absorption properties on the deposition mass thickness and substrate temperature was quantified. The structural and optical characterization of the MIFs, obtained using spectrometry, grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) evidences the evolution of SP characteristics depending on the fabrication parameters: the red shift of the absorption peaks with the increase of deposition thickness accompanied by peak widening and the blue-shift of peaks with the increase of deposition temperature followed by the peak narrowing. These findings were explained by the differences in the concentration, shape and size of the obtained silver islands.
Vacuum
Polymer electrolytes as nanostructured materials are very attractive for components of batteries ... more Polymer electrolytes as nanostructured materials are very attractive for components of batteries and opto-electronic devices. (PEO) 8 ZnCl 2 polymer electrolytes and nanocomposites were prepared using PEO -irradiated to a selected dose of 529 kGy and with addition of 10% of TiO 2 nanograins. The influence of the added nanosize TiO 2 grains to the polymer electrolytes and the effect of -radiation from a Co-60 source were studied by smallangle X-ray scattering (SAXS) simultaneously recorded with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) at the synchrotron ELETTRA. Infrared (IR) and impedance spectroscopy (IS) were also performed [1]. It was shown by previous impedance spectroscopy (IS) that the room temperature conductivity of nanocomposite polymer electrolyte increased more than two times above 65°C, relative to pure composites of PEO and salts. We observed changes between 293 K and 373 K for treated and as prepared polymer electrolyte in SAXS, DSC and WAXD spectra and during the phase transition to the superionic phase at 335 K [2, 3]. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as to differences due to different heating and cooling rates. The crystal structure and temperatures of melting and crystallization of the nanosize grains was revealed by the simultaneous WAXD measurements.
Photodiagnosis and Photodynamic Therapy, 2007
Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, wit... more Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, with the ability to accumulate in tumour tissue, by the use of fluorescence imaging. Of particular importance is the application of ␦-5-aminolaevulinic acid (ALA) that, through the process of biosynthesis causes formation of the protoporphyrin IX (PpIX). The PpIX has the ability of selective fluorescence after basal cell carcinoma (BCC) has been treated with ALA. Higher concentration of PpIX in tumour tissue compared to surrounding normal skin is the basis for PDD. Our contribution in this preliminary study is application of the independent component analysis (ICA) to extract the BCC spatial map, by processing fluorescent RGB image acquired under excitation with 405 nm light. Comparative performance analysis with other two widely used image processing methods: ratio imaging and optimal threshold based imaging, reveals that ICA produces BCC spatial map that is most consistent in term of diagnostic quality by both visual assessment and calculation of the BCC demarcation line. We believe this represents a solid basis for the design of a compact and low-cost multi-spectral fluorescence imaging system, capable for real time calculation of the skin tumour demarcation.
European Physical Journal B, 2000
We report a detailed characterization of an unique 3-fold commensurate insulating state in single... more We report a detailed characterization of an unique 3-fold commensurate insulating state in single crystals of the organic π – inorganic d hybrid Cu(DMe-DCNQI)2 systems with deuterated and partially deuterated DCNQI ring, by means of low-frequency dielectric spectroscopy. A broad relaxation mode of strength ∆ε ≈ 103-104 centred at ν0 ≈ 1-10 kHz is observed in the hysteresis temperature region in which the insulating phase coexists with metallic islands. At lower temperatures, outside the nucleation range, the relaxation narrows, approaching a Debye-like form for an overdamped response of a system with a single degree of freedom. Both, the relaxation strength and the mean relaxation time (T0= 1/2πν0) are much larger than that expected for single-particle excitations. These features suggest the origin of the dielectric relaxation as an intrinsic property of the N = 3 charge density wave state.
Journal of Physics-condensed Matter, 2003
Transport and low-frequency optical reflection measurements (180-380 GHz) are reported for the qu... more Transport and low-frequency optical reflection measurements (180-380 GHz) are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH3)2-DCNQI)0.70(2,5(CD3)2-DCNQI)0.30]2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott-Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.