Katarína Gmucová
Slovak Academy of Sciences
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Featured researches published by Katarína Gmucová.
Review of Scientific Instruments | 1999
I. Thurzo; Katarína Gmucová; Jozef Orlický; Juraj Pavlásek
As an alternative to the numerous state-of-the-art versions of voltammetry, a kinetics-sensitive double-step voltcoulometry is introduced. The transient current flowing in response to a potential step across the electrochemical cell is integrated and simultaneously processed by a deliberately selected time-domain “cascade” filter, while scanning the applied potential. In contrast to the widely used sampling scheme of sampling the transient current just before and in the end of the excitation pulse, three values of the transient charge are sampled in the interval between subsequent excitation pulses. Each measuring period is preceded by a single measurement of the steady-state current with the excitation pulse being switched off. The latter measurement makes it possible to actively compensate the parasitic charge across the feedback capacitor of the integrator, due to the steady-state current, while storing the steady-state current data. The goal of introducing the third sampling event resides in discrimin...
Solid State Ionics | 2000
M. Hartmanová; Katarína Gmucová; I. Thurzo
Abstract The dielectric permittivities of fcc yttria-stabilized zirconia (YSZ) and ceria (CeO 2 ) thin films as-grown on n-doped Si(100) substrates by electron beam evaporation at 200°C in the metal–insulator–semiconductor (MIS) configuration have been investigated. Two independent methods were used for this purpose, the high frequency limiting capacitance C P and feedback charge C – V plots. The values obtained are 16.8 (YSZ) and 2.8 (CeO 2 ) in the case of C P and 18.3 (YSZ) and 3.4 (CeO 2 ) from the C – V measurements. The hysteresis of C – V curves observed for both Al/YSZ and CeO 2 /Si/Au structures can be ascribed to the slow redistribution of negative mobile charges (oxygen ions O 2− ) present inside the YSZ and CeO 2 films.
Japanese Journal of Applied Physics | 2011
Martin Weis; Katarína Gmucová; Vojtech Nádaždy; E. Majkova; Daniel Haško; Dai Taguchi; Takaaki Manaka; Mitsumasa Iwamoto
We report on charge transport properties of polycrystalline pentacene films with variable average grain size in the range from 0.1 to 0.3 µm controlled by the preparation technology. We illustrate with the organic field-effect transistors decrease of the effective mobility and presence of traps with decrease of the grain size. Analysis of the charge transfer excitons reveals decrease of the mobile charge density and the steady-state voltammetry showed significant increase of oxygen- and hydrogen-related defects. We also briefly discuss accumulation of the defects on the grain boundary and show relation between the defect density and grain boundary length.
Solid State Ionics | 1999
M. Hartmanová; Katarína Gmucová; M. Jergel; I. Thurzo; František Kundracik; M. Brunel
Abstract Analyses of the phase composition and electrical characterization of double-layer CeO 2 /YSZ and single-layer CeO 2 , YSZ dielectrics grown on a Si (100) substrate at 200°C by electron beam evaporation as well as of the quality of interfaces between the oxide layers and silicon substrates were performed. The structure of all investigated oxide layers was found to be of the fcc fluorite type. The electrical conductivity of the investigated oxide layers and the average grain size change due to the post-deposition thermal treatment. The temperature dependence of the activation energy of the electrical conductivity is associated with different impurity phases in the oxide layers. Due to the lowest density of defects assessed from deep-level-transient-spectroscopy (DLTS) measurements, the CeO 2 /Si interface seems to be an optimum compared to the other oxide layer configurations. The dielectric constants e r (YSZ)=18.3 and e r (CeO 2 )=3.4 were estimated from the accumulation capacitances of the C – V curves.
ChemPhysChem | 2008
Katarína Gmucová; Martin Weis; Vojtech Nádaždy; E. Majkova
The effect of electric and magnetic fields on the sandwich structure Pt/hydrogenated amorphous silicon (a-Si:H)/stearic acid monolayer/Langmuir-Blodgett film of Ag/Co nanoparticles encapsulated in an organic envelope is studied. This structure is used as a working electrode in an electrochemical cell filled with NaCl solution (1 mM) and equipped with an Ag/AgCl reference electrode. Reversible changes in voltammograms are observed due to treatments (negative or positive bias voltage and simultaneous laser irradiation) applied to the designed structure before measurements. As an explanation of the observed phenomena we suggest that both the Co-up and Ag-up (on the a-Si:H surface) orientation orderings of nanoparticle Ag/Co cores are repeatedly reached. The role of the photovoltaic material (a-Si:H) in the observed behavior is explained. Voltammetric measurements with an applied magnetic field support our idea about the orientation ordering of nanoparticle cores.
Journal of Electroanalytical Chemistry | 2001
I. Thurzo; Katarína Gmucová; Jozef Orlický; Juraj Pavlásek
Abstract An alternative electroanalytical technique to the widely used differential pulse voltammetry (DPV) is presented in connection with monitoring proton redox reactions in strong acids (HCl, H2SO4, HNO3) and in l -ascorbic acid (AA) in the absence of any supporting electrolyte. Contrary to the DPV method, the current flowing through the working electrode in response to a double-step change of the applied potential is first integrated and subsequently processed by a three-channel correlator. Expressing the faradaic transient charge as Q(t)∝tβ, the ratio Rβ=[Q(t1)−2Q(5t1)+Q(9t1)/(Ilimt1), where t1 is the delay of the first sampling event with respect to the trailing edge of the potential double step and Ilim is the limiting current of the corresponding steady-state voltammetric wave, it is calculated and then compared to the values found experimentally. The sensitivity to the kinetics represented as dRβ/dβ has an optimum around β=0.5, a value consistent with the Cottrell equation. The experimental data point to a crucial role of CO2 (H2CO3) dissolved in the acid solution, envisaged as the reversed sign of the measured charge. After deaerating the solution by argon the sign became positive, nevertheless the experimental Rβ values were systematically higher than the predicted ones. The reaction of the protons of AA at negative potentials seems to be of the EC type when proceeding from negative to more positive potentials. Moreover, there is a dominant voltammetric wave of AA at positive potentials coming from an irreversible reaction, accompanied by a relatively weak peak of the correlated charge.
Russian Journal of Electrochemistry | 2003
M. Hartmanová; M. Jergel; I. Thurzo; František Kundracik; Katarína Gmucová; S. Chromik; L. Ortega
Data obtained in an investigation of yttria-stabilized zirconia (YSZ) and ceria thin films are reviewed and discussed with special regard to the preparation conditions, namely, the temperature of deposition and the post-deposition thermal treatment of films. The structure, phase composition, electrical and dielecric properties, and problems that can be met when measuring effective and real ohmic resistances are compared with the results reported by other authors. The YSZ (CeO2)/Si interfaces are studied by means of deep level transient spectroscopy and feedback charge method capacitance–voltage measurements.
AIP Advances | 2017
F. Schauer; L. Tkáč; M. Ožvoldová; Vojtech Nádaždy; Katarína Gmucová; M. Jergel; Peter Siffalovic
Low stability and degradability of polymers by ambient air, UV irradiation or charge transport are major problems of molecular electronics devices. Recent research tentatively suggests that the presence of a crystalline phase may increase polymer stability due to an intensive energy trapping in the ordered phase. Using the UV degradability, we demonstrate this effect on an archetypal model σ bonded polymer - poly[methyl(phenyl)silane] (PMPSi) - with partially crystalline and amorphous-like layers. UV degradation with 345 nm, derived from the branching state generation rate, was inversely proportional to the crystalline phase content, changing from 4.8x1011 s-1 (partially crystalline phase) to 1.8x1013 s-1 (amorphous-like phase). A model is proposed where crystallites formed by molecular packing act as effective excitation energy traps with a suppressed nonradiative recombination improving thus PMPSi film stability. The molecular packing and higher crystalline phase proportion may be a general approach for...
Physica Status Solidi (a) | 1997
I. Thurzo; Katarína Gmucová
Presented paper is devoted to both the validity and consequences of Meyer-Neldel rule (MNR) for the spectroscopy of surface states in GaAs. Model calculations of a first-order charge DLTS filter response originating from a spectrum of discrete traps at energies E i , having capture cross-sections activated according to MNR as σ i = σ i0 exp (E i /E 0 ), are shown. It is found that a critical temperature T 0 = E v /k appears in the DLTS spectrum, for which temperature the emission rates from all the levels are the same and, as follows, above this temperature the traps at higher energies E i release charge carriers at higher rates, compared to those at lower ones. Going out from the present results, a few guidelines are provided, how to extract correct data.
Journal of Applied Physics | 2018
F. Schauer; Vojtech Nádaždy; Katarína Gmucová
There is potential in applying conjugated polymers in novel organic optoelectronic devices, where a comprehensive understanding of the fundamental processes and energetics involved during transport and recombination is still lacking, limiting further device optimization. The electronic transport modeling and its optimization need the energy distribution of transport and defect states, expressed by the energy distribution of the Density of States (DOS) function, as input/comparative parameters. We present the Energy Resolved-Electrochemical Impedance Spectroscopy (ER-EIS) method for the study of transport and defect electronic states in organic materials. The method allows mapping over unprecedentedly wide energy and DOS ranges. The ER-EIS spectroscopic method is based on the small signal interaction between the surface of the organic film and the liquid electrolyte containing reduction-oxidation (redox) species, which is similar to the extraction of an electron by an acceptor and capture of an electron by...