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1
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Transport Properties of Nitrided VN-SiO_{2} Sol-Gel Derived Films

100%
Kościelska B.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 4
744-746
EN
This work presents transport properties of xVN-(100-x)SiO_{2} (where x = 90, 80, 70, 60 mol%) films. The films were prepared by thermal nitridation of sol-gel derived V_{2}O_{3}-SiO_{2} (in proper molar ratio) coatings. The coatings obtained by sol-gel method are especially suitable for the ammonolysis because of their porosity. The microporous structure allows both a significant incorporation of nitrogen and its distribution through the film. The nitridation process of V_{2}O_{3}-SiO_{2} coatings leads to the formation of disordered structures, with VN metallic grains dispersed in the matrix of insulating SiO_{2}. The critical temperatures of the superconducting transition of the samples T_{conset} are about 7.5 K.
2
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Superconducting Properties of NbN-SiO_2 Sol-Gel Derived Thin Films

51%
Kościelska B., Yuzephovich O., Bengus S., Witkowska A.
Acta Physica Polonica A
|
2010
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vol. 118
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issue 2
383-385
EN
This work presents results of superconducting properties studies of xNbN-(100-x)SiO_2 (where x = 80 mol%) films of the thickness from 450 to 1950 nm. The films were prepared by thermal nitridation of sol-gel derived xNb_2O_5-(100-x)SiO_2 coatings. The nitridation process of Nb_2O_5-SiO_2 coatings leads to the formation of weakly disordered structures, with NbN metallic grains dispersed in the matrix of insulating SiO_2. All the samples in the normal state exhibit negative temperature coefficient of resistivity. Superconducting transition was not observed for the sample 450 nm thick. To examine the influence of magnetic field on superconducting properties of the films, the resistance versus temperature of 1350 and 1650 nm thick samples was measured in high magnetic fields. Resistive superconducting transitions are broadened due to the magnetic flux creep. The perpendicular upper critical magnetic fields for 1350 and 1650 thick samples are about 4.4 T. The critical temperatures of the superconducting transitions are about 4.5 K. Specific features of the magnetic field induced superconductor-insulator transition are found.
3
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XPS Study of Superconducting LiTi_2O_4 and LiTi_{2-x}Cu_{x}O_4 Sol-Gel Derived Powders and Thin Films

51%
Łapinski M., Kościelska B., Winiarski A., Sadowski W.
Acta Physica Polonica A
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2014
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vol. 126
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issue 4a
A-107-A-110
EN
In this work X-ray photoelectron studies of lithium titanate and copper doped lithium titanate are presented. Both, powder and thin films samples were prepared by sol-gel method. After preparation, the samples were heated in argon atmosphere at various temperatures in a range from 500 °C to 600 °C for 20 h. The crystalline structure of the samples was investigated by X-ray diffraction, while the oxidation states of the elements were examined by X-ray photoelectron spectroscopy method. X-ray diffraction measurements confirmed spinel phase of all manufactured samples. However it is well known that electrical and superconducting properties of lithium titanate are strongly correlated not only with structure, but also with oxidation state of Ti ions. X-ray photoelectron spectroscopy investigations revealed mixture of Ti^{3+} and Ti^{4+} ions, although the Ti^{3+}/Ti^{4+} ratio is much smaller than 1/2 needed for superconductivity. In this work dependence between calcination temperature as well as amount of Cu dopant and Ti^{3+}/Ti^{4+} proportion are reported.
4
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Structural Studies of Titanium Oxide Multilayers

39%
Karwasz G., Miotello A., Zomer E., Brusa R., Kościelska B., Armellini C., Kuzmin A.
Acta Physica Polonica A
|
2005
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vol. 107
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issue 6
977-982
EN
Multilayers of titanium oxide on conductive glasses (silica, covered with indium/tin and tin oxides) were obtained by different methods (from suspension, by sol-gel, by vacuum sputtering). X-ray diffraction and positron annihilation depth-resolved characterization of these samples are presented. The data allow us to determine optimal deposition parameters, in order to obtain the anatase phase, important in practical applications in photoelectrochemical cells.
5
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Superconducting Properties of VN-SiO_{2} Sol-Gel Derived Thin Films

39%
Kościelska B., Yuzephovich O., Bengus S., Winiarski A., Sadowski W., Łapiński M.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 4
832-835
EN
In this work studies of structure and superconducting properties of VN-SiO_{2} films are reported. The films were obtained through thermal nitridation (ammonolysis) of sol-gel derived V_{2}O_{3}-SiO_{2} coatings (in a proper V_{2}O_{3}/SiO_{2} ratio) at 1200°C. This process leads to the formation of disordered structure with VN metallic grains dispersed in the insulating SiO_{2} matrix. The structural transformations occurring in the films as a result of ammonolysis were studied using X-ray photoelectron spectroscopy (XPS). The critical superconducting parameters are obtained. The magnetoresistance at high magnetic fields has been investigated.
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