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Wyświetlanie 1-15 z 15
Tytuł:
Room Temperature Ferroelectric Mixture of Chiral and Achiral Thioesters
Autorzy:
Czerwiec, J.
Ossowska-Chruściel, M.
Chruściel, J.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1538218.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
78.15.+e
64.70.M-
Opis:
Dielectric properties of the mixture of two thioester compounds: 4-8-alkoxy-benzoate-thio-carboxyl S-4-pentyl-phenyl (8OS5), (s)-4-(1-methyl-heptyloxy)biphenyl-4-thio-carboksyl 4-9-alkil-phenyl (MHOBS9) are presented. The chiral compound exhibits nematic (N*) and ferroelectric smectic C* phase (SmC*). The achiral compound shows N, SmA and monotropic SmC and SmB phases. the mixture of both compounds of 0.5 molar fraction shows SmC* in the wider temperature range than pure MHOBS9. The mixture was studied using frequency domain dielectric spectroscopy. Dielectric measurements for the SmC* phase of the mixture revealed Goldstone mode at higher frequencies and Maxwell-Wagner relaxation at low frequencies.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 549-552
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Properties of Ferroelectric Liquid Crystals with Diversified Molecular Structure
Autorzy:
Czerwiec, J.
Dąbrowski, R.
Żurowska, M.
Ziobro, D.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1538235.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
78.15.+e
64.70.M-
Opis:
Mesomorphic, thermodynamic, electro-optic and dielectric properties of three homologues of fluorosubstituted esters are described. Full chemical names of these compounds are as follows: (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-penta-fluoro-propano-ynloxyhex-1-oxy)-biphenyl-4-yl (in short 2F6BBiOC8), (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-nona-fluoro-pentano-yloxyhex-1-oxy)-biphenyl-4-yl (in short 4F6BBiOC8), (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-trideca-fluoro-heptano-yloxyhex-1-oxy)-biphenyl-4-yl (in short 6F6BBiOC8). The compounds exhibit ferroelectric smectic C* phase between crystalline and isotropic phase. Only one compound (6F6BBiOC8) shows antiferroelectric phase $(SmC_{A}^\ast)$ observed by dielectric spectroscopy, but the range of this phase is narrow of about 2°. All three compounds exhibit in the SmC* phase Goldstone mode and Maxwell-Wagner relaxation hidden in the conductivity contribution at low frequencies, whereas in the $SmC_{A}^\ast$ phase two anti-ferroelectric modes (AFM1) and (AFM2) contribute to the dielectric spectrum. The compounds were studied using differential scanning calorimetric, frequency domain dielectric spectroscopy, and reversal currents method to determine spontaneous polarization.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 553-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferroelectric Liquid Crystal for Use in a New Generation of LCDs
Autorzy:
Fitas, J.
Marzec, M.
Tykarska, M.
Wróbel, S.
Dąbrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399018.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.M-
Opis:
The key to improvements in liquid crystalline displays lies in the continuous synthesis and studies of new kinds of liquid crystalline substances. Among them, ferroelectric compounds are the subject of much attention, due to the potential progresses in switching time, colour depth, and other qualities of liquid crystal displays. In this paper we describe the research of the physical properties of 4-(2-methylbutoxy)phenyl 4-(octyloxy)-benzoate for purposes of its potential application in liquid crystal displays.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 954-958
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Reorientation Studies in Nd$\text{}_{2}$Fe$\text{}_{14-x}$Si$\text{}_{x}$B (0
Autorzy:
Gargula, R.
Pędziwiatr, A.
Bogacz, B.
Wróbel, S.
Bartolomé, J.
Stankiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/2030427.pdf
Data publikacji:
2002-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Ww
76.80.+y
64.60.-i
Opis:
Nd$\text{}_{2}$Fe$\text{}_{14-x}$Si$\text{}_{x}$B (x=0.25, 0.5, 0.75, 1.0, 1.5, 2.0) intermetallic compounds were investigated by magnetometry, $\text{}^{57}$Fe Mössbauer effect, electric resistivity, and differential scanning calorimetry mainly in the vicinity of the spin reorientation temperature, T$\text{}_{SR}$. The Curie temperature, T$\text{}_{C}$, and T$\text{}_{SR}$ were determined for different compositions and the spin phase diagram was constructed. $\text{}^{57}$Fe Mössbauer spectra showed noticeable changes in the reorientation region. For temperatures above the transition, the spectra were analysed using 6 Zeeman patterns associated with 6 inequivalent crystal sites in Nd$\text{}_{2}$Fe$\text{}_{14}$B according to site occupations (16k$\text{}_{1}$:16k$\text{}_{2}$:8j$\text{}_{1}$:8j$\text{}_{2}$:4c:4e). In the transition region, 12 subspectra had to be incorporated in the analysis. Electric resistivity measurements showed a typical metallic behaviour with no anomalies in the magnetic transition region. Differential scanning calorimetry measurements revealed broad endothermic two stage peaks around T$\text{}_{SR}$.
Źródło:
Acta Physica Polonica A; 2002, 101, 2; 289-294
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters
Autorzy:
Mikułko, A.
Fraś, M.
Marzec, M.
Wróbel, S.
Ossowska-Chruściel, M.
Chruściel, J.
Powiązania:
https://bibliotekanauki.pl/articles/1813171.pdf
Data publikacji:
2008-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
61.30.Eb
77.22.-d
66.10.Ed
Opis:
The main objective of this paper is to study dielectric properties of two compounds of acronyms 5OSCl and 6OSCl having strongly polar bond (C-Cl) at para position. Dielectric measurements were done in the frequency range from 40 Hz to 15 MHz. The dielectric spectra were measured for two principal alignments. For homeotropic alignment, the reorientation of molecule around the short molecular axis was observed. Both substances studied exhibit large positive dielectric anisotropy and the anisotropy of conductivity was obtained in smectic A as well as nematic phase.
Źródło:
Acta Physica Polonica A; 2008, 113, 4; 1155-1160
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous Dielectric Spectra of Ferro- and Ferrielectric Liquid Crystalline Phase in MHPNBC
Autorzy:
Dubois, F.
Douali, R.
Wawrzyniak, A.
Legrand, Ch.
Ropa, P.
Wróbel, S.
Dąbrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399013.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Gm
77.84.Nh
64.70.M
Opis:
MHPOBC analogue with long achiral alkyl chain has been investigated by dielectric spectroscopy studies in the wide temperature range. Low frequency dielectric spectroscopy revealed the existence of normal ferroelectric phase (in a narrow gap), two ferri- and three antiferroelectric phases in addition to paraelectric phase and alpha sub-phase. The compound studied shows exceptionally strong dependence of the dielectric permittivities on measuring electric field in the temperature range of ferro- and ferrielectric phases.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 937-939
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of New Antiferroelectric Liquid Crystal Based on Quantum-Chemical Model
Autorzy:
Tomczyk, W.
Marzec, M.
Juszyńska, E.
Dąbrowski, R.
Ziobro, D.
Wróbel, S.
Massalska-Arodź, M.
Powiązania:
https://bibliotekanauki.pl/articles/1399016.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.M-
Opis:
Physical properties of new thermotropic antiferroelectric liquid crystal have been studied. Experiments were done by use of complementary methods such as differential scanning calorimetry, polarizing optical microscopy and X-ray powder diffractometry. Acquired data from X-ray powder diffractometry was examined under application of quantum chemical approach. It has been found that compound studied exhibits stable enantiotropic antiferroelectric SmC_{A}* phase in the wide temperature range while ferroelectric phase SmC* is very narrow.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 949-953
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamics and Phase Transitions of 4-Bromobenzylidene-4'-pentyloxyaniline and 4-Bromobenzylidene-4'-hexyloxyaniline as Studied by Dielectric Spectroscopy
Autorzy:
Osiecka, N.
Massalska-Arodź, M.
Galewski, Z.
Chłędowska, K.
Wróbel, S.
Morito, T.
Yamamura, Y.
Saito, K.
Powiązania:
https://bibliotekanauki.pl/articles/1399008.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.pp
64.70.M-
33.15.Bh
Opis:
Significant differences in phase sequence and dynamics between 4-bromobenzylidene-4'-pentyloxyaniline (5BBA) and -bromobenzylidene-4'-heksyloxyaniline (6BBA) substances were detected by broadband dielectric spectroscopy. In the smectic A (6BBA), the smectic B (found in both substances) and the smectic E (5BBA) phases the relaxation was ascribed to reorientations of the molecules around the short axes. Slow dynamics detected in the smectic E and in two crystalline phases of 5BBA was ascribed to conformational changes of molecular chains. Coexistence of Cr(I) and Cr(II) conformationally disordered crystal (CONDIS) phases was observed and vitrification of Cr(II) was identified with help of polarizing microscopy.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 913-916
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters
Autorzy:
Wierzejska-Adamowicz, M.
Ossowska-Chruściel, D.
Chruściel, J.
Douali, R.
Legrand, Ch.
Marzec, M.
Mikułko, A.
Sikorska, A.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1538244.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
77.84.-s
78.20.Jq
Opis:
Electrooptic and dielectric measurements were done for B phases of two banana-shaped homologues 1,3-phenylene bis{4-[(4-nonylo-xy-benzoyl)sulfanyl]benzoate (9OSOR) and 1,3-phenylene bis{4-[(4-dodecylo-xy-benzoyl)sulfanyl]benzoate (12OSOR). Polarizing microscopy allowed to identify $B_{1}$ phase for 9OSOR and $B_{2}$ phase for 12OSOR on the basis of texture observation. Spontaneous polarization measurements were performed using reversal current method. The current response to applied triangular voltage shows that $B_{1}$ phase is a ferroelectric and $B_{2}$ phase - antiferroelectric one for which two well separated peaks were observed. Polarization for phase $B_{1}$ of 9OSOR is rather small and its temperature dependence is unusual for ferroelectric liquid crystals - it increases with temperature. Spontaneous polarization for $B_{2}$ phase of 12OSOR compound is of about 600 nC/$cm^{2}$. Dielectric spectra measured with bias field for $B_{2}$ phase of 12OSOR show two well separated relaxation processes. In the low frequency range the relaxation process is connected with fluctuations of ferroelectric domains. The relaxation process in the high frequency range appearing also without bias field is connected with molecular reorientation. The dielectric spectra measured for $B_{1}$ phase of 9OSOR with and without bias voltage showed only one dielectric relaxation process connected with molecular reorientation around the short axis.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 557-561
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy
Autorzy:
Wawrzyniak, A.
Chruściel, J.
Douali, R.
Dubois, F.
Leblond, J.
Legrand, Ch.
Ossowska-Chruściel, D.
Marzec, M.
Ropa, P.
Czerwiec, J.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1399012.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.M-
77.22.Gm
77.22.Ej
Opis:
(S)-(+)-4'-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short 10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addition to ferroelectric and antiferroelectric smectic C* phases it possesses three ferrielectric sub-phases. Phase transitions between the phases were revealed by differential scanning calorimetry and static dielectric permittivity measurements. The aim of this paper was to study phase transitions and differences in dielectric spectra shown by different phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other originating from fluctuations of antiferroelectric order parameters.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 933-936
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Chemistry of Zirconia Nanopowders Doped with $Pr_2O_3$: an XPS Study
Autorzy:
Suchorski, Y.
Wrobel, R.
Becker, S.
Opalińska, A.
Narkiewicz, U.
Podsiadly, M.
Weiss, H.
Powiązania:
https://bibliotekanauki.pl/articles/1811498.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.60.-i
61.46.-w
61.46.Hk
Opis:
Zirconia nanopowders of tetragonal crystallographic structure doped with $Pr_2O_3$ were prepared by the microwave-assisted hydrothermal synthesis and coprecipitation method. The surface compositions were studied by X-ray photoelectron spectroscopy. The nanopowder particles appear to be inhomogeneous in their structure: for the surface region an enrichment with praseodymium is detected by X-ray photoelectron spectroscopy measurements. This allows the assumption of a core-shell-like structure of single nanopowders particles. The X-ray photoelectron spectroscopy studies confirm also $Zr^{4+}$ and $Pr^{3+}$ as main oxidation states of zirconium and praseodymium in the studied compounds.
Źródło:
Acta Physica Polonica A; 2008, 114, S; S-125-S-134
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrostatic Gates for GaN/AlGaN Quantum Point Contacts
Autorzy:
Czapkiewicz, M.
Cywiński, G.
Dybko, K.
Siekacz, M.
Wolny, P.
Gierałtowska, S.
Guziewicz, E.
Skierbiszewski, C.
Wróbel, J.
Powiązania:
https://bibliotekanauki.pl/articles/1403637.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Qv
73.61.Ng
73.23.-b
Opis:
We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of $HfO_2$ or $Al_2O_3//HfO_2$ composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current $I_g < 10^{-11}$ A at gate voltages $|V_g|$ < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-off voltage at $V_g$ = - 3.5 V at a cost of $I_g ≈ 10^{-6} A$, which has been identified as a bulk leakage current.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 1026-1028
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence Properties of ZnO and ZnCdO Nanowires
Autorzy:
Zaleszczyk, W.
Fronc, K.
Aleszkiewicz, M.
Paszkowicz, W.
Wróbel, J.
Dłużewski, P.
Kret, S.
Klepka, M.
Kłopotowski, Ł.
Karczewski, G.
Wojtowicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/2047698.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Et
78.67.Bf
81.05.Dz
81.07.Bc
Opis:
We report on the photoluminescence studies of ZnO and ZnCdO nanowires grown on SiO$\text{}_{2}$/Si substrates by low-pressure vapor phase synthesis. X-ray diffraction and transmission electron microscopy measurements show that the crystallographic structure of these ZnO and ZnCdO nanowires is of wurtzite-type with a high crystal perfection. Surface morphology of samples was determined by scanning electron microscopy and atomic force microscopy. The photoluminescence spectra of as-grown nanowires, nanowires extracted from the substrate and deposited onto Si wafer, and nanowires dispersed in ethanol by sonication were investigated at room temperature and compared to each other. The temperature dependence of the near band-gap photoluminescence emitted by the as-grown nanowires was also measured and analyzed.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 357-362
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication and Electrical Characterization of PbS-EuS Ferromagnetic Semiconductor Microstructures
Autorzy:
Wrotek, S.
Morawski, A.
Tkaczyk, Z.
Mąkosa, A.
Wosiński, T.
Dybko, K.
Łusakowska, E.
Story, T.
Sipatov, A. Yu.
Pécz, B.
Grasza, K.
Szczerbakow, A.
Wróbel, J.
Powiązania:
https://bibliotekanauki.pl/articles/2038135.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.61.Le
75.30.Et
75.70.Cn
Opis:
Current-voltage characteristics and temperature dependence of differential conductance were studied in lithographically patterned (lateral dimensions from 10 x 10 μm$\text{}^{2}$ to 100 x 100 μm$\text{}^{2}$) ferromagnetic EuS-PbS-EuS microstructures. Below the ferromagnetic transition temperature a 4% decrease in the structure conductance was observed for mutual antiferromagnetic orientation of magnetization vectors of ferromagnetic EuS layers.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 615-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertical Electron Transport through PbS-EuS Structures
Autorzy:
Wrotek, S.
Dybko, K.
Morawski, A.
Mąkosa, A.
Wosiński, T.
Figielski, T.
Tkaczyk, Z.
Łusakowska, E.
Story, T.
Sipatov, A. Yu.
Szczerbakow, A.
Grasza, K.
Wróbel, J.
Palosz, W.
Powiązania:
https://bibliotekanauki.pl/articles/2036032.pdf
Data publikacji:
2003-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
Temperature dependence of current-voltage I-V characteristics and resistivity is studied in ferromagnetic PbS-EuS semiconductor tunnel structures grown on n-PbS (100) substrates. For the structures with a single (2-4 nm thick) ferromagnetic EuS electron barrier we observe strongly non-linear I-V characteristics with an effective tunneling barrier height of 0.3-0.7 eV. The experimentally observed non-monotonic temperature dependence of the (normal to the plane of the structure) electrical resistance of these structures is discussed in terms of the electron tunneling mechanism taking into account the temperature dependent shift of the band offsets at the EuS-PbS heterointerface as well as the exchange splitting of the electronic states at the bottom of the conduction band of EuS.
Źródło:
Acta Physica Polonica A; 2003, 103, 6; 629-635
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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