► Two arylenevinylene oligomers thin films deposited by vacuum evaporation. ► The best injector contact: 1,4-bis 4-(N,N’-diphenylamino)phenylvinylbenzene/p-type silicon. ► Higher roughness for ...3,3′-bis(N-hexylcarbazole)vinylbenzene film.
This paper discusses the properties of two arylenevinylene oligomers thin films deposited by vacuum evaporation on different substrates. The morphology of the thin films was investigated by scanning electron microscopy and atomic force microscopy, and the optical properties by UV–Vis and fluorescence spectroscopy. The optical nonlinear phenomenon of two-photon absorption induced fluorescence has been evidenced in the thin films of these compounds. We have also investigated the electrical properties of semiconductor/insulator/semiconductor (ITO/oligomer/Si) heterostructures in correlation with the contact energetic barriers, morphological and structural properties of the layers.
The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), ...spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance.
The present paper deals with the preparation and study of optical properties of ZnO nanowires. Nanoporous ion track polycarbonate foils were used as templates for ZnO nanowires growth by ...electrochemical deposition. The growth was performed using an aqueous electrochemical bath at a temperature of 70°C. SEM and TEM were employed to study the morphological properties of the nanowires. Electron diffraction was employed for structural characterization. Reflection and photoluminescence spectroscopy were used for optical characterization. A comparison between the properties of electrodeposited thin films and nanowires of ZnO was made from the point of view of photoluminescence properties.
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Propulsion by actin polymerization is versatilely used in cell motility. Here, we investigate a model of the semi-flexible region of an actin gel close to a propelled object describing the force ...generation, the dynamics of the propagation velocity, filament attachment to and detachment from the obstacle surface and dynamics of the number of filaments, which result from filament nucleation and capping. The model equations are derived as moment equations of the length distributions. We find a variety of dynamic regimes. The filament number may respond very sensitively to small changes of the attachment rate.
Structurally disordered Pr3+-doped Ca3(Ta,Ga)5O12 - Pr:CTGG single crystal was grown by the Czochralski technique for the first time and its spectroscopic properties were investigated. Modified ...Judd-Ofelt analysis was applied to determine spectroscopic and laser emission characteristics. Based on low-temperature absorption and emission spectra, the partial energy levels of Pr3+ ions have been obtained and a multicenter structure of the optical spectra was highlighted. The electron-phonon interactions were also observed in the emission spectra corresponding to the 3P0 → 3H4 transition under different excitation wavelengths. The fluorescence decays of the 3P0 and 1D2 levels were measured. The emission cross-sections corresponding to the 3P0 → 3H4 (486.5 nm) and 3P0 → 3F2 (652.7 nm) transitions were found to be σem = 19 × 10−20 cm2 and σem = 15 × 10−20 cm2, respectively. The values for other parameters that may predict the possibility of achieving efficient laser emission, especially at 486.5 nm, such as quantum efficiency (ⴄ = 50 %), gain bandwidth (σem× Δλeff, = 32.2 × 10−26 cm3), and optical gain (σem× τmeas = 12.86 × 10−25 cm2 s) were determined. The obtained results indicate that the Pr:CTGG crystal has a high potential for obtaining efficient laser emission in the blue domain.
•Pr:CTGG single crystal was grown by the Czochralski technique for the first time.•Influence of (Pr3+-Ta5+) IVCT state on the dynamics of Pr3+ ions is presented.•JO analysis was applied to determine spectroscopic and laser emission characteristics.•Pr:CTGG single crystal is a promising laser material in the blue and red domains.
Bi
2
O
3
and Bi-metal powders were mixed with MgB
2
powder. Starting compositions were (MgB
2
)(Bi
2
O
3
)
x
,
x
=0.0025, 0.005, 0.015, and (MgB
2
)(Bi)
y
,
y
=0.01. Mixtures were processed by Spark ...Plasma Sintering (SPS) technique. As obtained composite samples show high density, above 94 % of the theoretical density. Samples with Bi
2
O
3
for
x
=0.0025 and 0.005 show higher critical current densities,
J
c
, at high fields and at 20 K than for the pristine sample. Their irreversibility field,
H
irr
, is also higher. On the other hand, sample added with Bi-metal has lower
J
c
and
H
irr
at any temperature than for the pristine sample.
In melt-spun FePtB-based ribbons, the addition of Ag has been proven to decrease the temperature of phase transformation from the A1 fcc FePt phase to the hard magnetic tetragonal L1
0
phase. Alloys ...with 6 and 9 at.% Ag added to the initial FePtB have been synthesized by rapid solidification from the melt. The samples have been laser irradiated and submitted to nitriding procedure. This procedure has been proven beneficial for inducing complete transformation of A1 to L1
0
phase and a strong (001) texturing. Ag segregation combined to mechanisms of creation of vacancies and diffusion of N give rise to the formation of an intergranular disordered region and due to an improved interfacial coupling between FePt grains, enhanced coercivity and two-phase magnetic behavior is obtained.
Bulk MgB2 discs were prepared by an in situ route from mixtures of magnesium and boron powders. The boron powders were produced by two methods. The first one consisted of a self-propagating high ...temperature magnesiothermic synthesis (SHS) process followed by acid and fluorine cleaning and a heat treatment in inert atmosphere. This approach produced boron with purities between 86 % and 97 %, where the main impurity was Mg. Depending on the final heat treatment, these boron powders were amorphous or crystalline. In the second route, high purity nano powders (99 %) of boron were obtained by a diborane pyrolysis process. Bulks of MgB2 were characterized by structural, microstructural, and magnetic measurements. Critical current density, pinning force aspects and levitation force (including guiding force) details were assessed. Amorphous lower purity boron (86–97 %) obtained by the first processing route was found to promote the largest levitation forces of the MgB2 bulks and, among these samples, the best levitation results were recorded when using boron with a purity of 95–97 %. Use of a lower purity boron that decreases the cost of MgB2 promotes large scale production at industrial level of bulk MgB2 superconducting magnets for levitation applications and enhances the applicability potential of MgB2 superconductor. The relationship between levitation force and specific features of the samples such as pinning force details are discussed.
•Boron with purities between 86 % and 99 % was obtained by two routes.•Depending on the final heat treatment, boron powders were amorphous or crystalline.•By using boron of different types, bulks of MgB2 were obtained.•Amorphous lower purity B (86–97 %) promotes the largest levitation forces of MgB2.•Correlations between levitation force and Jc are not straightforward.
ZnO films were electrodeposited from an aqueous nitrate bath on ITO/glass substrates. The process was performed not by the usual potentiostatic approach but by using potential ramps with different ...sweep rates. We tested these ramps in both directions i.e. either towards electronegative (direct) or electropositive (inverse) potential. As expected, the samples prepared in different deposition conditions show different morphology, different quality of crystalline structure and different optical properties. By employing inverse ramps we prepared films with high quality structural and optical properties. We assume that in these conditions the growth is followed by an etching process which preferentially removes the areas with high defect concentration and leads to the formation of hollow hexagonal prisms.
► Electrodeposition using ramp potential was employed for tailoring structural, morphologic and optical properties of ZnO films. ► By reverse polarization deposition, hollow hexagonal prisms with uniform dimensions were obtained. ► Reverse polarization deposition leads to high structural quality, high intensity UV emission and low deffect content.
