Search results for "optoelectronic"

Effect of annealing on Co2FeAl0.5Si0.5thin films: A magneto-optical and x-ray absorption study

2011

A series of Al and MgO-capped Co${}_{2}$FeAl${}_{0.5}$Si${}_{0.5}$ epitaxial thin films grown on MgO with various levels of L2${}_{1}$ ordering was obtained by in situ annealing. The films were studied by means of x-ray absorption spectroscopy, x-ray magnetic circular dichroism (XMCD), magneto-optical Kerr effect magnetometry, and Brillouin light scattering. We find the anisotropy constants decrease, while the spin wave stiffness increases as the samples are annealed to higher temperatures. The magnetization as determined by Brillouin light scattering reveals a maximum value at intermediate annealing temperatures. Surprisingly, the orbital-to-spin-moment ratio (as seen from XMCD) is essenti…

Diffraction-efficiency oscillations in amorphous As_2S_3 films

1999

An experimental study of the holographic gratings recorded in nonannealed, thermally with time relaxed amorphous As2S3 films by 514.5-nm light in the presence of 632.8-nm readout light is carried out. The dependences of the maximal first-order diffraction efficiency on the holographic grating period was studied in a wide range of periods, from 0.40 to 70.0 µm. A peculiar oscillatory diffraction-efficiency temporal behavior occurring under certain conditions is reported. The obtained results are discussed in terms of photoinduced structural changes, relaxational structural changes, photoinduced anisotropy, and photoinduced recharging of the localized states in the bandgap. The diffraction-ef…

Model of holographic recording in amorphous chalcogenide films using subband-gap lightat room temperature

1997

The subband-gap light holographic recording in amorphous as-evaporated ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ films at room temperature is experimentally studied. Properties are considerably different from those of usual holographic recording based on the band-gap light induced structural changes. The most important characteristic features of this nonpermanent recording include photoinduced refractive index increase, weak photobleaching, the absence of the photoinduced thickness changes, light polarization dependence, large exposures, holographic grating shifts during the exposure and a peculiar two maxima spatial frequency response. The first order diffraction efficiency up to 4.1% is achie…

Radiation-Induced Defect and Charge Accumulation and Thermostimulated Relaxation Processes in Al<sub>2</sub>O<sub>3</sub> Cry…

1997

Thermal conductivity of thermoelectric Al-substituted ZnO thin films

2013

ZnO:Al thin films with a low electrical resistivity were grown by magnetron sputtering on sapphire substrates. The cross-plane thermal conductivity (κ = 4.5 ± 1.3 W/mK) at room temperature is almost one order of magnitude lower than for bulk materials. The thermoelectric figure of merit ZT at elevated temperatures was estimated from in-plane power factor and the cross-plane thermal conductivity at room temperature. It is expected that the thermal conductivity drops with increasing temperature and is lower in-plane than cross-plane. Consequently, the thin film ZT is at least three times higher than for bulk samples at intermediate temperatures. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinh…

Capacitance-voltage characteristics of organic light-emitting diodes varying the cathode metal: Implications for interfacial states

2007

Capacitance-voltage $(C\text{\ensuremath{-}}V)$ characteristics of organic light-emitting diodes based on a polyphenylenevinylene have been measured by means of impedance spectroscopy. The effect of the metallic cathode (Au, Ag, Al, Mg, and Ba) was analyzed in the low-frequency region $(2\phantom{\rule{0.3em}{0ex}}\mathrm{Hz})$ of the capacitive response. The $C\text{\ensuremath{-}}V$ curves collapse into a single pattern in the low bias region, and exhibit a dependence on the cathode work function showing a crossover from positive to negative (inductive) values. The voltage corresponding to the onset of the inductive behavior shifts toward higher bias as the cathode work function increases…

<title>Changes in the temperature dependence of the dielectric constant in irradiated antiferroelectric thin films</title>

2003

A model describing the changes of the Curie-Weiss temperature in lead-zirconate thin films under neutron irradiation is proposed. The Curie-Weiss temperature in the irradiated material decreases which is connected to charges caused by neutron irradiation. The charges located near the surfaces due to Schottky effect and in the bulk of the film results in different rates of the Curie-Weiss temperature decreases with neutron fluence. However the influence of the Schottky layers seems to be more pronounced. Satisfactory agreement between the theoretical results and the experimental data is obtained for different neutron fluences.© (2003) COPYRIGHT SPIE--The International Society for Optical Eng…

Direct observation of polar nanostructures in PLZT ceramics for electrooptic applications

2004

ABSTRACTTransparent Pb1-yLay(Zr1-xTix)1-y/4O3(PLZT, y=0.0975, x=0.35) ceramics prepared via hot pressing techniques were studied via piezoelectric force microscopy (PFM). Clear piezoelectric contrast is observed in a cubic relaxor phase indicating spatial distribution of polarization with an average cluster size of about 50 nm. The irregular polarization pattern is associated with the formation of a glassy state, where random electric and stress fields are responsible for the disruption of the long-range ferroelectric order. Local poling of the ceramics resulted in the formation of a stable micron-size domain that could be continuously switched under varying dc bias (local hysteresis loop).…

Ion-Selective Organic Electrochemical Transistors

2014

Ion-selective organic electrochemical transistors with sensitivity to potassium approaching 50 μA dec(-1) are demonstrated. The remarkable sensitivity arises from the use of high transconductance devices, where the conducting polymer is in direct contact with a reference gel electrolyte and integrated with an ion-selective membrane.

High voltage vacuum-processed perovskite solar cells with organic semiconducting interlayers

2020

In perovskite solar cells, the choice of appropriate transport layers and electrodes is of great importance to guarantee efficient charge transport and collection, minimizing recombination losses. The possibility to sequentially process multiple layers by vacuum methods offers a tool to explore the effects of different materials and their combinations on the performance of optoelectronic devices. In this work, the effect of introducing interlayers and altering the electrode work function has been evaluated in fully vacuum-deposited perovskite solar cells. We compared the performance of solar cells employing common electron buffer layers such as bathocuproine (BCP), with other injection mate…