Search results for "semiconductor"
showing 10 items of 974 documents
AMORPHOUS SEMICONDUCTOR-ELECTROLYTE JUNCTION. A NEW INTERPRETATION OF THE IMPEDANCE DATA OF AMORPHOUS SEMICONDUCTING FILMS ON METALS.
1986
On the basis of the theory of amorphous semiconductor Schottky barrier an equivalent electrical circuit of the amorphous oxide film/electrolyte interface is proposed.—The analytical expressions for the equivalent conductance and capacitance of the barrier are reported in the hypothesis of a constant density of states within the mobility gap.—According to this model, the semiconducting properties and the impedance behaviour at different frequencies of anodic oxide films on Niobium are interpreted by taking into account the amorphous nature of the films.—An explanation for the anomalous behaviour of the Mott-Schottky plots usually observed with amorphous anodic oxide films is presented.—The p…
Macroscopic description of the two-dimensionalLaAlO3/SrTiO3interface
2016
We propose a simple analytical model to explain the possible appearance of the metallic conductivity in the two-dimensional (2D) ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ interface. Our model considers the interface within a macroscopic approach, which is usual for semiconductor heterojunctions and is based on drift-diffusion equations. The solution of these equations allows us to obtain the positions of band edges as a function of distances from the interface. We show that for the 2D metallic conductivity to appear at the interface, the constituting substances should have the same type (either electronic or hole) of conductivity; in the opposite case the possible transition to metallic p…
Influence of thickness and interface on the low-temperature enhancement of the spin Seebeck effect in YIG films
2016
The temperature-dependent longitudinal spin Seebeck effect (LSSE) in heavy metal (HM)/Y_{3}Fe_{5}O_{12} (YIG) hybrid structures is investigated as a function of YIG film thickness, magnetic field strength, and different HM detection materials. The LSSE signal shows a large enhancement with reductions in temperature, leading to a pronounced peak at low temperatures. We find that the LSSE peak temperature strongly depends on the film thickness as well as on the magnetic field. Our result can be well explained in the framework of magnon-driven LSSE by taking into account the temperature-dependent effective propagation length of thermally excited magnons in the bulk of the material. We further …
Dynamic response of thin-film semiconductors to AC voltage perturbations
2012
A theoretical treatment of a Schottky barrier dynamic response is developed on the basis of a general model of a semiconductor with thickness comparable in length to the space charge region width. It is shown that, when the space charge region approaches the metal/semiconductor interface, the electric field at this interface, induced by the charge accumulated on the metal, becomes significant with respect to the electric field induced by the charge accumulated on the semiconductor. Under this condition, the total capacitance of the Schottky barrier becomes independent of the polarization potential and tends to the value ε/L, like in a pure dielectric insulator. The term thin film is intende…
PEDOT thin films with n-type thermopower
2019
peer-reviewed Synthesis of n-type organic semiconductors is challenging as reduced states are difficult to obtain due to their instability in air. Here, we report tailoring of semiconducting behavior through control of surfactant concentration during synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles. Nanoparticles were synthesized by mini-emulsion polymerization, where stable suspensions were used to produce polymer films by a simple casting technique on polyethylene terephthalate (PET) substrates. Electrical conductivity and Seebeck coefficients were measured as a function of surfactant concentration. It was found that conductivity decreases three orders of magnitude as s…
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…
Cytotoxicity of Metal and Semiconductor Nanoparticles Indicated by Cellular Micromotility
2009
In the growing field of nanotechnology, there is an urgent need to sensitively determine the toxicity of nanoparticles since many technical and medical applications are based on controlled exposure to particles, that is, as contrast agents or for drug delivery. Before the in vivo implementation, in vitro cell experiments are required to achieve a detailed knowledge of toxicity and biodegradation as a function of the nanoparticles' physical and chemical properties. In this study, we show that the micromotility of animal cells as monitored by electrical cell-substrate impedance analysis (ECIS) is highly suitable to quantify in vitro cytotoxicity of semiconductor quantum dots and gold nanorods…
Direct temporal reconstruction of picosecond pulse by cross-correlation in semiconductor device
2012
Cross-correlation measurements using the two-photon absorption process in a semiconductor is experimentally demonstrated for two pulses of different wavelengths (shifted by ~200 nm) and durations (20 times ratio). These measurements were found to be highly repeatable and fully suitable for the determination of the temporal intensity profile of picosecond (ps) pulses.
Heterogeneous photo-assisted catalytic hydration/dehydration reactions based on Keggin and Wells-Dawson type heteropolytungstates
2021
Polyoxometalates (POMs) are a wide class of metal-oxygen clusters that can be applied in acid and oxidation catalysis, medicine, electrochemistry, materials design, or models for self-assembling nanoscale systems as long as green and cheap photocatalysts. Heteropolyacids (HPAs) are a POM subclass extensively used as homogeneous photocatalysts for the oxidation of organic substrates. Dispersing HPAs onto solid supports with a high surface area increases their specific surface area and hence (photo)catalytic activity. This chapter reports the use of selected HPAs, heteropolytungstates, immobilized on different supports as heterogeneous photocatalysts.
Phosphomolybdic acid as an efficient hole injection material in perovskite optoelectronic devices.
2018
Efficient perovskite devices consist in a perovskite film sandwiched in between charge selective layers, in order to avoid non-radiative recombination. A common metal oxide used as p-type or hole transport layer is molybdenum oxide. MoO3 is of particular interest for its very large work function, which allows it to be used both as an interfacial charge transfer material as well as a dopant for organic semiconductors. However, high quality and high work function MoO3 is typically thermally evaporated in vacuum. An alternative solution-processable high work function material is phosphomolybdic acid (PMA), which is stable, commercially available and environmentally friendly. In this communicat…