National Repository of Grey Literature 158 records found  previous11 - 20nextend  jump to record: Search took 0.04 seconds. 
Study of layers of metal nanoparticles on semiconductor wafers for hydrogen detection
Muller, M. ; Žďánský, Karel ; Zavadil, Jiří ; Piksová, K.
Colloid solutions of metal Pt, Pd and Pt/Pd alloy nanoparticles by reverse micelle technique in isooctane were prepared. Layers of the nanoparticles on InP and GaN substrates using electrophoretic deposition were prepared. Metal nanoparticles in the colloid and in deposits were characterized by SEM. Schottky diodes were fabricated by application of colloidal graphite on nanoparticle layer. An increase in current in hydrogen-nitrogen mixture was measured for hydrogen concentrations between 5 and 1000 ppm.
Study of layers of Pd on InP
Černohorský, Ondřej ; Žďánský, Karel ; Proška, J.
Pd nanoparticles were prepared in colloid solution stabilized by AOT. The layers were prepared by electrophoretic deposition through the mask of polystyrene spheres. SEM measurement showed that particles in colloid solution are separated and after deposition they form small aggregates on InP. The size of these aggregates depends on the time of deposition. I-V characteristics were measured and then Schottky barrier height and ideality factor were calculated. The morphology of layers was monitored by SEM.
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Preparation and characterizatiobn of layers of Au, Pd and Rh nanoparticles deposited on n-InP substrates
Kostejn, M. ; Žďánský, Karel ; Piksová, K. ; Zavadil, Jiří
Colloids of Au, Pd and Rh nanoparticles (NPs) were prepared in reverse micelles and surface plasmon absorption bands were identified. Layers of metal NPs were deposited on InP substrates by electrophoretic deposition and imaged by SEM. Low-temperature photoluminescence spectrum of InP was found to be enhanced mainly by Au NPs. Sensitivity to hydrogen of Schottky barriers prepared by dropping colloidal graphite onto the surface of InP partly covered with Pd NPs was measured by current change in 100 ppm H2/N2.
Precision time transfer using satellite systems
Pánek, Petr
The paper deals with the use of the satellite navigation systems for a precise time transfer. Effects affecting the time transfer are described and examples of measurement results are presented.
Notes to multistage Wiener filter in DS-CDMA detector
Šimša, Jan
The contribution follows report oriented towards design of Wiener filter in DS-CDMA detector of signals as a multistage structure. Such approach avoids evaluation of the inverse of a known autocorrelation matrix of a sampled response of the chip matched filter to a wide-sense stationary input signal. The contribution gives more detailed description of detector signal processing and its consequences.
PD NANOLAYERS FOR HYDROGEN SENSORS
Yatskiv, Roman ; Žďánský, Karel ; Grym, Jan ; Piksová, K.
We presented study nanoparticle layers created by electrophoretic deposition. A possibility of using Pd nanolayers for the formation of Schottky barriers with a large Schottky barrier height (SBH) value on n-type tin doped InP is proposed together with its potential application in high-sensitive hydrogen sensors.
Analysis of spectral changes in speech affected by orthodontic appliances
Přibil, Jiří ; Přibilová, Anna
This paper is focused at investigation of influence of the upper removable plate and the lower fixed orthodontic brackets and their combination on spectral properties of produced speech. Spectral changes were analyzed and evaluated by spectrograms and mean Welch’s periodograms. From obtained results follows that the removable orthodontic appliance mainly affects spectrograms of speech, and these changes are most significant in voiced parts of spectrograms – corresponding to vowels, voiced consonants etc.
METALIC NANOPARTICLES AND NANOSTRUCTURES
Nohavica, Dušan
A brief overview of the field of metallic nanoparticles and nanocrystalline materials preparation and their properties is presented. Dependence of the chemical potential on surface curvature is important for particles solubility in the melt, vapour pressure of liquids as a function of droplet radius, Ostwald ripening and sintering of the individual particles. Melting point and lattice constant depends on the radius of nanoparticles as well. The major processing for nanocrystalline materials production includes chemical reaction, vapour condensation, electrodeposition, ball grinding, SPD etc.
ZnO NANOPARTICLES AND THEIR APPLICATIONS – NEW ACHIEVMENTS
Nohavica, Dušan ; Gladkov, Petar
The advantages of ZnO are a low price, good gas sensing properties, photocatalytic activity, antibacterial activity, possibility to prepare structures with interesting optical properties, like photonic crystals, catalytic materials etc. In our laboratory the special research type of MOCVD apparatus has been developed. In the study we have investigated the influence of the growth rate on the morphology of ZnO deposited on Si (100), GaP (111) as well as nanoporous GaP. The same apparatus has been used for ZnO nanoparticles preparation with the diameter of individual nanoparticles of about 25 nm.
EPITAXIAL OVERGROWTH OF InP and GaAs MICROPORES, MICROCAVITIES AND MICROLAMELLAS BY InAs AND InGaAs
Nohavica, Dušan ; Grym, Jan ; Hulicius, Eduard ; Pangrác, Jiří ; Gladkov, Petar ; Jarchovský, Zdeněk
Structural and optical properties of micro and nano-porous InP and GaAs substrates used for an epitaxial overgrowth of thin films were investigated. Both crystalographically oriented (CO) and current line oriented (CLO) pore networks were created by electrochemical dissolution. Heat treatment of InP pores at 650oC and GaAs pores at 750-850oC converted them into microcavities The capability of improved structural quality homo- and hetero-epitaxially overgrown films on the porous InP, was also demonstrated by LPE growth of InP and InAs and GaInAs on GaAs by MOVPE technology.

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