National Repository of Grey Literature 26 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Černohorský, Ondřej ; Žďánský, Karel ; Yatskiv, Roman ; Grym, Jan
Metal nanoparticles have many interesting properties which is given by their space restriction. Their large active surface is very well exploited during catalysis. Pd and Pt are metals know for their ability to dissociate molecular hydrogen on single atoms. We prepared Schottky diodes on semiconductors InP, GaN, GaAs, and InGaAs to obtain hydrogen sensor. Method of preparation such diodes is electrophoretic deposition of Pd or Pt nanoparticles from their colloid solution onto semiconductor substrate. Over the layer of nanoparticles, porous metal contact was prepared. Hydrogen molecules are dissociated on these metal nanoparticles and single atom which settles on the interface between metal and semiconductor and they increase or decrease Schottky barrier height. By this method we can measure from 1 ppm H2 in the air, where the current change is over one order of magnitude
Graphite/n-InP Schottky barrier with electrophoretically deposited Pt nanoparticles for hydrogen and nitrogen-monoxide detection
Žďánský, Karel ; Vaniš, Jan ; Černohorský, Ondřej ; Kacerovský, Pavel ; Fojtík, A.
N-type InP was deposited with Pt nanoparticles (NPs) by electrophoresis. The Pt NPs density was varied from a tenth of monolayer to several monolayers. Schottky contacts were made by colloidal graphite on the InP wafer site covered with Pt NPs. It was observed that H2 was detected by an increase of the current while NO was detected by its decrease. For explanation, we discuss mechanism which involves negative charging of adsorbed H atoms with electrons by increasing affinity level due to correlation efects
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Plný tet: UFE 0387602 - Download fulltextPDF
Graphite Schottky barriers on n-InP and n-GaN with deposited Pd, Pt or bimetallic Pd/Pt nanoparticles for H2 sensing
Žďánský, Karel ; Muller, M. ; Černohorský, Ondřej ; Yatskiv, Roman
High Schottky barriers have been achieved by applying colloidal graphite on n-type InP and on n-type GaN semiconductor crystal wafers. The barrier heights were shown to be close to Schottky-Mott limit ad thermionic emission theory. Porous properties of the graphite Schottky contacts were demonstrated by scanning electron microscopy.
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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Plný tet: UFE 0374575 - Download fulltextPDF
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.
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.
Žďánský, Karel ; Yatskiv, Roman ; Grym, Jan ; Černohorský, O. ; Zavadil, Jiří ; Kostka, František
Deposition of Pd nanoparticles (NPs) on InP or GaN single crystal wafer was performed from isooctane colloid solution. Diodes were prepared by making Schottky contact with colloidal graphite on Pd NPs partly coated surface and ohmic contact on the blank side of the wafer. It was found that several ppb of hydrogen in nitrogen gas can be detected by monitoring the change of diode current at a constant bias voltage. Diodes made on GaN were about ten times more sensitive to hydrogen than those made on InP.
Microscopy of nanoparticles and films with nanoparticles
Kacerovský, Pavel ; Žďánský, Karel ; Procházková, Olga ; Vaniš, Jan ; Grym, Jan ; Vasiliev, A. ; Pašajev, E. M.
To study the electrophoreticaly deposited nanolayers of reverse micelles with Pd nano-particles on n-type InP substrates a wide range of current microscopic methods has been used. What concerns analytical methods the X-ray diffraction and mass spectrometry SIMS were used. The most relevant results about Pd nanoparticles in the layer were obtained by using HRTEM microscopy and SIMS spectrometry. In nanolayers crystallographic arrangement of Pd nanoparticles has not been found.
Control system of the laser topographer
Kostka, František ; Žďánský, Karel ; Zavadil, Jiří ; Starý, Robert
Universal apparatus for measuring photoluminescence over surface of semiconductor samples was designed and realized.

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