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Effect of EU doping on the optical properties of ZnO nanorods prepared by chemical bath deposition
Yatskiv, Roman; Bašinová, Nikola; Grym, Jan; Vaniš, Jan
2019 - anglický
We report on the properties of Eu-doped ZnO nanorods prepared by chemical bath deposition from aqueous solutions in an autoclave. The autoclave enables to grow the nanorods above the boiling point of water. The nanorods were characterized by scanning electron microscopy, secondary ion mass spectroscopy, and low temperature photoluminescence spectroscopy. Under the UV light excitation, the nanorods show a strong blue emission at 450 nm, which is associated with the 4f(6)5d - 4f(4) transitions of Eu2+ ions. We discuss the mechanisms responsible for the blue luminescence. We further clarify how the growth parameters affect the morphology and the optical properties of the nanorods. Growth temperatures above the boiling point of water significantly influence the intensity ratio of the near band edge emission to the deep level emission and greatly enhance optical quality of the nanorods.
Klíčová slova:
ZnO nanorods; Europium; Energy transfer
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Effect of EU doping on the optical properties of ZnO nanorods prepared by chemical bath deposition
We report on the properties of Eu-doped ZnO nanorods prepared by chemical bath deposition from aqueous solutions in an autoclave. The autoclave enables to grow the nanorods above the boiling point of ...
Effect of heat treatment on the properties of sol-gel deposited ZnO seed layers
Bašinová, Nikola; Černohorský, Ondřej; Grym, Jan; Maixner, J.
2018 - anglický
Zinc oxide nanorods as a potential material for nanoscale devices are prepared by chemical bath deposition (CBD). The effect of the quality of the sol-gel deposited seed layer on the vertical alignment of the nanorods to a silicon substrate is discussed. Emphasis is put on the investigation of the impact of the heat treatment on the properties of the seed layer deposited by dip-coating. The sol-gel method is a multi-stage process consisting of three principal steps: (i) preparation of a solution with suitable precursors, (ii) deposition of the precursor solution, and (iii) the heat treatment. The preheating needs to be performed to thermally decompose the zinc acetate precursor into zinc oxide seeds. Three different temperatures of preheating are compared (300 degrees C, 350 degrees C, 400 degrees C) followed by annealing in argon at 800 degrees C and the influence on the quality of the seed layers and vertical alignment of nanorods are discussed. When the preheating temperature is higher than 350 degrees C, the seed layer comprises smaller and denser crystallites with a preferential orientation along the c-axis. CBD growth of ZnO nanorods on these seed layers results in their good vertical alignment
Klíčová slova:
ZnO nanorods; Chemical bath deposition; Sol-gel
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effect of heat treatment on the properties of sol-gel deposited ZnO seed layers
Zinc oxide nanorods as a potential material for nanoscale devices are prepared by chemical bath deposition (CBD). The effect of the quality of the sol-gel deposited seed layer on the vertical ...
Electrical properties of nanoscale heterojunctions formed between GaN and ZnO nanorods
Tiagulskyi, Stanislav; Yatskiv, Roman; Grym, Jan; Schenk, Antonín; Roesel, David; Vaniš, Jan; Hamplová, Marie
2018 - anglický
Vertical periodic arrays of ZnO nanorods are prepared by hydrothermal growth on GaN templates patterned by focused ion beam. Electro-physical properties of a single vertically-oriented ZnO nanorod are investigated by measuring the current-voltage characteristics using a nanoprobe in a scanning electron microscope. This technique enables to observe the surface morphology of ZnO nanorods simultaneously with their electrical characterization in vacuum. The vacuum chamber rejects the impact of gas adsorption and light irradiation, which both affect the properties of ZnO nanorods. Moreover, mechanical damage and strain induced during the nanorod transfer are eliminated. Nonlinear current-voltage characteristics under the forward bias are explained by the tunneling-recombination process and by the space charge limited current. The high reverse bias current in the p-n heterojunction is attributed to direct tunneling via a narrow tunnel barrier
Klíčová slova:
Scanning electron microscope; Hydrothermal growth; In-situ current-voltage measurements
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Electrical properties of nanoscale heterojunctions formed between GaN and ZnO nanorods
Vertical periodic arrays of ZnO nanorods are prepared by hydrothermal growth on GaN templates patterned by focused ion beam. Electro-physical properties of a single vertically-oriented ZnO nanorod are ...
Optoelectrical characterization of well oriented n-type zno nanorod arrays on p-type GaN templates
Yatskiv, Roman; Grym, Jan; Schenk, Antonín; Vaniš, Jan; Roesel, David; Chlupová, Šárka
2018 - anglický
A heterojunction formed between a single n-type ZnO nanorod and p-type GaN template was successfully prepared by low cost chemical bath deposition technique. Periodic circular patterns were fabricated by focused ion beam etching through poly(methyl methacrylate) mask to control the size, position, and periodicity of the ZnO nanorods. A possible growth mechanism is introduced to explain the growth process of the nanorods. Optical and electrical properties of the heterojunctions were investigated by low temperature photoluminescence spectroscopy and by the measurement of current-voltage (I-V) characteristics. The I-V characteristics were measured by directly contacting single ZnO nanorods with the conductive atomic force microscopy tip. The diode-like rectifying behavior was observed with a turn-on voltage of 2.3 V and the reverse breakdown voltage was 5 V
Klíčová slova:
Photoluminescence spectroscopy; Conductive atomic force microscopy; Focused ion beam
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Optoelectrical characterization of well oriented n-type zno nanorod arrays on p-type GaN templates
A heterojunction formed between a single n-type ZnO nanorod and p-type GaN template was successfully prepared by low cost chemical bath deposition technique. Periodic circular patterns were fabricated ...
Monolayers of platinum nanoparticles prepared by dip-coating
Černohorský, Ondřej; Grym, Jan; Yatskiv, Roman; Pham, V.H.; Hudry, D.; Dickerson, J.H.
2015 - anglický
Platinum is a transition metal known for its catalytic properties, which are further enhanced when employed in a nanoparticle form. We have recently shown that a monolayer of Pt nanoparticles deposited on semiconductor substrates forms high quality Schottky diodes, which were used in sensitive hydrogen sensors with a detection limit of 1 ppm of H-2 in N-2. Preparation of ordered monolayers of Pt nanoparticles is essential for the understanding of the behaviour of such an interface. To obtain a hexagonal closed-packed nanoparticle array, we prepared Pt nanoparticles stabilized by oleylamine and oleic acid with a narrow size distribution and uniform shapes. A monolayer prepared by dip-coating of Si substrate in the suspension containing Pt nanoparticles showed hexagonal arrangement within separate domains with the surface coverage up to 90%. The increase of the surface coverage with increasing withdrawal speed of the dip-coating process was observed
Klíčová slova:
Oleylamine; Pt nanoparticles; Self-assembly
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Monolayers of platinum nanoparticles prepared by dip-coating
Platinum is a transition metal known for its catalytic properties, which are further enhanced when employed in a nanoparticle form. We have recently shown that a monolayer of Pt nanoparticles ...
Influence of H2O2 treatment on morphological and photoluminescence properties of hydrothermally grown ZnO nanorods
Yatskiv, Roman; Grym, Jan
2015 - anglický
We report photoluminescence properties of hydrothermally grown ZnO nanorods (NRs) before and after hydrogen peroxide (H2O2) treatment. The H2O2 treatment introduces oxygen related defects and thus enhances chemisorption processes in ZnO NRs. These effects amplify interactions between the gas species and adsorbed oxygen and thus can influence sensing properties of ZnO NRs
Klíčová slova:
ZnO nanorods; Photoluminescence; H2O2 treatment
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of H2O2 treatment on morphological and photoluminescence properties of hydrothermally grown ZnO nanorods
We report photoluminescence properties of hydrothermally grown ZnO nanorods (NRs) before and after hydrogen peroxide (H2O2) treatment. The H2O2 treatment introduces oxygen related defects and thus ...
DEPOSITION OF PVP-PROTECTED PLATINUM NANOPARTICLES ON SEMICONDUCTOR SUBSTRATES FOR HYDROGEN SENSING
Černohorský, Ondřej; Yatskiv, Roman; Grym, Jan
2015 - anglický
High quality Schottky diode hydrogen sensors were prepared by the deposition of colloidal graphite on n-type InP substrates partly covered with PVP-protected Pt nanoparticles (NPs). A sub-monolayer of the Pt NPs was created by simple evaporation of the solvent in which Pt NPs were dispersed. The Pt NPs serve to dissociate hydrogen molecules into atomic hydrogen, which is absorbed at the metal-semiconductor interface. Hydrogen absorption leads to the formation of the dipole layer, which changes the Schottky barrier height and results in the increase of both forward and reverse current. The proposed hydrogen sensor showed high sensitivity response of similar to 10(6) to 1000 ppm H-2 in N-2 at room temperature
Klíčová slova:
Graphite based Schottky junction; PVP - protected Pt nanoparticles; Hydrogen sensors
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
DEPOSITION OF PVP-PROTECTED PLATINUM NANOPARTICLES ON SEMICONDUCTOR SUBSTRATES FOR HYDROGEN SENSING
High quality Schottky diode hydrogen sensors were prepared by the deposition of colloidal graphite on n-type InP substrates partly covered with PVP-protected Pt nanoparticles (NPs). A sub-monolayer of ...
Optical infrastructure for time and frequency transfer
Smotlacha, V.; Vojtěch, J.; Kuna, Alexander
2013 - anglický
The paper describes optical infrastructure for time and frequency transfer in the Czech republic. The infrastructure is heterogeneous and utilises resources of the Czech academic optical network. It allows to interconnect Cesium standards in distant sites with the national time and frequency laboratory and to distribute accurate time and stable frequency. We also present results and compare them with other methods of time transfer
Klíčová slova:
Stable frequencies; Time transfer; Time and frequencies
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Optical infrastructure for time and frequency transfer
The paper describes optical infrastructure for time and frequency transfer in the Czech republic. The infrastructure is heterogeneous and utilises resources of the Czech academic optical network. It ...
Evaluation of the accuracy of the method for measuring state-of-the-art ultra-high stability quartz crystal oscillators
Salzenstein, P.; Kuna, Alexander; Lefebvre, F.
2013 - anglický
The accuracy of the Three-Cornered Hat method is discussed when not simultaneously applied to the determination of the contribution on short term frequency stability performed on ultra-stable quartz oscillators
Klíčová slova:
oscillator; ultra-stable Quartz; non-simultaneity
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Evaluation of the accuracy of the method for measuring state-of-the-art ultra-high stability quartz crystal oscillators
The accuracy of the Three-Cornered Hat method is discussed when not simultaneously applied to the determination of the contribution on short term frequency stability performed on ultra-stable quartz ...
Local ties controlin application of laser time transfer
Kodet, J.; Schreiber, U.; Eckl, J.; Procházka, I.; Pánek, Petr
2013 - anglický
In many fundamental physical experiments time plays an important role. The standard way for the comparison of time and frequency is the application of GNSS signals and the Two-Way Satellite Time and Frequency Transfer - TWSTFT. This technique is based on radiofrequency signal transmission. Recently, there was a rapid increase of optical time comparison development, which uses the Satellite Laser Ranging network (SLR). Currently the French project T2L2 is in operation on board of Jason 2 and the European Space Agency project ELT in support of the Atomic Clock Ensemble in Space (ACES) is under development. The goal of both projects is the time synchronization with a precision below 40 ps rms and an absolute error well below 100 ps. Comparing the results of the optical time transfer with the GNSS time comparison requires unprecedented control of the local ties between the different observation techniques. One of the possible methods is the application of the Two Way Time Transfer (TWTT) on a single coaxial cable. Such a system can be implemented using two or more event timers, which are interconnected by a standard coaxial cable.
Klíčová slova:
time comparison; event timing; two way time transfer
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Local ties controlin application of laser time transfer
In many fundamental physical experiments time plays an important role. The standard way for the comparison of time and frequency is the application of GNSS signals and the Two-Way Satellite Time and ...
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