|
Motory HCCI
Varga, Michal
Tato bakalářská práce se zabývá vývojem, vlastnostmi a využitím vznětových motorů s homogenním naplněním spalovacího prostoru. Popisuje princip fungování takového motoru, konstrukční řešení a nastiňuje možná uplatnění v automobilovém průmyslu.
|
|
Fabrication of 3D diamond membranes for microfluidic systems
Varga, Marián ; Babchenko, Oleg ; Bauerová, Pavla ; Hruška, Karel ; Jurka, Vlastimil ; Kromka, Alexander ; Rezek, Bohuslav
Perfusion of cell medium, especially in microfluidic devices, can provide in-vivo-like conditions for cell cultures. The most recent demand on such systems is to include electronically active artificial cell support for in-situ monitoring. Diamond thin films exhibit advantageous combination of physical, mechanical, chemical, biocompatible and electronic properties for this purpose. In this work we explore two strategies for fabrication of self-standing three-dimensional nanocrystalline diamond membrane for implementation in microfluidic invivo like experiments: i) nucleation and chemical vapour deposition (CVD) growth of diamond on porous 3D carbon foam (with 80 pores per inch) and ii) selective diamond growth predefined by photolithographic processing using copper grid mask. The morphology and material quality of the fabricated membranes are characterized by scanning electron microscopy and Raman spectroscopy.
|
|
The optical spectra of carbon-based thin films measured by the photothermal deflection spectroscopy (PDS)
Remeš, Zdeněk ; Pham, T.T. ; Varga, Marián ; Kromka, Alexander ; Stuchlík, Jiří ; Mao, H.B.
Our photothermal deflection spectroscopy (PDS) setup allows to measure simultaneously the absolute values of the optical transmittance T, reflectance R and absorptance A spectra of thin layers on glass substrates in the spectral range from ultraviolet to near infrared light with the typical spectral resolution 5 nm in the ultraviolet, 10 nm in visible and 20 nm in the near infrared region. The PDS setup provides the dynamic detection range in the optical absorptance up to 4 orders of magnitude. Here we demonstrate the usability of this setup by comparing the optical absorbance on a series of the carbon layer and nanocrystalline diamond (NCD) thin layers deposited on glass substrates by using the magnetron sputtering and the microwave based surface wave discharge in linear antenna chemical vapor deposition (CVD) processes, respectively. The defect-induced localized states in the energy gap are observed in all carbon layers as well as in NCD.
|
|
Photonic structures and their preparation
Varga, Marián ; Ondič, Lukáš ; Hruška, Karel ; Potměšil, Jiří ; Libertínová, Jitka ; Kromka, Alexander ; Remeš, Zdeněk
Photonic crystals are periodically structured electromagnetic media, generally possessing photonic band gaps: ranges of frequency in which light cannot propagate through the structure. This periodicity, which length scale is proportional to the wavelength of light in the band gap, is the electromagnetic analogue of a crystalline atomic lattice, where the latter acts on the electron wavefunction to produce the familiar band gaps of semiconductors, and so on, in solid-state physics. Several examples of organisms and structures possessing photonic crystals and iridescence are visible all around us (Morpho didius, Pavo cristatus, Chrysochroa vittata, Chrysina resplendens, …).
|
|
Study of nucleation and growth of diamond thin films
Ižák, Tibor ; Babchenko, Oleg ; Varga, Marián ; Potocký, Štěpán ; Marton, M. ; Vojs, M. ; Domonkos, Mária ; Kromka, Alexander
This study deals with the nucleation and growth of CVD diamond films on Si substrates. In nucleation part two different nucleation methods were studied: (i) the bias enhanced nucleation (BEN) and (ii) ultrasonic seeding. In the case of BEN, (i) the nucleation time and (ii) the influence of bias voltage were studied. For ultrasonic seeding the effect of different solutions of ultradisperzed detonation nanodiamond (UDD) powder with metal particles on the nucleation efficiency and growth process was investigated (i.e. diamond powder, nanosized Ni, microsized Co and Y metal powders).
|
| |
|
Review of nanocrystalline diamond film deposition on silicon and glass substrates down to 400 °C
Potocký, Štěpán ; Babchenko, Oleg ; Ižák, Tibor ; Varga, Marián ; Kromka, Alexander ; Rezek, Bohuslav ; Michalka, M.
We present an overview of a nanocrystalline diamond (NCD) films deposition on silicon and glass substrates by microwave plasma CVD in hydrogen-based gas mixture. The temperature plays a crucial parameter as the diamond growth process is temperature controlled. Use of temperature sensitive substrates demanded reducing substrate temperature. Natural decrease of deposition rate resulted in search of new or nonstandard process parameters which could at least minimize or compensate it. Addition of oxygen containing gasses was found to improve film quality, and increasing deposition speed. Moreover improvement in pre-treatment of foreign substrates allowed deposition of fully closed films in less then 100 nm. Low thickness of NCD always favorable due to lattice mismatch between substrate material and NCD film. Successful adoption of NCD film deposition on silicon and glass allowed us to study surface chemical modification for protein attachment and DNA immobilization.
|
| |
| |
| |