National Repository of Grey Literature 12 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Technological challenges in the fabrication of MoS.sub.2./sub./diamond heterostructures
Varga, Marián ; Sojková, M. ; Hrdá, J. ; Hutar, P. ; Parsa Saeb, S. ; Vanko, G. ; Pribusova Slusna, L. ; Ondič, Lukáš ; Fait, Jan ; Kromka, Alexander ; Hulman, M.
Nowadays, 2D materials are one of the most studied classes of materials. In addition to the most famous graphene, progress has been achieved in studying and using fundamental properties of transition metal dichalcogenides (TMD). Complementary, diamond as a representative of 3D materials has gained a reputation as an extremely versatile material due to its extraordinary combination of physical/chemical/electrical/optical properties. Besides these particular forms of 2D and 3D materials, their heterostructures have become very attractive due to new phenomena and functions (bandgap engineering, enhanced charge transport, optical interaction, etc.). However, individual technological procedures are still minimally investigated and described. Here, we will demonstrate a proof-of-concept for the preparation of MoS2/diamond heterostructures, where two different strategies were employed: a) growth of MoS2 layers on diamond films, and b) growth of diamond films on Si/MoS2 substrates.
Correlated microscopy of electronic and material properties of graphene grown on diamond thin films
Rezek, Bohuslav ; Čermák, Jan ; Varga, Marián ; Tulic, S. ; Skákalová, V. ; Waitz, T. ; Kromka, Alexander
In this work we compare growth of graphene on diamond thin films that enable large area processing. We use films with different crystal size and surface roughness to obtain deeper insight into formation and properties of GoD. The diamond films are coated by a nm thin sputtered Ni layer and heated to 900°C in a forming gas atmosphere (H2/Ar) to initiate catalytic thermal CVD process. The samples are cleaned from residual Ni after the growth process. We employ scanning electron microscopy, Raman micro-spectroscopy and Kelvin probe force microscopy to correlate material, structural, and electronic properties of graphene on diamond. We show how grain size and grain boundaries influence graphene growth and material and electronic properties. For instance we show that the grain boundaries (with non-diamond carbon phases) in diamond films have an important role. They influence the electronic properties and they are beneficial for forming graphene on diamond higher quality.
Effect of H- and O-termination of nanocrystalline diamond films on cell adhesion and osteogenic differentiation
Lišková, Jana ; Babchenko, Oleg ; Varga, Marián ; Kromka, Alexander ; Hadraba, Daniel ; Švindrych, Zdeněk ; Bačáková, Lucie
In order to control the hydrophobic or hydrophilic character, the NCD film surfaces were grafted by hydrogen atoms (H-termination) or by oxygen atoms (O-termination). Human mesenchymal stem cells and primary human osteoblasts were used for biological studies on H- and O-terminated NCD films. We found that cells cultivated on O-terminated NCD films exhibit better adhesion than H-terminated NCD films. In addition, the expression of osteogenic cell markers collagen and alkaline phosphatase analysed by Realtime PCR and immunostaining was higher on O-terminated films.
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).
Foreign substrates pre-treatment using polymer composites in plasma-enhanced CVD growth of diamond fibers and layers
Potocký, Štěpán ; Babchenko, Oleg ; Ižák, Tibor ; Varga, Marián ; Kromka, Alexander ; Rezek, Bohuslav ; Tesárek, P.
Nanocrystalline diamond wires and layers were grown by microwave plasma CVD technique on Si substrates. The substrates were pretreated by non-woven composite nanofiber textile composed by poly(vinyl alcohol) matrix and ultra-dispersed diamond (UDD) nanoparticles prepared by needleless electrospinning method. High concentration of UDD in the PVA fibers lead to formation of diamond wires due to a combined effect of UDD particles used as seeding and high pressure difference across the fibers interface. A preferable growth of diamond layers was observed on areas with a low porosity volume of nanofiber textile. The influence of spundond structure on the growth of diamond decreased with lowering of UDD concentra-tion in the primary polymer matrix.
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.
Diamond thin film development and SIMS analysis on various substrates
Vincze, A. ; Michniak, P. ; Haško, D. ; Michalka, M. ; Varga, Marián ; Dobročka, E.
The contribution shows the possibilities of the diamond growth on various substrates. The thin film samples were prepared using hot filament CVD. The analysis of the diamond coatings were done by various methods. SEM, XRD, Raman spectrometry and SIMS were done in order to characterize the samples. The results of the diamond thin films are discussed.

National Repository of Grey Literature : 12 records found   1 - 10next  jump to record:
See also: similar author names
1 Varga, M.
3 Varga, Marek
8 Varga, Martin
2 Varga, Matúš
4 Varga, Michal
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