A5001659413- Graphene research and applications
- Electromagnetic wave absorption materials
- Carbon Nanotubes in Composites
- Diamond and Carbon-based Materials Research
- Advanced Antenna and Metasurface Technologies
- Photonic and Optical Devices
- Plasmonic and Surface Plasmon Research
- Graphene and Nanomaterials Applications
- Photonic Crystals and Applications
- Metamaterials and Metasurfaces Applications
- Terahertz technology and applications
- Optical Coatings and Gratings
- Mechanical and Optical Resonators
- Nonlinear Optical Materials Studies
- Gold and Silver Nanoparticles Synthesis and Applications
- Fiber-reinforced polymer composites
- GaN-based semiconductor devices and materials
- Advancements in Battery Materials
- Superconducting and THz Device Technology
- Laser-Ablation Synthesis of Nanoparticles
- Nanowire Synthesis and Applications
- Electromagnetic Compatibility and Noise Suppression
- Ocular and Laser Science Research
- Neural Networks and Reservoir Computing
- Polymer Nanocomposite Synthesis and Irradiation
University of Eastern Finland
2012-2021
Center for Physical Sciences and Technology
2019-2020
Finland University
2010-2020
We present an overview of the main techniques for production and processing graphene related materials (GRMs), as well key characterization procedures. adopt a 'hands-on' approach, providing practical details procedures derived from literature authors' experience, in order to enable reader reproduce results.
Thanks to its high electrical conductivity, a graphene plane presents good shielding efficiency against GHz electromagnetic radiations. Several planes separated by thin polymer spacers add their conductivities arithmetically, because each of them conserves the intrinsic properties isolated graphene. Maximum absorption radiations for frequency around 30 is achieved with six planes, which optimum number. This remarkable result demonstrated experimentally from measurements performed in Ka band...
Fresnel equations predict that an ultrathin free standing conductive film, thousands times thinner than skin depth, is capable to absorb up 50% of incident electromagnetic radiations. In the microwave range, same holds true for a graphene sheet. We demonstrate theoretically and prove experimentally absorptance can be enhanced considerably by depositing on dielectric substrate. On experimental side, we obtain 80% 65% at 30 GHz 1 THz, respectively. Theory predicts higher achieved with suitable...
Graphene-enhanced Raman scattering (GERS) spectra and coherent anti-Stokes (CARS) of thymine molecules adsorbed on a single-layer graphene were studied. The enhancement factor was shown to depend the molecular groups thymine. In GERS thymine, main bands are shifted with respect those for glass surface, indicating charge transfer graphene. probable mechanism is discussed. CARS in accord results, which indicates similar benefit from chemical enhancement.
The ability of thin conductive films, including graphene, pyrolytic carbon (PyC), graphitic PyC (GrPyC), graphene with islands (GrI), glassy (GC), and sandwich structures made all these materials separated by polymer slabs to absorb electromagnetic radiation in microwave-THz frequency range, is discussed. main physical principles making a basis for high absorption heterostructures are explained both the language theory using representation equivalent electrical circuits. idea carbonaceous...
Graphene has recently become a unique playground for studying light-matter interaction effects in low-dimensional electronic systems. Being of strong fundamental importance, these also open wide range opportunities photonics and optoelectronics. In particular, broadband light absorption graphene allows one to achieve high carrier densities essential observation nonlinear optical phenomena. Here, we make use photon-drag effect generate optically manipulate ultrafast photocurrents at room...
We demonstrate a thousand-fold enhancement of second-harmonic generation in an all-dielectric silicon nitride (SiN) resonant waveguide grating compared to flat SiN film. The strong output measured at 532 nm results from the combination enhanced local fields nanostructure and large second-order susceptibility SiN. conversion efficiency structure is found be order 10(-8), which significantly larger than that typically observed plasmonic metal nanostructures.
We report a comparative study of optical properties 5-20 nm thick pyrolytic carbon (PyC) films, graphite, and graphene. The complex dielectric permittivity PyC is obtained by measuring polarization-sensitive reflectance transmittance spectra the films deposited on silica substrate. Lorentz-Drude model describes well general features from 360 to 1100 nm. By comparing results with literature data for graphene highly ordered we found that in visible spectral range, effective ultrathin are...
We demonstrate that silver nanoisland film self-assembled on the surface of silver-containing glass in course thermal processing hydrogen is capable to detect 10-7 M concentration rhodamine 6G water using enhanced Raman spectroscopy (SERS) technique. The can be multiply restored same substrate via annealing hydrogen. showed after as much ten circles cleaning followed by annealing. proposed technique formation enables multiple usage SERS experiments.
Electromagnetic properties of pyrolytic carbon (PyC) films with thickness from 5 to 241 nm are studied experimentally and numerically at 28 GHz. We observe that PyC capable absorb up 50% microwave power in the Ka-band. By using boundary conditions rectangular waveguide, we demonstrate theoretically can be absorbed a conductive film much smaller than skin depth. The results modelling for on silica substrate excellent coincidence experimental data.
We report on strong UV third-harmonic generation from silicon nitride films and resonant waveguide gratings. determine the absolute value of third-order susceptibility at wavelength 1064 nm to be χ(³) (-3ω,ω,ω,ω) = (2.8 ± 0.6) × 10⁻²⁰m²/V², which is two orders magnitude larger than that fused silica. The further enhanced by a factor 2000 fabricating grating onto film. Our results extend operating range CMOS-compatible nonlinear materials spectral regime.
Ultrathin pyrolytic carbon films were synthesized in a single step on dielectric substrates, using methane-based chemical vapor deposition technique. The developed technique enables the production of wafer scale transparent conductive suitable for applications optics and optoelectronics.
Two-dimensional plasmons were investigated by terahertz time domain spectroscopy observing experimentally the distinctive minima and inflection points in transmission power amplitude phase spectra, respectively. Gratings of different periods (600, 800, 1000 nm) filling factors (50 80%) provided to two-dimensional electron gas AlGaN/GaN heterostructures order measure plasmon dispersion coupling efficiency with THz radiation. Comparative analysis experimental data revealed that resonant...
Temperature-dependent effective mass in AlGaN/GaN heterostructures was experimentally observed via THz time domain spectroscopy of 2D plasmons the range 80–300 K. Grating couplers with different periods and filling factors were developed order to monitor behavior plasma resonances transmission spectra frequency 0.5–3.5 THz. For grating a 50% factor, fundamental modes excited at temperatures below 225 The change factor 80% led excitation second harmonics observable up 300 K 220 K,...
We analyzed the electromagnetic (EM) shielding effectiveness in Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions 7.2 × 3.4 mm2, which consists randomly oriented and intertwined graphene flakes a typical size few nanometers. discovered that manufactured PyC films, whose thickness is thousand times less than skin depth conventional metals, provide reasonably high EM attenuation. The latter caused by absorption losses can be as...
We report on the experimental study of electromagnetic (EM) properties multilayered graphene in K(a)-band synthesized by catalytic chemical vapor deposition (CVD) process between nanometrically thin Cu catalyst film and dielectric (SiO2) substrate. The quality produced samples was monitored Raman spectroscopy. thickness films controlled atomic force microscopy (AFM) found to be a few nanometers (up 5 nm). discovered, that fabricated graphene, being only some thousandth skin depth, provided...
By exploring the Salisbury screen approach, we propose and demonstrate a thin film absorber of terahertz (THz) radiation. The is comprised less than 100 nm thick layer pyrolytic carbon deposited on stretchable polydimethylsiloxane (PDMS) followed by metal film. We that being overall 200 microns thick, such sandwich structure absorbs resonantly up to 99.9%of incident THz radiation, absorption resonance determined polymer thickness, which can be adjusted stretching.
A scalable technique of chemical vapor deposition (CVD) growth ultra-thin graphitic film is proposed. Ultra-thin films grown by a one-step CVD process on catalytic copper substrate have higher crystallinity than pyrolytic carbon non-catalytic surface and appear to be more robust graphene monolayer. The obtained material, not thicker 8 nm, survives during the transfer from Cu without template polymer layer, typically used in protect graphene. This makes much simple cost-effective. Having...
We show that reflectivity measurements enable the determination of thickness multilayered graphene on a metal substrate. The developed technique is based comparison substrate reflectance with and without relies strong absorbance high refractive index contrast. demonstrate by measuring CVD film grown copper
Despite that significant efforts have been made in the development of time-integrated graphene-based detectors operating vis/IR/THz ranges, little is known about coherent detection THz pulses with graphene. To date only a few time-resolved studies on-chip schemes, which significantly limit spectral range naturally provided by gapless band structure graphene, are known. Here we demonstrate free-space room-temperature radiation wide optically gated The principle based on registration...
We report on Z–scan measurements of the nonlinear refractive index semitransparent pyrolytic carbon films. The film is as high 8.23 × 10−9 cm2/W and shows a non–monotonous dependence thickness. demonstrate that, although linear absorption coefficient films comparable to that crystalline graphite, much lower than graphene.
The properties and synthesis procedures of the nanometrically thin pyrolyzed photoresist films (PPF) pyrolytic carbon (PCF) were compared, a number similarities found. Closer examination showed that optical these are almost identical; however, DC resistance PPF is about three times higher than PCF. Moreover, we observed wettability amorphous PCF was comparable to crystalline graphite. Potential applications executed by utilizing small difference in procedure two materials suggested.