V. Grigaliūnas

Fabrication of photonic structures by means of interference lithography and reactive ion etching

Abstract In this study, the fabrication of two-dimensional photonic structures by means of interference lithography is discussed. The proposed method provides flexible formation of various configuration two-dimensional interference patterns depending on the number of beams and their interorientation. Mainly, triangular and square lattice configurations are modeled. It is shown that the dimensions of substructure increase with the number of beams superpositioning. Mask fabrication by SF 6 /N 2 reactive ion etching, while transferring the pattern onto silicon substrate is presented.

Nitrogen-doped twisted graphene grown on copper by atmospheric pressure CVD from a decane precursor

We present Raman studies of graphene films grown on copper foil by atmospheric pressure CVD with n-decane as a precursor, a mixture of nitrogen and hydrogen as the carrier gas, under different hydrogen flow rates. A novel approach for the processing of the Raman spectroscopy data was employed. It was found that in particular cases, the various parameters of the Raman spectra can be assigned to fractions of the films with different thicknesses. In particular, such quantities as the full width at half maximum of the 2D peak and the position of the 2D graphene band were successfully applied for the elaborated approach. Both the G- and 2D-band positions of single layer fractions were blue-shifted, which could be associated with the nitrogen doping of studied films. The XPS study revealed the characteristics of incorporated nitrogen, which was found to have a binding energy around 402 eV. Moreover, based on the statistical analysis of spectral parameters and the observation of a G-resonance, the twisted nature of the double-layer fraction of graphene grown with a lower hydrogen feeding rate was demonstrated. The impact of the varied hydrogen flow rate on the structural properties of graphene and the nitrogen concentration is also discussed.

Analysis of a Microelectrostatic Motor

An electrostatic motor is a very complex dynamical system whose performance critically depends on the shape of the rotor and stator, number of poles, clearances between axis and rotor, friction, rotor vibrations, and levitation, etc. There are many possible micromotor constructions depending on the required accuracy, the speed of rotation and power of the motor. This work shows the technology required to build a micromotor using UV lithography. Studies of vibration characteristics using ANSYS and MATLAB modeling software and an experimental analysis to optimize the dynamical properties of the system and to improve its manufacturing process are also shown.

Modelling of relief of phase reflection diffraction grating

Abstract This article describes theoretical and experimental results on phase reflection diffraction gratings. Based on Fourier optics the mathematical formulation describing diffraction dispersion of light from a relief grating of the trapezium profile is derived. We propose a method that lets us estimate the grating’s geometric parameters in a versatile modelling system. We have designed an original programme that estimates diffraction intensities and calculates diffraction efficiency. The estimated intensities are used to reconstruct the grating’s geometrical properties using our mathematical model. The precision of the method is evaluated as the deviation of obtained results from microscopy data.

Micro-channel drilling of Ni and Pt films on silicon by using laser beam interference ablation for solid oxide fuel cells

Solid oxide fuel cells (SOFC) are widely studied because of their potential usage in power source applications. At present huge attention is paid to micro solid oxide fuel cells (μ-SOFC) based on thin film technologies with power capacity in the range of several watts. Porous nickel is an important part in many types of solid oxide fuel cells. This work presents experimental results of laser micro-channel formation in the 200 nm thick nickel and platinum films for the fuel cell membranes. The four-beam interference ablation was applied for fast and parallel formation of microchannel over a large area in thin metal film on a silicon substrate for μ-SOFC. Using this technique, regularly arranged circular holes with a period of 4.2 μm were formed in the 200 nm thick nickel and platinum films. The diameter of the holes ranged from 1.7 to 2.7 μm. The area where holes were ablated by a single laser exposure was approximately 250x250 μm. A silicon substrate was chemically etched from backside to release the patterned nickel film.