Mikhail Erdmanis

Comprehensive numerical analysis of a surface-plasmon-resonance sensor based on an H-shaped optical fiber

We present and numerically characterize a surface-plasmon-resonance sensor based on an H-shaped optical fiber. In our design, the two U-shaped grooves of the H-fiber are first coated with a thin gold layer and then covered by a uniform titanium dioxide layer to facilitate spectral tuning of the device. A finite element method analysis of the sensor indicates that a refractive-index resolution of up to 5 · 10(3) nm/RIU can be obtained.

Influence of aluminium doping on thermoelectric performance of atomic layer deposited ZnO thin films

We study the effect of Al doping on thermoelectric power factor of ZnO films grown using atomic layer deposition method. The overall doping level is tuned by either varying the precursor pulsing sequence or by varying the number of precursor pulses while keeping the sequence unchanged. We observe that commonly utilized doping approach when periodic dopant layers are densely packed results in reduced power factor. At the same time, we find that thermoelectric performance can be improved by clustering the dopants. In addition, the clustering was found to tune the preferred crystal orientation of the polycrystalline film.

Focused ion beam lithography for fabrication of suspended nanostructures on highly corrugated surfaces

We propose a nanofabrication method that allows for patterning on extremely corrugated surfaces with micrometer-size features. The technique employs focused ion beam nanopatterning of ion-sensitive inorganic resists formed by atomic layer deposition at low temperature. The nanoscale resolution on corrugated surfaces is ensured by inherently large depth of focus of a focused ion beam system and very uniform resist coating. The utilized TiO₂ and Al₂O₃ resists show high selectivity in deep reactive ion etching and enable the release of suspended nanostructures by dry etching. We demonstrate the great flexibility of the process by fabricating suspended nanostructures on flat surfaces, inclined walls, and on the bottom of deep grooves.

ALD-Assisted Multiorder Dispersion Engineering of Nanophotonic Strip Waveguides

We propose a new technique for the multiorder dispersion engineering of nanophotonic strip waveguides. Unlike other techniques, the method does not require wafers with customized parameters and is fully compatible with standard wafers used in nanophotonics. The dispersion management is based on the application of nanometer-thick TiO2 layer formed by atomic layer deposition. The method is simple and reliable and allows good control of dispersion up to the fourth-order terms. The additional advantages are the reduction of propagation losses and partial compensation of fabrication tolerances.

Focused ion beam high resolution grayscale lithography for silicon-based nanostructures

Nanofabrication techniques providing a fine control over the profile of silicon structures are of great importance for nanophotonics, plasmonics, sensing, micro- and nano fluidics, and biomedical applications. We report on the applicability of focused ion beam for the fine grayscale lithography, which yields surface profiles that are customized at nanoscale. The approach is based on a correlation between the ion beam irradiation dose of inorganic resist and the mask etching rate in the reactive ion etching. An exceptional property of this method is the number of gray tones that are not limited by the resist characteristics. We apply the process to fabricate unique periodic nanostructures with a slope angle varying across the structure and a period as small as 200 nm.

Towards broad-bandwidth polarization-independent nanostrip waveguide ring resonators

We demonstrate a new method for accessing the broad-bandwidth polarization-independent operation of a microring resonator based on the standard photonic nanostrip waveguides. The method employs the selective application of atomic layer deposition to form highly uniform TiO(2) overlayers with the specific dispersion properties. The wide operation window is achieved by matching the wavelength dependencies of the free spectral ranges of the two orthogonal polarizations.

Carbon nanotube network varactor

Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100%, of the capacitance with a low actuation voltage of 10 V. The functionality of the varactor is improved by implementing a flexible nanocellulose aerogel filling.

Building molecular surface gradients with electron beam lithography

We present a strategy for patterning self-assembled monolayers with control of the area density of the molecules on the surface in a continuous and tunable fashion. Variation of the electron beam lithography parameters on patterning an amino-terminated silane layer on silicon allows control of the effective area density of the silane molecules. Gold nanoparticles are used as labels to visualize the area density of the amino groups in scanning electron microscopy images. The ability to continuously vary the density of functional molecules on surfaces and prepare molecular gradients is of wide interest in the fields of electronics, sensing and biology.

A highly accurate engineering of silicon integrated microring resonators based on the nanofabrication technique

In this work we present our theoretical and experimental study on the technique for the fine modification of a silicon integrated microring resonator spectral response. The method involves the local atomic layer deposition of a thin TiO2 overlayer and is applicable for standard nanophotonic waveguides. The approach is based on the dispersion management due to the specific dispersion properties brought by the thin TiO2 film deposition. In addition, the technique is able to partially compensate the fabrication imperfections and reduce the propagation losses.