Table of contents

The Micromechanics and Microsystems Europe Workshop is a well-established European event in the area of micromachining, microengineering and microtechnology. The goals of the MME workshop include stimulation and improvement of the technical knowledge as well as the establishment of cooperation and friendship between the delegates. The presented works span over all aspects of MEMS and microsystems technology, including design and fabrication, modelling and simulation, experimental evaluation and commercial use.

The MME 2018 was held in the Smolenice Castle situated at the foothill of the Little Carpathians Mountains, 60 km northwest of Bratislava. The first written mention of the village of Smolenice dates back to middle of the 13^th century. In the 14^th century, a castle was built above the village, the last of several fortresses constructed to guard the Carpathian passes. During the years and centuries, the castle and the estates were owned by several families. The castle was burnt out during the Napoleonic wars at the beginning of the 19^th century and only part of the outer fortifications remained from the original Gothic castle. The castle was completely rebuilt after the Second World War. In 1945, the state became the owner of the castle. On 26 June 1953, the rebuilt and furnished castle was handed over to the Slovak Academy of Sciences to become a representative meeting place for scientists from all over the world. Currently the castle serves as a conference centre.

We have heard 4 very interesting lectures in the field of new graphene and 2D materials for gas sensors, nanometrology for MEMS and NEMS elements, carbon-based structures, as well as materials and sensor development for multifunctional smart-system integration. Similarly interesting were the 32 flash presentations and subsequent poster discussions, 15 participants were actively involved in the paper review session led by Leon Abelmann.

We believe that our short 2-day meeting has provided ample room for the intense exchange of thoughts and opinions, and has provided, in particular to PhD students and young researchers from different countries a great deal of new inspiration and impetus to their early scientific career. Certainly, it was also beneficial for older researchers, not only by being able to see our students and graduate students, but that we were able to convince ourselves that the emerging young scientific generation would be equally entertaining and aiming for new insights in these attractive areas like micromechanics, micromachining, microfabrication, microtechnology and microsystems.

We as organizers have tried to create a suitable environment and a relaxed atmosphere in a somewhat interesting and somewhat unusual environment of the Smolenice Castle surrounded by the woods of the Little Carpathians.

We think that the format of this already well-worked and long-standing workshop addresses young people and creates good conditions for mutual cooperation not only within Europe but also Asia (Japan, Taiwan).

We also thank the steering committee for enabling us to organize this workshop and thus provide our Slovak young researchers with a space for their presentation and contacts.

Ivan Hotovy and Miroslav Mikolasek

Institute of Electronics and Photonics

Slovak University of Technology in Bratislava

Slovakia

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Lifetime testing results of an electrostatically actuated microelectromechanical systems (MEMS) switch with Pt-Pt contact are presented. Moveable electrode of the switch is an aluminium beam with platinum contact bumps, which comes in contact with platinum thin-film electrodes. The switch operates in a cold DC mode. Testing is performed at several levels of the input current. Dependence of the switch resistance in the "on" state on the number of actuation cycles is measured. Lifetime of the device is limited by the sharp increase of the on-resistance up to 100 MΩ and depends on the switch design and the input current. Morphology and chemical composition of the contacting surfaces are investigated and mechanisms of the contact degradation are determined.

This paper presents two measurement setups to analyse hanging and falling droplets from different nozzles. The focus of these setups is on reducing costs and complexity of such systems compared to systems mentioned in literature which consists of an expensive high speed camera with according lens. Therefore the first setup uses an industrial camera and a corresponding lens having a resolution of up to 800 x 600 pixels and enabling the capturing of movies with more than 1000 frames per second (by using a reduced resolution). Additionally a weighing scale is implemented. The second setup represents a real low-cost approach, which nevertheless offers about 120 frames per second and a resolution of 640 × 480 pixels by using two RaspberryPi microcontrollers and the according camera modules. The cameras are placed in an angle of 90°. The presented setups are compared to each other and the advantages and disadvantages of each system are figured out. Subsequently the results of an exemplary measurement of the droplet volume are presented showing the quality of both setups with a maximum deviation of the optical results of less than ± 6 % compared to the results of the weighing scale.

Non-ideal phase responses on electro-thermally actuated piezoresistive cantilever sensors have led the phase-locked loop (PLL) systems into difficulties for real-time sensing applications. These outcomes are caused by thermal-parasitic coupling from the actuating part to the sensing part. Minimizing or eliminating parasitic effects is necessary to obtain an optimized phase response. To realize this, we adjusted the voltage supply of the sensing part, which is in form of a full Wheatstone bridge (WB). By increasing the WB supply voltage (V_WB), the phase response can be enhanced. Alternatively, a reference signal that differentially eliminates the parasitic parameter from the sensor output was employed. To investigate the resulting optimized phase response under real-time measurement conditions, two different microcantilevers were connected to an MFLI lock-in amplifier + PLL system (Zurich Instruments). Measurement results exhibited a good sensor performance under varying humidity and temperature conditions.

In this paper, a self-reading miniaturized cantilever design for highly sensitive airborne nanoparticle (NP) detection is presented. The cantilever, which is operated in the fundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. For maximum sensitivity and read-out signal amplitude, the geometric parameters of the sensor design were optimized by finite-element modelling (FEM). Piezo-resistive struts at both sides of the cantilever are employed for a Wheatstone half-bridge. This allows the electrical read-out of the phase information of a resonant cantilever of minimum mass. For electrostatic NP collection, the cantilever has a negative-biased electrode located at its free end. Moreover, μ-channels for guiding a particle-laden air flow and a counter-electrode around the cantilever tip are integrated. The presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, MEMS-based NP monitoring devices.

The goal of this contribution is to develop a process the most appropriate for the deposition of colloid gold nanoparticles on the surfaces of metal oxides (TiO₂, NiO) prepared on silicon and/or alumina substrates. Important procedures such as hydrophilization of metal oxide surface and its subsequent functionalization with a silane coupling agent 3 mercapto propyl tri metoxy silane (MPTMS) were examined so as to reach a metal oxide surface with the most satisfying properties for immobilization of gold nanoparticles having a uniform and dense distribution. TiO₂ nanotips prepared by reactive ion etching of oxide surface covered with selfmask gold nanoparticles as well as improved hydrogen gas sensing properties of the NiO film covered by gold nanoparticles are demonstrated.

Polarizing beam splitters are key elements widely used in different optical instruments. This paper introduces the design and simulation of a novel thin-film multilayer polarizing micro beam splitter based on airgap layers (n = 1.002828 at 400 nm). The negligible absorption coefficient of the air over a wide spectral region (κ ≈ 0 from about 200 nm and higher) satisfies the conditions of a perfect low refractive index material (L). Moreover, using titanium dioxide (TiO₂) as high refractive index material (H), a very high refractive index contrast is obtained. The micro beam splitter optical structure consists in a 7 optimized multilayer of TiO₂ and air, providing a refractive contrast higher than 1.2. The polarizing beam splitter cube is projected in a borosilicate glass substrate (BK7) and the optical multilayer obtained, expressed in multiples of the quarter wavelength optical thickness – QWOT, is 1.6H L 1.1H 1.5L 1.1H L 1.6H. This optical structure ensures the transmission of p- polarization and the reflection of s- polarization, from visible to NIR spectral range, over a bandwidth higher than 170 nm. Additionally, the designed polarizing beam splitter can be fabricated using standard microtechnology fabrication processes.

As microsystems are reduced in size and become integrated in the Internet of Things (IoT), they require an adequate power supply which can be integrated at the same size scale. Microsupercapacitors (MSCs), if coupled with on-chip harvesters, can offer solutions for a self-sustaining, on-chip power supply. However, the implementation of reliable MSC wafer-scale production compatible with CMOS technology remains a challenge. Palladium (Pd) is known as a CMOS compatible metal and, in this paper, we investigate the use of Pd as a contact material for vertical graphene (VG) electrodes in wafer-scale MSC fabrication. We show that a Ti diffusion barrier is required to prevent short-circuiting for the successful employment of Pd contacts. The fabricated MSCs demonstrate a capacitance of 1.3 μF/cm² with an energy density of 0.42 μJ/cm². Thus, utilization of a Ti diffusion barrier with a CMOS compatible Pd metal electrode is a step towards integrating MSCs in semiconductor microsystems.

In this paper we present an investigation of the influence of different roughness of etched silicon surfaces on the measured nanomechanical properties. For the etching, inductively coupled plasma (ICP) reactive ion etching (RIE) was performed on the surface of silicon samples with different crystal orientations (i.e., Si <100>, Si <110>, and Si <111>). Different roughness levels were obtained on each sample by changing the bias voltage through the high-frequency (HF) power. The surface roughness was measured using atomic force microscopy (AFM). The obtained surface roughness for the same etching conditions was different for different crystal orientations. The nanomechanical properties were measured using nanoindentation.

This paper introduces a new approach for preparation a gas sensor based on the potentiostatic electrodeposition of Cu₂O on interdigitated electrodes. Four Cu₂O gas sensors with different deposition charges were prepared from lactate-stabilized copper sulphate on Au IDE electrodes. Prepared sensors were characterised by scanning electron microscopy and electrical measurements in the air and H₂ ambient. It was found that the key aspect for high gas sensitivity is to achieve an appropriate rate of crystal interconnection between IDE electrodes. Low deposition charge results in an air gap between IDE electrodes, while high deposition charge causes strong, bulk-like interconnection of Cu₂O crystals. The low rate of Cu₂O interconnection formed by connection of individual crystals, where the conductance is affected by the surface area of the crystals, is shown as a most appropriate sensor. The sensitivity of 3.75 to 1000 ppm H₂ concentration and 200 °C operation temperature is achieved for the optimised Cu₂O based IDE sensor.

This paper presents a droplet-based method for detecting the mass of fluid-based microparticles. The degree of wettability on silicon-based substrates is therefore investigated for enhanced adsorption of microparticles. Contact angles of 47.3° (pre-treatment) and below 9° (enhanced hydrophilicity upon oxygen plasma treatment) have been realized. Segments of mono-layered particles on the substrate and the possibility of homogenous distribution are also demonstrated. The volume and the surface-contact area of droplets on the substrate have been determined, hence empowering an envisaged optimized design of a particle-well cantilever. The determination of the mass of adsorbed microparticles on the cantilever has also been investigated.

Chirped surface acoustic wave (SAW) resonators based on aluminum nitride (AlN) thin films have been designed and fabricated to comprehend the wave propagation characteristics induced by interdigitated transducers (IDTs) deposited on their surfaces. From the simulation results, design and geometry of the metal fingers including their width and pitch play critical roles on the wavelength of the acoustic wave and the mechanical displacement, which subsequently set the device resonant frequency. A single-step metal lift-off process involving photolithography and electron beam metal evaporation has been used to pattern and deposit Cr/Au IDT on AlN-on-Si wafers.

Transition metals alloys are the most studied getter films for wafer-level vacuum packaging of MEMS. In this work we investigated yttrium and Y_xTi_y alloys films that could possibly overcome the limitations of usual getter materials, i.e. reversible sorption of hydrogen and low sorption ability for hydrocarbon gases. As a preliminary step towards this objective, properties of (co-)evaporated yttrium and Y_xTi_y films were analyzed by SEM, EDS, XPS and in-situ sheet resistance measurements before, after and/or during annealing in vacuum. As deposited and annealed films have a small grain size and a columnar structure. It is shown that yttrium and Y_xTi_y films can be activated after 1 hour of annealing in vacuum at 250 °C if the Y-content is larger than ∼9 %. These results are promising for the use of Y-based films as low temperature getters for vacuum packaging.

By combining optical emission spectroscopy (OES) and Langmuir probes, the plasma properties of a Xenon-microplasma thruster have been investigated. Using IV-curve analysis the properties of the plasma have been determined and correlated to the power fed into it. Satisfactory agreement has been obtained with the results of OES measurements (line-ratio technique) and shock-cell distance calculations. While the fuel consumption of the thruster decreased very linearly with the power fed to the plasma, the plasma properties was found to have behave in a more complex way. In the studied power range, the density ratio between at least two ions, with upper configurations 5p⁵(²P°_3/2)7p and 5p⁵(²P°_3/2)6p, strongly indicated that the ionization processes of the former was favourable in terms of thrust for the geometry of the nozzle. This was supported electron temperature measurements from IV-curves.

This study presents a new approach to enhancing the gas sensor properties based on increasing the sensing area by a structured substrate. Two types of needle-shaped silicon substrates with surface areas of 40 and 14 μm² were used as substrate for the preparation of NiO gas sensing element with a thickness of 25 nm. The surface morphology and composition of the prepared samples were examined by SEM, FIB-SEM, and GD OES methods. Deposited NiO films were continuous consisting of an agglomeration of small nanosized grains with arbitrary forms created on each Si needle. It was found that NiO had a polycrystalline nature. The gas sensing measurements revealed that hydrogen responses were better for NiO sensing elements prepared on needle-shape Si substrates with 40 μm² surface area than those with 14 μm² for all investigated concentrations and temperatures. The maximum relative sensitivity of 26% was measured at 250 ppm of hydrogen.

This paper is focused on the preparation of boron doped diamond (BDD) cantilevers for MEMS applications. Hot filament CVD diamond deposition technique was used for preparation of highly boron doped thin film. The fabrication process consisted only of dry etching steps and masking process, no wet etching of substrate was used. Therefore, it was necessary to optimize both anisotropic and isotropic etching to release the cantilever structure from silicon substrate. Doped diamond cantilevers were etched by reactive ion etching using inductively coupled plasma (ICP RIE) through aluminum etching masks. The optimal properties of fabrication process led to high quality MEMS structures. The resulting cantilevers were investigated by scanning electron microscopy (SEM) and laser vibrometer system. Finally, we demonstrate a BDD cantilever (5 μm width) with the main resonant frequencies at 22.2 kHz, 46.6 kHz, 52.2 kHz and 65.6 kHz.

Phosphorus doped silicon carbide film as emitter in heterojunction structure was deposited on p-type Si(100) wafers at various deposition conditions by means of PECVD technology using silane (SiH₄), methane (CH₄), hydrogen (H₂) and phosphine (PH₃, 2 vol.% in H₂) gas as precursors. ITO or IZO film was RF magnetron sputtered on top of the different P doped a-SiC:H(n) film. Irradiation of structures with Xe ions to total fluency 5×10¹¹ cm⁻² was performed at room temperature. Influence of phosphorus concentration and type of transparent conducting oxide was investigated. A deeper insight on the impact of irradiation on the electrophysical properties of sample was obtained by the analysis of complex impedance spectra.

GaP(111)B substrate was etched through colloidal self-assembled randomly distributed 30nn Au nanoparticles by RIE. We looked into how GaP nanocones (NCs) formed with respect to the chamber pressure and etching duration, and the use of electron cyclotron resonance (ECR) RIE mode. The NCs were steep-walled in RIE, and those produced by ECR RIE were bell shaped. The NC length increased with etching duration for the same chamber pressure. The NCs were shorter and slightly steeper with decreased pressure for the same etching duration. The NCs that had the Au particles eradicated during the etching process became blunt and were gradually diminished.