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M. Schneider
Institute for Sensor and Actuator Systems, TU Wien, Gußhausstraße 27-29, Wien 1040, Austria

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Journal article
Published: 04 June 2021 in Journal of Applied Physics
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The electroactive polymer polyvinylidene fluoride (PVDF) has gained much interest in smart materials research with a wide application range for industry and consumer applications due to the low cost, flexibility, chemical resistance, non-toxicity, and light weight. In this work, we present an α-phase PVDF cantilever that exploits electrostriction as the main transducer mechanism for excitation. We realize thin PVDF films with a thickness of ∼190 nm and a low roughness (∼19 nm RMS). Electrostrictive cantilevers need high electric fields to achieve amplitudes comparable to piezoelectric counterparts. At thinner films, lower voltage levels are requested for comparable electric fields, thus making electrostrictive PVDF cantilevers a viable route and subsequently allowing broader use of PVDF in MEMS devices. We use an asymmetric electrode design that has the advantage of shifting the neutral axis out of the PVDF without enhancing cantilever thickness with a supporting device layer. In addition, these devices can be produced by CMOS compatible micromachining techniques. We measured the electrostrictive and piezoelectric actuation signal with laser-Doppler vibrometry and showed the frequency spectrum and curvature of such α-phase PVDF cantilevers. The cantilevers have a curvate of up to 120 m−1 at 1500 kV/cm. We demonstrate that the electrostrictive actuation has a low temperature dependency in the range from 25 up to 130 °C. A typical cantilever exhibits a geometry dependent low spring constant (k ∼ 0.3 N m−1) and a low quality factor (Q ∼ 75) in air.

ACS Style

F. J. Maier; M. Schneider; P. Ullmann; J. Hafner; U. Schmid. α-phase PVDF MEMS cantilever excited by electrostriction and evaluated up to 160 °C in air by laser-Doppler vibrometry. Journal of Applied Physics 2021, 129, 214507 .

AMA Style

F. J. Maier, M. Schneider, P. Ullmann, J. Hafner, U. Schmid. α-phase PVDF MEMS cantilever excited by electrostriction and evaluated up to 160 °C in air by laser-Doppler vibrometry. Journal of Applied Physics. 2021; 129 (21):214507.

Chicago/Turabian Style

F. J. Maier; M. Schneider; P. Ullmann; J. Hafner; U. Schmid. 2021. "α-phase PVDF MEMS cantilever excited by electrostriction and evaluated up to 160 °C in air by laser-Doppler vibrometry." Journal of Applied Physics 129, no. 21: 214507.

Journal article
Published: 08 April 2021 in Electrochem
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Ti/Au multi-layered micro-cantilevers with complex three-dimensional structures used as micro-components in micro-electromechanical systems (MEMS) sensors were prepared by lithography and electrodeposition, and the effective Young’s modulus was evaluated by the resonance frequency method and finite element method simulation. Effects of the constraint condition at the fixed-end of the micro-cantilever and the temperature dependency of the effective Young’s modulus were studied. Three types of the constraint at the fixed-end were prepared, which were normal type (constraining only bottom surface of the fixed-end), block type (constraining both top and bottom surfaces), and bridge type (top surfaces covering with a bridge-like structure). The temperature dependency test was conducted in a temperature range from 150 to 300 °C in a vacuum chamber. An increase in the effective Young’s modulus was observed as the constraint condition became more rigid, and the effective Young’s modulus merely changed as the temperature varied from room temperature to 300 °C.

ACS Style

Hitomi Watanabe; Tso-Fu Chang; Michael Schneider; Ulrich Schmid; Chun-Yi Chen; Shinichi Iida; Daisuke Yamane; Hiroyuki Ito; Katsuyuki Machida; Kazuya Masu; Masato Sone. Effective Young’s Modulus of Complex Three Dimensional Multilayered Ti/Au Micro-Cantilevers Fabricated by Electrodeposition and the Temperature Dependency. Electrochem 2021, 2, 216 -223.

AMA Style

Hitomi Watanabe, Tso-Fu Chang, Michael Schneider, Ulrich Schmid, Chun-Yi Chen, Shinichi Iida, Daisuke Yamane, Hiroyuki Ito, Katsuyuki Machida, Kazuya Masu, Masato Sone. Effective Young’s Modulus of Complex Three Dimensional Multilayered Ti/Au Micro-Cantilevers Fabricated by Electrodeposition and the Temperature Dependency. Electrochem. 2021; 2 (2):216-223.

Chicago/Turabian Style

Hitomi Watanabe; Tso-Fu Chang; Michael Schneider; Ulrich Schmid; Chun-Yi Chen; Shinichi Iida; Daisuke Yamane; Hiroyuki Ito; Katsuyuki Machida; Kazuya Masu; Masato Sone. 2021. "Effective Young’s Modulus of Complex Three Dimensional Multilayered Ti/Au Micro-Cantilevers Fabricated by Electrodeposition and the Temperature Dependency." Electrochem 2, no. 2: 216-223.

Journal article
Published: 08 January 2021 in Nature Communications
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Ferroelectric materials exhibit a phase transition to a paraelectric state driven by temperature - called the Curie transition. In conventional ferroelectrics, the Curie transition is caused by a change in crystal symmetry, while the material itself remains a continuous three-dimensional solid crystal. However, ferroelectric polymers behave differently. Polymeric materials are typically of semi-crystalline nature, meaning that they are an intermixture of crystalline and amorphous regions. Here, we demonstrate that the semi-crystalline morphology of the ferroelectric copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) strongly affects its Curie transition, as not only a change in crystal symmetry but also in morphology occurs. We demonstrate, by high-resolution nanomechanical measurements, that the semi-crystalline microstructure in the paraelectric state is formed by crystalline domains embedded into a softer amorphous phase. Using in situ X-ray diffraction measurements, we show that the local electromechanical response of the crystalline domains is counterbalanced by the amorphous phase, effectively masking its macroscopic effect. Our quantitative multi-scale characterisations unite the nano- and macroscopic material properties of the ferroelectric polymer P(VDF-TrFE) through its semi-crystalline nature.

ACS Style

Jonas Hafner; Simone Benaglia; Filipe Richheimer; Marco Teuschel; Franz J. Maier; Artner Werner; Sebastian Wood; Daniel Platz; Michael Schneider; Klaudia Hradil; Fernando A. Castro; Ricardo Garcia; Ulrich Schmid. Multi-scale characterisation of a ferroelectric polymer reveals the emergence of a morphological phase transition driven by temperature. Nature Communications 2021, 12, 1 -9.

AMA Style

Jonas Hafner, Simone Benaglia, Filipe Richheimer, Marco Teuschel, Franz J. Maier, Artner Werner, Sebastian Wood, Daniel Platz, Michael Schneider, Klaudia Hradil, Fernando A. Castro, Ricardo Garcia, Ulrich Schmid. Multi-scale characterisation of a ferroelectric polymer reveals the emergence of a morphological phase transition driven by temperature. Nature Communications. 2021; 12 (1):1-9.

Chicago/Turabian Style

Jonas Hafner; Simone Benaglia; Filipe Richheimer; Marco Teuschel; Franz J. Maier; Artner Werner; Sebastian Wood; Daniel Platz; Michael Schneider; Klaudia Hradil; Fernando A. Castro; Ricardo Garcia; Ulrich Schmid. 2021. "Multi-scale characterisation of a ferroelectric polymer reveals the emergence of a morphological phase transition driven by temperature." Nature Communications 12, no. 1: 1-9.

Journal article
Published: 01 July 2020 in Journal of Microelectromechanical Systems
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This work presents a new type of piezoelectric micromachined ultrasonic transducer (PMUT) based on a bi-stable MEMS membrane structure with integrated aluminum nitride (AlN) actuators. By switching the membrane between both stable ground states, large, design-dependent membrane center displacements in the range of 10 μm can be achieved, which result in sound pressure levels of up to 96.8 dB in the ultrasonic range at frequencies between 30 and 60 kHz at a distance of 10.5 mm. This bi-stable operation mode can be triggered by moderate voltage levels of up to 40 V, which is not uncommon for PMUT devices. The usage of AlN compared to the more commonly utilized lead zirconate titanates (PZT) significantly simplifies the device integration process and ensures CMOS compatibility. A comprehensive comparison with similar devices in literature shows that despite the lower piezoelectric coefficients of AlN compared to PZT, this bi-stable actuation approach features exceptionally high stroke levels with a correspondingly high overall sound pressure level. [2020-0104]

ACS Style

Michael Schneider; Manuel Dorfmeister; Philipp Moll; Manfred Kaltenbacher; Ulrich Schmid. Bi-Stable Aluminum Nitride-Based Piezoelectric Micromachined Ultrasonic Transducer (PMUT). Journal of Microelectromechanical Systems 2020, 29, 948 -953.

AMA Style

Michael Schneider, Manuel Dorfmeister, Philipp Moll, Manfred Kaltenbacher, Ulrich Schmid. Bi-Stable Aluminum Nitride-Based Piezoelectric Micromachined Ultrasonic Transducer (PMUT). Journal of Microelectromechanical Systems. 2020; 29 (5):948-953.

Chicago/Turabian Style

Michael Schneider; Manuel Dorfmeister; Philipp Moll; Manfred Kaltenbacher; Ulrich Schmid. 2020. "Bi-Stable Aluminum Nitride-Based Piezoelectric Micromachined Ultrasonic Transducer (PMUT)." Journal of Microelectromechanical Systems 29, no. 5: 948-953.

Originalarbeit
Published: 08 April 2020 in e & i Elektrotechnik und Informationstechnik
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Piezoelectric silicon micro-machined resonators triggered in the two-dimensional roof-tile shaped mode exhibit exceptionally high quality factors even in highly viscous liquids. In combination with an all-electric readout, this enables precise measurements in liquid media with high output signals, if the electrode design and the anchor geometry are tailored to match the selected order of the roof-tile shaped mode. This paper provides an overview of this promising class of resonator modes for micro-electromechanical systems (MEMS) and highlights three application scenarios. In the food industry, the MEMS sensor can be used to monitor the fermentation process in wine by tracking the density and hence, the concentration of ethanol. In technical lubricants, the concentration of ferrous particles can be monitored by integrating a magnetic actuator on the resonator. Finally, even in highly viscous bitumen, the MEMS sensor is successfully used to measure the viscosity of this material.

ACS Style

Michael Schneider; Georg Pfusterschmied; Florian Patocka; Ulrich Schmid. High performance piezoelectric AlN MEMS resonators for precise sensing in liquids. e & i Elektrotechnik und Informationstechnik 2020, 137, 121 -127.

AMA Style

Michael Schneider, Georg Pfusterschmied, Florian Patocka, Ulrich Schmid. High performance piezoelectric AlN MEMS resonators for precise sensing in liquids. e & i Elektrotechnik und Informationstechnik. 2020; 137 (3):121-127.

Chicago/Turabian Style

Michael Schneider; Georg Pfusterschmied; Florian Patocka; Ulrich Schmid. 2020. "High performance piezoelectric AlN MEMS resonators for precise sensing in liquids." e & i Elektrotechnik und Informationstechnik 137, no. 3: 121-127.

Journal article
Published: 20 March 2020 in Acta Materialia
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The flexoelectric effect describes the electromechanical coupling of a strain gradient to a polarization and vice versa. This effect scales linearly with permittivity and strain gradients can get very high for dimensions on the micro and nanoscale. Even though the flexoelectric effect can be best exploited within micro or nanoelectromechanical systems (M/NEMS) applications, it has not been established in today`s M/NEMS device architectures as other transducer principles, like piezoelectricity. In this work, values of the converse flexoelectric coefficient for one of the most promising flexoelectric materials, titanium dioxide (TiO2) are provided. The experimental results are based on a carefull characterization of IrO2/TiO2/IrO2 cantilevers. Besides CMOS compatiblity TiO2 is selected as functional thin film material as it offers a very high permittivity and shows no hysteresis or saturation effects as it is neither ferro- nor paraelectric. Additionally, it guarantees a low cost, lead-free realization and can be directly integrated in a standard silicon MEMS fabrication process by sputter deposition. In order to correctly determine the flexoelectric coefficient, other electromechanical coupling effects are considered and assessed. The flexoelectric coefficient is shown to be µeff = 1.78 ± 0.16 nC m−1 at 10 kHz. The flexoelectric coupling constant with a value of 2.75 V is in good agreement with that theoretically predicted by Kogan`s estimate of 3.14 V.

ACS Style

F.J. Maier; M. Schneider; J. Schrattenholzer; W. Artner; K. Hradil; A. Artemenko; A. Kromka; U. Schmid. Flexoelectricity in polycrystalline TiO2 thin films. Acta Materialia 2020, 190, 124 -129.

AMA Style

F.J. Maier, M. Schneider, J. Schrattenholzer, W. Artner, K. Hradil, A. Artemenko, A. Kromka, U. Schmid. Flexoelectricity in polycrystalline TiO2 thin films. Acta Materialia. 2020; 190 ():124-129.

Chicago/Turabian Style

F.J. Maier; M. Schneider; J. Schrattenholzer; W. Artner; K. Hradil; A. Artemenko; A. Kromka; U. Schmid. 2020. "Flexoelectricity in polycrystalline TiO2 thin films." Acta Materialia 190, no. : 124-129.

Journal article
Published: 01 July 2019 in Sensors and Actuators A: Physical
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ACS Style

P. Schmid; F. Triendl; C. Zarfl; S. Schwarz; W. Artner; M. Schneider; U. Schmid. Electro-mechanical properties of multilayered aluminum nitride and platinum thin films at high temperatures. Sensors and Actuators A: Physical 2019, 293, 128 -135.

AMA Style

P. Schmid, F. Triendl, C. Zarfl, S. Schwarz, W. Artner, M. Schneider, U. Schmid. Electro-mechanical properties of multilayered aluminum nitride and platinum thin films at high temperatures. Sensors and Actuators A: Physical. 2019; 293 ():128-135.

Chicago/Turabian Style

P. Schmid; F. Triendl; C. Zarfl; S. Schwarz; W. Artner; M. Schneider; U. Schmid. 2019. "Electro-mechanical properties of multilayered aluminum nitride and platinum thin films at high temperatures." Sensors and Actuators A: Physical 293, no. : 128-135.

Journal article
Published: 23 May 2019 in Sensors and Actuators A: Physical
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Micromachined resonators completely submerged in liquids suffer from high viscous damping and low measurement signals compared to the operation in gaseous environment or in vacuum, which drastically decreases the sensing performance. A promising approach to decrease damping is the utilization of higher order modes. However, with the increase in mode order also the fluid-structure interaction decreases. In this context, it is unclear how the use of higher order modes helps, when targeting the characterization of fluid properties such as density and viscosity. In this paper, we demonstrate how the use of higher order modes affects both the responsivity and sensitivity of resonantly excited MEMS sensors when operated in liquids. The latter two key device parameters are experimentally investigated with respect to the inverse viscosity-density product (ρfluid·µfluid)-0.5 for the quality factor Q, the electrical conductance peak height ΔG and for the resonance frequency fres in standardized liquids with dynamic viscosity values ranging from 5 to 700 mPa∙s. It is observed, that an increase in mode order significantly increases the quality factor by a factor of 7, when comparing 1st to 10th order mode in a sample fluid with a dynamic viscosity of 5 mPa∙s), allowing the characterization of high viscous liquid with a dynamic viscosity up to 700 mPa∙s. Even so, no influence on the relative responsivity of Q and ΔG is observed. In fact, a decrease in the relative responsivity of fres is observed, so that no gain in response is achieved for all three parameters when the mode order is increased. However, higher order modes show significantly improved strain profiles on the surface of the resonating structure, resulting in increased ΔG values for the piezoelectric readout mechanism. Therefore, the sensitivity is substantially increased resulting in an improvement by a factor of ˜30, when comparing the 1st and 10th order mode. Even higher factors of ˜50 are obtained for Q and ΔG, what enables a minimal detectable (ρ·µ)-0.5 value of 0.000998 (mPa·s·kg/l)-0.5in a high viscous sample fluid with (ρ·µ)-0.5 = 0.040 (mPa·s·kg/l)-0.5 (for comparison: a common engine oil such as SAE 5W-40 has (ρ·µ)-0.5 = 0.039 (mPa·s·kg/l)-0.5at 0 °C).

ACS Style

Georg Pfusterschmied; Florian Patocka; Christoph Weinmann; Michael Schneider; Daniel Platz; Ulrich Schmid. Responsivity and sensitivity of piezoelectric MEMS resonators at higher order modes in liquids. Sensors and Actuators A: Physical 2019, 295, 84 -92.

AMA Style

Georg Pfusterschmied, Florian Patocka, Christoph Weinmann, Michael Schneider, Daniel Platz, Ulrich Schmid. Responsivity and sensitivity of piezoelectric MEMS resonators at higher order modes in liquids. Sensors and Actuators A: Physical. 2019; 295 ():84-92.

Chicago/Turabian Style

Georg Pfusterschmied; Florian Patocka; Christoph Weinmann; Michael Schneider; Daniel Platz; Ulrich Schmid. 2019. "Responsivity and sensitivity of piezoelectric MEMS resonators at higher order modes in liquids." Sensors and Actuators A: Physical 295, no. : 84-92.

Journal article
Published: 01 May 2019 in Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena
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ACS Style

Fabian Triendl; Gernot Fleckl; Michael Schneider; Georg Pfusterschmied; Ulrich Schmid. Evaluation of interface trap characterization methods in 4H-SiC metal oxide semiconductor structures over a wide temperature range. Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena 2019, 37, 032903 .

AMA Style

Fabian Triendl, Gernot Fleckl, Michael Schneider, Georg Pfusterschmied, Ulrich Schmid. Evaluation of interface trap characterization methods in 4H-SiC metal oxide semiconductor structures over a wide temperature range. Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena. 2019; 37 (3):032903.

Chicago/Turabian Style

Fabian Triendl; Gernot Fleckl; Michael Schneider; Georg Pfusterschmied; Ulrich Schmid. 2019. "Evaluation of interface trap characterization methods in 4H-SiC metal oxide semiconductor structures over a wide temperature range." Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena 37, no. 3: 032903.

Letter
Published: 10 April 2019 in Light: Science & Applications
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Optical resonators are essential for fundamental science, applications in sensing and metrology, particle cooling, and quantum information processing. Cavities can significantly enhance interactions between light and matter. For many applications they perform this task best if the mode confinement is tight and the photon lifetime is long. Free access to the mode center is important in the design to admit atoms, molecules, nanoparticles, or solids into the light field. Here, we demonstrate how to machine microcavity arrays of extremely high quality in pristine silicon. Etched to an almost perfect parabolic shape with a surface roughness on the level of 2 Å and coated to a finesse exceeding F = 500,000, these new devices can have lengths below 17 µm, confining the photons to 5 µm waists in a mode volume of 88λ3. Extending the cavity length to 150 µm, on the order of the radius of curvature, in a symmetric mirror configuration yields a waist smaller than 7 µm, with photon lifetimes exceeding 64 ns. Parallelized cleanroom fabrication delivers an entire microcavity array in a single process. Photolithographic precision furthermore yields alignment structures that result in mechanically robust, pre-aligned, symmetric microcavity arrays, representing a light-matter interface with unprecedented performance.

ACS Style

Georg Wachter; Stefan Kuhn; Stefan Minniberger; Cameron Salter; Peter Asenbaum; James Millen; Michael Schneider; Johannes Schalko; Ulrich Schmid; André Felgner; Dorothee Hüser; Markus Arndt; Michael Trupke. Silicon microcavity arrays with open access and a finesse of half a million. Light: Science & Applications 2019, 8, 1 -7.

AMA Style

Georg Wachter, Stefan Kuhn, Stefan Minniberger, Cameron Salter, Peter Asenbaum, James Millen, Michael Schneider, Johannes Schalko, Ulrich Schmid, André Felgner, Dorothee Hüser, Markus Arndt, Michael Trupke. Silicon microcavity arrays with open access and a finesse of half a million. Light: Science & Applications. 2019; 8 (1):1-7.

Chicago/Turabian Style

Georg Wachter; Stefan Kuhn; Stefan Minniberger; Cameron Salter; Peter Asenbaum; James Millen; Michael Schneider; Johannes Schalko; Ulrich Schmid; André Felgner; Dorothee Hüser; Markus Arndt; Michael Trupke. 2019. "Silicon microcavity arrays with open access and a finesse of half a million." Light: Science & Applications 8, no. 1: 1-7.

Journal article
Published: 19 December 2018 in Thin Solid Films
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We proposed and demonstrated a preparation method of (001) preferentially oriented stress-free AlN piezoelectric thin films. The AlN thin films were deposited by a reactive sputtering technique at substrate temperatures up to 330 °C using a dual Kaufman ion-beam source setup. We deposited the AlN on Si (100), Si (111), amorphous SiO2, and a (001) preferentially oriented Ti thin film and compared their crystallographic, optical, and piezoelectric properties. The AlN thin films deposited on the (001) preferentially oriented Ti thin films have the highest crystallographic quality. The stress-free AlN reached a high value of the piezoelectric coefficient d33 = (7.33 ± 0.08) pC·N−1. The properties of the AlN thin film prepared at such low temperatures are suitable for numerous microelectromechanical systems, piezoelectric sensors, and actuators monolithically integrated with complementary metal-oxide-semiconductor signal-processing circuits.

ACS Style

Imrich Gablech; Vojtěch Svatoš; Ondřej Caha; Adam Dubroka; Jan Pekárek; Jaroslav Klempa; Pavel Neužil; Michael Schneider; Tomáš Šikola. Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup. Thin Solid Films 2018, 670, 105 -112.

AMA Style

Imrich Gablech, Vojtěch Svatoš, Ondřej Caha, Adam Dubroka, Jan Pekárek, Jaroslav Klempa, Pavel Neužil, Michael Schneider, Tomáš Šikola. Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup. Thin Solid Films. 2018; 670 ():105-112.

Chicago/Turabian Style

Imrich Gablech; Vojtěch Svatoš; Ondřej Caha; Adam Dubroka; Jan Pekárek; Jaroslav Klempa; Pavel Neužil; Michael Schneider; Tomáš Šikola. 2018. "Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup." Thin Solid Films 670, no. : 105-112.

Journal article
Published: 12 November 2018 in Sensors and Actuators A: Physical
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In this study the influence of film thickness, adhesion promoters such as chromium (Cr) and rutile titanium dioxide (TiO2), sputtering power and substrate temperature on the electro-mechanical properties of platinum (Pt) thin films is investigated. The bilayered samples consisting of an adhesion promoter and a Pt thin film are deposited using direct current magnetron sputtering on sapphire substrates und characterized by Van-der-Pauw as well as gauge factor measurements up to 500 °C in air. Additionally, transmission electron microscopy and energy dispersive X-ray spectroscopy analysis are performed to investigate the microstructure and the chemical composition of the thin films before and after temperature loading. No substantial impact of the Pt film thickness on the electro-mechanical properties is determined. The diffusion of Cr into the Pt thin film at elevated temperatures leads to a lower gauge factor with a higher scatter range. Furthermore, higher sputtering power and substrate heating during deposition lead to a higher crystallinity of the Pt thin film and thus promote higher gauge factors.

ACS Style

P. Schmid; C. Zarfl; F. Triendl; F.J. Maier; S. Schwarz; M. Schneider; U. Schmid. Impact of adhesion promoters and sputter parameters on the electro-mechanical properties of Pt thin films at high temperatures. Sensors and Actuators A: Physical 2018, 285, 149 -157.

AMA Style

P. Schmid, C. Zarfl, F. Triendl, F.J. Maier, S. Schwarz, M. Schneider, U. Schmid. Impact of adhesion promoters and sputter parameters on the electro-mechanical properties of Pt thin films at high temperatures. Sensors and Actuators A: Physical. 2018; 285 ():149-157.

Chicago/Turabian Style

P. Schmid; C. Zarfl; F. Triendl; F.J. Maier; S. Schwarz; M. Schneider; U. Schmid. 2018. "Impact of adhesion promoters and sputter parameters on the electro-mechanical properties of Pt thin films at high temperatures." Sensors and Actuators A: Physical 285, no. : 149-157.

Journal article
Published: 09 November 2018 in Sensors
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In atomic force microscopes (AFM) a resonantly excited, micro-machined cantilever with a tip is used for sensing surface-related properties. When targeting the integration of AFMs into vacuum environments (e.g., for enhancing the performance of scanning electron microscopes), a tuneable Q-factor of the resonating AFM cantilever is a key feature to enable high speed measurements with high local resolution. To achieve this goal, in this study an additional mechanical stimulus is applied to the cantilever with respect to the stimulus provided by the macroscopic piezoelectric actuator. This additional stimulus is generated by an aluminum nitride piezoelectric thin film actuator integrated on the cantilever, which is driven by a phase shifted excitation. The Q-factor is determined electrically by the piezoelectric layer in a Wheatstone bridge configuration and optically verified in parallel with a laser Doppler vibrometer. Depending on the measurement technique, the Q-factor is reduced by a factor of about 1.9 (electrically) and 1.6 (optically), thus enabling the damping of MEMS structures with a straight-forward and cheap electronic approach.

ACS Style

Martin Fischeneder; Martin Oposich; Michael Schneider; Ulrich Schmid. Tuneable Q-Factor of MEMS Cantilevers with Integrated Piezoelectric Thin Films. Sensors 2018, 18, 3842 .

AMA Style

Martin Fischeneder, Martin Oposich, Michael Schneider, Ulrich Schmid. Tuneable Q-Factor of MEMS Cantilevers with Integrated Piezoelectric Thin Films. Sensors. 2018; 18 (11):3842.

Chicago/Turabian Style

Martin Fischeneder; Martin Oposich; Michael Schneider; Ulrich Schmid. 2018. "Tuneable Q-Factor of MEMS Cantilevers with Integrated Piezoelectric Thin Films." Sensors 18, no. 11: 3842.

Journal article
Published: 18 September 2018 in Sensors and Actuators A: Physical
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This paper reports on the characteristic behaviour of bistable MEMS membranes before, during and after switching between the two ground states. For this purpose, silicon membranes with a diameter in the range of 300 to 800 µm and a thickness in the range of 2 to 5 µm were investigated. To achieve bistability, hydrogenated amorphous silicon carbide layers with different thicknesses in the range of 50 nm to 400 nm were deposited on the silicon membranes using an inductively-coupled plasma-enhanced chemical vapour deposition process. With this bi-layered approach, an initial deflection of 2.5 to 8.1 µm was achieved which results in a total switching displacement of 5 to 16.2 µm A setup for bulge testing in combination with a Whitelight interferometer was used to analyse the membrane behaviour before the bi-stable switching. The pressure difference required to initiate switching between the ground states was in the range of 20 to 320 mbar. Both parameters (i.e. static deflection and switching pressure) are in excellent agreement with an analytical model. When increasing the pressure the membranes deflect up to 2.4 µm before switching, strongly depending on the diameter of the membranes. The dynamic measurements with the laser Doppler vibrometer showed switching times in the range of 5 to 20 µs, maximum velocities in the range of 1.5 to 4.3 m∙s-1 and high maximum accelerations between 2 to 11∙106 m∙s-2 depending on membrane properties such as diameter, thickness and mechanical stress. Finally, with fast Fourier transform analyses of the measured velocity signal characteristics Eigenmodes of the membrane are determined dominating the oscillation behaviour after switching, thus indicating approaches for effective damping with integrated actuators.

ACS Style

M. Dorfmeister; M. Schneider; U. Schmid. Static and dynamic performance of bistable MEMS membranes. Sensors and Actuators A: Physical 2018, 282, 259 -268.

AMA Style

M. Dorfmeister, M. Schneider, U. Schmid. Static and dynamic performance of bistable MEMS membranes. Sensors and Actuators A: Physical. 2018; 282 ():259-268.

Chicago/Turabian Style

M. Dorfmeister; M. Schneider; U. Schmid. 2018. "Static and dynamic performance of bistable MEMS membranes." Sensors and Actuators A: Physical 282, no. : 259-268.

Journal article
Published: 22 August 2018 in Composites Part B: Engineering
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Outstanding material properties of low temperature co-fired ceramics (LTCC) make them the technology of choice when targeting the realization of robust, highly integrated substrates or packaging solutions for micromachined devices. However, the relatively high permittivity limits their utilization in high-frequency applications, as in addition defined areas with reduced permittivity in one single LTCC layer would be most beneficial. The wet-chemical porosification method under alkaline conditions is a novel and most advantageous approach which can be applied for permittivity reduction through locally embedding air into the LTCC surface in its as-fired state with low impact on the surface characteristics. The resulting porosity of the LTCC substrates after the etching process is strongly affected by the LTCC tape composition as well as the etch parameters. Since the chemical composition of the tape is desired to be unaltered, optimizing the etching parameters, namely etchant concentration, etching time, and bath temperature is a reasonable procedure which allows tailoring the porosification process for the LTCC tapes in their as-fired state. In this work the etching behavior and surface morphology of the LTCC substrates have been studied, both qualitatively and quantitatively, and detailed gravimetric and roughness measurements, as well as porosification depth investigations, were carried out. The conducted analyses suggest a dominating reaction-controlled mechanism for the etching process. In addition to generating a tailored porosity in the surface-near region, overall thickness reduction of the LTCC through the overall dissolution of the LTCC surface under a defined etching condition was also possible. The experimental results were finally fitted into a nonlinear polynomial model for providing an experimental basis in order to identify the most crucial parameters to achieve a tailored porosity.

ACS Style

Ali Hajian; Doruk Müftüoglu; Thomas Konegger; Michael Schneider; Ulrich Schmid. On the porosification of LTCC substrates with sodium hydroxide. Composites Part B: Engineering 2018, 157, 14 -23.

AMA Style

Ali Hajian, Doruk Müftüoglu, Thomas Konegger, Michael Schneider, Ulrich Schmid. On the porosification of LTCC substrates with sodium hydroxide. Composites Part B: Engineering. 2018; 157 ():14-23.

Chicago/Turabian Style

Ali Hajian; Doruk Müftüoglu; Thomas Konegger; Michael Schneider; Ulrich Schmid. 2018. "On the porosification of LTCC substrates with sodium hydroxide." Composites Part B: Engineering 157, no. : 14-23.

Journal article
Published: 01 July 2018 in Materials Science in Semiconductor Processing
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ACS Style

M. Gillinger; T. Knobloch; A. Markovic; G. Pfusterschmied; M. Schneider; U. Schmid. Performance of thin AlxOy, SixNy and AlN passivation layers for high temperature SAW device applications. Materials Science in Semiconductor Processing 2018, 81, 1 -6.

AMA Style

M. Gillinger, T. Knobloch, A. Markovic, G. Pfusterschmied, M. Schneider, U. Schmid. Performance of thin AlxOy, SixNy and AlN passivation layers for high temperature SAW device applications. Materials Science in Semiconductor Processing. 2018; 81 ():1-6.

Chicago/Turabian Style

M. Gillinger; T. Knobloch; A. Markovic; G. Pfusterschmied; M. Schneider; U. Schmid. 2018. "Performance of thin AlxOy, SixNy and AlN passivation layers for high temperature SAW device applications." Materials Science in Semiconductor Processing 81, no. : 1-6.

Editorial
Published: 15 May 2018 in Micromachines
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Note: In lieu of an abstract, this is an excerpt from the first page.Excerpt Electromechanical transducers that utilize the piezoelectric effect have been increasingly used in micro-electromechanical systems (MEMS) either as substrates or as thin films

ACS Style

Ulrich Schmid; Michael Schneider. Editorial for the Special Issue on Piezoelectric MEMS. Micromachines 2018, 9, 237 .

AMA Style

Ulrich Schmid, Michael Schneider. Editorial for the Special Issue on Piezoelectric MEMS. Micromachines. 2018; 9 (5):237.

Chicago/Turabian Style

Ulrich Schmid; Michael Schneider. 2018. "Editorial for the Special Issue on Piezoelectric MEMS." Micromachines 9, no. 5: 237.

Proceedings
Published: 16 January 2018 in Proceedings
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This study reports on a novel bi-stable actuator with an integrated aluminum nitride (AlN) piezoelectric layer sandwiched between two electrodes. To achieve bistability, the membranes must exceed a characteristic compressive stress value, also called the critical stress. For this purpose, we used highly c-axis orientated stress-controlled AlN with a thickness of 400 nm. First experiments showed, that it is possible to switch between the two stable ground states with at least two rectangular pulses at a frequency of 80 kHz and with a voltage Vpp of 40 V, resulting in a displacement of about 10 µm for each switching direction.

ACS Style

Manuel Dorfmeister; Bernhard Kössl; Michael Schneider; Ulrich Schmid. A Novel Bi-Stable MEMS Membrane Concept Based on a Piezoelectric Thin Film Actuator for Integrated Switching. Proceedings 2018, 2, 912 .

AMA Style

Manuel Dorfmeister, Bernhard Kössl, Michael Schneider, Ulrich Schmid. A Novel Bi-Stable MEMS Membrane Concept Based on a Piezoelectric Thin Film Actuator for Integrated Switching. Proceedings. 2018; 2 (13):912.

Chicago/Turabian Style

Manuel Dorfmeister; Bernhard Kössl; Michael Schneider; Ulrich Schmid. 2018. "A Novel Bi-Stable MEMS Membrane Concept Based on a Piezoelectric Thin Film Actuator for Integrated Switching." Proceedings 2, no. 13: 912.

Proceedings
Published: 01 January 2018 in Proceedings
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Recently, organic electromechanical transducers have attracted intense scientific and technological interest due to their unique mechanical flexibility and their piezoelectric properties. However, the fabrication of organic MEMS devices is challenging. For example, a lift-off process cannot be used on polymers, because of the solvent in photoresists. Here, we present a straightforward and low-cost batch process for organic MEMS devices using standard micromachining techniques. As organic material we used the ferroelectric (co-)polymer poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)). The integration of the polymer in a CMOS-compatible process was optimized in terms of deposition and patterning of the polymer and the corresponding metal layers. Micromachined devices, such as capacitors and cantilevers, were fabricated and analysed. The ferroelectric perfomance was evaluated by electrical and electromechanical measurements. Our first results indicate that the proposed fabrication process is reliable resulting in well-functioning organic MEMS devices. We measured as piezoelectric constant a d33 of −32 pm/V with our organic P(VDF-TrFE) capacitors.

ACS Style

Jonas Hafner; Marco Teuschel; Jürgen Schrattenholzer; Michael Schneider; Ulrich Schmid. Optimized Batch Process for Organic MEMS Devices. Proceedings 2018, 2, 904 .

AMA Style

Jonas Hafner, Marco Teuschel, Jürgen Schrattenholzer, Michael Schneider, Ulrich Schmid. Optimized Batch Process for Organic MEMS Devices. Proceedings. 2018; 2 (13):904.

Chicago/Turabian Style

Jonas Hafner; Marco Teuschel; Jürgen Schrattenholzer; Michael Schneider; Ulrich Schmid. 2018. "Optimized Batch Process for Organic MEMS Devices." Proceedings 2, no. 13: 904.

Proceedings
Published: 01 January 2018 in Proceedings
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We present a novel MEMS sensor for the detection of magnetic particles in liquids, which consists of a microcantilever excited piezoelectrically in resonance and having an integrated planar coil on its free end. Due to the latter component, magnetic particles are attracted and accumulate on the sensor surface. The additional mass introduced by the particles changes the resonance frequency of the microcantilever serving as measured quantity. To evaluate our design, we dispersed 250 nm iron-oxide particles in de-ionized water and monitored the resonance frequency during particle accumulation. 100 min after measurement start, a total resonance frequency shift of 6 kHz was found, which can easily be measured and shows the high potential of the proposed sensor design.

ACS Style

Florian Patocka; Matthias Schlögl; Michael Schneider; Ulrich Schmid. Novel MEMS Sensor for Detecting Magnetic Particles in Liquids. Proceedings 2018, 2, 868 .

AMA Style

Florian Patocka, Matthias Schlögl, Michael Schneider, Ulrich Schmid. Novel MEMS Sensor for Detecting Magnetic Particles in Liquids. Proceedings. 2018; 2 (13):868.

Chicago/Turabian Style

Florian Patocka; Matthias Schlögl; Michael Schneider; Ulrich Schmid. 2018. "Novel MEMS Sensor for Detecting Magnetic Particles in Liquids." Proceedings 2, no. 13: 868.