We have studied effects of H atom source on deposition profiles of carbon films, deposited by H assisted anisotropic plasma CVD method. Deposition rate normalized by that for the aspect ratio of 1 at sidewall and bottom decreases with increasing discharge power of H atom source from 0 W to 500 W, because the incident H atom flux per surface area in a trench increases and H atoms etch carbon films.

In this article we investigate the effect of relative humidity on dielectric charging/discharging processes in electrostatically actuated MEMS devices. The assessment procedure is based on surface potential measurements using Kelvin Probe Force Microscopy (KPFM) and it targets in this specific work PECVD silicon nitride films in view of application in electrostatic capacitive RF MEMS switches. Charges have been injected through the AFM tip and the induced surface potential has been measured under different relative humidity levels. The impact of the charge injection duration and the bias level as well as bias polarity applied during the charge injection step, have been explored. Finally, the effect of the dielectric film thickness under different relative humidity levels has been assessed through depositing SiN films with different thicknesses.

In this work we have developed novel microfabrication processes using wet anisotropic etchants to perform advanced bulk micromachining in {100}Si wafers for the realization of microelectromechanical systems (MEMS) structures with new shapes. The etching is performed in two steps in pure and Triton-X-100 [C14H22O(C2H4O)n, n = 9-10] added 25 wt% tetramethyl ammonium hydroxide (TMAH) solutions. The local oxidation of silicon (LOCOS) is attempted after the first anisotropic etching step in order to protect the exposed silicon. Two types of structures (fixed and freestanding) are fabricated. The fixed structures contain perfectly sharp corners and edges. Thermally grown silicon dioxide (SiO2) is used for the fabrication of freestanding structures. Present research is an approach to fabricate advanced MEMS structures, extending the range of 3D structures fabricated by silicon wet anisotropic etching.

Conducting polymers can act as actuators when an electrochemical stimulus causes the materials to undergo volumetric changes. Ion flux into the polymer causes volumetric expansion and ion outflow causes contraction. Polypyrrole is an attractive actuator material due to its ability to generate up to 30 MPa active stress and 10% to 26% maximum strain with voltage supply lower than 2 V. The polymer’s mechanical performance depends upon the solvent used and the dominating ion species. In this study, we used 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) to characterize the effect of temperature increase on ion flow and how it contributes to strain and maximum strain rate of polypyrrole. In this solvent, the cation BMIM+ diffuses in and out of the polymer under applied voltage to cause strain changes. For approximately each increment of 10°C from 27°C to 83°C, isotonic tests were done with +/-0.8 V square pulses, using a custom built device that is capable of performing temperature controlled dynamic mechanical analyses and electrochemistry simultaneously. Results showed that, independent of voltage polarity, from 27 to 83°C the strain increased from 0.4% to 2.0%. Both the maximum charge and strain rate rates increased with temperature, and were higher at positive voltage than at negative voltage throughout the same temperature range. Positive voltage caused the maximum strain rate to increase exponentially from 0.1 %/s to 0.67 %/s, while negative voltage caused it to increase more linearly from 0.06 %/s to 0.23 %/s. The results suggest that the increase in strain resulted from the charge delivered to the polymer in higher quantities at higher temperature. Furthermore, BMIM+ ions are expelled faster than those being attracted in to the polymer, perhaps due to the ions preferentially remaining in the bulk solution. As the temperature increased, the ionic mobility increased and as a result, BMIM+ ions are expelled back into the solvent even faster.

Nanocrystalline Ni0.5Zn0.5Fe2O4 thin films have been synthesized with various grain sizes by sol–gel method on polycrystalline silicon substrates. The morphology and microwave absorption properties of the films calcined in the 673–1073 K range were studied by using XRD, AFM, near–field evanescent microwave microscopy, coplanar waveguide and direct microwave heating measurements. All films were uniform without microcracks. The increase of the calcination temperature from 873 to 1073 K and time from 1 to 3h resulted in an increase of the grain size from 12 to 27 nm. The complex permittivity of the Ni-Zn ferrite films was measured in the frequency range of 2–15 GHz. The heating behavior was studied in a multimode microwave cavity at 2.4 GHz. The highest microwave heating rate in the temperature range of 315–355 K was observed in the film close to the critical grain size of 21 nm in diameter marked by the transition from single– to multi–domain structure of nanocrystals in Ni0.5Zn0.5Fe2O4 film and by a maximum in its coercivity.

In this work, thin ALD alumina films were fabricated for evaluating their capabilities as a barrier material for corrosive environments. The fracture toughness and the corrosion-resisting properties after fatigue cycle of these thin ALD alumina films have been characterized. Indentation tests indicate that the ALD alumina/Al structures could enhance both the yield strength of the metal and the effective fracture toughness of the coated ALD alumina films and this result could be useful for designing nanocomposite structures. However, the test results also indicate that the interfacial strength of the ALD/Al structures was prone to degrade under fatigue loading under corrosive environment. This could potentially be a problem for the long term reliability of related devices operated under a harsh environment. In addition, the strong correlation between indentation behavior and fatigue loading for the structure indicate that nanoindentation response could be possibly used to indicate the damage level of microstructures for future reliability evaluations.

In this paper we propose and demonstrate micro patterning processes of single crystal diamond using thermochemical reaction of diamond with a sidero-metal and elucidate the reaction involved. Single crystal diamond processes a variety of excellent characteristics, such as hardness and wear resistance, and hence, is expected to be a new material for not only micro machining tools but also innovative micro devices. It is mandatory to develop a patterning process of diamond with high precision and at low cost. Laser processing is currently widely used, but it is a serial process and costly. Film deposition and plasma etching are other effective methods while they are time consuming. Thermochemical reaction between diamond and sidero-metals is well known in the field of mechanical machining. Diamond tools cannot machine sidero-metals, such as iron, nickel, and cobalt, when the diamond tools wear instead of the sidero-metals. We used this reaction to micro pattern single crystal diamond. We used nickel as the sidero-metal that was patterned either directly on a bulk of single crystal diamond or on a silicon substrate. We term the former and the latter processes as direct and indirect patterning processes, respectively. In the indirect patterning a bulk of single crystal diamond was placed on the substrate. The pattern was negatively transferred to the diamond after thermal treatment in the air at ˜1000K in both processes. The sidero-metal layer can be patterned by photolithography, which enables precise manufacturing and mass production. The direct and indirect patterning achieved etching rates of ˜0.5μm/min and ˜0.2μm/min, respectively, both of which increased as the annealing temperature increased while the indirect patterning did not require micro patterning of photoresist on a bulk diamond several millimeters squire and involved much less difficult processes than the direct patterning. The thermochemical reaction is reported to be caused by; diffusion of carbon from diamond into the sidero-metal, oxidation-reduction reaction between diamond and the metal, oxidation of diamond, and carbide formation. Carbide formation was not observed when we used nickel as the sidero-metal. When the direct and indirect patterning was conducted in nitrogen, the pattern transfer was observed but the etching rate was extremely low. Therefore, oxidation-reduction reaction is dominant in the direct patterning. In the indirect patterning, the etching continued even after the nickel and diamond was not in contact. The thickness of removed diamond was by far greater than the thickness of the nickel layer. Hence, we consider that diamond was etched by oxide-reduction reaction between the diamond and the metal while they were in contact at the beginning and then, the oxidation of diamond became dominant in the indirect patterning. The process proposed herein is readily applicable to manufacture micro devices that exploit excellent characteristics of single crystal diamond.

We have fabricated highly resistive materials PrBa2 (Cu1-xMx) 3O7 (M=Al, Ga, x = 0.20) by doping metals Ga and Al on PrBa2Cu3O7(PBCO). X-ray data indicated no significant second phases in substituting Cu by Al or Ga up to 20%.The electrical resistivity of these materials were three to four orders in magnitude higher than PBCO at 200K, which may give an effective potential barrier to YBCO in high Tc S-I-S Josephson junction. Epitaxial thin films of these materials were grown using KrF excimer laser on LAO (110) single crystal substrates. X-ray diffraction (XRD) and atomic force microscopy (AFM) were deployed to study the crystal orientation, epitaxy and roughness of the single crystal thin films. Micro Raman spectroscopy was carried out to investigate the dopant site in PBCO.

Thermoplastic elastomer (TPE) based microfluidic devices integrated with a microfluidic pumping manifold which consists of 4 electromagnetic valves (EMV) were fabricated. The back and forth shuttling flow and its application in the DNA hybridization process were validated on a thermal plastic Zeonor 1060R substrate. The flow rate can be as fast as 23μl/min when the channel width and the channel height are in 100μm, and 25μm, respectively. The DNA hybridization process is detected by using a fluorescence microscopy. Remarkable DNA hybridization is achieved with the continuous flow of the target DNA at a concentration of 10 nM within the first 1 min by using this device.

A low-range pressure sensor (0-100kPa) based on the P(VDF-TrFE) piezoelectric thin film is proposed, where the long-term drift is eliminated by operating near the piezoelectric resonance. The pressure sensor is designed for blood pressure and tissue swelling pressure monitoring. The poled 50μm±1μm P(VDF-TrFE) copolymer film is used as the sensing element, with all fabrication and assembly materials biocompatible. A modified Butterworth-Van Dyke (BVD) [1] equivalent circuit model is used to characterize the sensor behavior. The pressure sensor exhibits negligible drift in weeks of operation. The device shows a sensitivity of 0.038MHz/kPa resonance frequency shift under stress, which leads to a maximum readout change of 1.1%/kPa in the present setup.