We report on a variable capacitor that is formed between Schottky contacts and the two dimensional electron gas (2DEG) in a planar metal-semiconductor-metal structure. Device capacitance at low bias is twice the series capacitance of anode and cathode, enhancing to a maximum value, Cmax, at a threshold voltage, before reaching a minimum, Cmin, lower than the geometric capacitance of the coplanar contacts, thus resulting in ultra high Cmax=Cmin tuning ratio. Sensitivity, the normalized change of capacitance with voltage, is also very large. The dense reservoir of the 2DEG charge maintained between contacts is shown to be responsible for this remarkable performance.

Capacitance-Voltage characteristics of a metal-semiconductor-metal structure with an embedded two-dimensional electron system are reported. The device functions based on a quantum capacitance, which is activated by local illumination. The giant sensitivity to light and voltage makes this device a candidate for capacitive-based photodetection. © OSA 2013.

In this work we develop surface-micromachinedRF MEMS switches in III-V technology making use ofmaterials which can be alternative to the ones commonly used.In this way, some technological constraints concerning RFMEMS reliability can be overcome. Specifically, we evaluatethe potential of tantalum nitride (TaN) and tantalumpentoxide (Ta2O5) to be used for the switches actuation padsand dielectric layers, respectively. To this scope, acompositional, structural and electrical characterization ofTaN and Ta2O5 films as a function of the depositionparameters (temperature, sputtering mixture composition, andfilm thickness) is performed. Both shunt and series switchesare prepared and show good switching capabilities by apreliminary analysis. The complete device characterization isin progress and will be presented.

Moderation of internal quantum mechanical energies, such as exchange energy of an unconventional contact, comprised of a system of 2-D charge carriers, improves performance merits of variable capacitors, varactors, mainly in tuning ratio (TR), and sensitivity, S. Energy transfer from the unconventional contact to the dielectric increases the energy density and enhances the capacitance of the varactor. Here, we analyze the performance of an unconventional varactor based on a planar metal-semiconductor-metal (MSM) structure with an embedded layer of high-density 2-D electron gas (2DEG). Through localized field-assisted manipulation of the 2DEG density, a twice larger equilibrium capacitance and a minimum capacitance, less than the geometric capacitance of a conventional MSM, are achieved. Moreover, the maximum capacitance increases through a Batman-shaped capacitance enhancement at a threshold voltage. Therefore, giant TR > 2000 is attained while maintaining quality factors of up to 30. Capacitance-voltage characteristics exhibit a switched-capacitor behavior with S as high as 350 that is due to localized transitions from a dense 2DEG to a complete depletion. This MSM 2-D varactor combines the unconventional features of 2DEG with superior electrical properties of MSMs.

Capacitance of capacitors in which one or both platesare made of a two-dimensional charge system (2DCS) can be increasedbeyond their geometric structural value. This anomalouscapacitance enhancement (CE) is a consequence of manipulationof quantum mechanical exchange and correlation energies in theground state energy of the 2DCS. Macroscopically, it occurs atcritical charge densities corresponding to transition from an interacting"metallic" to a noninteracting "insulator" mode in the 2-Dsystem. Here, we apply this concept to a metal-semiconductor-metal capacitor with an embedded two-dimensional hole system(2DHS) underneath the plates for realization of a capacitancebasedphotodetector. Under sufficient illumination, and at criticalvoltages the device shows a giant CE of 200% and a peak-tovalleyratio of over 4 at probe frequencies larger than 10 kHz.Remarkably, the light-to-dark capacitance ratio due to CE atthis critical voltage is well over 40. Transition of the 2DHSfrom insulator to metallic, enforced by charge density manipulationdue to light-generated carriers, accounts for this behavior,which may be used in optical sensing, photo capacitors, and phototransistors.

Digital holography (DH) is a well-established interferometric tool in optical metrology allowing the investigation of engineered surface shapes with microscale lateral resolution and nanoscale axial precision. With the advent of charged coupled devices (CCDs) with smaller pixel sizes, high speed computers and greater pixel numbers, DH became a very feasible technology which offers new possibilities for a large variety of applications. DH presents numerous advantages such as the direct access to the phase information, numerical correction of optical aberrations and the ability of a numerical refocusing from a single hologram. Furthermore, as an interferometric method, DH offers both a nodestructive and no-contact approach to very fragile objects combined with flexibility and a high sensitivity to geometric quantities such as thicknesses and displacements. These features recommend it for the solution of many imaging and measurements problems, such as microelectro-optomechanical systems (MEMS/MEOMS) inspection and characterization. In this work, we propose to improve the performance of a DH measurement on MEMS devices, through digital filters. We have developed an automatic procedure, inserted in the hologram reconstruction process, to selectively filter the hologram spectrum. The purpose is to provide very few noisy reconstructed images, thus increasing the accuracy of the conveyed information and measures performed on images. Furthermore, improving the image quality, we aim to make this technique application as simple and as accurate as possible. © 2014 SPIE.

In this paper, shunt capacitive RF microelectromechanical systems (MEMS) switches are developed in III-V technology using tantalum nitride (TaN) and tantalum pentoxide (Ta2O5) for the actuation lines and the dielectric layers, respectively. A compositional, structural, and electrical characterization of the TaN and Ta2O5 films is preliminarily performed, demonstrating that they are valid alternatives to the conventional materials used in III-V technology for RF MEMS switches. Specifically, it is found that the TaN film resistivity can be tuned from 0.01 to 30 ohmcm . cm by changing the deposition parameters. On the other hand, dielectric Ta2O5 films show a low leakage-current density of few nanoamperes per square centimeter for E similar to 1 MV/cm, a high breakdown field of 4 MV/cm, and a high dielectric constant of 32. The realized switches show good actuation voltages, in the range of 15-20 V, an insertion loss better than -0.8 dB up to 30 GHz, and an isolation of similar to -40 dB at the resonant frequency, which is, according to bridge length, between 15 and 30 GHz. A comparison between the measured S-parameter values and the results of a circuit simulation is also presented and discussed, providing useful information on the operation of the fabricated switches.

We develop shunt capacitive RF MEMS switches in III-V technology making use of materials which can be alternative to the ones commonly used, in order to overcome some technological constraints concerning the RF MEMS reliability. Specifically, we evaluate the potential of tantalum nitride (TaN) and tantalum pentoxide (Ta2O5) to be used for the switches actuation pads and dielectric layers, respectively. To this scope, a compositional, structural and electrical characterization of TaN and Ta2O5 films as a function of the deposition parameters, such as the substrate temperature and the sputtering mixture composition, is performed. The realized switches show good actuation voltages, in the range 15- 20 V, an insertion loss better than -0.8 dB up to 30 GHz, and an isolation of ~ -40 dB at the resonant frequency. A comparison between the measured S-parameter values and the results of a circuit simulation is also presented and discussed, providing useful information on the operation of the fabricated switches.

A detailed study of the electrical properties of planar AlGaN/GaN Schottky diodes is presented, the focus being on the role of the two dimensional electron gas (2DEG) depletion and the diodes non-idealities in different voltage regimes. The 2DEG depletion behavior is inferred from the analysis of capacitance and current measurements with transition from vertical to lateral diode operation occurring at Vpinch-off =4V. In particular, the sub-micrometer depletion width, laterally extending from the edge of the Schottky contact under high reverse voltages, is evaluated on the basis of a simple fringe capacitance model. Current transport mechanisms are discussed, investigating the interrelation between 2DEG, Poole-Frenkel effect, and defects. With regard to defects, the role of dislocations in the AlGaN/GaN diode non-idealities, usually interpreted in terms of Schottky barrier inhomogeneities, is critically addressed. Photocurrent spatial mapping under high reverse voltage points out the not uniform electric field distribution around the Schottky contact and highlights the presence of local photo-conductive paths, likely associated with the dislocations near the edge of the Schottky contact. Published by AIP Publishing.

In this work, the bridge imaging and the reliability of surface-micromachined capacitive RF MEMS switches in III-V technology are presented. A low cost scanning technique allowed us to image the shape of the moveable bridge with a micrometer spatial resolution, thus quantitatively valuating its lowering as a function of the applied voltage. The reliability of the switches was tested under the application of different unipolar and bipolar voltage waveforms, showing that a significant improvement of the switch operation and lifetime can be achieved by applying high frequency bipolar square pulses with suitable durations. © 2013 CMP.

Digital holographic microscopy is an important interferometric tool in optical metrology allowing the investigation of engineered surfaces with microscale lateral resolution and nanoscale axial precision. In particular, microelectromechanical systems (MEMS) surface analysis, conducted by holographic characterization, requires high accuracy for functional testing. The main issues related to MEMS inspection are the superficial roughness and the complex geometry resulting from the several fabrication steps. Here, an automatic procedure, particularly suited in the case of high-roughness surfaces, is presented to selectively filter the spectrum, providing very low-noise reconstructed images. The numerical procedure is based on Butterworth filtering, and the obtained results demonstrate a significant increase in the images' quality and in the accuracy of the measurements, making our technique highly applicable for quantitative phase imaging in MEMS analysis. Furthermore, our method is fully tunable to the spectrum under investigation and automatic. This makes it highly suitable for real-time applications. Several experimental tests show the suitability of the proposed approach. (C) 2015 Optical Society of America

Shunt capacitive radio-frequency microelectromechanical system (RF MEMS) switches were fabricated on silicon substrate and characterized in the RF domain. Various switch typologies were obtained by three different approaches, which are: (1) the change of the bridge geometric parameters, (2) the covering of the actuator with a floating metal, and (3) the deposition of the bridge directly on the actuator. The S parameters of the fabricated switches were measured in the up and down states, observing the impact on the RF performance of the variation of the geometric parameters and the fabrication process. The electromagnetic modelling of the fabricated switches was used to interpret the measured RF behaviour, allowing to elucidate the drawbacks of the non-perfect conforming of the bridge on the actuator. Finally, the reliability of the fabricated RF MEMS switches under a bipolar voltage excitation was evaluated by cycling tests. Hence, the study presented here provides guidelines to solve some issues of the tight correlation between design, fabrication, performance, and reliability of RF MEMS switches, in view of a large-scale development of these devices.

Shunt capacitive RF MEMS switches were developed on GaAs substrate, using a III-V technology process that is fully compatible with standard MMIC fabrication. The switches show an insertion loss lower than 0.8 dB and isolation better than 30 dB with resonance frequencies in K-band, according to the switch geometric parameters. Reliability limits due to dielectric charging were overcome by applying suitable fast bipolar actuation waveforms, making the developed switches good candidates for both redundancy (always on/off) and cycled applications.

The electrostatic actuation behaviour of the gold bridge in capacitive radio frequency microelectromechanical system switches, fabricated on GaAs substrate, is investigated. An unconventional imaging technique, based on the out-of-focus reflection, was used to evaluate the topographic profile of the suspended bridge and its lowering as a function of the voltage. Important parameters for the switch actuation, such as the pull-down voltage and the air gap between the bridge and the actuator, are estimated. Capacitance-voltage curves allow to evaluate the capacitance associated to the bridge in the up and down states as well as the dielectric constant of the Si<inf>3</inf>N<inf>4</inf> layer, which covers the actuator. The experimental values of the pull-down voltage and the dielectric constant are used to extract from the theoretical equations the residual stress of the fabricated gold membrane. Finally, the current through the dielectric Si<inf>3</inf>N<inf>4</inf> layer was measured as a function of the voltage applied to the actuator, finding that the Poole-Frenkel effect is the dominant conduction mechanism when the switch is actuated.

We present a microscopic characterization of an organic photovoltaic (OPV) module demonstrator, fabricated within the "freeOPV" project. The local properties of the module are discussed on different length scales, from the submicrometric to the centimeters one, inferring the module structure and the origin of the different contributionsto the optical and photoelectrical spatial inhomogeneity. We show that the local external quantum efficiency (EQE) in the individual cells of the module exhibits typical variations within 6-8% of the peak value over about 0.4 mm2. Larger variations are observed when comparing different cells across the module surface,with differences in the EQE peak values up to 1.6 times. Our results suggest that the roll-to-roll OPV module performance can be further improved by optimizing theprinting uniformity as well as the charge extraction efficiency of electrodes.

Simultaneous photoluminescence (PL) and external quantum efficiency (EQE) confocal mapping is used to investigate the correlation between the local PL and the EQE in a regioregular poly(3-exylthiophene): poly(9,9-dioctylfluorene-co-benzothiadiazole) inverted bulk heterojunction solar cell. We show that the charge generation and charge collection are strongly non-uniform on a length scale up to 100 mu m. Our results evidence that organic solar cells optimization requires not only the control of the submicrometric active materials arrangement but also the control of the large scale device uniformity.

We report on the transmission of a terahertz (THz) radiation through prototype structures based on a p-type silicon substrate. In particular, the bare substrate and progressively more complicated multilayer structures were investigated, allowing to address the effect on the transmission of different factors, such as the orientation of interdigitated contacts with respect to the polarized beam, the temperature, and the current flowing through a conductive SnO2 nanorods layer. A suitable experimental set-up was developed for the direct spectral measurement of transmission in the range of 0.75-1.1 THz at room and low temperatures. A simple Drude-Lorentz model was formulated, finding a quantitative agreement with the experimental transmission spectrum of the bare substrate at room temperature. For the multilayer structures, the spectra variations observed with temperature are well accounted by the corresponding change of the mobility of holes in the silicon p-type substrate. The influence of the contact orientation is consistent with that of a polarizing metallic grating. Finally, Joule heating effects are observed in the spectra performed as a function of the current flowing through the SnO2 nanorods layer. The experimental results shown here, together with their theoretical interpretation, provide insights for the development of devices fabricated on conductive substrates aimed to absorb/modulate radiation in the THz range. (C) 2014 AIP Publishing LLC.

The out-of-plane deformation and the pull-in voltage of electrostatically actuated cantilevers with a residual stress gradient,is investigated in the length range 100-300 um. Measured pull-in voltages are compared with calculations, which areobtained using previously proposed analytical expressions and a finite element method (FEM) modelling. In particular, asimplified model of the residual stress distribution inside cantilevers is formulated that enables FEM simulation ofmeasured out-of-plane deformations and pull-in voltages for all lengths of fabricated cantilevers. The presented experimentalresults and FEM model are exploitable in the design of cantilever-based microelectromechanical systems, in orderto provide a reliable prediction of the influence of residual stress gradient on device shape and pull-in voltage.

Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ~600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs detectors usually suffer from low responsivity due to low carrier mobility. Here we report electro-optic sampling time response measurements of a detector that employs an AlGaAs heterojunction, a thin layer of LT-GaAs, a channel of RT-GaAs, and a vertical electric field that together facilitate collection of optically generated electrons while suppressing collection of lower mobility holes. Consequently, these devices have detection efficiency near that of RT-GaAs yet provide pulse widths nearly an order of magnitude faster-~6 ps for a cathode-anode separation of 1.3 ?m and ~12 ps for distances more than 3 ?m. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

We report on photoconduction and optical properties of aligned assemblies of core-shell CdSe/CdS nanorods prepared by a seeded growth approach. We fabricate oriented layers of nanorods by drop casting the nanorods from a solution on substrates with prepatterned, micrometer-spaced electrodes and obtain nanorod alignment due to the coffee stain effect. The photoconductivity of the nanorod layers can be improved significantly by an annealing process under vacuum conditions. The spectral response of the photocurrent shows distinct features that can be assigned to the electronic level structure of the core-shell nanorods and that relate well to the spectra obtained by absorption measurements. We study assemblies of nanorods oriented parallel and perpendicular to the applied electric field by the combined use of photocurrent and photoluminescence spectroscopy. We obtain consistent results which show that charge carrier separation and transport are more efficient for nanorods oriented parallel to the electric field. We also investigate the light polarization sensitivity of the photocurrent for the oriented nanorod layers and observe higher conductivity in the case of perpendicular polarization with respect to the long axis of the nanorods.

The photoconduction properties of individual GaAs/AlGaAs core-shell nanowires under uniform and local optical excitation are investigated, allowing the external quantum efficiency, the polarization anisotropy, and the role of the nanocontacts to be valuated. © OSA 2013.

Conductivity and photoconductivity properties of individual GaAs/AlGaAs core-shellnanowires (NWs) are reported. The NWs were grown by Au-assisted metalorganic vaporphase epitaxy, and then dispersed on a substrate where electrical contacts were defined on theindividual NWs by electron beam induced deposition. Under dark conditions, the carriertransport along the NW is found to be limited by Schottky contacts, and influenced by thepresence of an oxide layer. Nonetheless, under illumination, the GaAs/AlGaAs core-shell NWshows a significant photocurrent, much higher than the bare GaAs NW. The spatialdependence of the photocurrent within the single core-shell NW, evaluated by a mappingtechnique, confirms the blocking behavior of the contacts. Moreover, local spectralmeasurements were performed which allow one to discriminate the contribution of carriersphotogenerated in the core and in the shell.

Tetrapod-shaped CdSe(core)/CdTe(arms) colloidal nanocrystals, capped with alkylphosphonic acids or pyridine, were reacted with various small molecules (acetic acid, hydrazine and chlorosilane) which induced their tip-to-tip assembly into soluble networks. These networks were subsequently processed into films by drop casting and their photoconductive properties were studied. We observed that films prepared from tetrapods coated with phosphonic acids were not photoconductive, but tip-to-tip networks of the same tetrapods exhibited appreciable photocurrents. On the other hand, films prepared from tetrapods coated with pyridine instead of phosphonic acids were already highly photoconductive even if the nanocrystals were not joined tip-to-tip. Based on the current-voltage behavior under light we infer that the tunneling between tetrapods is the dominant charge transport mechanism. In all the samples, chemically-induced assembly into networks tended to reduce the average tunneling barrier. Additionally, pyridine-coated tetrapods and the tip-to-tip networks made out of them were tested as active materials in hybrid photovoltaic devices. Overall, we introduce an approach to chemically-induced tip-to-tip assembly of tetrapods into solution processable networks and demonstrate the enhancement of electronic coupling of tetrapods by various ligand exchange procedures.

We investigate the photodetection properties of individual core/shell GaAs/AlGaAs nanowires (NWs) and, in particular, their behavior under linearly polarized light. The NWs are grown by Au-assisted metalorganic vapor phase epitaxy and electrical contacts are defined on NWs by electron beam induced deposition. The spectral photocurrent of the single NW is measured and the dependence of the polarization anisotropy rho (varying from similar to 0.1 to similar to 0.55) on the absorption wavelength is found to be clearly affected by the core/shell structure. High quantum efficiency values (10% at 600 nm) are obtained which are attractive for a wide range of optoelectronic devices.

In this paper, the reliability of shunt capacitive radiofrequency microelectromechanical systems switches developed onGaAs substrate using a III-V technology fabrication process,which is fully compatible with standard monolithic microwaveintegrated circuit fabrication, is investigated. A comprehensivecycling test is carried out under the application of different unipolarand bipolar polarization waveforms in order to infer howthe reliability of the realized capacitive switches, which is stilllimited with respect to the silicon-based devices due to the lessconsolidation of the III-V technology, can be improved. Underthe application of unipolar waveforms, the switches show a shortlifetime and a no correct deactuation for positive pulses longerthan ~10 ms probably due to the charging phenomena occurringin the dielectric layer underneath the moveable membrane. Thesecharging effects are found to vanish under the application ofa waveform including consecutive positive and negative voltagepulses, provided that proper durations of the positive and negativevoltage pulses are used. Specifically, a correct switch deactuationand a lifetime longer than 1 million cycles, being this value limitedby the duration of the used testing excitation, are achieved byapplying a 1-kHz waveform with 20-?s-long positive and negativeconsecutive pulses.

RF Micro-Electro Mechanical Systems (MEMS) have been developed during the last decade withseveral applications for commercial as well as space and military sub-systems [1-6]. Technologicalprocesses encompassing the utilization of typical microelectronic substrates like alumina, GaAs andSilicon have been considered for the realization of micro-switches by surface micromachining. Truetime delay lines (TTDL), single port multiple throw (SPMT), matrices and phase shifters takebenefit from the low insertion loss, all passive and distortion-free environment offered by RFMEMS. Antenna re-configuration through digital phase shifters based on RF MEMS switches arecurrently studied.

The potential of InAs quantum-dot (QD) photodetectors for room-temperature high-speed operation at wavelengths near 1.3 mu m is evaluated. Specifically, planar metal-semiconductor-metal structures on GaAs substrates containing one absorption layer of self-assembled InAs QDs embedded in Ga(In)As matrices are fabricated, characterized, and analyzed. Light absorption, optically generated carrier transport, and collection mechanisms are studied. The role of the QD embedding matrix in the lateral transport of the photogenerated carriers is also studied by comparing structures with QDs in GaAs and In0.15Ga0.85 As matrices. Devices show low dark currents in tens of nanoamperes and high light sensitivity when adjusted to QD volumes, whereas external quantum efficiency remains in the range 10(-5)-10(-4) for all fabricated samples. The time response of the fabricated devices is obtained using an excitation wavelength resonant with QD interband transitions, thus allowing the photogeneration of electron-hole pairs inside the dots. Results prove detection capability of a single layer of QDs in a common photodetector structure with a full-width half-maximum time response on the order of 10 ps. A long tail, about 100 ps, but at a small fraction of the peak response amplitude, is also observed, suggesting mechanisms for charge transport and collection.

The efficiency optimization of bulk heterojunction solar cells requires the control of the local active materials arrangement in order to obtain the best compromise between efficient charge generation and charge collection. Here, we investigate the large scale (10-100 ?m) inhomogeneity of the photoluminescence (PL) and the external quantum efficiency (EQE) in inverted all-polymer solar cells (APSC) with regioregular poly(3-hexylthiophene) (P3HT):poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) active blends. The morphology and the local active polymer mixing are changed by depositing the active layer from four different solvents and by thermal annealing. The simultaneous PL and EQE mapping allowed us to inspect the effects of local irregularities of active layer thickness, polymer mixing, polymer aggregation on the charge generation and collection efficiencies. In particular, we show that the increase of the solvent boiling point affects the EQE non-uniformity due to thickness fluctuations, the density non-uniformity of rrP3HT aggregate phase, and the blend components clustering. The thermal annealing leads to a general improvement of EQE and to an F8BT clustering in all the samples with locally decrease of the EQE. We estimate that the film uniformity optimization can lead to a total EQE improvement between 2.7 and 6.3 times.

Shunt capacitive RF MEMS switches have been developed using III-V technology and employing (tantalum pentoxide) Ta2O5 thin films as dielectric layers. In order to evaluate the potential of the Ta2O5 thin films for the considered application, the compositional, structural, and electrical characterization of the deposited films has been performed, demonstrating that they are good candidates to be used as dielectric layers for the fabrication of RF MEMS switches. Specifically, Ta2O5 films are found to show a leakage current density of few nA/cm2 for MV/cm and a high dielectric constant of 32. Moreover, the charging process has been investigated, finding that it follows a stretched exponential law. The fabricated switches show actuation voltages in the range 15-20 V, an insertion loss better than -0.8 dB up to 30 GHz, and an isolation of ~-40 dB at the resonant frequency which is around 25 GHz.

Shunt capacitive radio-frequency microelectromechanical (RF MEMS) switches were modelled, fabricated and characterized in the K-band domain. Design allowed to predict the RF behaviour of the switches as a function of the bridge geometric parameters. The modelled switches were fabricated on silicon substrate, using a surface micromachining approach. In addition to the geometric parameters, the material structure in the bridge-actuator area was modified for switches fabricated on the same wafer, thanks to the removal/addition of two technological steps of crucial importance for RF MEMS switches performance, which are the use of the sacrificial layer and the deposition of a floating metal layer on the actuator. Surface profilometry analysis was used to check the material layer structure in the different regions of the bridge area as well as to investigate the mechanical behaviour of the moveable bridge under the application of a loaded force. The RF behaviour of all the fabricated switches was measured, observing the impact on the isolation of the manipulation of the bridge size and of the variations in the fabrication process.

The potential of sputtered Ta2O5 thin films to be used as dielectric layers in capacitive radio frequency microelectromechanical system switches is evaluated by investigating two factors of crucial importance for the performance of these devices which are the transport mechanisms and the charging effects in the dielectric layer. We find that Ta2O5 films show good electrical and dielectrical properties for the considered application in terms of a low leakage current density of 4 nA/cm(2) for E=1 MV/cm, a high breakdown field of 4 MV/cm and a high dielectric constant of 32. For electric fields lower than 1 MV/cm the conduction mechanism is found to be variable-range hopping in the temperature range 300-400 K, while nearest-neighbor hopping is observed at higher temperatures. For fields in the range 1-4 MV/cm Poole-Frenkel becomes the dominant conduction mechanism. Current and capacitance transients used to investigate the charging effects show a decay which is well described by the stretched-exponential law, thus providing further insights on capture and emission processes.

In this work, a thin-film packaging was developedto be used for radio-frequency microelectromechanicalsystem configurations. The fabricated packages aresuspended membranes in the multilayer SixNy/aSi/SixNy onconductive coplanar waveguides (CPWs) of differentlength. Several geometric parameters of the membranes,which are the length, the curvature radius at the vertices ofthe rectangular base, the density and the diameter of holeson the capping surface, were also varied. The mechanicalproperties of the suspended membranes were investigatedby mechanical simulations and surface profilometry measurementsas a function of the geometric parameters. RFcharacterization was performed to evaluate the impact ofthe package on the CPW performance. Finally, networkanalysis was carried out, allowing to clarify the origin ofthe RF losses measured for the fabricated microdevices.

In this work, thin film packages were developed for radio-frequency microelectromechanical system (RF MEMS) configurations. The fabricated packages are suspended membranes in the multilayer SixNyHz/aSi/SixNyHz on conductive coplanar lines of different length. Several geometric parameters of the membranes, which are the length, the curvature radius at the vertices of the rectangular base, the density and the diameter of holes, were also varied. The mechanical properties of the suspended membranes were investigated by surface profilometry as a function of the geometric parameters. Finally, the RF characterization was performed to evaluate the impact of the package on the coplanar line performance. Hence, the proposed study provides results of crucial importance for the application of thin-film suspended microstructures for the packaging of RF MEMS devices.