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The Micronium is a musical instrument fabricated from silicon using microelectromechanical system (MEMS) technology. It is—to the best of our knowledge—the first musical micro-instrument fabricated using MEMS technology, where the actual sound is generated by mechanical microstructures. The Micronium consists of mass-spring systems that are designed to resonate at audible frequencies. Their displacement is measured by comb drives and is used as the audio signal to drive a loudspeaker. The instrument's sounds are pure sine waves. An extensive set of measurements of individual resonators is presented and discussed. Quality factor measurements at various ambient pressures show that an ambient pressure of 1 mbar results in a note duration of 1 s. The realized frequency deviates considerably from the designed resonator frequency. Measurement results of many resonators are shown to obtain understanding of this deviation. Initial experiments with electrostatic tuning using variable-gap comb drives show a tuning ratio of 5% maximum, depending on the resonator frequency. An audio recording of the instrument is included as a supplementary MP3 file.

Accurate manipulation of small objects is becoming more and more important. Besides accurate manipulation, the demand for small manipulators is also increasing. Some examples are high-density data storage, (digital) light processing, accelerometers, rate sensors, and the use of cantilevers in atomic force microscopy. Another example where small and accurate manipulators are beneficial is inside an electron microscope, for sample as well as beam manipulation. This work presents the design, fabrication and experimental validation of a thermal displacement sensor for accurate measurement of the position of a MEMS stage. The sensor was integrated with the manipulation stage in a singlemask production process.

This work presents a MEMS displacement sensor based on the conductive heat transfer of a resistively heated silicon structure towards an actuated stage parallel to the structure. This differential sensor can be easily incorporated into a silicon-on-insulator-based process, and fabricated within the same mask as electrostatic actuators and flexure-based stages. We discuss a lumped capacitance model to optimize the sensor sensitivity as a function of the doping concentration, the operating temperature, the heater length and width. We demonstrate various sensor designs. The typical sensor resolution is 2 nm within a bandwidth of 25 Hz at a full scale range of 110 µm.

In this chapter Magnetic Force Microscopy is treated in detail. The emphasis is on high resolution and the design and realisation of MFM tips.

Thin-film yoke-type magnetoresistive (MR) tape heads with eight channels have been used for scanning magnetoresistance microscopy. The NiFe read flux guides of the channels have been trimmed down from 12 /spl mu/m to widths varying between 5 /spl mu/m and 100 nm by focused ion-beam milling with Ga/sup +/ ions. The tape-bearing surface of the milled regions has been reconstructed in situ by the local deposition of Pt. Tracks with a minimum bit length of 1 /spl mu/m have been written on Co-Ni-O metal evaporated tape and Co-/spl gamma/-Fe/sub 2/O/sub 3/ particulate tape with trimmed and untrimmed write channels and have been successfully imaged with all the trimmed read channels. A linear decrease in readback voltage across the MR sensor is observed for channels possessing flux guides trimmed down to 2 /spl mu/m, in agreement with finite-element modeling of the trimmed heads. The severe attenuation in readback voltage observed for flux guides trimmed below 2 /spl mu/m is attributed to a combination of micromagnetic effects. Additionally, damage to the NiFe from Ga/sup +/ ion implantation may make a minor contribution to the loss in sensor performance. A 65% drop in readback voltage is observed for a channel possessing a flux guide that was trimmed by 98.3% to 200 nm.

The effect of intertrack intersymbol interference in a magnetic patterned medium is studied. A two-dimensional (2-D) channel code is proposed, dedicated to perpendicularly magnetized media without soft underlayer, which exhibit read pulses showing overshoot. Read pulse shapes were investigated using a magnetic-force microscope tip scanning the patterned medium row-by-row. To test different codes, a bit-detection simulation program was developed to generate large amounts of data on which bit error rates can be measured. Application of the 2-D channel code, which implies recording of particular dot positions with fixed bits ("ones", "zeros"), resulted in the elimination of 2-D worst-case bit patterns and a subsequent reduction of detected-bit errors. The accompanying redundancy of 22% is inevitable for this type of 2-D code.

We investigate the energy consumption and seek-time performance of different actuator types for nanopositioners, with emphasis on their use in a parallel-probe-based data-storage system. Analytical models are derived to calculate the energy consumption and performance of electrodynamic (coil and permanent magnet) and comb-drive actuators. The equations are used to simulate the operation of probe-storage devices with these actuator types under a realistic file system load. The electrostatic comb-drive actuators are more energy efficient than the electrodynamic actuators, by an order of magnitude for slow movements and a factor of 2.5 for high-acceleration movements. Overall in a probe-storage device, comb-drive actuation is a factor of 3.3 more energy efficient than electrodynamic actuation, at the same level of performance. The analytical model presented in this work can be used to direct the optimization of nanopositioners and their use, for example, in terms of the data layout on the medium and the ‘shutdown’ policy of probe-storage devices.

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2-7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm when the pulse voltage is above a threshold voltage. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. The emission area of our tip-sample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. This emission area is large compared to lateral heat diffusion in the film. Thus higher applied voltages lead to higher peak temperatures in the model of the write process, but the mark diameter remains relatively unchanged.

The transfer functions of tips with various sharpened tip ends were calculated and the resolution of these tips was estimated by considering the resolution limit due to thermal noise at room temperature. The tip having an ellipsoidal tip end (ellipsoidal tip) is found to be a suitable candidate for high-resolution magnetic force microscopy. Sharpening of the flat tip end makes zero signal frequencies disappear for tips with ellipticities larger than tan45/spl deg/. The sensitivity shows a maximum around an ellipticity of tan80/spl deg/. The ellipsoidal tip shows a much smaller tip thickness dependence compared to the tip having a flat tip end because only the tip end mainly contributes to signals in case of the ellipsoidal tip.

Throughout the ages humanity has stored data in order to preserve important information for generations to come. As the years have progressed the amount of data that can be stored efficiently has increased tremendously, the lifespan of this type of data storage however is severely limited. Within this paper we investigate the possibility to store data by encapsulating W in a SiN matrix.We show that using accelerated thermal aging the possible lifespan of this medium can be investigated and expected to reach well into the millions of years, preserving data for thousands of future generations. The first steps into fabrication of such a medium are discussed.

This paper presents a simple code to combat the 2-Dimensional Inter-Symbol Interference (2D-ISI) effect that is present in data storage on magnetic bit patterned media. Whether the ISI effect is constructive or destructive depends on the surrounding bits. Therefore, we propose a simple 2D coding scheme to mitigate the ISI effect. With this 2D coding scheme in square patterned media, every 2-by-3 array has one redundant bit which has the opposite or same value of one of its adjacent bits. Compared to the 2D coding scheme in \cite{Groenland2007} under the condition of the same areal density, the proposed 2D coding scheme increases the allowable bit-position jitter in square patterned media by 1\% at a BER of $10^{-4}$; while it allows the effective storage capacity to be increased by around 5.5\%.

This research presents the fabrication of all-oxide LaNiO3/Pb(Zr,Ti)O3/LaNiO3 thin films for applications in piezoelectric microelectromechanical systems (piezoMEMS). All oxide layers are fabricated on 4-inch silicon-on-insulator (SOI) wafer using large-area pulsed laser deposition (PLD) by SolMateS B.V. The determined film-thickness variation is less than 5% over the total wafer area. PZT thin-film of 1-μm-thick exhibits (100) texture orientation. The optimization of the electromechanical responses for piezoelectric membranes is investigated experimentally. In the optimization of membrane- and electrode-geometries, Pb(Zr,Ti)O3 (PZT) actuators consisting of a variety of membrane type, membrane diameter and electrode coverage are fabricated using microfabrication processes and characterized by laser Doppler interferometer for piezoelectric responses, like displacement and resonance frequency. The fabricated 500-μm-diameter PZT membrane provides high central displacement of 26 nm/V at a constant frequency well below its first resonance frequency (fr = 330 kHz). The results also indicated that the membrane diameter has a dominant effect on the magnitude of the out-of-plane displacement and the resonance frequency. The electrode-size to membrane-diameter ratio or electrode coverage is important and may be tailored to optimize the displacement. Electrode coverage of 36% produces the optimum displacement. Moreover, it shows an excellent long-term stability of membrane actuators with a displacement remains of about 95% after 10 billion actuations, by using the conductive-oxide LaNiO3 (LNO) layers as the electrodes.

Accurate manipulation of small objects is becoming more and more important. Besides accurate manipulation, the demand for small manipulators is also increasing. Some examples are high-density data storage, (digital) light processing, accelerometers, rate sensors, and the use of cantilevers in atomic force microscopy. Another example where small and accurate manipulators are beneficial is inside an electron microscope, for sample as well as beam manipulation. This work presents the design, fabrication and experimental validation of a thermal displacement sensor for accurate measurement of the position of a MEMS stage. The sensor was integrated with the manipulation stage in a singlemask production process.

This research presents the fabrication of all-oxide LaNiO3/Pb(Zr,Ti)O3/LaNiO3 thin films for applications in piezoelectric microelectromechanical systems (piezoMEMS). All oxide layers are fabricated on 4-inch silicon-on-insulator (SOI) wafer using large-area pulsed laser deposition (PLD) by SolMateS B.V. The determined film-thickness variation is less than 5% over the total wafer area. PZT thin-film of 1-μm-thick exhibits (100) texture orientation. The optimization of the electromechanical responses for piezoelectric membranes is investigated experimentally. In the optimization of membrane- and electrode-geometries, Pb(Zr,Ti)O3 (PZT) actuators consisting of a variety of membrane type, membrane diameter and electrode coverage are fabricated using microfabrication processes and characterized by laser Doppler interferometer for piezoelectric responses, like displacement and resonance frequency. The fabricated 500-μm-diameter PZT membrane provides high central displacement of 26 nm/V at a constant frequency well below its first resonance frequency (fr = 330 kHz). The results also indicated that the membrane diameter has a dominant effect on the magnitude of the out-of-plane displacement and the resonance frequency. The electrode-size to membrane-diameter ratio or electrode coverage is important and may be tailored to optimize the displacement. Electrode coverage of 36% produces the optimum displacement. Moreover, it shows an excellent long-term stability of membrane actuators with a displacement remains of about 95% after 10 billion actuations, by using the conductive-oxide LaNiO3 (LNO) layers as the electrodes.

In this thesis techniques are developed to read out nanoscale probes and arrays of probes.The main targeted application area is probe-based data storage.The work also contributes to other areas, such as metrology, biological sensing, materials research and nano-electro-mechanical switches. First, an exhaustive literature review of the accomplishments within probe storage is presented. It is found that optical readout techniques are used extensively in applications using probes; however, the very demanding application probe storage is not amongst them. Optical readout of probes offers reliability, high-speed, low noise and low complexity. It has to be extended to operation on arrays of probes for successful implementation in probe storage. The first technique that is developed in this work is parallel....

In this thesis techniques are developed to read out nanoscale probes and arrays of probes.The main targeted application area is probe-based data storage.The work also contributes to other areas, such as metrology, biological sensing, materials research and nano-electro-mechanical switches. First, an exhaustive literature review of the accomplishments within probe storage is presented. It is found that optical readout techniques are used extensively in applications using probes; however, the very demanding application probe storage is not amongst them. Optical readout of probes offers reliability, high-speed, low noise and low complexity. It has to be extended to operation on arrays of probes for successful implementation in probe storage. The first technique that is developed in this work is parallel....

The era of infinite storage seems near. To reach it, data storage capabilities need to grow, and new storage technologies must be developed.This thesis studies one aspect of one of the emergent storage technologies: optimizing electrostatic combdrive actuation for a parallel probe-based data storage system. It is no longer possible to store all created information. New storage technologies must be developed as current commercial technologies reach their fundamental limits. One promising technology is parallel probe-based data storage, using a nanometre-scale probe to write data on a moving platform. The working principle is very similar to that of a record player applied in parallel on the nano scale. In order to access all bits on the storage medium, a nano-positioner, or scanner, is used to move the storage medium relative to the read-out probes. Several nano-positioner designs for probe data storage are found in the literature. It is not clear which actuator type (electromagnetic, electrostatic, or piezoelectric) is most suited for probe data storage. We replaced the electrodynamic actuators by comb-drives in the scanner prototype by IBM, to enable a direct comparison. e comb-drive’s areal efficiency is low, due to a relatively low electrostatic force. e comb-drive finger profile is optimized for probe data storage, for an increased shock resistance. e suitability of electromagnetic and electrostatic actuation is, among others, determined by their energy consumption.Three (partly) hypothetical scanner designs using electrodynamic, electromagnetic and electrostatic comb-drive actuators are described. Their performance is approximately equal, however electrostatic comb-drive actuation requires an order of magnitude less energy. Equations are presented for further investigations into the performance and energy consumption of the different actuation types for different file-system use cases. We succeeded in making music with MEMS structures, and named our microinstrument ‘the micronium’. Due to fabrication inaccuracies, the instrument is outof- tune and requires tuning. Besides teaching students about MEMS technology in a fun way, the micronium succeeded in presenting MEMS technology to a broad audience.

The era of infinite storage seems near. To reach it, data storage capabilities need to grow, and new storage technologies must be developed.This thesis studies one aspect of one of the emergent storage technologies: optimizing electrostatic combdrive actuation for a parallel probe-based data storage system. It is no longer possible to store all created information. New storage technologies must be developed as current commercial technologies reach their fundamental limits. One promising technology is parallel probe-based data storage, using a nanometre-scale probe to write data on a moving platform. The working principle is very similar to that of a record player applied in parallel on the nano scale. In order to access all bits on the storage medium, a nano-positioner, or scanner, is used to move the storage medium relative to the read-out probes. Several nano-positioner designs for probe data storage are found in the literature. It is not clear which actuator type (electromagnetic, electrostatic, or piezoelectric) is most suited for probe data storage. We replaced the electrodynamic actuators by comb-drives in the scanner prototype by IBM, to enable a direct comparison. e comb-drive’s areal efficiency is low, due to a relatively low electrostatic force. e comb-drive finger profile is optimized for probe data storage, for an increased shock resistance. e suitability of electromagnetic and electrostatic actuation is, among others, determined by their energy consumption.Three (partly) hypothetical scanner designs using electrodynamic, electromagnetic and electrostatic comb-drive actuators are described. Their performance is approximately equal, however electrostatic comb-drive actuation requires an order of magnitude less energy. Equations are presented for further investigations into the performance and energy consumption of the different actuation types for different file-system use cases. We succeeded in making music with MEMS structures, and named our microinstrument ‘the micronium’. Due to fabrication inaccuracies, the instrument is outof- tune and requires tuning. Besides teaching students about MEMS technology in a fun way, the micronium succeeded in presenting MEMS technology to a broad audience.

In this paper we are investigating the potential to employ small devices in crucial areas with limited volumes in electron microscopes. We present the analysis of the electric fields that are present in an electrostatically actuated micro electro mechanical systems (MEMS) device. The electric fields are modeled using finite elements methods (FEM). Preliminary results are shown from scanning electron microscope (SEM) measurements of an electrostatically actuated two degrees of freedom (2DOF) nanometer precision table. From the FEM results the influence of the electric fields on an electron beam traversing the devices can be calculated. This influence is calculated to be a trajectory displacement in the order of tens of nanometers for typical acceleration voltages. SEM measurements show significant vibrations in the images of nonmovable parts of the devices when applying actuation voltages to the devices. This shows an effect of actuation on the detected electrons while imaging. Deflections up to 2.2 μm have been observed for a voltage of 80 Vpp. This deflection cannot be fully attributed to deflections of the incoming beam. Therefore we include in a qualitative analysis the trajectory of emitted secondary electrons that are detected.

This paper describes our work to magnetically steer self-propelled devices whichmove by catalysis of hydrogen peroxide. We demonstrate manipulation of paramagnetic particles with a diameter of 100μm to a given setpoint by means of magnetic field gradients, as well as self-propelled movement of gold-platinum rods. We discuss how to reach magnetic torque control of catalytic micro motors.

In this contribution we present the compositional dependence of the longitudinal piezoelectric coefficient (d33,f), residual stress and Young's modulus of Pb(Zrx,Ti1-x)O3 (PZT) thin films. Pulsed laser deposition (PLD) was used to deposit epitaxial PZT thin films with a < 110 > preferred orientation on silicon cantilevers. By using PLD, excellent piezoelectric properties of the PZT were observed which makes it an exciting piezoelectric material for the development of actuators and highly sensitive sensors. Our investigation of the compositional distribution of the piezoelectric coefficient (d33,f) for 250 nm thick films shows a maximum value of 93 pm/V for x=0.52. The static deflection of the cantilevers, measured after the deposition of PZT thin films was used to determine the residual stress for various compositions. The observed trend in the residual stress of PZT thin films is attributed to the varying coefficient of thermal expansion for different compositions. The Young's modulus of the PZT thin films was determined by measuring the flexural resonance frequency of the cantilevers both before and after the deposition. The Young's modulus increases for the zirconium rich PZT compositions, which is in agreement with the trend observed in their bulk ceramic counterparts.

Emerging nanotechnology-based systems encounter new non-functional requirements. This work addresses MEMS storage, an emerging technology that promises ultrahigh density and energy-efficient storage devices. We study the buffering requirement of MEMS storage in streaming applications. We show that capacity and lifetime of a MEMS device dictate the buffer size most of the time. Our study shows that trading off 10% of the optimal energy saving of a MEMS device reduces its buffer capacity by up to three orders of magnitude.

In this paper, a novel technique for fabricating Transmission Electron Microscopy (TEM) chips for investigating structural and piezoelectric properties of Pulse Laser Deposited (PLD) Lead Zirconium Titanate (PZT) thin films is presented. The method involves silicon-on-insulator (SOI) wafer technology together with deep reactive ion etching (DRIE) and highly selective etchants. This study is unique in the sense that it will facilitate in-situ characterization of the PLD PZT membranes during actuation. As well as PLD PZT, the proposed method can be applied to a variety of materials by proper selection of the etchants and tuning of the process parameters. Being a critical step of the process sequence, the deposition profile of the PZT layer on the Lanthanum Nickel Oxide (LNO) seed layer is characterized prior to fabrication. The results reveal that the PLD process is not conformal and the thickness of the LNO/PZT layer is different on surfaces with different topographies.

Recently, a silicon micromachining method to produce tetrahedral silicon particles was discovered. In this report we determine, using band structure calculations, the optical properties of diamond-lattice photonic crystals when assembled from such particles. We show that crystal structures built from silicon tetrahedra are expected to display small stop gaps. Wide photonic band gaps appear when truncated tetrahedral particles are used to build the photonic crystals. With truncated tetrahedral particles a band gap with a width of 23.6% can be achieved, which is more than twice as wide compared to band gaps in self-assembled diamond-lattices of hard-spheres. The width of the band gap is insensitive to small deviations from the optimal amount of truncation. This work paves the way to a novel class of silicon diamond-lattice band gap crystals that can be obtained through self-assembly. Such a self-assembly approach would allow for easy integration of these highly photonic crystals in existing silicon microfluidic and -electronic systems., Comment: Improvements to the text, changed equation 3, added reference 34

Scanning rates of the atomic force microscope (AFM) could be significantly increased by integrating the force sensing probe with microelectromechanical systems (MEMS). We present a micromachining method for batch fabrication of in-plane AFM probes that consist of an ultra-sharp silicon nitride tip on a single crystal silicon cantilever. Our fabrication method is fully compatible with the silicon-on-insulator (SOI) micromachining allowing a straightforward monolithic integration of the AFM probes with high-aspect-ratio monocrystalline silicon MEMS. Scanning probes with a sharp tip having diameter of less then 10 nm are successfully realized and tested in a commercial AFM set-up demonstrating feasibility and the large innovation potential of this method.

In this work we show for the first time that the effective in-plane Young’s modulus of PbZr0.52Ti0.48O3 (PZT) thin films, deposited by pulsed laser deposition (PLD) on dedicated single crystal silicon cantilevers, is independent of the in-plane orientation of cantilevers.

We report on progress in the fabrication of cantilever arrays with tips. The process features only one lithographic step for the definition of both the tips and cantilevers. The tips have a uniform height distribution and are placed by selfalignment on the cantilever. The arrays are fabricated for an optical readout technique under development in which the cantilever arrays serve as diffraction gratings. This work describes our ongoing effort in array fabrication as well as preliminary results on optical readout of a previously fabricated batch of tipless cantilever arrays using Fraunhofer diffraction.

Calculation of the resonance frequency of cantilevers fabricated from an elastically anisotropic material requires the use of an effective Young’s modulus. In this paper a technique to determine the appropriate effective Young’s modulus for arbitrary cantilever geometries is introduced. This technique is validated using a combined analytical and finite element simulations (FEM) approach. In addition, the effective Young’s modulus of PbZr0.52Ti0.48O3 (PZT) thin films deposited on dedicated micromachined cantilevers was investigated experimentally. The PZT films were deposited on the cantilevers by pulsed laser deposition (PLD). The change in flexural resonance frequency of the cantilevers was measured both before and after deposition of the PZT thin film. From this frequency difference we determined the Young’s modulus of PZT deposited by PLD to be 103 ± 2 GPa. Even though the PZT is grown epitaxially, this value is independent of the in-plane orientation.

To overcome the superparamagnetic effect caused by scaling bit and grain sizes in magnetic storage media different approaches are investigated. One alternative is bit patterned magnetic media (BPM) where each bit is represented by a single domain magnetic dot. A key problem with BPM is the large difference in magnetic field necessary to switch the magnetization direction of the various dot which is characterized by the switching field distribution.

Position sensing in MEMS is often based on the principle of varying capacitance [1]. Alternative position sensing principles include using integrated optical waveguides [2] or varying thermal conductance [3]. Lantz et al demonstrated a thermal displacement sensor achieving nanometre resolution on a 100mm range. However a multi-mask production process and manual assembly were needed to fabricate this displacement sensor. In this work we present a 1-DOF thermal displacement sensor integrated with an actuated stage, and its experimental characterization. The system was fabricated in the device layer of a silicon-on-insulator (SOI) wafer using a single-mask process.

The range of motion and output force of the often used electrostatic comb-drive with folded flexure straight guidance, as shown in Figure 1, is limited by sideways instability due to poor sideways stiffness of the folded flexure at relatively large deflections [1].

The continuous increase in capacity of non-volatile data storage systems will lead to bit densities of one bit per atom in 2020. Beyond this point, capacity can be increased by moving into the third dimension. We propose to use self-assembly of nanosized elements, either as a loosely organised associative network or into a cross-point architecture. When using principles requiring electrical connection, we show the need for transistor-based cross-talk isolation. Cross-talk can be avoided by reusing the coincident current magnetic ring core memory architecture invented in 1953. We demonstrate that self-assembly of three-dimensional ring core memories is in principle possible by combining corner lithography and anisotropic etching into single crystal silicon.

Debakel, fiasco, mislukking. Het zijn dagelijkse bezigheden voor ons onderzoekers. Je kan er dus maar beter mee leren omgaan. Veel mensen hebben zich uitgesproken over hun tevredenheid met mislukkingen. Bijvoorbeeld Albert Einstein’s “Anyone who has never made a mistake has never tried anything new.‿ Robert Oppenheimer leert ons dat we er juist trots op moeten zijn, want “Any man whose errors take ten years to correct is quite a man.‿ Je kan het ook te bont maken, dus opgepast. “Only a fool learns from his own mistakes. The wise man learns from the mistakes of others,‿ aldus Otto von Bismarck. Het inzetten van studenten op kansarme idee¨en lijkt dus een goede oplossing.

We present a process for batch fabrication of a novel scanning microscopy probe for thermal and magnetic imaging using standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four freestanding silicon nitride nanowires coated by conductive material. The nanowires form an electrical cross junction at the apex of the tip, addressable through the electrodes integrated on the cantilever. The cross junction on the tip apex can be utilized to produce heat and detect local temperature changes or to serve as a miniaturized Hall magnetometer enabling, in principle, thermal and magnetic imaging by scanning the probe tip over a surface. We have successfully fabricated a first probe prototype with a nanowire tip composed of 140 nm thick and 11 μ m long silicon nitride wires metallized by 6 nm titan and 30 nm gold layers. We have experimentally characterized electrical and thermal properties of the probe demonstrating its proper functioning. ©2010 IEEE.

An exciting class of storage devices is emerging: the class of Micro-Electro-Mechanical storage Systems (MEMS). Properties of MEMS-based storage devices include high density, small form factor, and low power. The use of this type of devices in mobile infotainment systems, such as video cameras is not at all obvious. We must explore their configuration and assess their benefit with respect to existing devices, such as Flash. In this paper, we study the configuration of the data layout of MEMS-based storage devices for predominately streaming applications. The configuration targets: the timing performance, energy consumption, and the capacity. We show that formatting the data layout based on knowledge of the expected streaming workload results in devices that consume at least 22\% less energy than Flash and perform comparably. We present a fast and effective configuration method to format the data layout. This method exploits the bimodal distribution of the request size in streaming applications. Using the fast method, we present a design rule for streaming environments: reducing the amount of prefetching of streaming data allows to reach configurations with small trade-offs between the design targets.

In this work we describe an electrostatic mass-balanced planar x/y-scanner, using an optimized comb finger shape, designed for parallel-probe storage applications. We show a new stepped comb finger shape design, that has superior force/displacement characteristics leading to a larger stroke at the same voltage and a larger available force compared to straight or tapered shapes.

In probe recording an array of thousands of nanometer-sharp probes is used to write and read on a storage medium. By using micro-electromechanical system technology (MEMS) for fabrication, small form factor memories with high data density and low power consumption can be obtained. Such a system is expected to offer a promising route towards extremely high-density recording, with bits of several nanometer or even atomic size. To reach these densities, individual control over the position of the probes is essential, to be able to operate the probes in non-contact as is for instance done in scanning tunneling microscopy (STM). At the MESA+ Institute for Nanotechnology at the University of Twente, we currently investigate the possibilities of probe recording using a magnetic medium. In the micro scanning probe array memory (μSPAM) concept, an array of magnetic probes is used to write and read on a patterned recording medium. In such a probe storage system, there is also a need to position individual probes at several nanometers above the recording medium, to be able to detect the small magnetic forces. For this non-contact operation, individual z-feedback should be achieved by integration of an actuator, proximity sensor and feedback loop for each probe of the probe array. As reported in literature, the fabrication of probe arrays and integration of actuators and logic circuitry have already been proven to be attainable, however current research still lacks a proximity sensor with sufficient lateral resolution that can be integrated in each probe. The objective of this thesis is to investigate whether field-emission can be used as an integrated method to control probe-medium distance for non-contact probe recording. Field emission can be used as a proximity sensing method, since the emission current varies exponentially with the electric field, which in turn is proportional to the electrode gap. The lateral resolution is determined by the probe tip radius, on the same order as the targeted bit size of about 10 nm. The signal to noise ratio is not affected by the small sensing area, which is an important advantage over other sensing methods. Moreover it provides an elegant solution for the problem of sensor integration in each probe of the array, since only one wire per probe is needed to connect to the field emitting tip.

The dependence of the field emission effect on distance is applied for displacement sensing and high-resolution positioning. Silicon atomic force microscopy probes were used as a field emission source by applying voltages up to 400 V between this probe and a counter-electrode sample consisting of TiW sputtered on a silicon wafer. From current-voltage characteristics measured for distances varying from 50 to 950 nm, values for the field enhancement factor were determined which show a dependence on the electrode separation. This dependence can be correctly described by a model the authors developed using finite-element calculations and is determined by the emitter geometry and tip radius. Feedback to the probe position was used to maintain a constant current to apply this distance dependence for positioning. When increasing the applied voltage from 5 to 40 V for a constant current of 3 nA, the probe position is raised similar to 90 nm. The nonlinear sensitivity of this positioning method is determined by the varying field enhancement and can be fitted by the same calculated model. Using feedback, the field emitter can be positioned with high lateral resolution and scanned over a conducting surface. Increasing the bias voltage from 3 to 50 V results in an increase in the emitter-sample distance and a decrease in lateral resolution. Damage to the scanned surface has to be prevented by using a current-limiting resistor and by annealing the probe and sample under ultra high vacuum conditions before use. (C) 2008 American Vacuum Society.

We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium.

We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium.

We present a novel ultrasensitive magnetometry technique using a micromachined magnetic cantilever that is brought in resonance. The induced magnetic moment generates a torque on the cantilever, thereby effectively stiffening the cantilever spring constant and changing its resonance frequency. Experiments are in good correspondence with the presented analytical model for this frequency shift, predicting the detection of nanotesla magnetic fields.

In this work we describe the design, fabrication and testing of a mass-balanced planar x/y-scanner designed for parallel-probe storage applications (see Fig. 1a). We explore electrostatic actuation as an alternative to electromagnetic actuation. To increase the shock resistance, mass-balancing is used and the scanner is fabricated by deep reactive ion etching through a complete wafer. To move the scan table in both positive and negative x and y directions, four comb drives are used. The comb-drive fingers are tapered to increase the generated force without decreasing the minimum trench width.

We describe how the compliance requirements for data retention from recent laws such as the US Sarbanes Oxley Act may be supported by a tamper-evident secure storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual dots. We report on an experiment to show that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. The write-once operation can be used to support flexible data retention by tamper-evident writing and physical data deletion.

In the past decades, there is a considerable interest in the sensor community to move from micron to nano-devices, typically scaling of resonators such as cantilever beams. The scaled beams give advantages in faster response and higher sensitivity; however the detection of their resonance becomes challenging as dimensions scale down. In our work, we demonstrate the use of field emission characteristics as a detection method for scaled resonators. The advantages of using field emission are several: it is geometrically scalable without loss of signal, it has a high bandwidth and it can be integrated using standard fabrication processes.

The effect of intertrack intersymbol interference in a magnetic patterned medium is studied. A two-dimensional (2D) channel code is proposed, dedicated to perpendicularly magnetized media without soft underlayer, which exhibit read pulses showing overshoot. Read pulse shapes were investigated using a magnetic-force microscope tip scanning the patterned medium row-by-row. To test different codes, a bit-detection simulation program was developed to generate large amounts of data on which bit error rates can be measured. Application of the 2D channel code, which implies recording of particular dot positions with fixed bits ("ones", "zeros"), resulted in the elimination of 2D worst-case bit patterns and a subsequent reduction of detected-bit errors. The accompanying redundancy of 22% is inevitable for this type of 2D code.

In this work, we present a novel concept for high resolution proximity sensing based on field emission and provide more insight in the vacuum conditions and electronics needed for stable operation. This study is focused on tip-medium distance control, and the aim is to apply this method in a vacuum probe storage device where thousands of field emission probes In this work, we present a novel concept for high resolution proximity sensing based on field emission and provide more insight in the vacuum conditions and electronics needed for stable operation. This study is focused on tip-medium distance control, and the aim is to apply this method in a vacuum probe storage device where thousands of field emission probes were individually positioned at several nanometers above a storage medium.

Field emission is used as a displacement sensing method, exploiting the exponential relation between field emission current and electrode gap. Atomic force microscopy (AFM) probes have been used as field emission source to measure I/V characteristics which were found to correspond well to theory. The field emission sensor was operated in a more linear regime by using feedback on the position of the probe in order to maintain a constant current. The sensitivity of the sensor for displacement was found to be 0.26 V/nm at a range of ~100 nm. From the experimental data, typical parameters for the Fowler-Nordheim equation were deduced and used to model the sensor performance. The measurements confirm that field emission can be applied to sense the distance between a probe tip and sample with

The scope of this thesis consists on the fabrication and magnetic characterization of CoNi/Pt and Co/Pt patterned films with perpendicular anisotropy with possible applications as an information storage medium. We have realized patterned magnetic nanodots arranged in square and hexagonal lattices with periodicites ranging from 600 nm down to 300 nm, which corresponds to bit densities from 1.8 Gb/sqi up to 7.2 Gb/sqi. The main aim has been focused towards the understanding of the problems involved in the fabrication of large samples (1 × 1 cm till 3 × 3 cm) and their write-ability. We discuss about the magnetic properties of an idealized magnetic pattern medium. Issues as the thermal stability, required magnetic anisotropy, bit to bit interaction and its consequences for the material’s switching field distribution are considered. Laser Interference Lithography has been the technique chosen to produce the patterned media samples studied in this work. A discussion about different photoresist stacks which were used in the course of this work is presented. We also discuss on the etching process and the photoresist removal afterwards. Regarding the magnetic analysis of the samples, three issues are mainly discussed: The possible damage to the magnetic properties of the material due to the fabrication process, in particular the ion beam etching step and the subsequent removal of the residual photoresist. The switching field distribution displayed by the samples and possible ways to reduce it are also discussed. Finally we examine the thermostability of our samples. Difficulties in writing and retrieving actual information are commented and possible lines for further research are sketched.

The scope of this thesis consists on the fabrication and magnetic characterization of CoNi/Pt and Co/Pt patterned films with perpendicular anisotropy with possible applications as an information storage medium. We have realized patterned magnetic nanodots arranged in square and hexagonal lattices with periodicites ranging from 600 nm down to 300 nm, which corresponds to bit densities from 1.8 Gb/sqi up to 7.2 Gb/sqi. The main aim has been focused towards the understanding of the problems involved in the fabrication of large samples (1 × 1 cm till 3 × 3 cm) and their write-ability. We discuss about the magnetic properties of an idealized magnetic pattern medium. Issues as the thermal stability, required magnetic anisotropy, bit to bit interaction and its consequences for the material’s switching field distribution are considered. Laser Interference Lithography has been the technique chosen to produce the patterned media samples studied in this work. A discussion about different photoresist stacks which were used in the course of this work is presented. We also discuss on the etching process and the photoresist removal afterwards. Regarding the magnetic analysis of the samples, three issues are mainly discussed: The possible damage to the magnetic properties of the material due to the fabrication process, in particular the ion beam etching step and the subsequent removal of the residual photoresist. The switching field distribution displayed by the samples and possible ways to reduce it are also discussed. Finally we examine the thermostability of our samples. Difficulties in writing and retrieving actual information are commented and possible lines for further research are sketched.