Showing papers on "Cantilever published in 1990"

Positive position feedback control for large space structures

Abstract: A new technique for vibration suppression in large space structures is investigated in laboratory experiments on a thin cantilever beam. This technique, called Positive Position Feedback, makes use of generalized displacement measurements to accomplish vibration suppression. Several features of Positive Position Feedback make it attractive for the large space structure control environment: The realization of the controller is simple and straightforward. Global stability conditions can be derived which are independent of the dynamical characteristics of the structure being controlled, i.e., all spillover is stabilizing. The method cannot be destabilized by finite actuator dynamics, and the technique is amenable to a strain-based sensing approach. The experiments control the first six bending modes of a cantilever beam, and make use of piezoelectric materials for actuators and sensors, simulating a piezoelectric active-member. The modal damping ratios are increased by factors ranging from 2 to 130.

Microfabrication of cantilever styli for the atomic force microscope

Abstract: Atomic force microscopy (AFM) is a newly developed high resolution microscopy technique which is capable of mapping forces near surfaces or, by means of these forces, the topography of the surface itself. In one mode of operation, AFM can resolve individual atoms on both conducting and insulating surfaces. A crucial component for the AFM is a flexible force‐sensing cantilever stylus, whose properties should include, among other things: a sharp tip, a low force constant, and a high mechanical resonance frequency. These requirements can be met by reducing the size of the cantilever stylus through microfabrication techniques and employing novel methods to construct a sharp tip. Presented here are a number of microfabrication processes for constructing cantilever styli with properties ideal for the AFM. These fabrication processes include (1) a method for producing thin film SiO2 or Si3N4 cantilevers without tips, (2) a method for producing Si3N4 cantilevers with integrated pyramidal tips formed by using an e...

Improved atomic force microscope images using microcantilevers with sharp tips

Abstract: Novel force‐sensing microcantilevers with sharp tips have been used to obtain atomic force microscope images of atomically flat, layered compounds as well as microfabricated samples with large‐scale topographies. When imaging atomically flat samples using cantilevers with sharp protruding tips, atomic corrugations are observed more consistently and with a higher signal‐to‐noise ratio than in the absence of tips. Some asymmetric distortions arise when tipped cantilevers are used with forces larger than 10−7 N. Side by side comparisons of images of rough samples obtained using cantilevers with and without tips reveal that the presence of a sharp tip yields superior image quality of vertical features and trenches. The cantilever assembly is a microfabricated, silicon nitride cantilever with an integral, single‐crystal silicon tip. The silicon tip is self‐aligned to the end of the cantilever and is created by a process which simultaneously fabricates and sharpens the silicon tip. Initial transmission electron...

Method of making an integrated scanning tunneling microscope

Abstract: An integrated scanning tunneling microscope and an integrated piezoelectric transducer and methods for making both. The device consists of one or two arm piezoelectric bimorph cantilevers formed by micromachining using standard integrated circuit processing steps. These cantilevers are attached to the substrate at one area and are free to move under the influence of piezoelectric forces which are caused by the application of appropriate voltages generated by control circuitry and applied to pairs of electrodes formed as an integral part of the bimorph cantilever structure. The electric fields caused by the control voltages cause the piezoelectric bimorphs to move in any desired fashion within ranges determined by the design. The bimorph cantilevers have tips with very sharp points formed thereon which are moved by the action of the control circuit and the piezoelectric bimorphs so to stay within a very small distance of a conducting surface. The movements of the tip can be tracked to yield an image of the surface at atomic resolution.

Residual stress and mechanical properties of boron-doped p+-silicon films

Abstract: Annealing was used to relax non-uniform tensile stress in boron-doped p + -Si cantilever beams. The optimum annealing condition was determined. A for

Method of forming microfabricated cantilever stylus with integrated pyramidal tip

Abstract: A dielectric cantilever arm stylus with an integrally formed pyramidal tip is provided. The tip is molded in a pyramidal pit etched in a later-removed (100) silicon substrate. An integrally-formed cantilever arm is also formed as the tip is being formed. Various thin film materials form the cantilever arm and the tip. In one embodiment of the invention, the dielectric is silicon nitride. The cantilever arm is anodically bonded to a glass block.

CMOS electrothermal microactuators

Abstract: Fabrication of electrothermal microactuators using a commercial CMOS technology is presented. The effect of differential thermal expansion of adjacent insulating layers is used to produce the mechanical deflection. The field oxide and CVD oxide of the CMOS process form the micromechanical structure. A heating element required to raise the temperature is formed by the polysilicon layer available in the CMOS process. A typical cantilever microactuator exhibits an elastic deflection of 4 mu m above the chip surface, and a suspended plate microactuator 1 mu m above the chip surface. Maximum frequency response is measured at 1.5 kHz and 2.0 kHz for the cantilever and the suspended plate microactuators, respectively. >

Synthetic Diamond Micromechanical Membranes, Cantilever Beams, and Bridges

Abstract: A novel process to selectively deposit polycrystalline diamond on a silicon surface was developed, establishing the capability to fabricate polycrystalline diamond microstructures using anisotropic etching of silicon. Micro‐mechanical beams, cantilevers, and optically transparent membranes/windows of polycrystalline synthetic diamond were fabricated on single‐crystal silicon wafers. These diamond films were deposited by high‐pressure microwave plasma‐assisted chemical vapor deposition from a gas mixture of methane and hydrogen. The Young's modulus of polycrystalline diamond thin film was estimated using the elastic deformation cantilever beam formulation. The fabrication procedure, optical and scanning electron microscopy views of various designs, and the evaluation of the elastic properties are reported.

A planar process for microfabrication of a scanning tunneling microscope

Abstract: With decreasing size, a scanning tunneling microscope (STM) becomes less sensitive to vibrations and thermal drift and easier to manufacture by batch fabrication techniques. An integrated-circuit-compatible planar process has been developed to fabricate arrays of STMs on Si wafers. Using planar technology, it is possible to integrate the tunneling tip, the actuation mechanism and (if desired) the counter electrode on a Si ‘chip’. The actuator mechanism is a cantilevered bimorph consisting of alternating layers of metal and piezoelectric zinc oxide. Each metal layer is divided into two electrodes that can be individually addressed, thereby enabling the cantilever to move in three orthogonal directions. The thin (3 μm) piezoelectric layers allow low voltage (< 30 V) operation. The theoretical response of the actuator is 2500 A/V in z, 104 A/V in y and 14 A/V in x. The device has been successfully fabricated and its operation has been demonstrated by imaging the surface of graphite with atomic resolution. A planar process for microfabrication of an integrated STM has been developed and operation of this ‘STM on a chip’ has been demonstrated by imaging the surface of graphite with atomic resolution. The devices are small (typically 8 × 200 × 1000 μm) and are fabricated in large batches of over 200 cantilevers per wafer. By utilizing the bimorph action of a cantilever made of metal and piezoelectric ZnO, it is possible to achieve three-dimensional scanning motions using low-voltage feedback circuits. Initial results show a z-sensitivity of up to 2500 A/V for the cantilever, which is sufficient to use the device as an STM and obtain atomic resolution images. Processes for growing a sharp tunneling tip on the cantilever are being prepared and we envision integrating onboard signal-processing circuitry with the device. The piezoelectric bimorph cantilever with three-dimensional motion is likely to have numerous and diverse applications in the field of microfabrication.

Method of producing micromechanical sensors for the afm/stm profilometry

Abstract: A micromechanical sensor is described for the AFM/STM profilometry, incorporating a cantilever beam with at least one tip at its end and a mounting block at the opposite end. A method is described incorporating the steps of coating a wafer substrate with an insulating layer, forming a mask in the insulating layer, etching a trench in the wafer substrate, removing the insulating layer, coating the desired cantilever beam and tip material, respectively, etching the cantilever beam and tip material, and removing at least a portion of the supporting wafer material from the bottom side. The invention overcomes the problem of forming a micromechanical sensor having a cantilever beam, a tip with a predetermined shape and a mounting block.

A UHV‐compatible thin‐film stress‐measuring apparatus based on the cantilever beam principle

Abstract: A stress‐measuring apparatus based on the cantilever beam principle is described that can be used to determine the internal stress of thin films continuously during and after their deposition. The displacement of the free end of the cantilever beam−which is proportional to the film stress−is determined with high sensitivity and long time stability using a differential capacitance method in combination with phase‐sensitive detection. The entire apparatus is fully compatible with UHV requirements and includes provisions for heating and cooling the substrate. The reproducible performance of the stress‐measuring apparatus is demonstrated with silver films deposited onto MgF2‐coated substrates.

System for moving drilling module to fixed platform

Abstract: A jack-up rig includes a cantilever beam assembly and a drilling module is mounted on the cantilever beam assembly. The jack-up rig also includes means for moving the cantilever beam assembly from the storage position to extended positions wherein a rearward end of the cantilever beam assembly is extended from the jack-up rig. The fixed platform comprises a fixed platform support structure having a drilling module support surface and a beam opening. The jack-up rig is positioned near the fixed platform with the cantilever beam assembly generally aligned with the beam opening in the fixed platform support structure. The cantilever beam assembly then is extended through a portion of the beam opening to an extended position wherein the drilling module is supported on the cantilever beam assembly a distance generally above the drilling module support surface. The jack-up rig then is lowered to a position wherein the drilling module is supported on the fixed platform support structure. The cantilever beam assembly then is withdrawn from the beam opening and moved to the storage position thereby leaving the drilling module supported on the drilling module support surface of the fixed platform support structure. A bridge is movably connected to the fixed platform and the jack-up rig. A floor is removably supported on the cantilever beam assembly generally below the drilling module.

Multiple mode micromechanical resonators

Abstract: Two resonant micromechanical structures that have been designed, fabricated, and tested and which exhibited multiple modes of vibration are described. The first had a cantilevered inertial mass that was actuated by a curved-comb electrostatic drive attached near the root of the cantilever. The second structure had a straight-comb electrostatic-drive with a folded flexure suspension that was used to actuate the cantilevered inertial mass. The first structure exhibited two distinct vibration modes, and the second structure exhibited three distinct vibration modes. An analytic dynamic model has been developed and it predicted the vibrational mode shapes of the structures. Tests of the fabricated structures have demonstrated that peak-to-peak lateral displacements greater than 10 microns were feasible. Further, peak-to-peak angular displacements greater than 10 degrees have been measured during second mode vibration. The resonant frequencies of the structure varied from 1.7 to 33 kHz, depending on structure geometry. Cantilever structures with overhang lengths as great as 864 microns have been fabricated and operated with no perceptible contact between the inertial mass and the substrate. >

Sensor having a cantilever

Abstract: A sensor comprises a tiny cantilever (14) of a thin film having a detection region at its free end portion, a detector (21) for detecting a displacement of the can­tilever (14) caused by material acting on the detecting region, and calculation unit (15) for calculating an amount of the material acting on the detection region, based on the displacement of the cantilever (14) which has been detected by the detector (21), thereby to mea­sure the intensity of a particle-stream applied to the detection region or the thickness of a film formed on the detection region.

Optically activated ZnO/Sio2/Si cantilever beams

Abstract: The photomechanical effect induced by periodically varying sub-bandgap illumination in thin ZnO films deposited on oxidized Si has been demonstrated for the first time. The efficiency of this effect is at least one order of magnitude higher as compared to the photothermal activation of Si. Thus it can be considered as a powerful optical drive for resonant sensors. A phenomenological model of the mechanisms involved in the process is proposed. The optomechanical effect can also be used as a complementary method in determination of the surface state parameters of ZnO films.

Tapered cantilever beam for sensors

Abstract: A method of making a sensor with a mass (14) that is supported by at least one tapered cantilever beam (11). Tapered cantilever beam or beams (11) can be used in either capacitive or piezo-resistive structure. Increased sensitivity and decreased fragility is obtained by using the tapered cantilever beam.

A novel silicon accelerometer with a surrounding mass structure

Abstract: A new accelerometer with a surrounding mass structure is proposed to achieve the extreme reduction in sensor die size. The sensor has a very high sensitivity due to a high seismic mass area ratio compared to a conventional accelerometer. This structure provides a heavy seismic mass without a plating which lowers compatibility with standard IC processes. This sensor has one support at a gravitation center for the sensor die, four cantilever beams spread symmetrically around the support and a surrounding seismic mass which is linked to the cantilever beams. The fabricated sensor has a rhombic structure with a 5 mm × 3.5 mm diagonal size. The 0.02 mV/ g /V sensitivity is obtained with a beam size of 500 × 100 × 10 μm. This paper describes the structure and the fabrication process as well as the characteristics for the sensor.

Method for making an electrical contact

Abstract: A method of making electrical contacts (10) for either tin or gold-plating without changing the overall dimensional shape of the contact (10) has been disclosed. The method includes the step of providing a given spring rate for a pair of cantilever beams (26) by cutting the beam (26) to a predetermined width without changing the length thereof.

Dynamic mechanical measurements: Comparison between bending and torsion methods on a graphite-reinforced and a rubber-modified epoxy

Abstract: Dynamic mechanical measurements in the cantilever bending and torsion rectangular modes were compared on two epoxy samples: one unidirectionally reinforced by 42 vol.% graphite fibers, the other modified by 15 wt.% carboxy terminated acrylonitrile butadiene rubber. Two forced oscillation instruments were used: cantilever bending on a Polymer Labs DMTA and torsion with a Rheometrics System Four. In the cantilever mode, the storage modulus on both samples was measured at about two to three times too low because of compliance of the instrument. The two instruments agreed and appeared to measure accurately tan δ on the graphite-reinforced samples. Agreement was only fair on tan δ for the rubber-modified sample. Multiple frequency data were used to separate the glass-transition temperature of the rubber from the epoxy β transition. Activation energies of these transitions are within the range reported. This study demonstrates the value of forced oscillation methods and the importance of selecting sample dimensions to fit instrument limits.

Barber-pole magnetoresistive magnetic field sensor

Abstract: A magnetic field sensor for an acceleration sensor including a cantilever beam having a free end to which a permanent magnet is attached. A pair of the magnetic sensors, each consisting of a barber-pole type magnetoresistive sensing element, are arranged opposite to and symmetrically. The cantilever is bent and the magnet is moved according to an acceleration, which is detected as outputs from the magnetoresistive sensing elements.

Results for the cantilever beam moving in crossed magnetic fields

Abstract: Problem 12 of the TEAM (Testing Electromagnetic Analysis Methods) Workshops for Eddy Current Code Comparison is a cantilever beam in crossed steady and time‐varying magnetic fields. A total of six solutions to this coupled problem are described and compared with experimental results. Most solutions treated the electromagnetic aspects of the problem numerically, but the mechanical motion aspects analytically with a single degree of freedom. In general, the numerical predictions are in very good agreement with experiments.

Spring biased paper clip

Abstract: A paper clip comprising a pair of plate elements having clamping edges, hingedly connected together. A cantilever spring extends from an inner surface of one plate element and engages with the inner surface of the opposite plate element. The cantilever spring can provide increasing clamping force with increasing document thickness.

An undergraduate experiment on the vibration of a cantilever and its application to the determination of Young’s modulus

Abstract: An experiment is described to test the theory for the frequencies of lateral vibrations of a uniform cantilever. Good agreement between experiment and theory is obtained. Young’s modulus for the cantilever material (steel) is determined from the observed frequencies of the fundamental mode for a series of different lengths, and the result is compared with that obtained from static deflection of the cantilever. The agreement between the dynamic and static determinations is satisfactory.