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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2379-2383 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Random fluctuations of displacement or velocity in mechanical systems can be calculated by using the analogy between electrical circuits and mechanical systems. The fluctuation-dissipation theorem expresses the relation between the generalized mechanical admittance and the noise in velocity. Similarly, correlation of mechanical noise can be calculated by using the generalized Nyquist theorem which states that the current noise correlation between two ports in an electrical circuit is dictated by the real part of the transadmittance. In this article, we will present the determination of the mechanical transadmittance and we will use the mechanical transadmittance to calculate the noise correlation on geometrically complex structures where it is not possible to approximate the noise by using the simple harmonic oscillator model. We will apply our method to atomic force microscope cantilevers by means of finite element method tools. The application of the noise correlation calculation method to rectangular cantilever beams shows some interesting results. We found that on the resonance frequencies, the correlation coefficient takes values 1 (full correlation) and −1 (anti-correlation) along the cantilever axis depending on the mode shapes of the structure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3294-3297 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new procedure for high-speed imaging with the atomic force microscope that combines an integrated ZnO piezoelectric actuator with an optical lever sensor has yielded an imaging bandwidth of 33 kHz. This bandwidth is primarily limited by a mechanical resonance of 77 kHz when the cantilever is placed in contact with a surface. Images scanned with a tip velocity of 1 cm/s have been obtained in the constant force mode by using the optical lever to measure the cantilever stress. This is accomplished by subtracting an unwanted deflection produced by the actuator from the net deflection measured by the photodiode using a linear correction circuit. We have verified that the tip/sample force is constant by monitoring the cantilever stress with an implanted piezoresistor. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1742-1744 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a 4 mm2 image taken with a parallel array of 10 cantilevers, an image spanning 6.4 mm taken with 32 cantilevers, and lithography over a 100 mm2 area using an array of 50 cantilevers. All of these results represent scan areas that are orders of magnitude larger than that of a typical atomic force microscope (0.01 mm2). Previously, the serial nature and limited scan size of the atomic force microscope prevented large scale imaging. Our design addresses these issues by using a modular micromachined parallel atomic force microscope array in conjunction with large displacement scanners. High-resolution microscopy and lithography over large areas are important for many applications, but especially in microelectronics, where integrated circuit chips typically have nanometer scale features distributed over square centimeter areas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3674-3676 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Broadband transmission of ultrasound in water using capacitive, micromachined transducers is reported. Transmission experiments using the same pair of devices at 4, 6, and 8 MHz with a signal-to-noise ratio greater than 48 dB are presented. Transmission is observed from 1 to 20 MHz. Better receiving electronics are necessary to demonstrate operation beyond this range. Furthermore, the same pair of transducers is operated at resonance to demonstrate ultrasound transmission in air at 6 MHz. The versatile transducers are made using silicon surface micromachining techniques. Computer simulations confirm the experimental results and are used to show that this technology promises to yield immersion transducers that are competitive with piezoelectric devices in terms of performance, enabling systems with 130 dB dynamic range. The advantage of the micromachined transducers is that they can be operated in high-temperature environments and that arrays can be fabricated at lower cost. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7405-7415 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interdigital (ID) cantilever with two sets of interleaving fingers is an alternative to the conventional cantilever used in the atomic force microscope (AFM). In this paper we present a detailed analysis of the interdigital cantilever and its use as a sensor for the AFM. In this study, we combine finite element analysis with diffraction theory to simulate the mechanically induced optical response of the ID. This model is used to compare this system with the optical lever detector as used in conventional instruments by analyzing the ratio of signal to noise and overall performance. We find that optical detection of the cantilever motion with interdigital fingers has two advantages. When used in conjunction with arrays of cantilevers it is far easier to align. More importantly, it is immune to laser pointing noise and thermally excited mechanical vibrations and this improves the sensitivity as compared to the optical lever. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3944-3946 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a sensor for the atomic force microscope (AFM) where a silicon cantilever is micromachined into the shape of interdigitated fingers that form a diffraction grating. When detecting a force, alternating fingers are displaced while remaining fingers are held fixed. This creates a phase sensitive diffraction grating, allowing the cantilever displacement to be determined by measuring the intensity of diffracted modes. This cantilever can be used with a standard AFM without modification while achieving the sensitivity of the interferometer and maintaining the simplicity of the optical lever. Since optical interference occurs between alternating fingers that are fabricated on the cantilever, laser intensity rather than position can be measured by crudely positioning a photodiode. We estimate that the rms noise of this sensor in a 10 hz–1 kHz bandwidth is ∼0.02 A(ring) and present images of graphite with atomic resolution. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1427-1429 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an atomic force microscope (AFM) with a silicon cantilever partially covered with a layer of zinc oxide (ZnO), we have imaged in the constant force mode by employing the ZnO as both a sensor and actuator. The cantilever deflection is determined by driving the ZnO at the second mechanical resonance while the tip is in contact with the sample. As the tip-sample force varies, the mechanical boundary condition of the oscillating cantilever is altered, and the ZnO electrical admittance is changed. Constant force is obtained by offsetting the ZnO drive so that the admittance remains constant. We have also used the ZnO as an actuator and sensor for imaging in the intermittent contact mode. In both modes, images produced by using the ZnO as a sensor are compared to images acquired with a piezoresistive sensor. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2340-2342 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An expandable system has been developed to operate multiple probes for the atomic force microscope in parallel at high speeds. The combined improvements from parallelism and enhanced tip speed in this system represent an increase in throughput by over two orders of magnitude. A modular cantilever design has been replicated to produce an array of 50 cantilevers with a 200 μm pitch. This design contains a dedicated integrated sensor and integrated actuator where the cells can be repeated indefinitely. Electrical shielding within the array virtually eliminates coupling between the actuators and sensors. The reduced coupling simplifies the control electronics, facilitating the design of a computer system to automate the parallel high-speed arrays. This automated system has been applied to four cantilevers within the array of 50 cantilevers, with a 20 kHz bandwidth and a noise level of less than 50 Å. For typical samples, this bandwidth allows us to scan the probes at 4 mm/s. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2957-2959 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a sensitive detection method for capacitive ultrasonic transducers. Detection experiments at 1.6 MHz reveal a minimum detectable displacement around 2.5×10−4 Å/Hz. The devices are fabricated on silicon using surface micromachining techniques. We made use of microwave circuit considerations to obtain a good displacement sensitivity. Our method also eliminates the dependence of the sensitivity on the ultrasound frequency, allowing the method to be used at low audio frequency and static displacement sensing applications. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1637-1639 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A flexible system for increasing the throughput of the atomic force microscope without sacrificing imaging range is presented. The system is based on a nested feedback loop which controls a micromachined cantilever that contains both an integrated piezoelectric actuator and an integrated thermal actuator. This combination enables high speed imaging (2 mm/s) over an extended range by utilizing the piezoelectric actuator's high bandwidth (15 kHz) and thermal actuator's large response (300 nm/V). A constant force image, where the sample topography exceeds the range of the piezoelectric actuator alone, is presented. It has also been demonstrated that the deflection response of the thermal actuator can be linearized and controlled with an integrated diode. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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