Venkat Chandrasekhar
In: Review of Scientific Instruments, vol. 91, pp. 023705, 2020.
Abstract | Links | BibTeX | Tags: scanning probe, Tuning fork
@article{Chandrasekhar2020,
title = {A microchip microcontroller-based transducer controller for non-contact scanning probe microscopy with phase-locked loop, amplitude, and Q control},
author = {Venkat Chandrasekhar},
url = {https://aip.scitation.org/doi/10.1063/1.5131657},
doi = {10.1063/1.5131657},
year = {2020},
date = {2020-02-11},
journal = {Review of Scientific Instruments},
volume = {91},
pages = {023705},
abstract = {An inexpensive yet versatile transducer controller for non-contact scanning probe microscopy (SPM) based on a PIC32 microcontroller from Microchip Technology, Inc is described. In addition to feedback control using the amplitude or phase of the signal from the non-contact transducer, the controller includes a phase-locked loop for frequency-shift feedback, as well as fixed-amplitude, quality factor (Q) control, and self-excitation modes. Apart from the input amplifiers, output buffers, and the Q-control circuit, all other functions of the controller are instantiated in software on the microchip, enabling rapid changes in operating parameters if needed. The controller communicates with a host personal computer via a simple serial connection. The controller has been tested with a quartz tuning-fork transducer but can be used with any oscillating non-contact transducer.},
keywords = {scanning probe, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
An inexpensive yet versatile transducer controller for non-contact scanning probe microscopy (SPM) based on a PIC32 microcontroller from Microchip Technology, Inc is described. In addition to feedback control using the amplitude or phase of the signal from the non-contact transducer, the controller includes a phase-locked loop for frequency-shift feedback, as well as fixed-amplitude, quality factor (Q) control, and self-excitation modes. Apart from the input amplifiers, output buffers, and the Q-control circuit, all other functions of the controller are instantiated in software on the microchip, enabling rapid changes in operating parameters if needed. The controller communicates with a host personal computer via a simple serial connection. The controller has been tested with a quartz tuning-fork transducer but can be used with any oscillating non-contact transducer.
Patrick Krantz; Venkat Chandrasekhar
Etching sharp tips from thin metallic wires for tuning-fork-based scanning probe microscopy Journal Article
In: Journal of Vacuum Science and Technology B, vol. 38, pp. 024004, 2020.
Abstract | Links | BibTeX | Tags: scanning probe, Tuning fork
@article{Krantz2020,
title = {Etching sharp tips from thin metallic wires for tuning-fork-based scanning probe microscopy},
author = {Patrick Krantz and Venkat Chandrasekhar},
url = {https://avs.scitation.org/doi/10.1116/1.5132848},
doi = {10.1116/1.5132848},
year = {2020},
date = {2020-02-07},
journal = {Journal of Vacuum Science and Technology B},
volume = {38},
pages = {024004},
abstract = {Sharp tips are critical for obtaining high resolution images in scanning probe microscopy (SPM), particularly in samples with large variations in topography. For tuning-fork-based SPM, such tips are commonly obtained by electrochemical etching of metallic wires (e.g., tungsten). Electrochemical etching of metallic wires is the preferred means of preparing tips for scanning tunneling microscopy (STM), and techniques for obtaining sharp tips have been investigated extensively. However, the requirements for STM and tuning-fork-based SPM are different. In particular, the wires used in STM are typically 250−500 μm in diameter, while the wires used for tuning-fork-based SPM are usually an order of magnitude narrower in order to minimize loading of the tuning fork: 25−50μm and sometimes down to a few micrometers in diameter. Consequently, many of the recipes developed for etching thicker metallic wires for STM tips do not give optimal results for smaller diameter wires. The authors describe here a modification of the etching circuit of Ibe et al. that significantly improves the reproducibility and reliability of the etching process for thin wires, and discuss the parameters that affect the aspect ratio of produced tips.
},
keywords = {scanning probe, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
Sharp tips are critical for obtaining high resolution images in scanning probe microscopy (SPM), particularly in samples with large variations in topography. For tuning-fork-based SPM, such tips are commonly obtained by electrochemical etching of metallic wires (e.g., tungsten). Electrochemical etching of metallic wires is the preferred means of preparing tips for scanning tunneling microscopy (STM), and techniques for obtaining sharp tips have been investigated extensively. However, the requirements for STM and tuning-fork-based SPM are different. In particular, the wires used in STM are typically 250−500 μm in diameter, while the wires used for tuning-fork-based SPM are usually an order of magnitude narrower in order to minimize loading of the tuning fork: 25−50μm and sometimes down to a few micrometers in diameter. Consequently, many of the recipes developed for etching thicker metallic wires for STM tips do not give optimal results for smaller diameter wires. The authors describe here a modification of the etching circuit of Ibe et al. that significantly improves the reproducibility and reliability of the etching process for thin wires, and discuss the parameters that affect the aspect ratio of produced tips.
Yongho Seo; Paul Cadden-Zimansky; Venkat Chandrasekhar
Low-temperature scanning force microscopy using a tuning fork transducer Journal Article
In: JOURNAL-KOREAN PHYSICAL SOCIETY, vol. 50, no. 2, pp. 378, 2007.
Links | BibTeX | Tags: scanning probe, Tuning fork
@article{seo_low-temperature_2007,
title = {Low-temperature scanning force microscopy using a tuning fork transducer},
author = { Yongho Seo and Paul Cadden-Zimansky and Venkat Chandrasekhar},
url = {https://www.researchgate.net/profile/Yongho_Seo/publication/1852213_Low-temperature_scanning_probe_microscopy_using_a_tuning_fork_transducer/links/02e7e528341b71ee62000000.pdf},
year = {2007},
date = {2007-01-01},
urldate = {2016-12-28},
journal = {JOURNAL-KOREAN PHYSICAL SOCIETY},
volume = {50},
number = {2},
pages = {378},
keywords = {scanning probe, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
Yongho Seo; Paul Cadden-Zimansky; Venkat Chandrasekhar
Low-temperature high-resolution magnetic force microscopy using a quartz tuning fork Journal Article
In: Applied Physics Letters, vol. 87, no. 10, pp. 103103, 2005, ISSN: 00036951.
Links | BibTeX | Tags: Magnetic force microscopy, scanning probe, Tuning fork
@article{seo_low-temperature_2005,
title = {Low-temperature high-resolution magnetic force microscopy using a quartz tuning fork},
author = { Yongho Seo and Paul Cadden-Zimansky and Venkat Chandrasekhar},
url = {http://scitation.aip.org/content/aip/journal/apl/87/10/10.1063/1.2037852},
doi = {10.1063/1.2037852},
issn = {00036951},
year = {2005},
date = {2005-01-01},
urldate = {2015-10-23},
journal = {Applied Physics Letters},
volume = {87},
number = {10},
pages = {103103},
keywords = {Magnetic force microscopy, scanning probe, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
S. Rozhok; S. Jung; V. Chandrasekhar; Xiwei Lin; Vinayak P. Dravid
Atomic force microscopy of nickel dot arrays with tuning fork and nanotube probe Journal Article
In: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, vol. 21, no. 1, pp. 323, 2003, ISSN: 0734211X.
Links | BibTeX | Tags: nanomagnets, Nanotube, scanning probe, Tuning fork
@article{rozhok_atomic_2003,
title = {Atomic force microscopy of nickel dot arrays with tuning fork and nanotube probe},
author = { S. Rozhok and S. Jung and V. Chandrasekhar and Xiwei Lin and Vinayak P. Dravid},
url = {http://scitation.aip.org/content/avs/journal/jvstb/21/1/10.1116/1.1539066},
doi = {10.1116/1.1539066},
issn = {0734211X},
year = {2003},
date = {2003-01-01},
urldate = {2015-10-23},
journal = {Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures},
volume = {21},
number = {1},
pages = {323},
keywords = {nanomagnets, Nanotube, scanning probe, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
S Rozhok; V Chandrasekhar
Application of commercially available cantilevers in tuning fork Scanning Probe Microscopy (SPM) studies Journal Article
In: Solid State Communications, vol. 121, no. 12, pp. 683–686, 2002, ISSN: 0038-1098.
Abstract | Links | BibTeX | Tags: atomic force microscopy, Atomic resolution, Magnetic force microscopy, Nickel dot arrays, Tuning fork
@article{rozhok_application_2002,
title = {Application of commercially available cantilevers in tuning fork Scanning Probe Microscopy (SPM) studies},
author = { S Rozhok and V Chandrasekhar},
url = {http://www.sciencedirect.com/science/article/pii/S0038109802000352},
doi = {10.1016/S0038-1098(02)00035-2},
issn = {0038-1098},
year = {2002},
date = {2002-03-01},
urldate = {2016-12-28},
journal = {Solid State Communications},
volume = {121},
number = {12},
pages = {683--686},
abstract = {We describe the construction and operation of an atomic force microscope based on a tuning fork sensor with probe tips obtained from commercially available cantilevers. Only the tip from the cantilever is mounted on the tuning fork, minimizing the change in resonant frequency and the quality factor Q of the tuning fork. The technique allows the use of a variety of commercially available tips for use in different probe microscopy applications like magnetic force microscopy. The compact design of the microscope and its simple feedback electronics make it well suited for operation in novel environments such as at cryogenic temperatures. We present high resolution atomic force images of graphite surfaces, as well as scanning probe images of magnetic domains and Ni dot arrays taken with this microscope.},
keywords = {atomic force microscopy, Atomic resolution, Magnetic force microscopy, Nickel dot arrays, Tuning fork},
pubstate = {published},
tppubtype = {article}
}
We describe the construction and operation of an atomic force microscope based on a tuning fork sensor with probe tips obtained from commercially available cantilevers. Only the tip from the cantilever is mounted on the tuning fork, minimizing the change in resonant frequency and the quality factor Q of the tuning fork. The technique allows the use of a variety of commercially available tips for use in different probe microscopy applications like magnetic force microscopy. The compact design of the microscope and its simple feedback electronics make it well suited for operation in novel environments such as at cryogenic temperatures. We present high resolution atomic force images of graphite surfaces, as well as scanning probe images of magnetic domains and Ni dot arrays taken with this microscope.
