Diamond-like carbon (DLC) is a unique material that exhibits both low friction and high hardness.... more Diamond-like carbon (DLC) is a unique material that exhibits both low friction and high hardness. This material is being considered as a coating for a wide range of applications, including micromachines, where friction and adhesion play a critical role in performance. In the present study, we seek to understand more fully the fundamental relations that govern the tribology of DLC at the nanoscale. In particular, we wish to understand the way in which humidity tends to reduce the superior frictional properties of DLC. Coatings of DLC were deposited on silicon flats using the plasma source ion deposition process. These coatings are studied using atomic force microscopy, where a nanoscale tip is placed in contact with a sample to measure relative adhesive and frictional forces. Dependence of friction and adhesion on relative humidity, load, and sliding history for a DLC / silicon nitride interface are discussed.
Submitted for the MAR07 Meeting of The American Physical Society A nanotribology study of self-ma... more Submitted for the MAR07 Meeting of The American Physical Society A nanotribology study of self-mated vs. unmated interfaces and local packing density effects for octadecyltrichlorosilane monolayers and silicon ERIN FLATER, Luther College, W. ROBERT ASHURST, Auburn University, ROBERT CARPICK, University of Pennsylvania — We use atomic force microscopy (AFM) to determine the frictional properties of nanoscale single asperity contacts involving octadecyltrichlorosilane (OTS) monolayers and silicon. Quantitative AFM measurements are performed using both uncoated and OTS-coated silicon AFM tips and surfaces. Friction is reduced by the presence of the OTS coating, and the overall shape of the friction vs. load plot strikingly depends on whether or not the substrate is coated with OTS, regardless of tip material. Uncoated substrates exhibit the common sublinear dependence, while coated substrates exhibit an unusual superlinear dependence. These results can be explained qualitatively by inv...
The key to the quantification of many modes of AFM is to calibrate the AFM probe properties and s... more The key to the quantification of many modes of AFM is to calibrate the AFM probe properties and specifically the tip shape and the spring or force constant. The spring constant converts the cantilever deflection into a calibrated force and is essential for a wide variety of applications from measuring the rupture force of protein bonds to determining the nanoscale modulus of soft materials [1]. The tip shape is critical for an even broader range of applications including dimensional measurements, nanomechanics, frictional force, chemical force and some electrical and magnetic modes [2]. In this talk I will discuss the progress made at NPL and elsewhere on the metrology and standardisation of these properties. For spring constant calibration there are many published methods, each having its own merits and falling within three broad categories: dimensional, static experimental and dynamic experimental [3]. The progress in all three methods, along with international standardisation act...
In contact resonance force microscopy and related dynamic atomic force microscopy methods, an acc... more In contact resonance force microscopy and related dynamic atomic force microscopy methods, an accurate description of the real-time cantilever dynamics is essential to the mapping of local material properties, such as viscoelasticity, piezo response, and chemical composition. Stiffness and damping variations of the tip-sample contact result in variations in the cantilever's resonance frequency and quality factor as it scans a sample of interest. When measuring characteristics of the resonance, generally, there is a tradeoff between full spectral coverage, best obtained by sweeping the amplitude versus frequency response in the time or frequency domain, and high-speed information, obtained by observing the cantilever response at one or two discrete frequencies, that may be required to track a resonance frequency that changes spatially. Here, we introduce a new option for performing contact resonance force microscopy with a low-cost multifrequency lock-in amplifier system with up to eight simultaneous independent excitation and detection frequencies. We demonstrate how the multifrequency approach can measure contact resonance frequency, quality factor, amplitude, and phase during imaging, with high precision and error estimation, without the need for frequency-tracking feedback. We show, using a wood composite sample, that this multifrequency approach can determine resonance frequency and quality factor, and associated uncertainty. This ability to estimate uncertainty of resonance parameters is not possible with 1 and 2 frequency methods. We further utilize the multifrequency lock-in to develop a novel means of increasing the stiffness range for highly sensitive nanomechanical sensing by dividing the eight lock-in frequencies to monitor two or four simultaneous eigenmodes, each of which is optimized for sensitivity in a particular stiffness regime. Overall, we show how multifrequency lock-in amplifiers with observation frequency chosen to coincide with an expected eigenmode's contact resonance can benefit the characterization of strongly heterogeneous samples, while maintaining fast measurement speed.
UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive c... more UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissertations and theses. Learn more... ProQuest, Toward prediction of MEMS performance: A multiscale approach to understanding friction. ...
... Creator/Author, Carpick, Robert W. (University of Wisconsin Madison, Madison, WI) ; Redmond, ... more ... Creator/Author, Carpick, Robert W. (University of Wisconsin Madison, Madison, WI) ; Redmond, James Michael ; Bora, Can K. ; Street, Mark D. (University of Wisconsin Madison, Madison, WI) ; Plesha, Michael E. (University of Wisconsin Madison, Madison, WI) ; Starr, Michael ...
Diamond-like carbon (DLC) is a unique material that exhibits both low friction and high hardness.... more Diamond-like carbon (DLC) is a unique material that exhibits both low friction and high hardness. This material is being considered as a coating for a wide range of applications, including micromachines, where friction and adhesion play a critical role in performance. In the present study, we seek to understand more fully the fundamental relations that govern the tribology of DLC at the nanoscale. In particular, we wish to understand the way in which humidity tends to reduce the superior frictional properties of DLC. Coatings of DLC were deposited on silicon flats using the plasma source ion deposition process. These coatings are studied using atomic force microscopy, where a nanoscale tip is placed in contact with a sample to measure relative adhesive and frictional forces. Dependence of friction and adhesion on relative humidity, load, and sliding history for a DLC / silicon nitride interface are discussed.
Submitted for the MAR07 Meeting of The American Physical Society A nanotribology study of self-ma... more Submitted for the MAR07 Meeting of The American Physical Society A nanotribology study of self-mated vs. unmated interfaces and local packing density effects for octadecyltrichlorosilane monolayers and silicon ERIN FLATER, Luther College, W. ROBERT ASHURST, Auburn University, ROBERT CARPICK, University of Pennsylvania — We use atomic force microscopy (AFM) to determine the frictional properties of nanoscale single asperity contacts involving octadecyltrichlorosilane (OTS) monolayers and silicon. Quantitative AFM measurements are performed using both uncoated and OTS-coated silicon AFM tips and surfaces. Friction is reduced by the presence of the OTS coating, and the overall shape of the friction vs. load plot strikingly depends on whether or not the substrate is coated with OTS, regardless of tip material. Uncoated substrates exhibit the common sublinear dependence, while coated substrates exhibit an unusual superlinear dependence. These results can be explained qualitatively by inv...
The key to the quantification of many modes of AFM is to calibrate the AFM probe properties and s... more The key to the quantification of many modes of AFM is to calibrate the AFM probe properties and specifically the tip shape and the spring or force constant. The spring constant converts the cantilever deflection into a calibrated force and is essential for a wide variety of applications from measuring the rupture force of protein bonds to determining the nanoscale modulus of soft materials [1]. The tip shape is critical for an even broader range of applications including dimensional measurements, nanomechanics, frictional force, chemical force and some electrical and magnetic modes [2]. In this talk I will discuss the progress made at NPL and elsewhere on the metrology and standardisation of these properties. For spring constant calibration there are many published methods, each having its own merits and falling within three broad categories: dimensional, static experimental and dynamic experimental [3]. The progress in all three methods, along with international standardisation act...
In contact resonance force microscopy and related dynamic atomic force microscopy methods, an acc... more In contact resonance force microscopy and related dynamic atomic force microscopy methods, an accurate description of the real-time cantilever dynamics is essential to the mapping of local material properties, such as viscoelasticity, piezo response, and chemical composition. Stiffness and damping variations of the tip-sample contact result in variations in the cantilever's resonance frequency and quality factor as it scans a sample of interest. When measuring characteristics of the resonance, generally, there is a tradeoff between full spectral coverage, best obtained by sweeping the amplitude versus frequency response in the time or frequency domain, and high-speed information, obtained by observing the cantilever response at one or two discrete frequencies, that may be required to track a resonance frequency that changes spatially. Here, we introduce a new option for performing contact resonance force microscopy with a low-cost multifrequency lock-in amplifier system with up to eight simultaneous independent excitation and detection frequencies. We demonstrate how the multifrequency approach can measure contact resonance frequency, quality factor, amplitude, and phase during imaging, with high precision and error estimation, without the need for frequency-tracking feedback. We show, using a wood composite sample, that this multifrequency approach can determine resonance frequency and quality factor, and associated uncertainty. This ability to estimate uncertainty of resonance parameters is not possible with 1 and 2 frequency methods. We further utilize the multifrequency lock-in to develop a novel means of increasing the stiffness range for highly sensitive nanomechanical sensing by dividing the eight lock-in frequencies to monitor two or four simultaneous eigenmodes, each of which is optimized for sensitivity in a particular stiffness regime. Overall, we show how multifrequency lock-in amplifiers with observation frequency chosen to coincide with an expected eigenmode's contact resonance can benefit the characterization of strongly heterogeneous samples, while maintaining fast measurement speed.
UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive c... more UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissertations and theses. Learn more... ProQuest, Toward prediction of MEMS performance: A multiscale approach to understanding friction. ...
... Creator/Author, Carpick, Robert W. (University of Wisconsin Madison, Madison, WI) ; Redmond, ... more ... Creator/Author, Carpick, Robert W. (University of Wisconsin Madison, Madison, WI) ; Redmond, James Michael ; Bora, Can K. ; Street, Mark D. (University of Wisconsin Madison, Madison, WI) ; Plesha, Michael E. (University of Wisconsin Madison, Madison, WI) ; Starr, Michael ...
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