In situ wear studies of surface micromachined interfaces subject to controlled loading

Flater, Erin E.; Corwin, Alex D.; Boer, Maarten P. de; Carpick, Robert W.

doi:10.1016/j.wear.2005.02.070

Cited by 46 publications

(40 citation statements)

References 34 publications

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“…Based on previous studies of nanotractor friction and wear, we hypothesize that wear of the sliding interface begins as the FOTAS coating breaks down [14] within the contact zone and advances via moderate gouging, Si material removal (including the removal of individual grains as observed in the sidewall friction tests [23]), and debris formation within and around the contacting regions. Debris is mechanically polished and becomes oxidized to amorphous SiO 2 , as does the wear scar.…”

Section: µMmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of Microscale Wear in a Polysilicon-Based MEMS Device Using AFM and PEEM–NEXAFS Spectromicroscopy

et al. 2009

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Mechanisms of microscale wear in siliconbased microelectromechanical systems (MEMS) are elucidated by studying a polysilicon nanotractor, a device specifically designed to conduct friction and wear tests under controlled conditions. Photoelectron emission microscopy (PEEM) was combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) to quantitatively probe chemical changes and structural modification, respectively, in the wear track of the nanotractor. The ability of PEEM-NEXAFS to spatially map chemical variations in the nearsurface region of samples at high lateral spatial resolution is unparalleled and therefore ideally suited for this study. The results show that it is possible to detect microscopic chemical changes using PEEM-NEXAFS, specifically, oxidation at the sliding interface of a MEMS device. We observe that wear induces oxidation of the polysilicon at the immediate contact interface, and the spectra are consistent with those from amorphous SiO 2 . The oxidation is correlated with gouging and debris build-up in the wear track, as measured by AFM and scanning electron microscopy (SEM).Keywords Microscale wear Á Microelectromechanical systems (MEMS) Á Nanotractor Á Photoelectron emission microscopy (PEEM) Á Atomic force microscopy (AFM)

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Section: µMmentioning

confidence: 99%

“…Coating the polysilicon surfaces of the nanotractor with this film is known to improve wear performance [14], though premature device failure still occurs. Understanding the failure mechanism(s) of this microfabricated tribometer may guide future design of microscale tribosystems.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Microscale Wear in a Polysilicon-Based MEMS Device Using AFM and PEEM–NEXAFS Spectromicroscopy

et al. 2009

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“…The most recent example of a MEMS tribometer in the literature is the ''Nanotractor'', developed by De Boer et al [22][23][24][25][26][27]. The nanotractor is a micromachined ''inchworm actuator'' that can walk over the surface in small steps against a restoring spring.…”

Section: Mems Tribometersmentioning

confidence: 99%

The Leiden MEMS Tribometer: Real Time Dynamic Friction Loop Measurements With an On-Chip Tribometer

Spengen

Frenken

2007

Tribol Lett

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On-chip MEMS tribometer devices until now have been much less sophisticated for dynamically sensing frictional forces than their FFM (friction force microscope) counterparts. In this article, we present a MEMS-based tribometer that can be used to measure dynamically, onchip and in-situ, the frictional properties of MEMS-scale contact geometries. The device provides the first FFM-like friction loops with contacting MEMS sidewall surfaces. Depending on the normal load two regimes of operation are identified. At low and intermediate loads, the frictional behaviour reflects wear-less relative motion of the silicon oxide surfaces of the MEMS device and we observe repeatable, irregular stick-slip behaviour, related to the surface roughness. At very high loads, wear causes changes in the topography of the contacting surfaces.

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“…Details of this technique are given in ref. [5]. Our results indicate that for the FOTAS film used here, µ d =0.28 while µ s =0.34.…”

Section: True Dynamic Friction Measurementmentioning

confidence: 52%

High fidelity frictional models for MEMS.

Carpick

Reedy²,

Bitsie³

et al. 2004

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The primary goals of the present study are to: 1) determine how and why MEMSscale friction differs from friction on the macro-scale, and 2) to begin to develop a capability to perform finite element simulations of MEMS materials and components that accurately predicts response in the presence of adhesion and friction.Regarding the first goal, a newly developed nanotractor actuator was used to measure friction between molecular monolayer-coated, polysilicon surfaces. Amontons' law does indeed apply over a wide range of forces. However, at low loads, which are of relevance to MEMS, there is an important adhesive contribution to the normal load that cannot be neglected. More importantly, we found that at short sliding distances, the concept of a coefficient of friction is not relevant; rather, one must invoke the notion of "pre-sliding tangential deflections" (PSTD). Results of a simple 2-D model suggests that PSTD is a cascade of small-scale slips with a roughly constant number of contacts equilibrating the applied normal load.Regarding the second goal, an Adhesion Model and a Junction Model have been implemented in PRESTO, Sandia's transient dynamics, finite element code to enable asperity-level simulations. The Junction Model includes a tangential shear traction that opposes the relative tangential motion of contacting surfaces. An atomic force microscope (AFM)-based method was used to measure nano-scale, single asperity friction forces as a function of normal force. This data is used to determine Junction Model parameters. An illustrative simulation demonstrates the use of the Junction Model in conjunction with a mesh generated directly from an atomic force microscope (AFM) image to directly predict frictional response of a sliding asperity.Also with regards to the second goal, grid-level, homogenized models were studied. One would like to perform a finite element analysis of a MEMS component assuming nominally flat surfaces and to include the effect of roughness in such an analysis by using a homogenized contact and friction models. AFM measurements were made to determine statistical information on polysilicon surfaces with different roughnesses, and this data was used as input to a homogenized, multi-asperity contact model (the classical Greenwood and Williamson model). Extensions of the Greenwood and Williamson model are also discussed: one incorporates the effect of adhesion while the other modifies the theory so that it applies to the case of relatively few contacting asperities.5

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In situ wear studies of surface micromachined interfaces subject to controlled loading

Cited by 46 publications

References 34 publications

Characterization of Microscale Wear in a Polysilicon-Based MEMS Device Using AFM and PEEM–NEXAFS Spectromicroscopy

Characterization of Microscale Wear in a Polysilicon-Based MEMS Device Using AFM and PEEM–NEXAFS Spectromicroscopy

The Leiden MEMS Tribometer: Real Time Dynamic Friction Loop Measurements With an On-Chip Tribometer

High fidelity frictional models for MEMS.

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