Madison, WI, United States
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Kim-Lee H.-J.,University of Wisconsin - Madison | Kim-Lee H.-J.,Samsung | Carlson A.,University of Illinois at Urbana - Champaign | Grierson D.S.,University of Wisconsin - Madison | And 4 more authors.
Journal of Applied Physics | Year: 2014

Microtransfer printing is a versatile process for retrieving, transferring, and placing nanomembranes of various materials on a diverse set of substrates. The process relies on the ability to preferentially propagate a crack along specific interfaces at different stages in the process. Here, we report a mechanics-based model that examines the factors that determine which interface a crack will propagate along in microtransfer printing with a soft elastomer stamp. The model is described and validated through comparison to experimental measurements. The effects of various factors, including interface toughness, stamp geometry, flaw sizes at the interfaces, and nanomembrane thickness, on the effectiveness of transfer printing are investigated using a fracture-mechanics framework and finite element modeling. The modeling results agree with experimental measurements in which the effects of interface toughness and nanomembranes thickness on the transfer printing yield were examined. The models presented can be used to guide the design of transfer printing processes. © 2014 AIP Publishing LLC.


Moldovan N.,Advanced Diamond Technologies, Inc | Dai Z.,Advanced Diamond Technologies, Inc | Zeng H.,Advanced Diamond Technologies, Inc | Carlisle J.A.,Advanced Diamond Technologies, Inc | And 9 more authors.
Journal of Microelectromechanical Systems | Year: 2012

A common method for producing sharp tips used in scanning probe microscopy (SPM) and other applications involving nanoscale tips is to deposit thin-film materials, such as metals, silicon nitride, or diamond-based films, into four-faceted pyramidal molds that are formed by anisotropic etching into a (100) silicon substrate. This well-established method is capable of producing tips with radii as small as a few nanometers. However, the shape of the tip apex is difficult to control with this method, and wedge-shaped tips that are elongated in one dimension are often obtained. This limitation arises due to the practical difficulty of having four planes intersecting at a single point. Here, a new method for producing three-sided molds for SPM tips is demonstrated through the use of etching in (311) silicon wafers. It is shown that silicon nitride and ultrananocrystalline diamond tips fabricated with this new method are wedge free and sharp (< 10 nm radius), thereby restoring tip molding as a well-controlled manufacturing process for producing ultrasharp SPM tips. © 2012 IEEE.


Grierson D.S.,University of Wisconsin - Madison | Grierson D.S.,systeMech | Liu J.,University of Wisconsin - Madison | Liu J.,Applied Materials | And 3 more authors.
Journal of the Mechanics and Physics of Solids | Year: 2013

The behavior of single-asperity micro- and nanoscale contacts in which adhesion is present is important for the performance of many small-scale mechanical systems and processes, such as atomic force microscopy (AFM). When analyzing such problems, the bodies in contact are often assumed to have paraboloidal shapes, thus allowing the application of the familiar Johnson-Kendall-Roberts (JKR), Derjaguin-Müller-Toporov (DMT), or Maugis-Dugdale (M-D) adhesive contact models. However, in many situations the asperities do not have paraboloidal shapes and, instead, have geometries that may be better described by a power-law function. An M-D-n analytical model has recently been developed to extend the M-D model to asperities with power-law profiles. We use a combination of M-D-n analytical modeling, finite element (FE) analysis, and experimental measurements to investigate the behavior of nanoscale adhesive contacts with non-paraboloidal geometries. Specifically, we examine the relationship between pull-off force, work of adhesion, and range of adhesion for asperities with power-law-shaped geometries. FE analysis is used to validate the M-D-n model and examine the effect of the shape of the adhesive interaction potential on the pull-off force. In the experiments, the extended M-D model is applied to analyze pull-off force measurements made on nanoscale tips that are engineered via gradual wear to have power-law shapes. The experimental and modeling results demonstrate that the range of the adhesive interaction is a crucial parameter when quantifying the adhesion of non-paraboloidal tips, quite different than the familiar paraboloidal case. The application of the M-D-n model to the experimental results yields an unusually large adhesion range of 4-5 nm, a finding we attribute to either the presence of long-range van der Waals forces or deviations from continuum theory due to atomic-scale roughness of the tips. Finally, an adhesion map to aid in analysis of pull-off force measurements of non-paraboloidal tips is presented. The map delineates the cases in which a simplified rigid analysis can be used to analyze experimental data. © 2012 Elsevier Ltd. All rights reserved.


Ryan K.E.,U.S. Naval Academy | Keating P.L.,U.S. Naval Academy | Jacobs T.D.B.,University of Pennsylvania | Grierson D.S.,systeMech | And 3 more authors.
Langmuir | Year: 2014

The work of adhesion is an interfacial materials property that is often extracted from atomic force microscope (AFM) measurements of the pull-off force for tips in contact with flat substrates. Such measurements rely on the use of continuum contact mechanics models, which ignore the atomic structure and contain other assumptions that can be challenging to justify from experiments alone. In this work, molecular dynamics is used to examine work of adhesion values obtained from simulations that mimic such AFM experiments and to examine variables that influence the calculated work of adhesion. Ultrastrong carbon-based materials, which are relevant to high-performance AFM and nano- and micromanufacturing applications, are considered. The three tips used in the simulations were composed of amorphous carbon terminated with hydrogen (a-C-H), and ultrananocrystalline diamond with and without hydrogen (UNCD-H and UNCD, respectively). The model substrate materials used were amorphous carbon with hydrogen termination (a-C-H) and without hydrogen (a-C); ultrananocrystalline diamond with (UNCD-H) and without hydrogen (UNCD); and the (111) face of single crystal diamond with (C(111)-H) and without a monolayer of hydrogen (C(111)). The a-C-H tip was found to have the lowest work of adhesion on all substrates examined, followed by the UNCD-H and then the UNCD tips. This trend is attributable to a combination of roughness on both the tip and sample, the degree of alignment of tip and substrate atoms, and the surface termination. Continuum estimates of the pull-off forces were approximately 2-5 times larger than the MD value for all but one tip-sample pair. © 2014 American Chemical Society.


Jiang Y.,University of Pennsylvania | Grierson D.S.,University of Wisconsin - Madison | Grierson D.S.,systeMech | Turner K.T.,University of Pennsylvania
Journal of Physics D: Applied Physics | Year: 2014

The adhesion of a cylindrical flat punch to a surface due to interatomic forces is a well-known problem that is important in many applications, including indentation experiments and the adhesion of fibrillar structures. Traditionally, the pull-off force has been related to the work of adhesion and punch geometry via the Kendall solution that uses a Griffith energy balance to assess crack propagation and pull-off. More recently, it has been shown that under certain conditions, notably at small punch diameters, the contact can behave in a 'strength-limited' fashion in which the interface separates uniformly rather than via crack propagation. Here, a Maugis-Dugdale-type analysis of power-law-shaped bodies in contact is used to examine the change in behaviour from the fracture-based Kendall solution to strength-limited pull-off for cylindrical flat punches. The transition from fracture-based to strength-limited behaviour is described in terms of a non-dimensional parameter that is similar to previous quantities used to describe the transition and is a function of the punch size, the elasticity of the contact, and the adhesion properties. The results of this relatively simple analysis compare favourably with results from more complex computational simulations. In addition, the results are used to develop a function that quantifies the transition between the Kendall solution and the strength-limited solution in order to facilitate interpretation of adhesion measurements in the transition regime between the two limits. Finally, the power-law analysis is used to assess the sensitivity of the transition to the exact shape of the punch. © 2014 IOP Publishing Ltd.


Jacobs T.D.B.,University of Pennsylvania | Ryan K.E.,U.S. Naval Academy | Keating P.L.,U.S. Naval Academy | Grierson D.S.,systeMech | And 4 more authors.
Tribology Letters | Year: 2013

The effect of atomic-scale roughness on adhesion between carbon-based materials is examined by both simulations and experimental techniques. Nanoscale asperities composed of either diamond-like carbon or ultrananocrystalline diamond are brought into contact and then separated from diamond surfaces using both molecular dynamics simulations and in situ transmission electron microscope (TEM)-based nanoindentation. Both techniques allow for characterization of the roughness of the sharp nanoasperities immediately before and after contact down to the subnanometer scale. The root mean square roughness for the simulated tips spanned 0.03 nm (atomic corrugation) to 0.12 nm; for the experimental tips, the range was 0.18-1.58 nm. Over the tested range of roughness, the measured work of adhesion was found to decrease by more than an order of magnitude as the roughness increased. The dependence of adhesion upon roughness was accurately described using a simple analytical model. This combination of simulation and experimental methodologies allows for an exploration of an unprecedented range of tip sizes and length scales for roughness, while also verifying consistency of the results between the techniques. Collectively, these results demonstrate the high sensitivity of adhesion to interfacial roughness down to the atomic limit. Furthermore, they indicate that care must be taken when attempting to extract work of adhesion values from experimental measurements of adhesion forces. © 2013 Springer Science+Business Media New York.


Grant
Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 225.00K | Year: 2015

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I is the development of a disruptive manufacturing technology that will enable a new class of nanomembrane-based electronic devices to be assembled and integrated on flexible substrates. This innovative technology promises to provide flexible electronics developers and manufacturers a new option for fabricating a wide range of flexible devices that require the integration of high-performance semiconductors. It is anticipated that printing tools and processes based on this core technology will significantly lower the technological barriers that are hindering the widespread manufacture of next-generation flexible devices. This Small Business Innovation Research (SBIR) Phase I project aims to develop a direct printing tool that surpasses the available technologies in terms of both precision and scalability. Current flexible device manufacturing processes do not have the capabilities needed to realize high-performance flexible devices through the integration of high-quality semiconductor materials. Therefore, new strategies are required for fabricating and printing the thin device layers that are essential in emerging high-performance flexible electronics. This project will involve mechanics simulations,tool design and fabrication, process experiments to meet resolution and yield metrics, and establishment of design constraints and operating conditions for a manufacturing process.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: | Award Amount: 225.00K | Year: 2015

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I is the development of a disruptive manufacturing technology that will enable a new class of nanomembrane-based electronic devices to be assembled and integrated on flexible substrates. This innovative technology promises to provide flexible electronics developers and manufacturers a new option for fabricating a wide range of flexible devices that require the integration of high-performance semiconductors. It is anticipated that printing tools and processes based on this core technology will significantly lower the technological barriers that are hindering the widespread manufacture of next-generation flexible devices.

This Small Business Innovation Research (SBIR) Phase I project aims to develop a direct printing tool that surpasses the available technologies in terms of both precision and scalability. Current flexible device manufacturing processes do not have the capabilities needed to realize high-performance flexible devices through the integration of high-quality semiconductor materials. Therefore, new strategies are required for fabricating and printing the thin device layers that are essential in emerging high-performance flexible electronics. This project will involve mechanics simulations,tool design and fabrication, process experiments to meet resolution and yield metrics, and establishment of design constraints and operating conditions for a manufacturing process.


Grant
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2011

The objective of this phase I STTR project is to develop and demonstrate a roll-to-roll process for printing semiconductor and metal nanostructures with lateral dimensions as small as 100 nm on flexible substrates. systeMech will collaborate with the University of Wisconsin-Madison (Prof. M.G. Lagally"s group) to develop and characterize a process for transferring semiconductor and metal nanomembranes, which have been patterned via nanoimprint lithography at the wafer-level, to flexible substrates. The transfer of nanostructures patterned at the wafer-level has significant advantages over direct nanoimprinting, including better etching capabilities and fewer distortion problems. The primary objectives for phase I are: (1) Demonstrating retrieval of patterned nanostructures using a rotating stamp, (2) Demonstrating printing of nanostructures on flexible substrates using a rotating stamp, and (3) Designing a complete roll-to-roll manufacturing process capable of patterning>0.1 square meters. These objectives will be accomplished through mechanical modeling of the manufacturing process, retrieval and printing experiments, and process characterization. systeMech is a newly-formed small business, and the founders have experience in semiconductor manufacturing, mechanics, and nanoengineering. Prof. Max Lagally at the University of Wisconsin-Madison is a leader in nanomembrane processing for electronic and photonic devices and currently leads an AFOSR-funded MURI on nanomembranes.


Grant
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase II | Award Amount: 389.84K | Year: 2013

Flexible electronic and optical devices, including sensors/detectors, waveguides, and photonic crystal structures, have significant promise for improving communication and information processing capabilities in a number of military and commercial applications. However, the development of such flexible devices has been hindered by the lack of effective manufacturing processes for producing these devices on flexible substrates with small feature sizes over large areas. In our Phase I STTR project, we developed and demonstrated the feasibility of a novel rolling-based manufacturing process for directly transferring large-area arrays of inorganic patterned nanomembrane (NM) structures onto flexible substrates. Our approach realizes the fabrication of nanostructured devices on flexible substrates by combining established lithography techniques (optical and/or nanoimprint) with our rollingbased direct-transfer process. During Phase I, arrays of silicon nanomembranes (SiNMs) were patterned on rigid wafers and then transferred from the rigid substrates to flexible polyethylene terephthalate substrates with high yield and excellent placement fidelity. In Phase II, we will develop and optimize a prototype transfer tool that advances the capability of our rolling-based transfer process and enables the transfer of large-area arrays of NM components that have sub-optical-wavelength dimensions. We will demonstrate the transfer of arrays components patterned via nanoimprint lithography over large areas on flexible substrates and will also use the process and prototype tool to fabricate photonic devices on flexible substrate. The prototype tool will serve as a basis for a system that can be commercialized in order to allow industrial, academic, and military customers to manufacture a range of NM-based flexible electronic and photonic devices.

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