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Your search keyword '"Leseman, Zayd C."' showing total 137 results
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137 results on '"Leseman, Zayd C."'

2. Thermal conductivity measurements of sub-surface buried substrates by steady-state thermoreflectance

Author

Hoque, Md Shafkat Bin, Koh, Yee Rui, Aryana, Kiumars, Hoglund, Eric, Braun, Jeffrey L., Olson, David H., Gaskins, John T., Ahmad, Habib, Elahi, Mirza Mohammad Mahbube, Hite, Jennifer K., Leseman, Zayd C., Doolittle, W. Alan, and Hopkins, Patrick E.

Subjects
Physics - Instrumentation and Detectors
Abstract

Measuring the thermal conductivity of sub-surface buried substrates are of significant practical interests. However, this remains challenging with traditional pump-probe spectroscopies due to their limited thermal penetration depths (TPD). Here, we experimentally and numerically investigate the TPD of recently developed optical pump-probe technique steady-state thermoreflectance (SSTR) and explore its capability for measuring the thermal properties of buried substrates. The conventional definition of the TPD does not truly represent the upper limit of how far beneath the surface SSTR can probe. For estimating the uncertainty of SSTR measurements of a buried substrate a priori, sensitivity calculations provide the best means. Thus, detailed sensitivity calculations are provided to guide future measurements. Due to the steady-state nature of SSTR, it can measure the thermal conductivity of buried substrates typically inaccessible by traditional pump-probe techniques, exemplified by measuring three control samples. We also discuss the required criteria for SSTR to isolate the thermal properties of a buried film. Our study establishes SSTR as a suitable technique for thermal characterizations of sub-surface buried substrates in typical device geometries.

Published
2021
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3. Atomistic Field Theory for contact electrification of dielectrics

Author

Abdelaziz, Khalid M, Chen, James, Hieber, Tyler J, and Leseman, Zayd C

Subjects
Condensed Matter - Materials Science
Abstract

The triboelectrification of conducting materials can be explained by electron transfer between different Fermi levels. However, triboelectrification in dielectrics is poorly understood. The surface dipole formations are shown to be caused by the contact-induced surface lattice deformations. An Atomistic Field Theory (AFT) based formulation is utilized to calculate the distribution of the polarization, electric and potential fields. The induced fields are considered as the driving force for charge transfer. The simulation results show that a MgO/BaTiO3 tribopair can generate up to 104 V/cm^2, which is comprable with the data in the published literature., Comment: It is to be published in Journal of Electrostatics

Published
2018
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13. Thermal conductivity measurements of sub-surface buried substrates by steady-state thermoreflectance

Author

Hoque, Md Shafkat Bin, primary, Koh, Yee Rui, additional, Aryana, Kiumars, additional, Hoglund, Eric R., additional, Braun, Jeffrey L., additional, Olson, David H., additional, Gaskins, John T., additional, Ahmad, Habib, additional, Elahi, Mirza Mohammad Mahbube, additional, Hite, Jennifer K., additional, Leseman, Zayd C., additional, Doolittle, W. Alan, additional, and Hopkins, Patrick E., additional

Published
2021
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15. High In-Plane Thermal Conductivity of Aluminum Nitride Thin Films

Author

Hoque, Md Shafkat Bin, primary, Koh, Yee Rui, additional, Braun, Jeffrey L., additional, Mamun, Abdullah, additional, Liu, Zeyu, additional, Huynh, Kenny, additional, Liao, Michael E., additional, Hussain, Kamal, additional, Cheng, Zhe, additional, Hoglund, Eric R., additional, Olson, David H., additional, Tomko, John A., additional, Aryana, Kiumars, additional, Galib, Roisul, additional, Gaskins, John T., additional, Elahi, Mirza Mohammad Mahbube, additional, Leseman, Zayd C., additional, Howe, James M., additional, Luo, Tengfei, additional, Graham, Samuel, additional, Goorsky, Mark S., additional, Khan, Asif, additional, and Hopkins, Patrick E., additional

Published
2021
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18. A fracture mechanics description of stress-wave repair in stiction-failed microcantilevers: theory and experiments

Author

Leseman, Zayd C., Koppaka, Sai B., and Mackin, Thomas J.

Subjects
Fracture mechanics -- Research, Strains and stresses -- Observations, Stress relaxation (Materials) -- Observations, Stress relieving (Materials) -- Observations, Microelectromechanical systems -- Equipment and supplies, Microelectromechanical systems -- Mechanical properties, Engineering and manufacturing industries, Science and technology
Abstract

Microcantilever beams are frequently utilized as sensor platforms in microelectromechanical system devices. These highly compliant surface-micromachined structures generally fail by adhering to the underlying substrate during processing or subsequent operation. Such failures, which are commonly known as 'stiction' failures, can be prevented or repaired in a number of ways, including low adhesion coatings, rinsing with low surface energy agents, and active approaches such as laser irradiation. Gupta et al. [J. Microelectromech. Syst. vol. 13, pp. 696-700, 2004] recently demonstrated that stress waves could be used to repair stiction-failed structures. This paper extends the work of Gupta et al. by developing a fracture mechanics theory of the repair process and compares that theory with corresponding experiments. We show that: 1) incremental crack growth is associated with each laser pulse, the extent of which is directly related to the laser fluence; 2) repeated pulsing fully repairs all of the microcantilevers; and 3) a fracture mechanics model accurately predicts the observed experimental results. [1664] Index Terms--Fracture mechanics, laser, stiction, stress waves.

Published
2007

19. On the use of structural vibrations to release stiction failed MEMS

Author

Savkar, Amit A., Murphy, Kevin D., Leseman, Zayd C., Mackin, Thomas J., and Begley, Matthew R.

Subjects
Microelectromechanical systems -- Design and construction, Vibration -- Analysis, Engineering and manufacturing industries, Science and technology
Abstract

This paper identifies dynamic excitation parameters that promote decohesion of stiction-failed microcantilevers. The dynamic response of 's-shaped' adhered beams subjected to harmonic loading is described using modal analysis; this model is then used to predict the onset of debonding in the context of a critical interface energy. These theoretical results are used to rationalize preliminary experiments, which illustrate that dynamic excitation may be used to affect partial or complete repair of stiction-failed microcantilevers. The theoretical results provide fundamental insight regarding regimes where resonant effects trigger debonding and can serve as a potential mechanism for stiction repair. The models illustrate that driving a structure at resonance is usually beneficial with regards to debonding. However, this is not universally true; there is no benefit to driving a device at frequencies with unfavorable mode-shapes. Thus, these results provide a reasonable physical and mathematical explanation for the preliminary experimental results, while providing a roadmap for identifying parameters in future tests. Index Terms--Repair, stiction failure, vibrations.

Published
2007

20. Experimental measurements of the strain energy release rate for stiction-failed microcantilevers using a single-cantilever beam peel test

Author

Leseman, Zayd C., Carlson, Steven P., and Mackin, Thomas J.

Subjects
Microelectromechanical systems -- Design and construction, Polysilicon -- Mechanical properties, Polysilicon -- Electric properties, Engineering and manufacturing industries, Science and technology
Abstract

In this paper, we present experimental measurements of the strain energy release rate for stiction-failed polysilicon microcantilevers using a newly developed single cantilever beam peel test. Our experiments show that dry-contacting microcantilevers adhere exclusively as tip-stuck, 'arc-shaped' stiction failures, while adhesion under 'wet' conditions generate exclusively 's-shaped' stiction failures. Microcantilevers were 'peeled' from the substrate under displacement control using a piezoelectric actuator attached to one end of an array of microcantilever beams. The crack length was monitored using interferometric imaging, and related to the applied displacement using established equations from linear elastic fracture mechanics. The pull-off forces associated with 'arc-shaped' stiction failures were an average value of 89.7 nN, for 1000 [micro]m long beams, and an average value of 123 nN for 1500 [mirco]m long beams. Adhesion energies for s-shaped failures were measured as 13.7 mJ/[m.sup.2] for IPA released beams and 15.4 mJ/[m.sup.2] for deionized water released beams. These values are in good agreement with previous measurements. The proposed experimental method enables application of a simple fracture mechanics model using a standard specimen geometry. These experiments, using both wet and dry adhesion failure conditions, show that the quality of the adhesive failure depends upon the magnitude of the forces pulling the microcantilever into contact with the underlying substrate. Index Terms--Cantilever, peel test, stiction, strain energy.

Published
2007

27. Preface

Author

Khraishi, Tariq A., Al-Haik, Marwan S., and Leseman, Zayd C.

Published
2008
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