The method we introduced in 1992 for measuring hardness and elastic modulus by instrumented indentation techniques has widely been adopted and used in the characterization of small-scale mechanical behavior. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques as well as from advances in our understanding of the mechanics of elastic–plastic contact. Here, we review our current understanding of the mechanics governing elastic–plastic indentation as they pertain to load and depth-sensing indentation testing of monolithic materials and provide an update of how we now implement the method to make the most accurate mechanical property measurements. The limitations of the method are also discussed.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400085800

Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology

Characterization of amorphous and nanocrystalline carbon films

Part I: Background and Fundamentals Introduction, Mohamed Gad-el-Hak, University of Notre Dame Scaling of Micromechanical Devices, William Trimmer, Standard MEMS, Inc., and Robert H. Stroud, Aerospace Corporation Mechanical Properties of MEMS Materials, William N. Sharpe, Jr., Johns Hopkins University Flow Physics, Mohamed Gad-el-Hak, University of Notre Dame Integrated Simulation for MEMS: Coupling Flow-Structure-Thermal-Electrical Domains, Robert M. Kirby and George Em Karniadakis, Brown University, and Oleg Mikulchenko and Kartikeya Mayaram, Oregon State University Liquid Flows in Microchannels, Kendra V. Sharp and Ronald J. Adrian, University of Illinois at Urbana-Champaign, Juan G. Santiago and Joshua I. Molho, Stanford University Burnett Simulations of Flows in Microdevices, Ramesh K. Agarwal and Keon-Young Yun, Wichita State University Molecular-Based Microfluidic Simulation Models, Ali Beskok, Texas A&M University Lubrication in MEMS, Kenneth S. Breuer, Brown University Physics of Thin Liquid Films, Alexander Oron, Technion, Israel Bubble/Drop Transport in Microchannels, Hsueh-Chia Chang, University of Notre Dame Fundamentals of Control Theory, Bill Goodwine, University of Notre Dame Model-Based Flow Control for Distributed Architectures, Thomas R. Bewley, University of California, San Diego Soft Computing in Control, Mihir Sen and Bill Goodwine, University of Notre Dame Part II: Design and Fabrication Materials for Microelectromechanical Systems Christian A. Zorman and Mehran Mehregany, Case Western Reserve University MEMS Fabrication, Marc J. Madou, Nanogen, Inc. LIGA and Other Replication Techniques, Marc J. Madou, Nanogen, Inc. X-Ray-Based Fabrication, Todd Christenson, Sandia National Laboratories Electrochemical Fabrication (EFAB), Adam L. Cohen, MEMGen Corporation Fabrication and Characterization of Single-Crystal Silicon Carbide MEMS, Robert S. Okojie, NASA Glenn Research Center Deep Reactive Ion Etching for Bulk Micromachining of Silicon Carbide, Glenn M. Beheim, NASA Glenn Research Center Microfabricated Chemical Sensors for Aerospace Applications, Gary W. Hunter, NASA Glenn Research Center, Chung-Chiun Liu, Case Western Reserve University, and Darby B. Makel, Makel Engineering, Inc. Packaging of Harsh-Environment MEMS Devices, Liang-Yu Chen and Jih-Fen Lei, NASA Glenn Research Center Part III: Applications of MEMS Inertial Sensors, Paul L. Bergstrom, Michigan Technological University, and Gary G. Li, OMM, Inc. Micromachined Pressure Sensors, Jae-Sung Park, Chester Wilson, and Yogesh B. Gianchandani, University of Wisconsin-Madison Sensors and Actuators for Turbulent Flows. Lennart Loefdahl, Chalmers University of Technology, and Mohamed Gad-el-Hak, University of Notre Dame Surface-Micromachined Mechanisms, Andrew D. Oliver and David W. Plummer, Sandia National Laboratories Microrobotics Thorbjoern Ebefors and Goeran Stemme, Royal Institute of Technology, Sweden Microscale Vacuum Pumps, E. Phillip Muntz, University of Southern California, and Stephen E. Vargo, SiWave, Inc. Microdroplet Generators. Fan-Gang Tseng, National Tsing Hua University, Taiwan Micro Heat Pipes and Micro Heat Spreaders, G. P. "Bud" Peterson, Rensselaer Polytechnic Institute Microchannel Heat Sinks, Yitshak Zohar, Hong Kong University of Science and Technology Flow Control, Mohamed Gad-el-Hak, University of Notre Dame) Part IV: The Future Reactive Control for Skin-Friction Reduction, Haecheon Choi, Seoul National University Towards MEMS Autonomous Control of Free-Shear Flows, Ahmed Naguib, Michigan State University Fabrication Technologies for Nanoelectromechanical Systems, Gary H. Bernstein, Holly V. Goodson, and Gregory L. Snider, University of Notre Dame Index

The MEMS Handbook

Functional microporous conducting carbon with a high surface area of about 1230 m2 g−1 is synthesized by single-step pyrolysis of dead plant leaves (dry waste, ground powder) without any activation and studied for supercapacitor application. We suggest that the activation is provided by the natural constituents in the leaves composed of soft organics and metals. Although the detailed study performed and reported here is on dead Neem leaves (Azadirachta indica), the process is clearly generic and applicable to most forms of dead leaves. Indeed we have examined the case of dead Ashoka leaves as well. The comparison between the Neem and Ashoka leaves brings out the importance of the constitution and composition of the bio-source in the nature of carbon formed and its properties. We also discuss and compare the cases of pyrolysis of green leaves as well as un-ground dead leaves with that of ground dead leaf powder studied in full detail. The concurrent high conductivity and microporosity realized in our carbonaceous materials are key to the high energy supercapacitor application. Indeed, our synthesized functional carbon exhibits a very high specific capacitance of 400 F g−1 and an energy density of 55 W h kg−1 at a current density of 0.5 A g−1 in aqueous 1 M H2SO4. The areal capacitance value of the carbon derived from dead (Neem) plant leaves (CDDPL) is also significantly high (32 μF cm−2). In an organic electrolyte the material shows a specific capacitance of 88 F g−1 at a current density of 2 A g−1.

From dead leaves to high energy density supercapacitors

Nanocomposite materials in forms of membranes, fi lms, and coatings are gaining surging interests in structural and functional applications, because they are more effi cient in loading transfer than conventional composites and can substantially eliminate catastrophic failure caused by poor loading transfer between components. To enhance the mechanical properties of polymeric nanocomposites, carbon nanotubes, intercalated clay, graphene, and graphene oxide are added as high-performance reinforcing nanofi llers. For example, ultrahigh toughness was reported for polyvinyl alcohol nanocomposite fi lms fi lled with single-walled carbon nanotubes; [ 1 ] and ultrahigh modulus was reported for crosslinked nanoclay containing nanocomposites. [ 2 ] However, improving toughness is usually achieved by increasing the ultimate strain and compromising the strength, which is not desired for high-performance applications. [ 3 ]

Ultra‐Robust Graphene Oxide‐Silk Fibroin Nanocomposite Membranes

Due to its interesting mechanical properties, silicon carbide is an excellent material for many applications. In this paper, we report on the mechanical properties of amorphous hydrogenated or hydrogen-free silicon carbide thin films deposited by using different deposition techniques, namely plasma enhanced chemical vapor deposition (PECVD), laser ablation deposition (LAD), and triode sputtering deposition (TSD). a-SixC1−x: H PECVD, a-SiC LAD, and a-SiC TSD thin films and corresponding free-standing membranes were mechanically investigated by using nanoindentation and bulge techniques, respectively. Hardness (H), Young’s modulus (E), and Poisson’s ratio (v) of the studied silicon carbide thin films were determined. It is shown that for hydrogenated a-SixC1−x: H PECVD films, both hardness and Young’s modulus are dependent on the film composition. The nearly stoichiometric a-SiC: H films present higher H and E values than the Si-rich a-SixC1−x: H films. For hydrogen-free a-SiC films, the hardness and Young’s modulus were as high as about 30 GPa and 240 GPa, respectively. Hydrogen-free a-SiC films present both hardness and Young’s modulus values higher by about 50% than those of hydrogenated a-SiC: H PECVD films. By using the FTIR absorption spectroscopy, we estimated the Si-C bond densities (NSiC) from the Si-C stretching absorption band (centered around 780 cm−1), and were thus able to correlate the observed mechanical behavior of a-SiC films to their microstructure. We indeed point out a constant-plus-linear variation of the hardness and Young’s modulus upon the Si-C bond density, over the NSiC investigated range [(4–18) × 1022 bond · cm−3], regardless of the film composition or the deposition technique.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400072708

Hardness and Young's modulus of amorphous a -SiC thin films determined by nanoindentation and bulge tests

Diamond-like-carbon (DLC) thin films have been deposited at room temperature on Si substrates by ablation of a graphite target using a KrF excimer laser at intensities ranging from 0.9×108 W/cm2 to 6.0×109 W/cm2. The microstructure of the films was studied by x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The macroscopic properties were evaluated by measurement of their optical constants using in-situ laser reflectometry and their hardness using the continuous stiffness measurement technique. Analysis of the XPS C 1s core level spectra of the DLC films shows that their sp3 hybridized carbon atom content increases with laser intensity up to a maximum value of about 60% obtained at 7.0×108 W/cm2. At higher laser intensities, the sp3 content appears to stabilize at about 53%. Such an evolution of the sp3 content can be understood in terms of the subsurface carbon ions implantation model which has been proposed for ion beam deposited films. On the other hand, Raman analysis indicates that an i...

Effect of laser intensity on the microstructural and mechanical properties of pulsed laser deposited diamond-like-carbon thin films

Amorphous a-SiC films exhibiting excellent hardness and elastic modulus mechanical properties, as determined by nanoindentation, have been deposited by means of the pulsed laser deposition (PLD) technique onto either Si(100) or fused quartz substrates, at deposition temperatures ranging from 20 to 650 °C. The increase of the deposition temperature of PLD a-SiC films (from 20 to 650 °C) markedly enhances both their hardness and their elastic modulus. PLD a-SiC films with hardness and elastic modulus characteristics as high as 50 and 380 GPa, respectively, are obtained at 650 °C deposition temperature. On the microstructural level, the increase of the substrate deposition temperature (from 20 to 650 °C) favors the formation of Si–C bonds, leading thereby to a substantial increase of the Si–C bond density in PLD a-SiC films, as evidenced by Fourier-transform infrared analysis. This work clearly reinforces the concept that the Si–C bond density (NSi–C) is the dominant microstructural parameter that determines...

Linear dependence of both the hardness and the elastic modulus of pulsed laser deposited a-SiC films upon their Si–C bond density

In this work, we report on both the microstructural (sp 3 carbon atoms content) and the mechanical properties (hardness and elastic modulus) of pulsed laser deposited diamond-like-carbon (DLC) thin films. The sp 3 content of the films was determined by analysis of the XPS C 1s core-level signal, and the hardness and elastic modulus were measured by nanoindentation using the continuous stiffness measurement (CSM) technique. By investigating the effect of process parameters, such as deposition temperature and KrF excimer laser intensity on the diamond-like characteristics of the films, we were able to point out that: (1) deposition at 25°C, as opposed to deposition at 300°C, enhances the diamond-like properties of the coatings, (2) the sp 3 content increases with laser intensity up to a maximum value of about 60% obtained at 7.0×10 8 W/cm 2 and (3) the hardness and elastic modulus of the coatings both increase with laser intensity as they respectively reach 44 and 375 GPa at 7.0×10 8 W/cm 2 . It is finally shown that the observed variations in the hardness value and elastic modulus correlate well with the variations of the sp 3 content of the DLC coatings.

M. E. O’Hern

Papers

Hardness and Young's modulus of amorphous a -SiC thin films determined by nanoindentation and bulge tests

Effect of laser intensity on the microstructural and mechanical properties of pulsed laser deposited diamond-like-carbon thin films

Linear dependence of both the hardness and the elastic modulus of pulsed laser deposited a-SiC films upon their Si–C bond density

Synthesis of diamond-like-carbon coatings by pulsed laser deposition: optimization of process parameters