Micro/nanomechanical characterization of the shell of a scallop, a member of the Pectinidae family, has been carried out. Hardness and elastic modulus were measured by nanoindentation using a nanoindenter. Micro/nanoscale cracks were generated by microindentation using a microindenter. The shell’s crossed lamellar structure and indentation cracks were imaged using an optical microscope, an atomic force microscope and a scanning electron microscope. It was found from nanoindentation tests that the shell exhibits a hardness of about 5 GPa and elastic modulus of about 87 GPa. Nanoindentation resulted in pile-up around the indent. In the middle and bottom layers primary cracks propagate along the first-order lamellar boundaries and numerous secondary cracks branch off along the second-order lamellar boundaries. The additional energy required for crack propagation results from the secondary cracks along the second-order lamellar boundaries. Cracks formed in the top layer of the shell do not show the crack diversion mechanism due to the lack of first-order lamellar organization. Fracture mechanisms were discussed in conjunction with architecture, hardness, elastic modulus, and energy-dissipation during cracking.

Nanomechanical characterization of gold nanowires with a height of 160 nm, width of 350 nm and length of 5 µm has been carried out. Hardness and elastic modulus of the unreleased wires were measured by nanoindentation techniques using a nanoindenter. Post-fabrication mechanical machining of the gold nanowires is demonstrated. An array of nanoscale indents was successfully made on the gold nanowires. Nanochannels, nanoslots and complex nanopatterns were fabricated on a single gold nanowire by directly scratching/sliding the wire surface with the atomic force microscope (AFM) tip. Bending tests were performed to generate nanogaps on the wires using the nanoindenter. Direct machining techniques using a nanoindenter and an AFM should find more applications in the integration and manufacturing of micro/nanodevices.

A thermodynamic model of cavity nucleation and growth in ion-implanted single-crystal BaTiO 3 layer is proposed, and cavity formation is related to the measured mechanical properties to better understand hydrogen implantation-induced layer transfer processes for ferroelectric thin films. The critical radius for cavity nucleation was determined experimentally from blistering experiments performed under isochronal anneal conditions and was calculated using continuum mechanical models for deformation and fracture, together with thermodynamic models. Based on thermodynamic modeling, we suggest that cavities grow toward the cracking criteria at a critical blister size whereupon gas is emitted from ruptured cavities. The main driving force for layer splitting is the reduction of the overall elastic energy stored in the implanted region during the cavity nucleation and growth as the gaseous H 2 entrapped within the cavities is released. Nanoindentation measurements reveal locally the mechanical property changes within the vicinity of a single cavity. Using the measured mechanical properties at the single-cavity level, we developed three-dimensional strain and stress profiles using finite element method.

This paper presents a CMOS stress sensor chip including arrays of piezoresistive sensor elements with high spatial resolution sensitive to the in-plane stress components σxx – σyy and σxy, to the out-of-plane stress σxz and σyz, and to the normal stress sum σΣ = (σxx + σyy)/2 − σzz. For the first time, an application of novel vertical stress sensors is presented, measuring the mechanical stress distributions below electroless nickel (eNi) bumps subject to lateral shear forces and vertical compression. All measured stress values are linearly proportional to the applied forces. The vertical shear stress sensors resolve residual vertical shear stresses of up to 51 MPa in the shear experiments. An adjustable numerical model is established assuming two different Young’s moduli of silicon nitride (SiN) emulating the adhesion between the SiN and eNi. Qualitative agreement of the in-plane stress distributions between experiment and numerical simulation is found in the shear and compression experiments, while good correlation for σΣ is found only for temperature uncompensated stress values in the compression test. The modeling of the absolute values shows differences to the experimental data of about ±30%.

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