Encouraged by the results of He and Yang [1], we have designed and fabricated silicon test chips to investigate the piezoresistive properties of both crystalline and polycrystalline nanowires using a top-down approach, in order to comply with conventional fabrication techniques. The test chip consists of 5 silicon nanowires and a reference resistor, each with integrated contacts for electrical 4-point measurements. We show an increase in the piezoresistive effect of 633% compared to bulk silicon. Preliminary temperature measurements indicate a larger temperature dependence of silicon nanowires, compared to bulk silicon. An increase of up to 34% compared to bulk polysilicon is observed in polysilicon nanowires with decreasing dimensions.

Advances in electronics and life sciences have generated interest in "lab-on-a-chip" systems utilizing complementary metal oxide semiconductor (CMOS) circuitry for low-power, portable, and cost-effective biosensing platforms. Here, we present a simple and reliable approach for coating "high-κ" metal oxide dielectric materials with "non-fouling" (protein- and cell-resistant) poly(oligo(ethylene glycol) methyl ether methacrylate (POEGMA) polymer brushes as biointerfacial coatings to improve their relevance for biosensing applications utilizing advanced electronic components. By using a surface-initiated "grafting from" strategy, POEGMA films were reliably grown on each material, as confirmed by ellipsometric measurements and X-ray photoelectron spectroscopy (XPS) analysis. The electrical behavior of these POEGMA films was also studied to determine the potential impact on surrounding electronic devices, yielding information on relative permittivity and breakdown field for POEGMA in both dry and hydrated states. We show that the incorporation of POEGMA coatings significantly reduced levels of nonspecific protein adsorption compared to uncoated high-κ dielectric oxide surfaces as shown by protein resistance assays. These attributes, combined with the robust dielectric properties of POEGMA brushes on high-κ surfaces open the way to incorporate this protein and cell resistant polymer interface into CMOS devices for biomolecular detection in a complex liquid milieu.

We calculate the shear piezocoefficient 44 in p-type Si with a 6 ϫ 6 k · p Hamiltonian model using the Boltzmann transport equation in the relaxation-time approximation. Furthermore, we fabricate and characterize p-type silicon piezoresistors embedded in a ͑001͒ silicon substrate. We find that the relaxation-time model needs to include all scattering mechanisms in order to obtain correct temperature and acceptor density dependencies. The k · p results are compared to results obtained using a recent tight-binding ͑TB͒ model. The magnitude of the 44 piezocoefficient obtained from the TB model is a factor of 4 lower than experimental values; however, the temperature and acceptor density dependencies of the normalized values agree with experiments. The 6 ϫ 6 Hamiltonian model shows good agreement between the absolute value of 44 and the temperature and acceptor density dependencies when compared to experiments. Finally, we present a fitting function of temperature and acceptor density to the 6 ϫ 6 model that can be used to predict the piezoresistance effect in p-type silicon.

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