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We developed a lead oxide PbO film of ~170 nm thickness by RF sputtering on a fused silica substrate. When this film sample is annealed in an oven at 650 °C for 4 min, its physical thickness measured using a surface profiler decreases to ~163 nm, but its optical film thickness determined using a spectrophotometer increases to 382 nm. This fact implies that PbO will diffuse into the fused silica substrate and form a PbO–SiO2 mixed film that is a graded-index planar waveguide with two transverse electric (TE) modes at 633 nm wavelength. Although the Maker fringe patterns of both fused silica and PbO–SiO2 mixed film samples thermally poled at 6 kV, 275 °C and 30 min look similar, we speculate that second-order nonlinearity exists in poled PbO–SiO2 mixed film because of the higher refractive index contrast at the air-to-film interface. A nonlinear optical coefficient of approximately 1 pm/V in poled PbO–SiO2 mixed film is calculated using a double-step nonlinear profile and grid search fitting technique. The induced second-order nonlinearity is stable for at least several months.

In this study, distinct regions of trapped charges on glass substrates created by electron beam bombardment were utilized to attract and to immobilize DNA molecules. The negatively charged DNA molecules were attracted by the positive charge layer beneath the substrate surface resulting from escape of secondary electrons. With this mechanism, we demonstrated high-precision patterning of unmodified DNA molecules, independent of the length, sequence, and number of DNA strands, and with an attachment to the glass surface strong enough to withstand vigorous washing with water. DNA patterns with the line width of 50 nm were achieved.

Recent developments in the analysis and the application of DNA often require the stretching of individual DNA molecules to specific surfaces. We propose and demonstrate a method for the positioning of unmodified extended DNA molecules. A local microscopic circular flow is created by a non-uniform AC field and utilized to stretch the λ-DNA on a gold surface or between gold electrodes. The electrical-field amplitude and frequency responses of DNA motion are studied. The method can be applied to position the DNA with accuracy on a microscopic scale while requiring no modification of the DNA for terminal binding. With a diluted DNA solution, the number of DNA molecules across the electrodes is controllable and the positioning of a single extended DNA across electrodes is achievable.

The stiffness of a micromachined beam is usually restricted to the thickness of the thin-film materials. In this research, the rib-reinforced beam is proposed to increase the bending stiffness of thin-film micromachined structures. The increase of the bending stiffness of micromachined cantilevers has been demonstrated through analytical and experimental approaches. The fabrication processes required for the structure are compatible with the standard bulk micromachining processes. The primary contribution of the proposed design is that it can remarkably increase the bending stiffness of the micromachined structure without changing the thickness of the films. Hence, the design of the micromachined structure becomes more flexible. In application of the rib-reinforced structure, a micromachined lever mechanism is also designed and fabricated.

A series of Parylene C film/silicon substrate bilayer microcantilever beams were fabricated by microelectromechanical processes for the study of residual stresses. The Parylene C films of 2 µm thickness were deposited on the Si substrates with various thicknesses. After deposition at room temperature, deflection of the beam was observed with deposited Parylene C on the concave side. While Parylene C has a higher coefficient of thermal expansion than Si, this deflection is believed to result from the thermal mismatch between Parylene C and Si, and the temperature of monomer gas (which is formed at 690 °C) flowing across the sample could be higher than 25 °C. It is estimated to be 73 °C based on the fitting of the curvature versus substrate thickness relation between the measurements and analytical solutions. In this case, Parylene C films are subjected to tension. In addition, the residual stress in the Parlyene C film decreases with decreasing substrate thickness.

This study reports a novel micro electrostatic vertical comb-drive actuator (VCA) driven by the photovoltaic effect that results from incident light. The vertical comb electrodes have a pn junction structure (named pn-combs). The VCA with pn-combs can be driven by the photovoltaic effect. The combination of the photovoltaic effect and reverse bias can further increase the driving amplitude of the VCA. To demonstrate the feasibility of the proposed concept, the VCA with pn-combs was fabricated on an epitaxial silicon wafer (epi-wafer) and successfully driven resonantly by intensity-modulated laser light. The first torsional mode of a typical fabricated VCA is at 1.46 kHz. Moreover, VCA driven using (1) optical driving, and (2) optical driving with dc reverse bias, were also demonstrated. The angular displacement of the VCA was ±3.8 m deg by optical driving. The angular displacement of the VCA significantly increased to ±41 m deg after applying an additional dc reverse bias of 5 V. (Some figures in this article are in colour only in the electronic version)