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While stress-free and tensile films are well-suited for released in-plane MEMS designs, compressive films are needed for released out-of-plane MEMS structures such as buckled beams and diaphragms. This study presents a characterization of stress on a variety of sputtered and plasma-enhanced chemical vapour deposition (PECVD)-deposited films, including titanium tungsten, invar, silicon nitride and amorphous silicon, appropriate for the field of bistable MEMS. Techniques and strategies are presented (including varying substrate bias, pressure, temperature, and frequency multiplexing) for tuning internal stress across the spectrum from highly compressive (−2300 MPa) to highly tensile (1500 MPa). Conditions for obtaining stress-free films are also presented in this work. Under certain conditions during the PECVD deposition of amorphous silicon, interesting ‘micro-bubbles’ formed within the deposited films. Strategies to mitigate their formation are presented, resulting in a dramatic improvement in surface roughness quality from 667 nm root mean square (RMS) to 16 nm RMS. All final deposited films successfully passed the traditional ‘tape test’ for adhesion.

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This work explores methods for forming and characterizing biomimetic planar membranes composed of amphiphilic block copolymers. The membranes are diblocks and triblocks with hydrophilic blocks of poly(2-methyl-2-oxazoline) (PMOXA) and hydrophobic blocks of poly(dimethylsiloxane) (PDMS). Experiments with the lipid diphytanoyl phosphocholine (DPhPC) serve as a basis for comparison with the polymeric membranes. Phase-contrast microscopy is used to study how membranes evolve over time after their formation. Capacitance measurements as a function of the thinned membrane area (prepared from two separate solvent systems) are performed to clarify the importance of the Plateau-Gibbs border in electrical measurements. Finally, functional reconstitution of the two ion channels, alamethicin and gramicidin, is investigated. Imaging in transmitted phase-contrast mode provides visualization of thinned regions that contain monolayers or bilayers (in the case of diblock copolymer). The specific capacitance measurements yield 0.28 μF/cm with a corresponding thickness of 8.5 nm for PMOXA-PDMS-PMOXA (blocks of 6 PMOXA and 35 PDMS repeat units) formed from a solution of ethanol-decane, 0.55 μF/cm and 4.4 nm in chloroform-toluene, and 0.46 μF/cm and 5.4 nm for the diblock PMOXA-PDMS in ethanol-decane. Alamethicin reconstitution in the block copolymers shows slower channel-forming kinetics with somewhat higher conductance values than found in DPhPC. Gramicidin in the block copolymer shows a slightly voltage-dependent conductance as a function of time, with little stochastic conductance state switching, in contrast to reconstitution in DPhPC where gramicidin switches states at ∼3 Hz.

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