Structure, fabrication process, and switching mechanism of the Pd/Cr bimorph chemo-mechanical H2 switch. (IMAGE)
Caption
Structure, fabrication process, and switching mechanism of the Pd/Cr bimorph chemo-mechanical H2 switch. a Schematic of the Pd/Cr bimorph chemo-mechanical H2 switch composed of Pd/Cr bilayer cantilevers and a predefined nanogap. b Lithography-free fabrication flow: (i) directional electrospinning of aligned sacrificial PEO nanofibers on thermally oxidized Si using field-assisted alignment; (ii, iii) tilt angle e-beam deposition of Cr (20 nm) and Pd (50 nm) at θ = 15°, 30°, 45°, and 60° to form bilayer cantilevers; (iv) additional normal-incidence Pd deposition (30/40/50 nm) to extend the free end for reliable contact upon bending; (v) release by immersion and bath sonication in DI water (3 h) to dissolve the sacrificial PEO and open nanogaps; (vi) IPA displacement (3 h) to lower surface tension and suppress stiction, followed by oven drying. c Operating principle (no H2): Pd remains in the α-phase; the cantilevers stay unbent and the nanogap is open (I = 0). d Operating principle under H2: Pd transforms to β-PdHx (~3.5% lattice expansion), inducing bimorph bending, contact formation with the lower electrode, and the onset of current (I = ISignal).
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Microsystems & Nanoengineering
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