Investigation of a single Pd nanowire for use as a hydrogen sensor.

Interest in nanowire technology has grown significantly over the past several years, due to their potentially broad applications in optics, electronics, and sensors (e.g., resonators, molecular detection, nanoconnectors, biosensors, and gas sensors). Due to their small size, sensitivity, real-time detection, and ultra-low power demands, nanowire sensors are being investigated for detection of a wide range of chemical and biochemical species. The techniques used to fabricate these sensors include laser ablation cluster formation, focused ion-beam etching of electrodes to create a small gap ( 100 nm), use of ion-track membranes, use of alumina templates, and electrochemical step-edge decoration. These techniques have drawbacks of limited controllability and manufacturability, therefore reliable and controllable nanowire fabrication remains a significant challenge. We have previously reported a method of electrodepositing Pd wires with micrometer diameters and conducting polymer nanowires of polyaniline and polypyrrole with diameters of 100 nm. In this work, single Pd nanowires are fabricated by electrodeposition in electrolyte channels patterned with electron-beam lithography, and hydrogen sensing is demonstrated. This fabrication technique can produce nanowires with controlled dimensions, positions, alignments, and chemical compositions, and potentially enables the use of a wide range of materials for creating arrays of singlenanowire sensors. Additionally, the growth of nanowires using this technique would allow for easy integration with existing silicon technology. Figure 1 shows SEM images of typical electrodeposited nanowires between electrodes. The magnified image in Figure 1b shows a single Pd nanowire with a diameter ranging from 70 to 85 nm. An EDS (energy dispersive spectroscopy) elemental analysis detected only Pd metal in the nanowire.