On-chip planar hydrogen sensor with sub-micrometer spatial resolution

We present an on-chip thin film device with a planar geometry suited for electronic detection of atmospheric hydrogen with a spatial resolution well below 1 μm. A titanium stripe of a few nanometers thickness is defined on an insulating substrate and separated into two metallically disconnected electrodes by oxidizing it locally to titanium dioxide with the tip of an atomic force microscope. The titanium dioxide line forms the active area. It is sensitized by a platinum sputtering step such that the two Ti electrodes remain disconnected. It is shown that electroformation processes can interfere with the sensing response above a threshold bias voltage, and the influences of oxygen gas as well as water vapor on the sensing are discussed.