Properties of Fast Response Room Temperature ZnO-Si Heterojunction Gas Nanosensors

A highly responsive gas nanosensor operating at room temperature is reported. The nanosensor is formed by self-assembly of ZnO nanoparticles in a polyacrylic matrix spin-cast on p-type (100) Si at room temperature, in a CMOS compatible processing. The ZnO nanoparticles formed n-p heterojunction nanodiodes with the Si substrate that were bias controlled to achieve fast response times and high sensitivity at room temperature. Responsivity and sensitivity were found to be dependent on ZnO nanoparticle size and density. For hydrogen gas under optimum bias conditions and room temperature operation, the nanosensors demonstrated response and recovery times of 8 and 17 s, respectively, for the smaller ZnO nanoparticles, and 60 and 100 s, respectively, for the larger nanoparticles. Sensitivity was consistently higher for the small nanoparticles especially for lower gas concentrations. The self-assembly copolymer technique allowed large area nanofabrication and functionalization of the metal-oxide nanostructures on Si wafers suitable for monolithic integration with CMOS technology.