One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with ∼90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence.
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We thank W. I. Park for SEM measurements and appreciate S. H. Hong and K. T. Nam for fruitful discussions. The authors gratefully acknowledge support from the Korea Ministry of Intelligence and Economy (contract no. K0004114), the Korea Institute of Science and Technology (grant no. 2E22121) and a research program of the Korea Ministry of Environment. H.G.M. is supported by a Hi Seoul Science Fellowship from the Seoul Scholarship Foundation. H.W.J. is grateful to Seoul National University for financial support.
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