Mn-doped zinc oxide nanopowders for humidity sensors

Mn-doped ZnO nanopowders have been prepared by the sol–gel technique using zinc and manganese (II) acetates as precursors. The as-prepared nanopowders were characterized by scanning electron microscopy and Micro-Raman spectroscopy. Humidity sensors based on ZnO nanopowders with different Mn concentrations of 0, 1, 3 and 6 at% were fabricated. Linear behavior of the I–V curves at various relative humidity (RH) indicates the ohmic contact between the sensing material and gold electrodes. Sensing characterization reveals that the 6 at% Mn-doped ZnO nanopowders have linear response to RH over the range of 11–95%, which offers higher sensitivity than the commonly reported exponential response. The response and recovery time of the sensor are 6 s and 20 s, respectively, versus the changes of RH from 20% to 80%. The sensors with high reproducibility and stability, as well as high sensitivity throughout a large dynamic range have been obtained.