Inversion of NH3 sensor signal and paramagnetic centers of nanocrystalline ZnO(Ga)

Inversion of nanocrystalline ZnO(Ga) sensor signal during ammonia detection is reported for the first time. In the middle temperature region (250-300 °C) the presence of ammonia in air results in increase of resistance. Comparative EPR study and dc conductance measurements allows to attribute this effect to changes in donor and acceptor defect concentration.