ZnO/SnO2 based composite heterostructure for NO2 gas sensing properties

In recent years, interest in heterostructures and research on them has been increasing day by day. While semiconductors mainly exhibit different characteristics, they can exhibit different characteristics when they come together to form a heterostructure, and investigating the reasons for these is of great interest. For this purpose, in this study, such a hetero structure (ZnO/SnO2) was obtained by the Sol-Gel Dip Coating (SGDC) combined method and its effects on its characteristics against NO2 gas were tried to be examined. In this study, SnO2/ZnO composite heterostructures were grown by SGDC method. In this sense, this study is a first in the literature in terms of enlarging this structure with the SGDC technique. The number of SnO2 cycles was kept constant at 1 cycles and the ZnO layers were at different cycles as 1, 2, 3 and 5. The effect of ZnO cycles number on structural, morphological and most importantly NO2 gas detection properties was investigated in the formed heterostructures. In the XRD results, both ZnO and SnO2 peaks were observed and it was determined that these peaks belonged to the hexagonal wurtzite phase for ZnO and to the tetragonal rutile phase for SnO2. The lattice strain and crystallite size were calculated using Williamson-Hall and Scherrer method. The SEM images of ZnO-SnO2 manifest the change in the microstructure with increasing ZnO layer. The microstructure consisted of thin crystalline plates and small round-shape particles. The nano plates and walls shape and size changed with increasing ZnO layers. The operating temperature was defined as 165 °C for all sensors from NO2 gas sensing measurements. The responses of 1 ppm NO2 gas concentrations were calculated as 20 %, 201 %, 1078 % and 676 % for Z1S1, Z2S1, Z3S1 and Z5S1 heterosturucture respectively.