New insights into controlling boundary layer thickness are investigated in growth of hierarchical metal oxides on a tilted substrate. Cr2O3-decorated ZnO nanostructures with different densities and lengths were successfully synthesized by a combination of chemical and physical techniques and investigated as a H2S sensor. By tilting the substrate relative to the incoming gas flow, a boundary layer of non-uniform thickness was created over the substrate. The sensing results of Cr2O3-ZnO hierarchical structures indicated that decoration of the Cr2O3 nano-particles on ZnO nanostructures significantly enhanced the response to H2S, Liquefied petroleum gas and ethanol at low temperature.
