Tailoring of highly porous SnO2 and SnO2-Pd thin films

Tin oxide is a material that attracts attention due to variety of technological applications. The main parameters that influence its properties are morphology, crystalline structure and stoichiometry. Researchers try to develop nanostructured thin films with tunable parameters that would conform its technological applications. Herein, we report on the preparation and characterization of highly porous SnO2 and Pd-doped SnO2 thin films. These films were deposited in the form of nanorods with controllable geometry. Such morphology was achieved by utilizing glancing angle deposition (GLAD) with assisted magnetron sputtering. This arrangement allowed preparation of slanted pillars, zig-zag structure, vertically standing posts, spiral posts and ``bush''-like structures. We calculated that slanted pillars feature the highest surface area among the listed. Then, sets of slanted pillars were deposited and studied in more details. Tin oxide films were thoroughly characterized by means of scanning electron microscopy (SEM), transmission electron microscopy CTEM), X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoelectron spectroscopy (SRPES). The influence of substrate annealing during the deposition and Pd doping on the morphology, crystalline structure and stoichiometry of the films are discussed. GLAD with assisted magnetron sputtering allowed us to deposit broad range of SnO2 nanostructures while annealing of the substrate during deposition affected the films crystallinity. Also, we found out that doping of the SnO2 films with Pd leads to alloy phase formation. These findings can be applied in variety of applications including gas sensing, catalysis, optics and electronics.