Nanomechanical Properties of Tungsten Trioxide (WO3) Grown by Atomic Layer Deposition

Tungsten oxide (WO3) films were deposited on p-type Si (100) substrates using atomic layer deposition (ALD) technology with 200 and 600 ALD deposition cycles and furnace annealed at different temperatures. The thicker 600 ALD cycle WO3 samples were annealed at 150, 250, and 300 °C, whereas the thinner 200 ALD cycle sample was annealed at 250 °C. We tested these films for structural and nanomechanical properties and for surface morphology using nanoindentation. The structural and surface properties were explored using scanning electron microscopy and atomic force microscopy. We discuss the influence of the deposition technique on the structure and properties of the WO3 films citing the characteristic features of the ALD technique that was used in the synthesis of the films that are presented in this study. The results depict no significant difference in the hardness among the different films and annealing temperatures. The SEM images exhibit radial cracks in all the samples tested for 1 µm deep indents