Investigation of the Nanomechanical Properties of Crystalline Anatase Titanium Dioxide Films Synthesized Using Atomic Layer Deposition

Abstract

Crystalline titanium dioxide (TiO2) polycrystalline films of 500 nm thickness were synthesized using atomic layer deposition (ALD) on p-type Si (100) substrates. The crystal structure, phase purity, film thickness and morphology were characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The nanomechanical properties were measured using nanoindentation. Due to low temperature ALD deposition, XRD revealed a single anatase phase growth. FE-SEM images indicate columnar grain structure growth primarily in the vertical directions. The hardness was measured as 5 GPa at 24% film thickness, which is considerably softer compared to the reported benchmark values of the well-known rutile phase of ~ 12 GPa. The elastic moduli were estimated as 138 and 145 GPa for samples A and B, respectively. Samples A and B are identical except that sample A is slightly thicker; the slight difference in thickness has no influence on the results.