Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon

We investigated mechanical properties of TiN as a function of microstructur e varying from nanocrystalline to single crystal TiN films deposited on (10 0) silicon substrates. By varying the substrate temperature from 25 to 700 degreesC during pulsed laser deposition, the microstructure of TiN films ch anged from nanocrystalline (having a uniform grain size of 8 nm) to a singl e crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffract ion and high-resolution transmission electron microscopy. Hardness measurem ents were made using nanoindentation techniques. The nanocrystalline TiN co ntained numerous triple junctions without any presence of amorphous regions . The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sl iding, which is particularly relevant in the case of hard materials such as TiN.