Natural diamond is one of the most rare and precious gemstones known to mankind. In addition, it is also known for its exceptional material properties including extreme heat conducting capacity at room temperature, chemical inertness to aqueous environments and excellent electrical insulation that are interesting to both fundamental as well as applied sciences. These attractive properties of natural diamond and the difficulty of its mining led to the production of synthetic diamond via high pressure and high temperature (HPHT) and chemical vapour deposition (CVD) techniques. Gradually, with the utilization and improvements of these techniques, there has been a growing interest in the research community to exploit the superior material properties of diamonds. In this thesis, the chemical, electronic and mechanical properties of CVD diamonds were investigated to mainly elucidate their fundamental properties and also to evaluate their commercial applicability in terms of processing. The thesis is divided into three sections: the surface chemistry (Chapter 2), the bulk (opto)electronic properties (Chapters 3, 4 and 5) and the mechanical properties of thin films (Chapter 6). All chapters deal with CVD diamond, typically nanocrystalline diamond.