Using phenylcarbyne polymer as a precursor, flake-like diamond crystals can be grown by conventional hot filament chemical vapor deposition system (HF-CVD) in methane and hydrogen mixture. The flake-like diamond crystals which show two dimensional (layer by layer) growth features formed in the temperature range of 500 degrees C to 700 degrees C. The large flattened diamond crystals several tens of micrometers in size have been observed. It is proposed that a single crystalline diamond layer formed using polymer precursor in the initial nucleation process, followed by homo-epitaxial growth resulting in the formation of single crystalline diamond thin film.