Abstract: Diamond thin films deposited by known PLD processes are composed of diamond crystal grains with a size of about 1 ?m and have an irregular surface. A process for producing an ultraflat nanocrystalline diamond thin film by laser ablation includes creating atomic hydrogen and a supersaturated state of carbon in a space between a target and a substrate in a hydrogen atmosphere inside a reaction chamber at a substrate temperature of 450° C. to 650° C., a laser energy of 100 mJ or more, and a target-substrate distance of 15 to 25 mm to enable the growth of an ultraflat, single-phase nanocrystalline diamond thin film containing substantially no non-diamond component. The hydrogen atmosphere has a sufficient pressure to selectively completely etch off sp2 bond fractions (graphite fractions) deposited on the substrate with sp3 bond fractions remaining.