Amorphous carbon nitride (a-CN) films on Si(100) were grown by plasma-enhanced chemical vapor deposi-tion at room temperature, followed by H2 plasma and thermal annealing treatments, which produced densely and uni-formly distributed nanodot- and nanostripe-like structures. The as-grown CN films showed two weak emission peaksat 2.1 and 2.4eV, but the a-CN nanostructures showed a strong peak at 2.2eV.