A new nucleation method, which is different from bias-enhanced nucleation, was employed for the preparation of (001)-oriented diamond films on untreated, mirror-polished silicon substrates. The nucleation was realized in an electron cyclotron resonance enhanced microwave plasma at a pressure of about 10(-3) Torr which was 4 orders of magnitude lower than that normally used for bias-enhanced nucleation (similar to tens Torr). Scanning electron microscopy and Raman spectroscopy were used to investigate the surface morphology and phase purity of the deposited diamond films. The new findings may provide us a route to further understand the nucleation mechanism of diamond films by chemical vapor deposition.