Spontaneous generation of charged clusters of a few nanometers during thermal evaporation of copper

Charged copper clusters of a few nanometers were spontaneously generated under typical copper thin film processing by evaporation at 1573 K. The deposition behavior of these clusters was drastically influenced under an electric field. After deposition for 10 s with a bias of +200, 0, and −200 V applied to the substrate, the number density of clusters was negligible on a positively biased substrate but ∼10 10 mm −2 on neutral and negatively biased substrates. After deposition for 5 min, the film thickness was 10, 100 and 120 nm on positive, neutral and negative substrates, respectively.