The technique of simultaneous twin-beam processing has been investigated and used to deposit thin films of silicon on a silicon substrate.

An argon ion laser was used to create a large concentration of free carriers in the Si conduction band. These carriers were spatially localized in the beam spot on the surface of the substrate. The effective absorption coefficient of 10.6 radiation (carbon dioxide laser) can thus be increased to greater than 104 cm−1 . Experimental evidence illustrates that this efficient coupling of the high-power CO2 radiation (10–30 W) to the otherwise non-absorbing silicon can be totally controlled by the low-power (1–4 W) argon ion incident beam. The difference between absorption increase due to optically created carriers and thermally created carriers is clearly illustrated.

This synergistic effect has been used to induce pyrolytic deposition of Si from SiH4 non-flowing gas onto a Si substrate. Lines and spots of various widths and thicknesses have been grown by the controlling low-power argon ion beam spot.

Preliminary investigations on the quality of the deposits using i.r. spectroscopy ellipsometry, SEM and Auger analysis have been carried out.