Thermally deposited a-Si for solar cells

Remote plasma deposition of thin films with a thermal plasma source offers the advantages of high rates and of choice in at. compn. and structure. The radical flux can be large at low pressure, with small power flux and low substrate temp. With expanding thermal plasmas very high growth rates can be reached with good (and sometimes even with growth rate improving) properties. From measured radical densities in the plasma and at the surface detailed mechanisms are being unraveled. Dissocn. of injected radicals proceeds via charge transfer with ions and dissociative recombination or by abstraction with at. radicals. These processes can be tuned to deliver the appropriate radicals, with not too high and not too low sticking coeff. A discussion of the mechanisms and of the favorable results will be used to indicate future strategies for deposition and surface modification with thermal plasmas