HIGH-QUALITY HYDROGENATED AMORPHOUS-SILICON CARBON LAYERS AS OBTAINED BY A PARTICULAR PHOTOCHEMICAL VAPOR-DEPOSITION METHOD

A new photochemical vapor deposition system is used to deposit thin films of hydrogenated amorphous silicon carbon alloys (a-SiC:H). This system employs a newly designed excimer lamp that can work with Ar, Kr, and Xe or a deuterium lamp. The deposition is carried out by means of direct photolysis of Si2H6, avoiding by this way contamination problems connected with the Hg sensitization of the process. The presence of carbon in the films can be related to the presence of fomblin oil on the MgFe2 window. Even if the compositional disorder induced by C atoms is not in principle negligible, the defect density, as inferred by photothermal deflection spectroscopy (PDS), is low, if compared to plasma deposited a-Si:H films with approximately the same thickness. This can be related to the absence of ion bombardment in photoCVD: this peculiarity suggests the possibility of employing photoCVD in the deposition of high quality layers in which the interface states can be dramatically reduced.