Features of the structure and defect states in hydrogenated polymorphous silicon films

The structural and electronic properties of thin hydrogenated polymorphous silicon films obtained by plasma-enhanced chemical vapor deposition from hydrogen (H$_2$) and monosilane (SiH$_4$) gas mixture have been studied by means of transmission electron microscopy, electron paramagnetic resonance (EPR) spectroscopy, and Raman spectroscopy. It has been established that the studied films consist of the amorphous phase containing silicon nanocrystalline inclusions with the average size on the order of $4$–$5$ nm and the volume fraction of $10\%$. A signal was observed in the hydrogenated polymorphous silicon films during the EPR investigation that is attributed to the electrons trapped in the conduction band tail of microcrystalline silicon. It has been shown that the introduction of a small fraction of nanocrystals into the amorphous silicon films nonadditively changes the electronic properties of the material.