Paramagnetic Defects in Amorphous Hydrogenated Silicon Carbide and Silicon Carbonitride Films

In this chapter, the nature of the defects and their relation to the incorporation of carbon, hydrogen, nitrogen and thermal treatment were investigated by electron paramagnetic resonance (EPR) spectroscopy for the fundamental insight of the electronic, optical and magnetic characteristics of the amorphous hydrogenated carbonrich silicon-carbon (a-Si1-xCx:H) and amorphous silicon carbonitride (a-SiCxNy) thin films. The paramagnetic defects due to the silicon dangling bonds (SiDBs), carbonrelated defects (CRDs) and K-center with Si-N2Si configuration were revealed in a-Si1-xCx:H films. The observed strong rise of the CRD spin density in annealed a-Si1-xCx:H films is caused by the hydrogen effusion process that takes place at Tann > 400°C. The rise of the CRD density was occurring with the exchange narrowing of its EPR linewidth owing to the appearance of carbon clusters with ferromagnetic ordering. The temperature variation of g-tensor anisotropy, measured at 37 GHz and 140 GHz frequencies for the CRD EPR line in the a-Si1-xCx:H film annealed at 950°C, was interpreted by the existence of graphite-like sp2-hybridized carbon clusters and demagnetization field. Examination of the temperature variation of the integrated intensity of the SiDB and CRD EPR lines was demonstrated that their spin systems reveal superparamagnetic and ferromagnetic features, correspondingly. The CDB and Si-related surface defects were observed in a-SiCxNy. It was found that the CDB spin concentration significantly increases with the increase of the nitrogen content.Due to the temperature variation of the linewidth and integrated intensity of the CDB EPR line, it has been supposed that the antiferromagnetic ordering takes place in the spin system.

Keywords: Amorphous hydrogenated carbon-rich silicon-carbon films, Amorphous silicon carbonitride, Annealing, Anisotropy, Carbon clusters, Carbonrelated defect, Dangling bonds, Demagnetization, EPR, EPR signal intensity, Exchange interaction, Ferromagnetic ordering, High-frequency EPR, Hydrogen, Multifrequency EPR, Nitrogen, SiC, Stoichiometry, Temperature dependence, Thin films.