Nanoparticles formation in PECVD discharge is investigated using in situ Optical Emission spectroscopy characterization. Thin films have been deposited from pure HMDSO in Low Frequency reactor for different pressure and power discharge. results showed a relevant relation between some species (SiH, CO and CHO) [1-3] appearances and nanoparticles Formation. In this paper OES spectra were analysed to detect the presence of nanoparticles in plasma. SiH intensity increases were nanoparticles are formed upon the surface of samples. Also, Silicon molecules tend to band with hydrogen to form SiH, like it is shown in Fig. 1.

Figure 1: SiH and H(Beta) Intensities during film deposition at 26 W, 0.8 mbar