Stability Improvement of a-Si:H Films Deposited in Sqwm-55 kHz Glow Discharge Plasma

Abstract

ABSTRACTIn this work we have used square-wave-modulated (SQWM) low frequency (55kHz) glow discharge plasma for deposition of a-Si:H films and observed a significant stability improvement. To investigate the origin of stability improvement the relation between growth mechanism, film microstructure and metastability was analyzed. It was shown that the use of SQWM-plasma decreases the concentration and average size of inhomogeneities calculated from AFM data while photoconductivity under He-Ne laser illumination (Staebler-Wronski effects) didn't degrade during standard time of experiments. Differential scanning calorimetry (DSC) measurements were carried out and it was found that in SQWM samples hydrogen effusion occurs at higher temperatures than in cw a-Si:H which is connected with increased structural stability of films deposited in SQWM-plasma. Taking into account the high photoconductivity and low defect density of SQWM samples it is concluded that modulating of LF plasma is a perspective method for deposition of stable a-Si:H films and its alloys.