Theory and calculation To assist interpretation

The crystallite size ‘D’ was about 86 nm for the samples deposited at 0.05 FB boron gas flow and which decreased to 36 nm for the films deposited from 0.30 FB boron concentration. The decrease in crystallite size with increase in diborane flow suggests that the dopant B2H6 induces an amorphization in the μc-Si:H/nc-Si:H film structure. Here, it is important to analyze the cause of non-crystallization at highly boron-doped silicon films. Firstly it is accepted that about one-third of boron atoms are used in doping and act as ICG001 acceptors [26]. Already, it has been confirmed for Si films deposited at low temperature i.e. 200 °C there were no segregation of boron inside silicon nanoclusters [27]. Hydrogen atoms play an important role in termination and passivation of silicon dangling bonds [28]. In the disordered amorphous region with B–Si, hydrogen atoms form B–Si–H heterodimers [29]. In μc/nc-Si grain boundaries B–Si bond is shorter than Si–Si bonds and boron atoms were distributed on the surface of nc-Si grains to form ordered reconstruction [30] resulting disorder in the grain boundaries or may be boron atoms form self agglomerates of low potential barrier and silicon settles their irregularly around these boron agglomerates and results increasing amorphous content in the film. With rise in boron doping, eventually the film loses their crystallinity. The films were deposited at too low pressure that is at 0.25 torr so, with this deposition pressure the number of silicon atoms per unit area were too less available to form nucleation so we use very high frequency (VHF-60 MHZ) to form more nucleation centers/sites which is favorable to the growth of nc-Si grains in the microcrystalline film. The growth of nc-Si in prefential direction is not an accidental or by chance deposition, there exists relation between preferred growth and plasma components which would require further study in detail [31].