Microcrystallisation in Si:H: the effect of gas pressure in Ar-diluted SiH4 plasma

Abstract

Abstract Using noble gas argon as a diluent of SiH 4 in RF glow discharge, undoped μc-Si:H thin films have been developed at a low power density of 30 mW/cm 2 . It has been found that the gas pressure is a critical factor for the growth of μc-Si:H films. Undoped μc-Si:H films having σ D ∼10 −6 S/cm and Δ E 2 , a more crystalline as well as highly conducting ( σ D ∼10 −4 S/cm) μc-Si:H film has been achieved at a deposition rate of 30 A/min, which is much higher than that attained from H 2 -diluted SiH 4 plasma, by conventional approach. The crystallinity of the films has been identified by the sharp Raman peak at ∼520 cm −1 and a large number of micrograins in the TEM micrographs. The metastable state of Ar, denoted as Ar * , plays the crucial role in inducing microcrystallisation by transferring its de-excitation energy at the surface of the growing film. A mechanism has been proposed to explain the dependence of the formation of μc-Si:H film on the working gas pressure in the plasma.