Bimodal crystal size distribution in annealed r.f. magnetron silicon films: a memory effect of the local order inhomogeneities in the initial amorphous state

• Published in: Journal of non-crystalline solids Vol. 227; pp. 906 - 910
• Main Authors: Touir, H., Dixmier, J., Zellama, K., Morhange, J.-F., Elkaim, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.1998
• Subjects: Microcrystalline silicon; Radio frequency magnetron sputtering; Thermal annealing; R770; Microcrystalline silicon; M215; Thermal annealing; Radio frequency magnetron sputtering; X130
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(98)00222-1

Microcrystalline silicon ( μc-Si) layers have been obtained by thermal annealing of amorphous films prepared by radio frequency (r.f.) magnetron sputtering. X-ray diffraction (XRD) and Raman spectra were measured. A systematic effect has been observed in these samples on both the diffraction lines and the Raman spectrum profiles, i.e., a distribution of the crystal size peaking at two different means. The diffraction pattern has tails superimposed on the 111, 220, 311 powder lines, while the Raman spectra have a shoulder on the low wave number side of the 520-cm −1 band at about 500 cm −1. A relationship is established between this effect and the local order inhomogeneities observed in the initial amorphous state by XRD. The first halo of the diffraction pattern can be reproduced by two components, one being located on the low angle side (left side) of the theoretical 111 line of c-Si (relaxed domains), the other one on its right side (disordered domains). This bimodal size distribution is the result of heterogeneous nucleation and crystal growth process during the amorphous–crystalline transition. Relaxed domains favor a nucleation rate leading to small crystals, while disordered domains increase the nucleation activation energy, i.e., yield fewer nuclei and larger crystals.