Microcrystalline Si grown by plasma-enhanced chemical vapor deposition consisted of a phase mixture of amorphous Si and sub-micrometer sized columnar crystalline Si grains. These grains did not exhibit perfect translational symmetry but exhibited a high density of micro-twins, evidenced by structural investigations by use of transmission electron microscopy and X-ray diffraction. The high twin fault density of typically every tenth {111} bilayer led to anisotropic size broadening effects for Bragg reflection peaks. This anisotropic behavior of size broadening interferes with grain-size and strain measurements from X-ray diffractograms. Experimentally measured apparent grain sizes were up to a few ten nanometers and were subject to significant scatter due to the effect of micro-twinning. Numerical modeling of the shape of Bragg reflection peaks was presented for the two characteristic modifications of micro-twinning, i.e., lamellar and random twinning, to assess quantitatively the effect of micro-twinning on size broadening and grain-size measurements from Bragg reflection width.

Micro-Twinning in Microcrystalline Silicon and its Effect on Grain-Size Measurements. L.Houben, M.Luysberg, R.Carius: Physical Review B, 2003, 67[4], 045312 (10pp)