Nano-columnar grain growth structure of boron-compensated silicon thin films by transmission electron microscopy

Here in we present a study of the influence of Boron concentration upon the growth, and structural properties of hydrogenated nano and microcrystalline silicon thin films. The films were deposited in a RF plasma reactor using a mixture of silane and diborane as reactive gas, both highly diluted in hydrogen. The Boron concentration in the reactive gas was modified from 0 to 100 ppm. Increased concentration of Boron induces a change in the amorphous–crystalline transition, showing an increase in the crystal volume fraction (Xc) of the samples with concentrations from 0–75 ppm; whereas, there is a decrease of this parameter for the Boron concentration at 100 ppm. This fact is related to amorphization of the material for higher doping concentrations. A grain type with columnar structure embedded in an amorphous matrix was observed via electron microscopy micrographs and SEM images. A correlation between morphological properties and defects in the material at the grain boundaries of the columnar grains were also studied.

Graphical Abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Study of Boron concentration on the growth of hydrogenated microcrystalline silicon thin films. ► Evidence of a columnar structure formed of both crystalline and amorphous silicon parts. ► Structural properties and nucleation process in microcrystalline silicon during preparation stage.