多孔硅薄膜微结构的分形特性

Characterization on the Fractal Microstructures of Porous Silicon Films

用扫描电镜(SEM)对厚度不同的多孔硅膜的微结构进行了研究。对于23μm厚的多孔硅膜,其横截面微结构好似海底生长的海藻;而对于6μm厚的多孔硅膜,其表面微结构则像龟壳上的裂纹。通过对在不同放大倍数情况下拍摄的多孔硅的SEM图片进行分析,结果表明多孔硅薄膜的这两种微结构都具有分形特征,而且其分形维数为2.3～2.6。利用扩散限制凝聚模型(diffusion limited aggregation)对这两种微结构的形成过程进行了模拟。

The typical microstructures of thick and thin porous silicon films were investigated by scanning electron microscopy （SEM） . The cross-section morphology of the thick porous silicon film （23 um） was similar to the seaweeds growing onto a seabed, while the microstructure of the top surface of the thin porous silicon film （6 um） looked like the cracks on a turtle shell. Detailed analysis on the SEM micrographs taken at different magnifications indicates that the two kinds of microstructures possess fractal characteristics, with fractal dimensions of 2.3~2.6. The growth processes were simulated for the two kinds of fractal microstructures with the diffusion limited aggregation model.