A novel silicon-based micron/nanometer structural composite system, silicon nanoporous pillar array(Si-NPA), was prepared on the substrate of single-crystal silicon (sc-Si) wafers by a hydrothermal etching method; and the studies on its morphological structural and optical properties were carried out. Structural experiments disclose that Si-NPA could be well described by triple hierarchical structures: the array composed of micron-sized silicon pillars, the nanopores densely distributing on each pillar, and...