Nano-structure includes a substrate and a non-oxidized portion of a metal layer (having an expansion coefficient, during oxidation, that is more than 1) on the substrate. An oxide layer is formed on the non-oxidized portion. A plurality of metal oxide nano-pillars is grown from the oxide layer. Each nano-pillar is grown through a plurality of pores defined in a template. A space is defined between adjacent nano-pillars. A continuous metal oxide cap layer is over the nano-pillars and over, but not in, the space between adjacent nano-pillars. The cap layer is formed from end portions of the nano-pillars that merge together over a template surface. The cap layer is in contact with all of the nano-pillars. The oxide layer, the nano-pillars, and the oxide cap layer are formed from anodization of portions of the metal layer.