Formation of metal nanospheres and microspheres

A photovoltaic device, comprising:

• a single-material, insulating substrate having an upper surface and a lower surface, the upper surface including peaks of pillars attached to the lower surface;
• the peaks having a density defined at the upper surface by an array of hemispherical metal structures that act as a mask to etch away substrate material down to the lower surface to form the pillars, the hemispherical metal structures are formed using a process that includes adjusting a deposition rate for depositing a metal film on a substrate, wherein the deposition rate controls a density of future formed dots on a surface of the substrate, and annealing the metal film to form the dots from the metal film that which adhere to the substrate material and include the density, the pillars being dense and uniform and having an upper surface including a microscale average diameter greater than 1 micron, wherein dense and uniform means an average distance between pillars is no larger than two times the average pillar diameter;
• and
• a continuous photovoltaic stack conformally formed over the substrate and extending over and between the plurality of pillars to form a three-dimensional structure, the photovoltaic stack configured to transduce incident radiation into current flow.