Formation of metal nanospheres and microspheres

Abstract

Hemispheres and spheres are formed and employed for a plurality of applications. Hemispheres are employed to form a substrate having an upper surface and a lower surface. The upper surface includes peaks of pillars which have a base attached to the lower surface. The peaks have a density defined at the upper surface by an array of hemispherical metal structures that act as a mask during an etch to remove substrate material down to the lower surface during formation of the pillars. The pillars are dense and uniform and include a microscale average diameter. The spheres are formed as independent metal spheres or nanoparticles for other applications.

What is claimed is: 
     
         1 . A photovoltaic device, comprising:
 a substrate having an upper surface and a lower surface, the upper surface including peaks of pillars attached to the lower surface, the pillars being dense and uniform and having an upper surface including a microscale average diameter, 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.   
     
     
         2 . The device as recited in  claim 1 , wherein the microscale average diameter of the pillars is between about 1 to 3 microns. 
     
     
         3 . The device as recited in  claim 1 , wherein the height of the pillars is between about 0.5 micron to about 20 microns. 
     
     
         4 . The device as recited in  claim 1 , wherein the height of the pillars is between about 3 and 6 microns. 
     
     
         5 . The device as recited in  claim 1 , further comprising an angle between a horizontal base and an edge of the pillar is between 90° and 92°. 
     
     
         6 . The device as recited in  claim 1 , wherein the substrate includes glass. 
     
     
         7 . The device as recited in  claim 1 , wherein the an upper surface of the pillars has a width substantially equal to a width of the base of the pillars. 
     
     
         8 . The device as recited in  claim 1 , wherein an upper surface of each of the pillars has a width provides a width for the upper surface of the plurality of the pillars having a standard deviation between 5% and 15%. 
     
     
         9 . The device as recited in  claim 1 , wherein 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. 
     
     
         10 . The device as recited in  claim 1 , wherein the substrate is comprised of a single-material, wherein the single-material of the substrate is an insulating material. 
     
     
         11 . A nanoparticle, comprising:
 a metal sphere having a diameter of less than 1 micron formed by employing surface tension on a non-wetting surface;   the metal sphere having the diameter defined in accordance with a thickness and deposition rate of a metal film from which the metal sphere is formed.   
     
     
         12 . The nanoparticle as recited in  claim 11 , wherein the metal sphere is formed concurrently with a plurality of metal spheres and a standard deviation of diameters of the metal spheres from a mean diameter is less than 15%. 
     
     
         13 . The nanoparticle as recited in  claim 11 , wherein the diameter is between 20 nm and 1 micron. 
     
     
         14 . The nanoparticle as recited in  claim 11 , wherein the metal sphere includes one or more of tin, indium, lead, antimony, bismuth, zinc and alloys thereof.