TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Parameters: The growth occurs by cation vacancy diffusion, where the incorporation of sulfur atoms generate VCu' which diffuse down towards the copper substrate, and where copper oxidation at an interface between the cuprous sulfide film and the copper substrate produces copper (Cu+) cations which diffuse up to complete cuprous sulfide propagation. Flow rate of oxygen gas ranges from about 25 standard cubic centimeters per minute (seem) to about 300 seem. Concentration of oxygen gas is about 13.3x10-3 mole/L. Flow rate of hydrogen sulfide gas ranges from about 2.5 seem to about 100 seem. Concentration of hydrogen sulfide gas is about 1.7x10-3 mole/L. Flow rate of nitrogen gas ranges from about 100 seem to about 200 seem. Concentration of nitrogen gas is about 26.5x10-3 mole/L. In nanostructure array, approximately 10 standard cubic centimeter per minute (seem) of hydrogen sulfide gas, approximately 80 seem of oxygen gas and approximately 160 seem of nitrogen gas are co-flowed over the copper substrate to spontaneously grow the vertically aligned copper (I) sulfide nanostructures. Hydrogen sulfide gas is present at a concentration of about 1.7x10-3 mole/L, the oxygen gas (O2) is present at a concentration of about 13.3x10-3 mole/L, and the nitrogen gas (N2) is present at a concentration of about 26.5x10-3 mole/L. Vertically aligned copper (I) sulfide nanostructure has a diameter of about 100 nm and a length of about 500 nm. Preferred Method: In fabricating cuprous sulfide nanowire array, the nitrogen gas is passed through the bubbler for mixing the nitrogen gas with water vapor so that the relative humidity is about 60%. The copper substrate is electropolished prior to subjecting the copper substrate to the atmosphere of oxygen gas, hydrogen sulfide gas and nitrogen gas. Preferred Components: In nanostructure array, the copper (I) sulfide nanostructures are growable by subjecting the copper substrate to an atmosphere of oxygen gas, hydrogen sulfide gas and nitrogen gas at ambient conditions, and where the nitrogen gas is passed through a bubbler for mixing the nitrogen gas with water vapor so that a relative humidity is between about 25% and about 100%. Vertically aligned copper (I) sulfide nanostructures are selected from a nanowire array, a nanotube array, a nanorod array, and a nanobeam array. Vertically aligned copper (I) sulfide nanostructures are nanowires having a morphology selected from at least one of a double-comb structure or a helical nanowire structure.