Abstract: The invention concerns a single detector with two designable wavelengths and bandwidths for ultraviolet detection based on n?/n+-GaN and AlGaN structures grown over sapphire substrates. The detector has several layers grown over a sapphire substrates, including a buffer layer comprising AlN; a first band-edge comprising AlX Ga1-X N; a second band-edge comprising AlYGa1-Y N; a third band-edge comprising AlZ Ga1-Z N. The detector also has ohmic contacts formed on the AlX Ga1-X N band-edge. A bias voltage is applied to the detector through the ohmic contacts so as to select a range of wavelengths in the UV region of interest.

Abstract: A method of forming an array of pointed structures comprises depositing a ferrofluid on a substrate, applying a magnetic field to the ferrofluid to generate an array of surface protrusions, and solidifying the surface protrusions to form the array of pointed structures. The pointed structures may have a tip radius ranging from approximately 10 nm to approximately 25 ?m. Solidifying the surface protrusions may be carried out at a temperature ranging from approximately 10 degrees C. to approximately 30 degrees C.