Arrays containing carbon nanostructure-oxide-metal diodes, such as carbon nanotube (CNT)-oxide-metal diodes and methods of making and using thereof are described herein. In some embodiments, the arrays contain vertically aligned carbon nanostructures, such as multiwall carbon nanotubes (MWCNTs) coated with a conformal coating of a dielectric layer, such as a metal oxide. The tips of the carbon nano-structures are coated with a low work function metal, such as a calcium or aluminum to form a nanostructure-oxide-metal interface at the tips. The arrays can be used as rectenna at frequencies up to about 40 petahertz because of their intrinsically low capacitance. The arrays described herein produce high asymmetry and non-linearity at low turn on voltages down to 0.3 V and large current densities up to about 7,800 mA/cm2 and a rectification ratio of at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60.