Some embodiments include methods of forming diodes. The methods may include oxidation of an upper surface of a conductive electrode to form an oxide layer over the conductive electrode. In some embodiments, the methods may include formation of an oxidizable material over a conductive electrode, and subsequent oxidation of the oxidizable material to form an oxide layer over the conductive electrode. In some embodiments, the methods may include formation of a metal halide layer over a conductive electrode. Some embodiments include diodes that contain a metal halide layer between a pair of diode electrodes.