Electrochemical deposition of n-type semiconducting nickel hydroxide thin films

Nickel hydroxide (Ni(OH)(2)) is a wide bandgap semiconductor with a bandgap energy of 3-3.5 eV, but the use of Ni(OH)(2) as a semiconductor is still limited. In this study, Ni(OH)(2) thin films were synthesized on indium tin oxide (ITO) coated glass substrates by electrochemical deposition and subsequent annealing in water vapor at 180 degrees C. The as-deposited Ni(OH)(2) films were amorphous alpha-Ni(OH)(2) intercalated with water and nitrate molecules. Nanocrystallites of beta-Ni(OH)(2) were formed in the films during annealing in water vapor at 180 degrees C. The content of beta-Ni(OH)(2) nanocrystallites increased with increasing annealing time. The as-deposited and annealed Ni(OH)(2) films exhibited an n-type photo response in photoelectrochemical measurements. The resistivity of the annealed films was about 1 x 10(4) omega cm. This resistivity value was one order of magnitude lower than that of the as-deposited film. The Ni(OH)(2)/NiO/ITO heterostructure was fabricated by depositing Ni(OH)(2) on nickel oxide. The n-Ni(OH)(2)/p-NiO/ITO heterostructure diode exhibited clear rectification behavior.