Nickel Oxide NiO PLD Target

Introduction to the Properties of NiO

NiO is a material known for its unique optoelectronic properties, particularly in electrochromic applications and energy storage. Furthermore is it one of the few p-type metal oxides making it a material of interest in semiconductor devices.

Electrochromic Properties and Applications

Electrochromism refers to the ability of a material to change its optical properties in response to an applied electric field. NiO is an electrochromic material and is commonly used in applications such as smart windows and mirrors, where it can switch between green (bleached) and brown (NiOOH, coloured state) 

Crystal Structure of NiO

The crystal structure of NiO is cubic (rocksalt), with a lattice constant of 4.18 Å.

P-type Semiconductivity of NiO

NiO is a wide bandgap semiconductor which exibits  p-type conductivity so has been studied for applications in solar cells, junction diodes, and other optoelectronic devices. In a nominally undoped NiO, depending on its oxygen stoichiometry, it only has a modest p-type conductivity of ∼0.1 S/cm due to Ni vacancy acceptors. However doping thin films with e.g. Li, Ag, and Cu have been investigated to promote increase p-type conductivity in NiO thin films.

Substrates for NiO growth

NiO can be grown epitaxially on a range of substrates with good lattice matching, including SrTiO3 and MgO. However, to be studied in optical and semiconducting applications, it is often deposited on transparent (glass, quartz) or semiconducting (Si) substrates.

Other Electrochromic Thin Film Materials

Some of the other electrochromic thin film materials include:

• WO3
• IrO2
• Cu2O
• SnO2
• Nb2O5