Chapter 2: ZnO Nanostructures - An Overview

Zinc Oxide is found in nature as the mineral Zincite, ‘Zincum Oxydatum’ is the Latin name of Zinc Oxide and it is commonly used in homeopathic medicines. The chemical formula of Zinc oxide is ZnO. Zinc oxide is a type of material which exhibits semiconducting and piezoelectric dual properties (in its crystalline form). Zinc Oxide is a ‘direct band gap’ and wurtzite (hexagonal) type semiconductor; it has band gap energy of 3.37 eV at room temperature. It is insoluble in water but easily soluble in acids and alkalis. It is also thermo chromic i.e. it changes color when heated (from white to yellow) and regains the original color when cooled down. When Zinc Oxide comes in contact with air it forms, a nervous malady called metal fume fever. The ZnO nanostructure has many applications in optoelectronics, sensors, and transducers and in the biomedical field. ZnO nanobelts can also be used as nanosensors, nanocantilivers, field effect transistors and nanoresonators. The lack of centre of symmetry in wurtzite combined with large electrochemical coupling, results in strong piezoelectric and pyroelectric properties. Consequently, ZnO is used in mechanical actuators and piezoelectric sensors. Due to its wide band gap, it is suitable for short wavelength optoelectronic applications.