Atomic layer deposition (ALD) method, also known as atomic layer epitaxy (ALE), offers very conformal thin film growth over large area substrates at low growth temperatures. These features are caused by two principles, under which ALD operates: a sequentiality of precursor doses and the saturation effect. They also ensure an uniform coverage of porous or nanostructured surfaces by films with precisely controlled thicknesses. ALD is especially useful for deposition of various metal oxides including high-k materials or wide band gap semiconductors such as zinc oxide (ZnO). ZnO films attract a lot of attention in recent years due to their prospective applications in optoelectronics, photovoltaics, transparent electronics or hybrid heterostructures with organic materials. A possibility of applying low deposition temperatures is of great advantage, since the usage of organic or flexible substrates limits a device processing to temperatures well below 200 °C.
In my talk, I will focus on low temperature growth of ZnO films by the ALD method and show how choosing various ALD growth conditions results in ZnO films having different structural, optical and electrical properties. In particular, I will show that electrical properties of ALD-grown ZnO films can be controlled over a wide range of free electron concentrations as well as electron mobilities, measured at room temperature. Depending on this, different applications of ZnO or doped ZnO films in electronic devices, namely as an n-type partner to p-type semiconductors or as a transparent electrode, will be presented.
This work was partially supported by the European Union within the European Regional Development Fund, through the Innovative Economy grant (POIG.01.01.02-00-108/09).