Zinc Oxide with Alumina Sputtering Targets
Zinc oxide sputtering targets can be used in many various applications. After doping alumina to zinc oxide sputtering targets application areas can be extended. Now let's see the properties of alumina doped zinc oxide sputtering targets.
Transparent conductive oxides have been extensively studied because of being one of the most important components for large area electronics devices such as solar cells, flat panel displays, optical sensors or touch screens. For the choice of the proper TCO, it has to be taken into account that its optoelectronic properties have a big influence on device performance. In the field of photovoltaic applications, the main criteria that transparent conductive oxides should fit are the following: first, to be highly transparent in the visible wavelength range where the solar cell is operating to minimize the photon absorption; second, to have high conductivity to reduce the resistive losses and finally, to have low carrier concentration to avoid absorption losses in the red and near-infrared wavelength ranges. On the other hand, an efficient light-trapping scheme is also essential to enhance the intrinsically low absorbance of the thin-film absorbers in the long wavelength range. For this reason, surface morphology is also an important characteristic within this area of application, where a developed surface texture is required to provide light scattering and subsequent light trapping inside the solar cell structure.
As a promising and suitable transparent conductive oxide material due to its potential properties, aluminum-doped zinc oxide (ZnO:Al) (AZO) has received great attention in the recent years. This is particularly interesting because of its low cost, a wide availability of its constituent raw materials and, besides, it is chemically stable in a hydrogen plasma, in comparison with other transparent conductive oxides used such as indium–tin oxide (ITO). Hence, the use of this material is a reliable and cost effective alternative for Si-based solar cells, thanks to the ease while etching with diluted acid, only to obtain a useful post-deposition texturing.
There are several deposition techniques to grow aluminum doped zinc oxide films such as chemical vapor deposition (CVD), spray pyrolysis, pulsed laser deposition, magnetron sputtering and sol–gel. However, most of these techniques need moderate temperatures to achieve aluminium doped zinc oxide showing low values of resistivity. On the other hand, low deposition temperatures are required to be compatible with the fabrication of the solar cells on several substrates, especially in thin-film cell technology on flexible substrates.
Taking this into account, radio-frequency (RF) magnetron sputtering is considered as a favorable deposition technique. This technique allows the deposition at low temperatures, down to room temperature, at high deposition rates and the films show good adhesion on substrates.