Atmospheric pressure dielectric barrier discharge (DBD) for post-annealing of aluminum doped zinc oxide (AZO) films

a r t i c l e i n f o Keywords: Aluminum doped zinc oxide Post-annealing Dielectric barrier discharge Indium–tin oxide DC magnetron X-ray photoelectron spectroscopy Aluminum-doped zinc oxide (AZO) is a material that can have high electrical conductivity while being highly transparent at the same time. It has been used in many applications such as displays, mobile devices and solar cells. Currently AZO films are considered as attractive alternatives to materials such as indium–tin oxide (ITO) due to its much cheaper cost and comparable high electrical conductivity. A process of depositing AZO film by dual DC magnetron and RF enhancement system has been developed. Film thicknesses were measured to be at about 200 nm by a stylus contact profilometer and transparency of greater than 90% in the visible range was measured with spectrophotometry methods. Film conductivities were on the order of 10 −3 Ω-cm using the four-point probe method. By using a dielectric barrier discharge operating at atmospheric pressure, the conductivity of film can be further lowered. A 300 mm × 60 mm line source operating at a nitrogen flow of ~ 250 L/min was used and ~0.4 L/min hydrogen gas was also introduced into the discharge system to create hydrogen radicals for surface modification. A 10%–15% decrease in electrical resistance was observed with no changes in the optical properties of the AZO films. Transparent conducting oxides (TCOs) are an important class of metal oxide semiconductor materials that is used in photovoltaic, display and LED technologies [1]. In order to help in decreasing the cost associated with mass production of thin film and enable a flexible roll to roll production for these applications, low cost materials, such as plastic substrates, are needed [13]. The use of polymeric substrates, however, limits deposi-tion temperature as well as post-deposition annealing temperatures that have been shown to significantly improve the quality of TCOs, such as aluminum–zinc oxide (AZO) thin films [2–5]. For example, polyethylene terephthalate (PET) is a common polymer substrate material that is suitable for these applications. However, it has a glass transition temperature of 100 °C which markedly limits the process temperature window. Metal oxide semiconductors such as zinc oxide (ZnO) can replace the existing indium-based TCOs, as the supply of indium in the world market is depleting [7]. Thin ZnO films can be deposited via sputtering techniques with high optical transmission and low resistivity. Doped ZnO is used as …