Aluminum-doped zinc oxide (AZO) is a transparent conductor that can be used in thin film form as transparent electrode of electro-optical devices. For most of actual applications, a large conductivity is required on large surface areas.
The rapid growth of transparent electronics and electro-optical devices on flexible supports calls for the development of methods that enable the synthesis of transparent conducting films without thermal assistance while keeping high electrical and optical performances. Magnetron sputtering has emerged as a reference method for the synthesis of AZO films. It is particularly due to, its scalability to industrial scale. Unfortunately, AZO films usually produced without thermal assistance using magnetron sputtering tend to a strong inhomogeneity of the electrical properties with a large sensitivity to the process parameters (composition of the gas phase, geometry of the experiment) [1].
It has been shown that the properties of AZO films can be improved using high power Impulse Magnetron Sputtering (HiPIMS) [2]. This method uses short pulses of high electrical power density that produce a highly ionized vapor.
This presentation first highlights the interest of HiPIMS to synthesize AZO films of high electronic conductivity on large surface areas and without thermal assistance. Electronic structure measurements using X-ray absorption spectroscopy evidence a correlation between the distribution of the electrical behavior and dopant activation/inactivation [3,4]. A deactivation mechanism, complementary to the well-known compensation of dopants, is proposed in the case of conventional sputtering. A model explaining the minimization of the deactivation amplitude is proposed in case of HiPIMS [5, 6].
In a second part we will show how the electrical properties of AZO films degraded after long term exposure to ambient moisture can be restored by low temperature thermal annealing and how thermal assistance during growth can prevent degradation upon exposure to ambient moisture [7, 8].
Finally, self-nanostructured AZO films could be obtained using HiPIMS under certain conditions and their interest for flexible electronics is highlighted.
References
[1] D. Horwat, A. Billard, Thin Solid Films 515 (2007) 5444 [2] F. Ruske, et al., Thin Solid Films 516 (2008) 4472 [3] D. Horwat, et al, J. Phys. D : Appl. Phys. 43 (2010) 132003 [4] M. Jullien, et al. Sol. Energ. .Mater. Sol. Cells. 95 (2011) 2341 [5] M. Mickan et al., Sol. Energ. Mater. Sol. Cells. 157 (2016) 742 [6] D. Horwat, M. Mickan, W. Chamorro, Phys. Stat. Sol. C 13 ( 2016) 951 [7] M. Mickan, M. Stoffel, H. Rinnert, U. Helmersson, D. Horwat, J. Phys. Chem. C 121 (2017) 14426 [8] M. Mickan, U. Helmersson, D. Horwat, Effect of substrate temperature on the deposition of Al-Doped ZnO thin films using high power impulse magnetron sputtering, under press
Universidad Autónoma de Madrid © 2008 · Ciudad Universitaria de Cantoblanco · 28049 Madrid · Información y Conserjería: 91 497 43 31 E-mail: informacion.ciencias@uam.es Gestión de estudiantes de Grado y Posgrado: 91 497 8264 / 4329 / 4353 / 4349 / 6879 / 8362 E-mail: administracion.ciencias@uam.es
