Roll-to-Roll Sputter Deposition of Low Resistance Electrodes on Ultrathin Glass

Ultrathin glass is a new flexible material. It is distinguished from its polymer counterparts by a couple of outstanding properties. Most importantly, the permeation barrier for moisture and oxygen is virtually infinite. Thus, lifetime problems for organic electronics can effectively be avoided. Further, the possibility to exert heat on the substrate offers considerable advantages for transparent conductive oxides. The paper features the roll-to-roll sputter deposition of indium tin oxide (ITO) based transparent electrodes. The deposition technology was the dual anode sputtering from a rotatable ceramic target. The paper provides results for ITO coatings which were either deposited at substrate temperatures of up to 300°C or which were annealed at those temperatures after the deposition. The lowest resistivity of the coatings was 1.6x10-4 Ohm-cm, corresponding to a sheet resistance of less than 11 Ohm/square.This value is much better compared to ITO coatings deposited at room temperature or annealed to moderate temperaturelevels around 150 °C. In addition to the optical and electrical properties, surface roughness and mechanical stability are also crucial propertiesfor the applicability of the substrates.Various annealing routes were compared. The indium tinoxide properties achieved by room temperature and subsequent annealing were related to those obtained by the depositionon a heated substrate. Besides the transmission, reflection and resistivity, atomic force microcopy and X-ray diffraction results were also included in the discussion.