Transparent metal electrodes

A crucial challenge in the optoelectronics industry is the realization of cheap and reliable transparent electrodes, i.e. films that permit to bring electrical current or potentials in proximity of optically active regions without significant loss of optical energy. The state of the art solution lies in large band gap semiconductors heavily doped with metals, known as transparent conductive oxides (TCOs), including indium tin oxide (ITO). Metal films, when sufficiently thin (<10 nm), become transparent to light, still maintaining continuity, thus having good electrical properties. This paper discusses, with respect to ITO, that ultrathin metal films (UTMFs) can possess similar levels of transparency in the visible range, larger UV and IR transmittance and larger electrical conductivity. AFM images reveal that RMS roughness and a peak-to-valley level are found to be 0.3 and 1.7 nm, respectively, both being well below deposited thickness.