Investigation of Laser-Induced Changes in Structural and Optoelectrical Properties of Pulsed Laser-Deposited Diamond-Like Carbon Layers

In the next years, one of the biggest challenges for optoelectronic devices will be the necessity to provide a suitable and reliable alternative to the use of transparent conducting oxide (TCO) like Indium Thin Oxide (ITO) as transparent electrodes. We recently demonstrated a promising fully laser-based method to produce transparent conductive electrodes only made of pure carbon materials. In a first step, we use the Pulsed Laser Deposition (PLD) to synthetize high performance Diamond-Like Carbon (DLC), an amorphous pure carbon material composed of a mixture of sp2 (graphitic) sp3 (diamond) hybridized carbon atoms. DLC thin films show very interesting properties comparable to those of diamond, like a high transparency in the visible range, high wear resistance, biocompatibility, chemical inertness and high electrical insulation. DLC also presents one particularity compared to diamond which its relative high opacity in the UV range. This feature is used in a second step to perform an UV laser surface treatment to graphitize the very first atomic layers of the DLC thin film. DLC opacity at treatment wavelength will help to restrict the laser interaction at the surface and will break dominant diamond bindings, allowing carbon atoms to reorganize into its stable form, forming by their way a Thin Graphitic Layer (TGL). Raman spectroscopy (RS) and X-ray Photoemission Spectroscopy (XPS) perform before and after laser annealing clearly demonstrate the DLC surface graphitization kinetic. Transmittance and surface conductivity measurement show very promising results and performances that can clearly compete with those of ITO. In addition to all these analyses, this pure laser process will be fully compatible with standard microelectronic technological steps and will have a low ecological footprint compared to other much heavier processes.