Light emission, light detection and strain sensing with nanocrystalline graphene.

Graphene is of increasing interest for optoelectronic applications exploiting light detection, light emission and light modulation. Intrinsically, the light-matter interaction in graphene is of a broadband type. However, by integrating graphene into optical micro-cavities narrow-band light emitters and detectors have also been demonstrated. These devices benefit from the transparency, conductivity and processability of the atomically thin material. To this end, we explore in this work the feasibility of replacing graphene with nanocrystalline graphene, a material which can be grown on dielectric surfaces without catalyst by graphitization of polymeric films. We have studied the formation of nanocrystalline graphene on various substrates and under different graphitization conditions. The samples were characterized by resistance, optical transmission, Raman and x-ray photoelectron spectroscopy, atomic force microscopy and electron microscopy measurements. The conducting and transparent wafer-scale material with nanometer grain size was also patterned and integrated into devices for studying light-matter interaction. The measurements show that nanocrystalline graphene can be exploited as an incandescent emitter and bolometric detector similar to crystalline graphene. Moreover the material exhibits piezoresistive behavior which makes nanocrystalline graphene interesting for transparent strain sensors.