Thermoelectrically Driven Photocurrent Generation in Femtosecond Laser Patterned Graphene Junctions

Single and few-layer graphene photodetectors have attracted much attention in the past few years. Pristine graphene shows a very weak response to visible light; hence, fabrication of complex graphene-based detectors is a challenging task. In this work, we utilize the ultrafast laser functionalization of single-layer CVD graphene for highly desirable maskless fabrication of micro- and nanoscale devices. We investigate the optoelectronic response of pristine and functionalized devices under femtosecond and continuous wave lasers irradiation. We demonstrate that the photocurrent generation in p-p(+) junctions formed in single-layer graphene is related to the photothermoelectric effect. The photoresponsivity of our laser patterned single-layer graphene junctions is shown to be as high as 100 mA/W with noise equivalent power less than 6 kW/cm(2). These results open a path to a low-cost maskless technology for fabrication of graphene-based optoelectronic devices with tunable properties for spectroscopy, signal processing, and other applications.