Potential broadband photodetector concept based on three-dimensional graphene foam

In this work, optical and structural properties of three-dimensional graphene (Gii ^TM) foam have been analysed to validate the potential of this material as an active layer in broadband optoelectronic devices. The chemical structure of Gii ^TM foam was characterized by Raman spectroscopy carried out at different wavelengths (455, 532, 644, and 780 nm) and laser powers (1-8 mW). In this study, two types of Gii ^TM foam were analysed, including standard graphene (ST-Gii), and low resistance graphene (LR-Gii) whose main difference is the defects density modulating their electric conductivity. The performance of both ST-Gii and LR-Gii was determined by examining intensity and position, of G, D, and 2D peaks as a function of light source conditions (i.e., wavelength and power). Results demonstrate that ST-Gii presents a 1.37 G/D intensity ratio, which is 0.2 lower than that observed in LR-Gii, evidencing the drastic change in the electronic properties of both materials obtained during the synthesis process. Moreover, the study of the materials as a function of the wavelength showed - in the case of ST-Gii material - a clear 'optical switch' behaviour from G/D of 1.37 to 0.79 when the material is irradiated with light below and above 532nm, respectively. This interesting result indicates that Gii ^TM could be a potential candidate for optoelectronic devices (phototransistors, photodiodes, and photodetectors), thanks to the modulation of its electronic properties by irradiating the material to different light wavelengths. To further investigate this effect, in this work, we present the concept of a photo-resistive detector based on ST-Gii.