This study investigated the fabrication and performance of highly responsive photodetectors, constructed of turbostratic stacked graphene produced via chemical vapor deposition (CVD) and using the photogating effect. This effect was induced by situating photosensitizers around a graphene channel such that these materials coupled with incident light and generated large electrical changes. The responsivity of such devices correlates with the carrier mobility of the graphene, and so improved mobility is critical. This work assessed the feasibility of using turbostratic stacked CVD graphene to improve mobility since, theoretically, multilayers of this material may exhibit linear band dispersion, similar to monolayer graphene. This form of graphene also exhibits higher carrier mobility and greater conductivity than monolayer CVD graphene. The turbostratic stacking can be accomplished simply by the repeated transfer of graphene monolayers produced by CVD. Furthermore, it is relatively easy to fabricate CVD graphene layers having sizes suitable for the mass production of electronic devices. Unwanted carrier scattering that can be caused by the substrate is also suppressed by the lower graphene layers when turbostratic stacked graphene is applied. The infrared response properties of the multilayer devices fabricated in the present work were found to be approximately tripled compared with those of a monolayer graphene photodetector. It is evident that turbostratic stacked CVD graphene, which can be produced on a large scale, serves to increase the responsivity of photodetectors in which it is included. The results of this study are expected to contribute to the realization of low-cost, mass-producible, high-responsivity, graphene-based infrared sensors.
Disorderly stacked multilayer graphene, called turbostratic graphene, is a promising candidate for highly responsive infrared detectors due to its higher carrier mobility than well-ordered multilayer graphene, and facility to suppress the Coulomb scattering from the substrate. Such properties are expected to enhance photogating for high-responsivity infrared detection. The electronic structure of turbostratic graphene was investigated using first-principles calculations. The turbostratic graphene was modeled by introducing disorder to bilayer graphene in terms of the distance and the rotation angle between the graphene layers. The calculation results show that an increase in these parameters leads to linear band dispersion and a structure similar to monolayer graphene.
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