Thursday 22 Jun 2017: Emerging 2D materials and its integration into optics and electronics: Graphene
Dr Evgeniya Kovalska - Laboratory of Smart Materials and Devices, Department of Physics, Bilkent University, Ankara/Turkey, 06800
An incessant interest toward graphene’s exceptional electronic properties encourages the scientific community to take further steps in the development of new graphene-based platforms for bioelectrical, electromechanical, optoelectronic, and thermal management purposes.
Atomically thin two-dimensional (2d) crystals provide a new perspective for novel optoelectronic devices. Since the thickness of 2d crystals is much shorter than the wavelength of light, their response originates from the free charge carriers. Ability to tune the free carrier on graphene through electrostatic doping, enables to control optical absorption in a very broad spectrum. We discovered a very simple device design to control optical properties of graphene using a supercapacitor structure. In this device architecture, we used two graphene electrodes and electrolyte medium. Application of a voltage bias polarized the electrolyte and yield a large shift in the Fermi energy (in the order of 1.5 eV). The electrical and chemical properties of the electrolyte are the key parameters that define the performance of these optical modulators. Thus we investigated various organic electrolytes for graphene optical modulators: liquid, gel and solid electrolytes. We expect that solid electrolyte employing, besides getting the desired electro-optical properties, will allow us to minimize the size of the device and to vary its form.
The applicability of diverse graphene-based devices could be limited by the insufficient surface reactivity, unsatisfied shaping or zero bandgap of graphene. Managing the graphene lattice by creating artificial alignment will impact on the surface area of graphene providing a higher capacity of devices. Besides, created super periodic potential and arising of active external/inner/edge surface centers determine the multifunctionality of graphene surface and corresponding devices as well. Thus we report on the first implementation of nonlinear laser lithography (NLL) technique for multilayer graphene patterning. The regularly patterned multilayer graphene is obtained by CVD-method on NLL structured Ni foil. After the CVD process, the graphene is transferred onto the polymer substrate for characterizations and device applications. In conclusion, we have shown a great promise of fabricated devices in supercapacitor and battery designs by using NLL assisted graphene nanopatterning. We anticipate our approach as a new avenue to patterned graphene for multifunctional device engineering.