Graphene is two-dimensional allotrope of carbon with a honeycomb-like lattice structure. It shows exceptional properties in electrical, optical, thermal, mechanical and chemical fields. And due to its excellent properties, it is being researched to be used in many applications su
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Graphene is two-dimensional allotrope of carbon with a honeycomb-like lattice structure. It shows exceptional properties in electrical, optical, thermal, mechanical and chemical fields. And due to its excellent properties, it is being researched to be used in many applications such as, sensors, graphene transistors, opto-electronics, etc. To realize these applications in an industrial scale, reliable methods to grow and transfer graphene need to be developed. Methods such as chemical and mechanical exfoliation, chemical vapour deposition (CVD), etc. are a few methods which are used to synthesize graphene. And wet transfer, electrochemical delamination, etc, are a few methods to transfer graphene on to the required substrate. Graphene is sensitive to chemicals and processing steps, hence the properties/behaviour of graphene varies based on the fabrication and transfer technique used. Applied Nano-Layer(ANL) is a company based in Delft, that fabricates and transfers wafer-scale mono-layer graphene. Asmentioned before, the properties/behaviour of graphene changes based on the fabrication and transfer technique used. Therefore, in this thesis, the properties/behaviour of monolayer graphene provided by ANL, is analyzed. In this thesis, electrical properties like channel resistance, resistivity and mobility were analyzed. Also, the optical behaviour of graphene where pauli-blocking stops the absorption of light at dirac point, is analyzed. Few questions related to design of the process flow, working of the fabricated devices, propagation of light in the waveguides, modulation of light and effect of process flow on graphene, were answered to properly analyze the above stated properties/behaviour of graphene. First, a wafer-scale silicon waveguide was designed using COMSOL and BeamLab. The derived width of the waveguide was found to be for the values of 1 um to 4 um and the optimal cladding thickness was found to be 20 nm. Then, the designed waveguide structures were translated onto a mask that would be used in the fabrication of the electro-absorption modulators. Second, a cleanroom compatible process flow for the fabrication of Hall bars and electro-absorption optical modulators was designed and optimized. Several testing steps were performed to find the optimal parameters required in the process flow. Third, the hall bars and the optical modulators were fabricated in the clean room , Else-Kooi Lab(EKL), using the designed masks and process flows. The electrical properties were analyzed by extensively measuring the hall bars. As an example, the average channel resistance, dirac voltage, average resistivity and average mobility of a graphene hall bar with dimensions 2 um x 2 um was measured/calculated to be 6.74 k, 75.9 V, 1.7 k and 1573.28 cm2/Vs respectively. Similarly, the values for 11 other dimensional devices were measured/calculated. The optical behaviour was analyzed by testing the electro-absorption optical modulator. A few waveguides were tested for propagation of light and a power of 0.8 uW wasmeasured for an input power of 0.6mW, which suggests that light successfully propagates though the waveguides. Graphene modulation was tested using back gate biasing and an average dirac voltage of 73.33 V was observed for 2 um x 2 um hall bar device on the optical modulator die. These two when done simultaneously theoretically should modulate light. Lastly, the impact of process flow on graphene/ graphene devices was checked. And a drastric fall to 30% working devices(for optical modulators) from 60% working devices (for hall bars) with increase in process flow steps concludes that the number of processing steps does affect the graphene/ graphene devices.