Investigation of optical, structural and electrochemical properties of graphene layers synthesized by chemical vapor deposition technique

One of the materials that can be used as an alternative in the infrastructure of many advanced technologies due to its many superior properties, as a result of recent scientific and technological studies, is graphene. Due to their high optical transparency, excellent electrical conductivity, and mechanical strength, graphene layers are remarkable candidates for use as transparent conductive electrodes. Therefore, this thesis study examined the optical, electrochemical, and structural properties of graphene films synthesized at 1000 °C by chemical vapor deposition (CVD) and at 850 °C by plasma-enhanced chemical vapor deposition (PECVD). The amount of ions intercalated to and deintercalated from the sample surface during electrochemical processes was calculated using the cyclic voltammetry (CV) curves of the samples, and the amount of ions intercalated to and deintercalated from the sample surface during voltage pulses applied to the sample surface was calculated using chronoamperometry (CA) curves. The optical transmittances of the synthesized films were observed to vary between 71% and 90%. From the CV curve obtained by applying ±2.5 V to sample G1, the highest amounts of ions intercalated and deintercalated were calculated as QC = 2138 µC/cm2 and QA = 2788 µC/cm2, respectively. Additionally, the optical transmittances of the graphene films synthesized by PECVD were observed to vary between 79 % and 81 %. From the CV curves (±2.5 V) of sample P7 synthesized under 50W power, the highest amounts of ions intercalated and deintercalated were calculated as QC = 419.20 µC/cm2 and QA = 674.88 µC/cm2. Accordingly, it was noted in this thesis that the samples synthesized using PECVD and CVD methods in the Thin Film Preparation and Characterization Laboratory of the Department of Physics Engineering at Hacettepe University were stable during electrochemical processes and did not change their properties significantly over long cycles. Hence, it is thought that the aforementioned graphene layers can be used as transparent conductive layers in electrochromic applications.