Graphene, a material made up from a single atomic layer of honeycomb structured sp2 bonded carbon atoms, has been gaining interest in the last decade for its integration in optoelectronic devices in a wide range of fields. Many methods of graphene growth and deposition have been developed over the years. These methods range from high cost and high quality of deposited graphene to low cost and low quality of deposited graphene, depending on the applications wanted. An overview and comparison of these methods is presented in this work. More focus is placed on one such deposition method; the electrostatic deposition of graphene. This work aims to show the possibility to deposit micro graphene sheet arrays directly for the use in optoelectronic device active layers, such as bolometers and photoconductive switches. Improvements to the current technologies involving deposition of graphene using electrostatic forces have been investigated, more precisely, improvements to the control of the shape, size and position of the deposited graphene. These improvements are realised primarily via surface etching of the graphitic material used for deposition by pulsed UV Laser radiation. Etching of the graphitic material is performed to limit and therefore control the size of the deposited graphene. Patterning of the deposition substrate is also explored as a method of modifying local electric field strengths, moreover the possibility of direct deposition of graphene onto pattern SiO2 substrate to create suspended membranes is explored. However, deposition of graphene onto un-patterned SiO2 substrate are the main deposition results presented in this work. The optoelectronic properties of the deposited graphene were studied. More precisely, the deposited graphene is shown to have a direct electrical response to incident light of multiple wavelengths, thus making it suitable for photoconductive switch devices. The calorimetric properties of the deposited graphene were also studied, these results, however, were less conclusive, casting doubt on the effectiveness of graphene as a bolometer active layer. Improvements to the homogeneity of the cleaving process used in the electrostatic deposition of graphene were performed and are shown to lead to large scale graphene depositions, previously only thought to be achievable with more costly methods of graphene growth. A simple and accurate method of characterising the number of graphene layers present in the deposition is developed using the center of a single fitted gaussian curve on the 2D graphene Raman peak.
Trudeau, C. (Author),
Cloutier (Supervisor) &
Zednik (Co-supervisor),
16 Oct 2015Student thesis: Master's thesis › Master in Engineering: Electrical Engineering