Laser-Scribed Photo-thermal Reduction of Graphene-Oxide for Thin Film Sensor Applications

In this thesis, a cost effective, simple and fast method of reduction of Graphene Oxide thin film is proposed. Graphene oxide is a non-conductive material intrinsically and one of the techniques to convert it to conductive material is using laser beam to remove oxygen groups from its surface, in other words, to reduce it. Laser parameters must be optimized for an effective and successful reduction. Thin film of non-conductive Graphene oxide is converted into conductive thin layer by fast laser scribing. Laser variables such as, power, speed, laser head distance to surface need to be selected precisely. Optical and atomic microscopies are used to study the changes of thin film surface. Chemical analysis shows that the reduction is successful and the structure is Graphene and removing of oxygen groups from surface is successful. Electrical properties also confirm the conductivity of scribed Graphene oxide. To show the application of reduced Graphene oxide, laser scribing method is used to fabricate pressure sensors arrays and the final product shows acceptable sensitivity to light touches similar to scrolling with finger on a touch screens. The fabricated sensor array is attachable on any surface for monitoring applied forces or pressure and maintains good electrical conductivity under mechanical stress and thus holds promise for durable sensors. Beside the pressure sensor, reduced Graphene oxide thin film has been used to fabricate temperature sensor. Also thin layer of hybrid (Graphene oxide mixed with silver nano wire) is deposited and patterned in the form of interdigitated capacitor to test the capacitance change of touch sensor