THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING   GEORGIA INSTITUTE OF TECHNOLOGY   Under the provisions of the regulations for the degree DOCTOR OF PHILOSOPHY   on Monday, August 21, 2017 12:00 – 2:00PM in Marcus 1116   will be held the   DISSERTATION DEFENSE for   Meng-Yen Tsai   “Materials Challenges of Two-Dimensional Materials for Flexible Sensing Applications”   Committee Members:   Dr. Eric Vogel, Advisor, MSE Dr. Vladimir Tsukruk, MSE Dr. Oliver Brand, ECE Dr. Samuel Graham, MSE Dr. Valeria Milam, MSE     Abstract:   Sensors are playing an increasingly important role in our lives because they enable the detection of environmental changes and, therefore, initiate a response accordingly. Sensors convert detected physical or chemical changes, for example, motion, radiation, heat, acidity, chemicals, etc., to useful and readable signals. Field-effect transistors (FETs), a class of semiconductor device in which the electrical current is controlled through an applied gate voltage, are promising for many sensing applications. Even though FETs-based sensors have been well-developed, flexible version of such sensors remains a big challenge and requires new materials and new sensing designs. Two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are promising candidates for FET-based sensors due to their flexibility, transparency and potential for high electrical performance. Because of the atomically thin nature of 2D materials, their electrical properties are extremely sensitive to their atomic-scale structure as well as to their surfaces and interfaces with other materials. Specifically, defects, dopants, attached molecules or change in the band structure due to strain can shift the Fermi level resulting in a measured change in current. The goal of this work is to meet the challenges faced by the 2D TMD-based electronics in sensor applications by developing a fundamental understanding of the impact of materials processing, structure, interfaces and surfaces on resultant electronic properties. Furthermore, a simplified strategy for chemical and biological electrical sensors based on FETs is developed to bridge the current sensing technology to the use of next generation flexible 2D transducers.