UC Davis

Manipulation of terahertz (THz) waves provides an avenue for exploration and technological advancement because of their capability to interface with biological systems, imaging, security, space exploration, and sensing, as well as enabling ultra-fast communications (1000x current speeds). Unfortunately, this part of the electromagnetic spectrum is susceptible to substantial loss through the atmosphere, sizable enough to make it unusable over long distances in communication. However, over short distances (such as within the human body or on a chip) or in atmosphere-free conditions (such as space), THz can be capable of delivering unprecedented responses. The last decade has seen a surge in THz research for these applications due to advances in sources, detectors, and nanofabrication. Miniaturizing such systems is of importance because of their capability to be introduced into bioelectronic and microelectronic systems. Graphene has been a material of interest since its experimental discovery in 2004 [1] because of its exceptional electronic, mechanical, and electromagnetic properties [2]. In addition, its compatibility with current CMOS (complementary metal oxide semiconductor) processes make it interesting to study using current semiconductor analysis techniques. Graphene’s strong interaction with infrared and THz radiation make it a great candidate material for systems that exploit these regions of the electromagnetic spectrum. Its atomic thickness makes it appealing for the next generation of small scale electronics and its biocompatibility opens new doors for researchers in various fields of bioengineering to utilize this 2D material in their systems. This thesis proposes and develops graphene-based devices that demonstrate state-of- the-art quality. These devices are then characterized electrically, optically, and at THz frequencies. Methodology to further test these devices is proposed and future capabilities as well as potential application are described. This thesis starts by introducing the state of the art of THz

and graphene technologies in Chapter 1. Chapter 2 introduces graphene’s interesting electronic properties. Chapter 3 reports the fabrication of graphene-based devices, and Chapter 4 evaluates the quality of such devices. Chapter 5 subsequently reports the device's response to infrared (IR) light, and explores the influence of light polarization & intensity coupled with electronic stimulation. Chapter 6 reports the THz response and a methodology for determining the Faraday rotation in the THz spectrum. Chapter 7 finalizes the thesis and proposes how all of these fields of study can be combined to develop and implement novel graphene based devices that interact with the electromagnetic spectrum in innovative ways that would enable future research and exciting applications.