Relaxation Dynamics of Photoexcited Carriers in Graphene

Abstract

Electronics are ubiquitous and essential for our daily lives. To improve upon existing technologies, new materials and their electronic properties need to be explored. The proposed mid-infrared spectroscopy experiments in this thesis place an emphasis on understanding the physical phenomena in graphene. Graphene on its own has many peculiar layer-dependent properties which make it an interesting material to study. The first chapter is dedicated to looking at some basic theories of graphene and its corresponding multilayers, showing some of its peculiar properties.

In the second chapter, graphene device fabrication techniques and tools that were used throughout this thesis are described. The device fabrication plays a crucial role in understanding properties of graphene and without high-quality devices, some properties could not be observed as shown in the actual experiments done in chapter three.

To date, there have not been many ultrafast studies using a mid-infrared probe for studying solid-state materials, let alone studies specifically looking at charge dynamics of photo-excited carriers in graphene. So in the third chapter, a homebuilt near-infrared pump and mid-infrared probe spectroscopy system is described which is designed to have a high temporal resolution to study photo-excited carriers in graphene and other novel materials. It is also shown that for low-mobility materials, the mid-infrared probe can also be used to estimate mobility without the need for electrical contacts.