Graphene-based Devices for More than Moore Applications

University dissertation from KTH Royal Institute of Technology

Abstract: Moore's law has defined the semiconductor industry for the past 50 years. Devices continue to become smaller and increasingly integrated into the world around us. Beginning with personal computers, devices have become integrated into watches, phones, cars, clothing and tablets among other things. These devices have expanded in their functionality as well as their ability to communicate with each other through the internet. Further, devices have increasingly been required to have diverse of functionality. This combination of smaller devices coupled with diversification of device functionality has become known as more than Moore. In this thesis, more than Moore applications of graphene are explored in-depth.Graphene was discovered experimentally in 2004 and since then has fueled tremendous research into its various potential applications. Graphene is a desirable candidate for many applications because of its impressive electronic and mechanical properties. It is stronger than steel, the thinnest known material, and has high electrical conductivity and mobility. In this thesis, the potentials of graphene are examined for pressure sensors, humidity sensors and transistors.Through the course of this work, high sensitivity graphene pressure sensors are developed. These sensors are orders of magnitude more sensitive than competing technologies such as silicon nanowires and carbon nanotubes. Further, these devices are small and can be scaled aggressively.Research into these pressure sensors is then expanded to an exploration of graphene's gas sensing properties -- culminating in a comprehensive investigation of graphene-based humidity sensors. These sensors have rapid response and recovery times over a wide humidity range. Further, these devices can be integrated into CMOS processes back end of the line.In addition to CMOS Integration of these devices, a wafer scale fabrication process flow is established. Both humidity sensors and graphene-based transistors are successfully fabricated on wafer scale in a CMOS compatible process. This is an important step toward both industrialization of graphene as well as heterogeneous integration of graphene devices with diverse functionality. Furthermore, fabrication of graphene transistors on wafer scale provides a framework for the development of statistical analysis software tailored to graphene devices.In summary, graphene-based pressure sensors, humidity sensors, and transistors are developed for potential more than Moore applications. Further, a wafer scale fabrication process flow is established which can incorporate graphene devices into CMOS compatible process flows back end of the line.

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