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Open Access Publications from the University of California

Novel Processing Schemes for Material Systems on Amorphous and Flexible Substrates

  • Author(s): Chen, Kevin Qiwen
  • Advisor(s): Javey, Ali
  • et al.

With the rise of the Internet of Things (IOT), demand for novel devices and sensors for a variety of applications has exploded, and as a result, there is a need for the development of new processing schemes and materials systems to accommodate the expanding needs of these applications. In particular,

Chapter 2 explores the growth of III-V semiconductors with quality approaching that of epitaxial thin films directly onto amorphous substrates using a new growth mode known as template liquid phase (TLP) crystal growth. The fundamental theory and limitations of TLP growth are explored and the toolboxes necessary for enabling this method to be widely used such as in-situ doping and growth of ternary III-V compounds are demonstrated. Proof of concept demonstrations of multilayer growth for 3D integration, transistors and phototransistors for electronic and optoelectronic integration, and transfer onto plastic for flexible applications are shown.

Chapter 3 extends the concept of using liquid metals to the field of flexible and deformable electronics. As an analogy to solid state electronics, where materials with varying electronic properties (metallic, semiconducting, insulating, etc) are connected together to form functional devices, the concept of “liquid state electronics” is introduced. Liquids, being able to conform to any shape, can enable electronic devices which can sustain extremely large amounts of deformation. By using microchannels to prevent intermixing, liquid-liquid heterojunctions composed of liquid metal (InGaSn) as the interconnect and ionic liquids as sensors are demonstrated.

Chapter 4 focuses on the usage of solution processed carbon nanotubes for enabling high-performing flexible electronic devices. First, a method for n-type doping of carbon nanotubes for CMOS applications is introduce using fixed charge in silicon nitride films. An extension of this doping method to other materials systems, in particular 2D WSe2 is demonstrated as well. The usage of carbon nanotubes in printed electronics for enabling large scale, high throughput, flexible electronics manufacturing is explored, with >97% pixel yield in a 20×20 active matrix backplane array being achieved. A proof of concept demonstration of tactile pressure mapping using the printed nanotube active matrix backplane is shown as a potential application of such devices.

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