Abstract
This thesis focusses on printable flexible switches for sub 6 GHz operation, their fabrication, improvement, and stability, for 5G and IOT devices. Indium arsenide nanowire field effect transistors were initially thought as a good semiconductor candidate. Their stability was studied under a variety of atmospheres and substantial long term decay was found preventing their use in printed electronics. This was attributed to either oxidation or leeching of the arsenic into the substrate. Fully printed low resistance carbon nanotube FETs are investigated in detail and their stability, speed, and uses discussed. Resistances in devices as low as 25 Ohms are shown to be possible and their challenges are discussed in detail. A novel method for the creation of micron sized gaps using ink-jet printing is developed which relies only on intrinsic properties of ink-jet printing. This simple method is shown to produce gaps as low at 0.7 microns with limited optimisation necessary.
Fully printed carbon nanotube electrolyte gated RF switches are developed and the first ever s-parameter measurements of these switches are undertaken. A simple circuit model for their operation is given and insights into the measurement of flexible RF electronics are discussed. Novel circuits containing these switches are made, measured, and their operation and limitations such as switching speed discussed. An ink-jet printed frequency reconfigurable dipole antenna incorporating the switches for IOT is developed and shown to match simulations closely. Ultra wide band antenna horns are investigated and used to measure the ink-jet printed devices used in this work.Paper based electronics are developed using the above technology, and low impedance switches are fabricated for the first time. Issues surrounding paper technology and fabrication are investigated from a RF point of view with the aim of making novel origami circuits.