September 26, 2013
Hosted by: Ken Shepard
Speaker: Dr. Hongki Kang, University of California, Berkeley
Printed electronics employing solution-processed electronic materials has been proposed to be the key to realizing low-cost large-area electronic systems on flexible substrates such as disposable RFID tags and various types of sensors. However, the performance of printed transistors on plastic is not generally adequate so far for most proposed applications due to the large dimension of the transistors and limited performance of printable semiconductor. In this talk, I propose a highly-scaled roll-based printing technique that allows sub-femtoliter scaling of printed inks, resulting in printed features as small as 2~3 µm while printed at high speed up to 1 m/s. By using this novel printing technique with optimization of printable organic semiconductor, beyond MHz operation of printed inverters on plastic is achieved, which can open up new applications. Along with the demonstration, I will discuss how printing process is different from conventional lithography process, particularly focusing on accurate pattern generation. In addition, I will discuss experimental results on understanding of the origin of 1/f noise in organic TFTs, which limits signal-to-noise ratio during low-frequency operation of the same. Based on detail analysis of observed non-idealities in the 1/f noise with respect to different grain size and operation region, it is found that the trapping/de-trapping of carriers by/from the traps within the semiconductor is the dominant mechanism of low-frequency noise generation. Lastly, if time permits, recent efforts on using printed electronics for bio/bio-medical applications will be discussed.