cfaed Seminar Series

cfaed Seminar Series

Dr. Ulrike Kraft , Murmann-Mixed-Signal-Group, Stanford University, USA

Organic Thin-Film Transistors and Circuits on Flexible and Stretchable Substrates

20.12.2016 (Tuesday) , 10:00 - 12:00
Lecture Theatre , Würzburger Str. 46 , 01187 Dresden

Potential applications of organic thin-film transistors (TFTs) are flexible sensors, bendable
displays, and integrated circuits on unconventional substrates, e.g., electronic anti-counterfeiting
features on banknotes. For these applications, the TFTs must meet a number of
requirements, such as low-voltage operation, good shelf-life stability and high switching
The first part of the talk will be dedicated to organic TFTs on flexible plastic and paper
substrates based on the high-mobility small-molecule organic semiconductor DNTT and its
didecyl and diphenyl derivatives C10-DNTT and DPh-DNTT. TFTs with channel lengths ranging
from 100 μm down to 0.5 μm have been fabricated using high-resolution silicon stencil masks
and low-voltage operation (3V) has been enabled by a very thin gate dielectric consisting of a
thin AlOx layer and a self-assembled monolayer (SAM) of an alkylphosphonic acid. For 11-stage
unipolar and complementary ring oscillators on plastic substrates, signal propagation delays per
stage as short as 240 ns and 4.2 μs have been measured in ambient air at a supply voltage of 4 V.
Building on the recent technology advances in the area of flexible electronics, novel applications
scenarios can be explored. For example, a novel and attractive target are health-monitoring
devices interlinked with the human body, e.g. skin-like epidermal sensor sheets, artificial skin
on prosthetics and wearable electronics. To accommodate for deformations such as twisting
and stretching, these next-generation electronics need to be extremely stretchable. Therefore,
the next frontier is to merge mechanical and electrical requirements and realize not only flexible
but also reliable stretchable electronics that are compatible with the soft, curvilinear surfaces of
biological tissue. The second part of the talk will address stretchable electronic materials and
transistors that are studied at Stanford University. A special focus will be on the development
and characterization of printed, intrinsically stretchable interconnects that will be a key-component
for stretchable circuits.


Ulrike Kraft studied Applied Natural Science at the TU Bergakademie Freiberg and performed
her PhD work on organic electronics in the group of Dr. Hagen Klauk at the Max Planck Institute
for Solid State Research Stuttgart, under the supervision of Prof. Edwin Weber, TU
Bergakademie Freiberg. Her PhD work focused on the contact resistance and air stability of
organic TFTs and the fabrication and analysis of organic transistors and circuits on flexible plastic and paper substrates. In 2015, she was awarded a PhD in Chemistry by the TU Bergakademie Freiberg in 2015. Currently, Ulrike Kraft is a postdoctoral researcher with Prof. Murmann in the Electrical Engineering Department at Stanford University, where she focuses on intrinsically stretchable organic devices and circuits.

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