Reminder: EE PhD Oral Examination - Yoonyoung Chung, Tuesday, June 7, 3:30 PM

Yoonyoung Chung yychung at
Mon Jun 6 15:50:04 PDT 2011

Stanford University Oral Defense - Department of Electrical Engineering 

Speaker: Yoonyoung Chung 
Principal Advisor: Prof. Zhenan Bao 
Co-advisors: Prof. Boris Murmann and Prof. Yoshio Nishi 

Date: Tuesday, June 7, 2011 
Time: 3:30 PM (Refreshments at 3:15 PM) 
Location: Packard 101 

Title: Organic Transistors for Flexible Electronics: fabrication and device physics 

Organic transistors have shown promising potentials in flexible electronics. Because the transistors can be directly fabricated on flexible plastic substrates at low temperatures less than 100 °C, researchers envision development of novel electronic applications, such as flexible displays, flexible circuits, and conformal sensors. However, there are still several challenges to be solved for making practical applications, beyond laboratory-level demonstrations. 

In the first part of my talk, I will present fabrication technologies for organic transistors. I have demonstrated high-capacitance gate dielectric on plastic substrates using atomic layer deposition. This low-temperature process was used to fabricate high-performance flexible organic transistors. Also, I will describe flexible shadow masks made of parylene-C for making small patterns. Due to their good adhesion on a variety of surfaces, the shadow masks patterned small feature sizes of less than 10 μm with high yield. 

Second, I will present controlling current-voltage characteristics of organic transistors from the device physics point of view. Self-assembled monolayers and different gate electrodes were used to modify electric dipoles in the gate dielectric and gate work functions, respectively. Engineering the dipoles and the gate work functions provided a wide range of threshold voltage control over 0.6 V at a supply voltage of 2.5 V. I will also show that the dipoles can be used to improve significantly the air stability of n-channel (electron conducting) organic transistors, which are generally not stable in air.

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