AVS2011 Session TC-ThP: Transparent Conductors and Printable Electronics Poster Session

Thursday, November 3, 2011 6:00 PM in East Exhibit Hall

Thursday Evening

Time Period ThP Sessions | Topic TC Sessions | Time Periods | Topics | AVS2011 Schedule

TC-ThP-1 A Combinatorial Thin Film Sputtering Approach of the Synthesis and Characterization of Al2O3-TiO2 High-k Dielectrics for Oxide TFT Application
JooHyon Noh, Jiyong Noh, Philip Rack (The University of Tennessee)
For the last decade, oxide based thin-film transistors (TFTs) have been extensively investigated because of their transparency, high mobility, low process temperature which are expected to serve as the basis for new optoelectronic and flexible devices. However, most of the work on oxide TFTs still rely on conventional dielectrics from Si technology, such as plasma-enhanced chemical vapor deposited (PECVD) SiO2 or SiNx with process temperature of 250–300°C. For high performance, low-cost and flexible electronics, high-k dielectrics at low process temperatures are needed. rf sputtering is alternative process for low temperature dielectrics. Usually, the deposition rate with oxide target is very low, so it is not compatible for mass production. In order to overcome this problem, reactive sputtering is adapted in this study. Although oxide TFTs with low-temperature sputtered materials such as Al2O3, HfO2, Y2O3, Ta2O5 have already been reported in the literature, TFTs performance are worse than standard higher temperature dielectrics because of high interface trap density due to low temperature. In order to improve the TFT performance, high-k materials are preferable. However, most of the high-k materials show a polycrystalline structure and small bandgap, hence the leakage current is high and breakdown voltage is low. These problems can be overcome through a combination of high-k but low bandgap and low-k but large bandgap materials. In this study, TiO2 is chosen as a high-k material because of very high dielectric constant of ~ 80, and Al­2O3 is chosen as a low-k material because of large bandgap of 8.7 eV. For optimization of high dielectric constant and low leakage current, a combinatorial thin film sputtering approach is used for the synthesis and characterization of Al2O3-TiO2 high-k dielectrics because a combinatorial thin film sputtering approach can yield a wide range of compositions via a single co-sputter deposition process. The composition ranges of the films are simulated using a co-sputtering simulation and compared favorably to compositions measured by the wavelength dispersive spectrometer (WDS). The TFTs are fabricated with a bottom-gate staggered structure using amorphous indium gallium zinc oxide (a-IGZO) and In2O3 as the semiconducting active layer. Standard I-V and C-V data on the dielectric multilayers will be compared as a function of composition and finally, the TFTs’ performance will be presented according to the relative contents of TiO2 and Al2O3.
TC-ThP-2 Fabrication and Characterization of Sub-micron OTFT Using Ink Jet Combined Imprint Process
Kyohyeok Kim, Namyong Kwon, Ilsub Chung (Sungkyunkwan Univ., Republic of Korea)
We fabricated sub-micron organic thin film transistors on polyethersulphone (PES) substrate using ink jet printing combined with an imprint method. The channel lengths of OTFTs were in the range between 500 nm and 1 um. 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene was used as an active material and Polyvinyl alcohol (PVA) was chosen as a gate insulator. TIPS pentacene was printed by jetting onto the confined channels which were prepared using imprinting. The surface of confined channel was modified by UV irradiation in order to enhance the crystallinity of tips pentacene. The physical properties were analyzed using SPM, SEM, and XRD. The electrical properties were extracted from the transfer characteristics which were measured using Keithley-4200.
TC-ThP-3 Study on Multiple Stacked 6,13-bis(triisopropylsilylethynyl) (TIPS) Pentacene for Improved Organic Thin Film Transistor
Sanguk Lee (Sungkyunkwan Univ. & Samsung Mobile Display, Republic of Korea); Jaejun Han, Kyohyeok Kim, Injune Bae, Ilsub Chung (Sungkyunkwan Univ., Republic of Korea)
We found that the crystallization of TIPS pentacene thin film plays an important role in determining the electrical property of organic thin film transistor (OTFT). Ink jetted TIPS pentacene film reveals 2 different types of grains namely due to the coffee strain effect. The better electrical properties were obtained from the OTFTs with bigger grains that had been possible due to the multiple stacked TIPS pentacene layer. Poly-4-vinylphenol (PVP) was used as a gate insulator, and Au electrode was evaporated using a shadow mask. The channel lengths of OTFTs with the bottom gate structure were 20-50 um. The physical properties of the TIPS pentacene films were analyzed using optical microscope (OM), x-ray diffraction (XRD) and secondary electron microscopy (SEM). The electric characteristics of OTFT were obtained using Keithley- 4200.
Time Period ThP Sessions | Topic TC Sessions | Time Periods | Topics | AVS2011 Schedule