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Boampong, Amos Amoako,Kim, Ju Ryong,Lee, Jae-Hyun,Kim, Min-Hoi American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.8
<P>We suggest a feasible method to enhance the electrical performance of the organic nonvolatile memory transistor by reducing the surface roughness of the ferroelectric polymer insulator. A homobilayer of poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] was used to control the high surface roughness of the conventional single layer [P(VDF-TrFE)] polymer insulator. The smoothening of the polymer insulator was achieved as the Z(rms) roughness was as low as 11.9 nm compared to the aboriginal single P(VDF-TrFE) film of 18.8 nm. The homo-bilayer P(VDF-TrFE) thin film transistor showed a higher memory on-off ratio (about 100) and mobility (2 x 9x10(-2) cm(2)v(-1)s(-1)) compared with the native P(VDF-TrFE) with memory on-off ratio of 16 and mobility of 2.1x10(-2) cm(2)v(-1)s(-1). The underlying mechanism for the mobility enhancement which resulted in a high on-off ratio is mainly attributed to the reduction of the surface roughness of the ferroelectric polymer insulator.</P>
Huseynova Gunel,Boampong Amos Amoako,Yu Kyeong Min,Lee Ye-Seul,Lee Jonghee,Kim Min-Hoi,Lee Jae-Hyun 한국정보디스플레이학회 2023 Journal of information display Vol.24 No.1
We present an n-doped poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer and its application in n-type oxide thin-film transistors (OxTFTs) as a source and drain electrode material. A reduced molecule of a cationic dye, methyl red (MR), was used as an effective solution-processed n-type dopant. The sequential de-doping and doping of the initially p-doped PEDOT:PSS polymer with the reduced MR (r-MR) effectively removed positive charges via cancellation by the added electrons. As a result, the electron conductivity of PEDOT:PSS increased from 3.4 S/cm to ∼51 S/cm, while its work function decreased from 4.8 eV to 3.5 eV. This is one of the lowest values of the work function reported for PEDOT:PSS. The n-doped PEDOT:PSS films were eventually applied as a suitable material to fabricate the contact electrodes of solution-processed bottom-gate top-contact amorphous indium-gallium-zinc oxide-based OxTFTs. The resultant devices exhibited electron mobility over ten times better compared to those with undoped PEDOT:PSS electrodes. Therefore, we suggest this method as a highly suitable and low-cost technique for improving electron transport in PEDOT:PSS and all solution-processed conductors. Further investigations with this method are expected to expand the application of PEDOT:PSS to other sectors of optoelectronics.
Selective Etching of Dielectric Buffer Layer for Organic Ferroelectric Memory Cell
Jae-Hyeok Cho,Amos Amoako Boampong,Min-Hoi Kim 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.5
Ferroelectric random access memory cell (FeRAM) consists of one selection transistor with high switching performanceand one memory transistor with large hysteresis. The simple fabrication method for the selection transistor with high mobilityand the memory transistor with large hysteresis within one cell has been a challenge and not adequately explored. Wedemonstrated the selective etching of dielectric polymer buffer layer for the organic ferroelectric memory cell. The dielectricbuffer layer of polymethylmethacrylate (PMMA) is formed on the ferroelectric gate insulator of poly(vinylidenefluoride-cotrifluoroethylene)[P(VDF-TrFE)] to enhance mobility of selection transistors. The UV ozone was partially treated on thePMMA/P(VDF-TrFE) bilayer which enables the top PMMA layer to be selectively etched due to the large process marginbecause the UV ozone etch rate of PMMA to P(VDF-TrFE) is more than 50 times. While the selection transistor with thePMMA buffer layer shows an enhanced mobility of 0.2 cm2V−1 s−1, the memory transistor undergoing UV ozone etchingprocess with post-annealing exhibits conventional ferroelectric memory properties such as large hysteresis and good memoryretention characteristics. In our ferroelectric memory cell, the memory transistor is electrically isolated completely fromthe high negative bias in the bit-line during switching-off of the selection transistor. Our polymer selective etching for aferroelectric memory cell is a useful technique in developing nonvolatile polymer FeRAM.