Fig 4-8 SCLT without SAMs treatment, output current varies with voltage from emitter to collector, and step by grid voltage.
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Chapter V Conclusion
We have fabricated a high on/off ratio SCLT from 2×104 to 2×105. More important is the yield, we demonstrated a reliable and easy process. To achieve this result, we modified and optimized every parameter in SCLT. Compared to P3HT horizontal TFT, our performance is tremendously well. From the starting chapter, we pursued a high on/off ratio, high output current, and low cost devices, thus we cannot achieve all best results at same time, but we still reached every goal from the following experiment.
By this mature process, we varied grid positions, and we knew that grid position adjust on and off state voltage, impact subtreshold swing voltage. This is important for future device designing, especially analog devices. Second is purposed an inverted (top injection SCLT) structure here. Before this device, many methods have been tried. This top injection SCLT is useful for new polymer as active layer, especially air stable polymer. Although we noticed that current would be lower if Al electrode had been treated by O2 plasma. Third is an extremely simple devices, we used n-octadecylphosphonic replacing SiOx layer. This devices is very suitable for large area fabrication, although performance is not good, but acceptable. The only one vacuum deposition process is the Al grid and Al emitter layer, and the Al deposition requirement is cheap. The goal of “all solution process” is possible if we can find a method to replace this Al deposition.
In the future, we will try smaller porous structure. We can get dramatically improve when decreasing the radius of PS ball (the “hole” of channel) base on a very tentative simulation (Appendix). Maybe SAM treatment is suit for this small radius structure, because
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the small PS ball limits the grid and insulator thickness to PS ball’s radius.
Another way is using soft lithography to define the porous. As we mentioned, PS ball distribution is random, we’d like to control this distribution from random to ordering.
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Chapter VI Appendix
Figure A-1 Various structures simulation results
This is very a very tentative simulation. A lot of conditions SCLTs have been simulated, through not completely match our result, but acceptable. The blue one is our bottom injection SCLT, and the lowest one is scale down this PVP2000 bottom injection SCLT to PVP1000, and the hole radius decrease from 100nm to 50nm, P3HT thickness also decrease. We can see on/off ratio is dramatically increasing. Practically this smaller devices is hard to control the insulator breakdown, hope this problem can be solved in the future.
Appreciate Lin’s simulation.
Raius 50nm PS ball
PVP 2000
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