We report a low-voltage organic field-effect transistor consisting of an extended gate sensory area to detect various ions in a solution. The device distinguishes various ions by the shift in threshold voltage and is sensitive to multiple ions with various concentrations. X-ray photoelectron spectroscopy measurements and the resistance changes at the sensor area prove that the ions are doped into the sensitive film at the sensor area. Because of the effect of doping, the conductivity of the semiconductor polymer film changes thus causing a threshold voltage shift.
Metal organic pentacene based low voltage organic thin film transistors with field effect mobility as large as 0.8 cm2/V-1.s-1 and on/off current ratio larger than 106 have been fabricated. Thin films deposited by evaporation at different deposition rate has different morphology which leads to a difference in transistor characteristics. The films with a deposition rate of 2A/sec has better morphology and also the transistor behavior. AFM (atomic force microscope) and STM (scanning tunneling microscope) were used to understand the morphology and ordering of the molecules on the silicon surface which helps the transistor to operate at low voltages. The results presented here show a strong correlation between molecular ordering and the need of well-ordered films for the performance of organic thin film transistors (OTFT's).
Tris (8-hydroxyquinoline) aluminum (Alq3) is a commonly used electron transporting and/or light emitting material in organic light emitting diodes (OLEDs). However, it is well known that Alq3 is very sensitive to atmosphere exposure and that photoluminescence of Alq3 films decreases with the time of atmosphere exposure. Degradation is also a serious problem in Alq3 based OLEDs. Several degradation mechanisms have been identified in these devices, including formation of unstable cationic species due to passage of holes. Therefore, there is lots of interest in improving the stability of Alq3. We have synthesized Tris (8-hydroxyquinoline-5 sulphonic acid) aluminum [Al(qS)3] in order to improve the stability. We performed electron spin resonance measurements on Alq3 and Al(qS)3 powders. Unlike Alq3 which exhibited strong ESR signal, Al(qS)3 produced no detectable ESR signal indicating absence of free radicals in this material. To test the environmental stability of Al(qS)3 films, we have performed photoluminescence (PL) measurements in humid air at different temperatures and found that Al(qS)3 exhibits improved stability. After comparing the stability of Alq3 and Al(qS)3 thin films, fabrication of the light emitting diodes with Al(qS)3 emitting layer was attempted in order to compare the performance with Alq3 based devices.
In this work, we report a simple method for mass production of ZnO tetrapod nanorods. A mixture of Zn and graphite powders (ratio 2:1) was placed in a quartz tube. The quartz tube was placed in a horizontal tube furnace and heated up to 950°C. The tube was then removed from the furnance and quenched to room temperature. Fluffy products white in color were formed on the walls of the tube. Obtained products were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence. SEM images showed tetrapod-like ZnO nanorods. The four tetrapod legs were approximately equal in length, and the length of tetrapod legs was in the range ~1-3 μm. We investigated influence of the growth temperature (in the range from 700°C to 1100°C) and Zn to catalyst ratio to the properties of obtained products. Fabrication is different atmospheres (air, argon, nitrogen, humid argon, and humid nitrogen) was also performed. The influence of growth conditions (temperature, atmosphere, and catalyst concentration) to the formation and properties of ZnO nanorods is discussed.
Conference Committee Involvement (3)
Hybrid Memory Devices and Printed Circuits 2017
10 August 2017 | San Diego, California, United States
Printed Memory and Circuits II
1 September 2016 | San Diego, California, United States
Printed Memory and Circuits
11 August 2015 | San Diego, California, United States
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