Seung Hee Nam

DNA-Base Guanine as Hydrogen Getter and Charge-Trapping Layer Embedded in Oxide Dielectrics for Inorganic and Organic Field-Effect Transistors

DNA-base small molecules of guanine, cytosine, adenine, and thymine construct the DNA double helix structure with hydrogen bonding, and they possess such a variety of intrinsic benefits as natural plentitude, biodegradability, biofunctionality, low cost, and low toxicity. On the basis of these advantages, here, we report on unprecedented useful applications of guanine layer as hydrogen getter and charge trapping layer when it is embedded into a dielectric oxide of n-channel inorganic InGaZnO and p-channel organic heptazole field effect transistors (FETs). The embedded guanine layer much improved the gate stability of inorganic FETs gettering many hydrogen atoms in the gate dielectric layer of FET, and it also played as charge trapping layer to which the voltage pulse-driven charges might be injected from channel, resulting in a threshold voltage (Vth) shift of FETs. Such shift state is very ambient-stable and almost irrevocable even under a high electric-field at room temperature. So, Boolean logics are nicely demonstrated by using our FETs with the guanine-embedded dielectric. The original Vth is recovered only under high energy blue photons by opposite voltage pulse (charge-ejection), which indicates that our device is also applicable to nonvolatile photo memory.

NOT and NOR Logic Circuits Using Passivation Dielectric Involved Dual Gate in a-InGaZnO TFTs

Dual-gate amorphous (a)-InGaZnO thin-film transistors (TFTs) are simply realized using the passivation layer of already fabricated bottom-gate TFTs as top-gate dielectric, so that an electrical biasing of either top or bottom gate may control the threshold behavior of the device. By applying a voltage to the top gate of a TFT that is serially connected to the next adjacent TFT, we could form a logic inverter with a decent voltage gain and desirable transition voltage, while a NOR logic circuit was also achieved by independent control of the dual gates. On the one hand, when both of the top and bottom gates are simultaneously controlled by single bias, our dual-gate TFT displays an excellent subthreshold swing property that leads to an excellent voltage gain in an inverter.