Direct grazing-angle X-ray scattering evidence of the order–disorder transition and interdigitation of side chains in a conjugated polymer poly­(3-hexylthiophene) (P3HT) is presented. The free methyl ends of the side chains exhibit closest packing, as in n-alkane crystallization, and cause a structural mismatch due to the difference between their packing density and the areal density of the attached ends. This mismatch is resolved by increases in the tilt angle of the side chains and local interdigitation. In situ X-ray scattering and electrical measurements show that the structural transition and interdigitation of these side chains strongly affect its surface morphology as well as the charge transport properties of the resulting P3HT-based organic field-effect transistor. Since most conjugated polymers have side chains, the results of this study provide a deeper understanding of the effects of side chains on the structural and electrical properties of conjugated backbones. These results also provide a new perspective on the formation of a metastable polymorph consisting of interdigitated P3HT.

We report the fabrication and characterization of indium gallium zinc oxide (IGZO)-based synaptic thin-film transistors. Radio-frequency (RF) magnetron-sputtered AlOx thin films are embedded in the IGZO channel as charge-trapping layers to provide synaptic behavior. The voltage pulse introduced at the gate electrodes traps or de-traps charges in the embedded AlOx layer thus modulates the channel current, which in turn leads to the ability to mimic biological synaptic behaviors such as excitonic postsynaptic current, paired-pulse facilitation, and potentiation and depression. Simulation results suggest that the device can perform properly as a synaptic unit in an artificial neural network.

We report the fabrication and characterization of indium gallium zinc oxide (IGZO) tunneling thin-film transistors (TFTs). Both the IGZO channel and an Al2O3 tunneling barrier layer were deposited using the radio-frequency (RF) magnetron sputtering method. Compared with a conventional device, our device exhibited rapid saturation at a much smaller drain bias. Interestingly, we observed two different current saturation mechanisms within a single device, which can be explained as competition between the depletion envelop near the source electrode and channel depletion near the drain electrode. This work represents an industry-friendly method to implementing the tunnel-contact approach in the display industry.

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