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Reversible switching characteristics of organic nonvolatile memory transistors (ONVMTs) using chemically synthesized graphene oxide (GO) nanosheets as a charge-trapping layer are reported. The transfer curves of GO based ONVMTs showed large gate bias dependent hysteresis with threshold voltage shifts over 20 V. After writing and erasing, stored data were well maintained showing more than two orders of ON/OFF ratio (ION/IOFF=∼102) for 104 s. These results suggest that GO nanosheets are one potential candidate as the charge-trapping layer in ONVMTs.

Precise control over the threshold voltage of pentacene-based organic thin film transistors was achieved by inserting a genetically engineered quartz-binding polypeptide at the semiconductor-dielectric interface. A 30 V range was accessed with the same peptide by adjusting the pH of the solution for peptide assembly while leaving other device properties unaffected. Mobility of 0.1–0.2 cm2 V−1 s−1 and on/off current ratio of >106 could be achieved for all devices regardless of the presence of the neutral peptide or the peptide assembled in acidic or basic conditions. This shift in threshold voltages is explained by the generation of charged species and dipoles due to variation in assembling conditions. Controlling device characteristics such as threshold voltage is essential for integration of transistors into electronic circuits.

Low-voltage pentacene-based organic thin film transistors (OTFTs) are demonstrated with polystyrene (PS)/hafnium oxide (HfOx) hybrid dielectrics. Thermal annealing of PS films on HfOx at 120 °C (PS-120) induces a flatter orientation of the phenyl groups (tilt angle 65°) at the surface compared to PS films without annealing (PS-RT) (tilt angle 31°). The flatter phenyl group orientation leads to better matching of surface energy between pentacene and PS. Pentacene deposited on PS-120 display higher quality thin films with larger grain sizes and higher crystallinity. Pentacene OTFTs with PS-120/HfOx hybrid dielectrics can operate at low-voltage (

A vacuum-free solution processed hybrid dielectric composed of an n-octadecyl-phosphonic acid self-assembled monolayer on amorphous sol-gel processed hafnium oxide (HfOx) is demonstrated for low-voltage polymer semiconductor-based thin film transistors (TFTs). The phosphonic acid/HfOx hybrid dielectric provides high capacitance (0.41 μF/cm2), low leakage current (5×10−8 A/cm2), and is compatible with plastic substrates. The utility of this dielectric is demonstrated by fabricating high performance polymer TFTs based on a spin coated thiophene-thiazolothiazole copolymer with operating voltages under −2 V, negligible hysteresis, subthreshold slopes as low as 100 mV/dec, and hole mobilities up to 0.11 cm2 V s.

C60-based organic thin film transistors (OTFTs) have been fabricated using a n-octadecylphosphonic acid self-assembled monolayer/sol-gel processed hafnium oxide hybrid dielectric. With the combination of high capacitance (580 nF/cm2) and low leakage current density (8×10−9 A/cm2), this hybrid dielectric yields C60 OTFTs operating under 1.5 V with an average n-channel saturation field-effect mobility of 0.28 cm2/V s, high on-off current ratio of 105, and low subthreshold slope of 100 mV/decade. The low surface energy of the n-octadecylphosphonic acid allows C60 to form a thin film with large grains that provide an efficient charge carrier pathway for the low-voltage OTFTs.

Pentacene-based organic thin-film transistors (OTFTs) have been fabricated using π-σ-phosphonic acid self-assembled monolayers (SAMs) on top of aluminum oxide as the gate dielectrics. With ultrathin dielectrics, high capacitances up to 760nF∕cm2 and low leakage current densities of 10−8A∕cm2 at 2V could be obtained, allowing operation of OTFTs within −3V. Vast improvements in the gate leakage current (∼2 orders), on/off current ratio (1 order), and subthreshold slope down to 85mV∕decade are achieved compared to control devices without SAMs. The OTFTs with pentacene vapor deposited at room temperature on SAM dielectrics-modified substrates exhibit mobilities of 0.14–0.30cm2∕Vs, on/off current ratios of 105, and threshold voltages of −(1.3–1.5)V.