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Herein, this study reports scalable and selective n-type conversion (N/C) approach for single walled carbon nanotube (SWNT) transistors with high reproducibility by using novel control of hydroxyl groups through condensation on the surface of SWNTs, via the patternable cross-linked polyvinyl alcohol (C-PVA), followed by encapsulation of photo-definable hydrophobic polymer (~SU8). Moreover, N/C process capability is statistically evaluated in terms of selective doping, process yield, and statistical variation in electrical parameters, and as practical validation, complementary inverters, NOR and NAND logic gates are fully demonstrated. As one of key findings, it is elucidated that N/C uniformity and its underlying physics, supported by Fourier-transform infrared spectroscopy (FTIR) and Raman analysis, are highly correlated with ambient condition, C-PVA thickness, and encapsulation. More practically, reproducible field effect mobility for n-type (or p-type) SWNT TFTs after (or before) N/C are achieved at ~ 3.65 ± 1.30 (or 8.76 ± 2.16) cm2 V−1 s−1, with magnificent process yield (~100%) and reasonable mobility reduction, which is on par with the previous report. Hence, all demonstration and their analyses suggest that this scalable N/C scheme for SWNT TFTs can be one of core technologies for the next generation semiconductor-based devices and their envisioned application.

Cost-effective gas-phase synthesized single walled carbon nanotubes (SWCNTs) were first employed for the surface modification of indium tin oxides (ITO) via electrostatic coating of poly-l-lysine (PLL). Compared with control substrates of bare ITO and SWCNT-PLL-slide glasses, SWCNT-PLL-ITO, with high catalytic properties associated with large surface areas, showed significant improvement of electro catalytic activity toward the oxidation of dopamine (DA) and uric acid (UA). The cyclic voltammetric (CV) peak separation of oxidation for both DA and UA was estimated to be ∼ 0.13 V, which renders them capable of simultaneously detecting DA and UA in a mixed solution. The differential pulse voltammetry (DPV) technique was further performed to obtain a linear detection range of DA from 1.0 μM to 100 μM, and a detection limit of 1.0 μM was confirmed in the mixed solution. Furthermore, the practical analytical ability of the method was finally confirmed by selective detection of both DA and UA in human urine samples without any preliminary treatment, implying the feasibility of applying bio-sensors in a low-cost manner.

In recent past, for next-generation device opportunities such as sub-10 nm channel field-effect transistors (FETs), tunneling FETs, and high-end display backplanes, tremendous research on multilayered molybdenum disulfide (MoS2 ) among transition metal dichalcogenides has been actively performed. However, nonavailability on a matured threshold voltage control scheme, like a substitutional doping in Si technology, has been plagued for the prosperity of 2D materials in electronics. Herein, an adjustment scheme for threshold voltage of MoS2 FETs by using self-assembled monolayer treatment via octadecyltrichlorosilane is proposed and demonstrated to show MoS2 FETs in an enhancement mode with preservation of electrical parameters such as field-effect mobility, subthreshold swing, and current on-off ratio. Furthermore, the mechanisms for threshold voltage adjustment are systematically studied by using atomic force microscopy, Raman, temperature-dependent electrical characterization, etc. For validation of effects of threshold voltage engineering on MoS2 FETs, full swing inverters, comprising enhancement mode drivers and depletion mode loads are perfectly demonstrated with a maximum gain of 18.2 and a noise margin of ≈45% of 1/2 VDD . More impressively, quantum dot light-emitting diodes, driven by enhancement mode MoS2 FETs, stably demonstrate 120 cd m-2 at the gate-to-source voltage of 5 V, exhibiting promising opportunities for future display application.

In this letter, spray-coated single walled carbon nanotubes (SWNTs) as one of alternative electrodes in SnO thin-film transistors are demonstrated for emerging electronic applications. Herein, the device architecture of SnO TFTs with a polymer etch stop layer (SU-8) enables the selective etching of SWNTs in a desired region without the detrimental effects of SnO channel layers. Moreover, SnO TFTs with SWNT electrodes as substitutes successfully demonstrate decent width normalized electrical contact properties (~1.49 kΩ cm), field effect mobility (~0.69 cm2 V−1 s−1), sub-threshold slope (~0.4 V dec−1), and current on–off ratio (I on/I off ~ 3.5 × 103). Systematic temperature dependency measurements elucidate that SnO channel transports with an activation energy within several tens of meV, together with decent contact resistance as compared to that of conventional Ni electrodes.

We demonstrated highly stable multilayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with negligible hysteresis gap (ΔV(HYS) ∼ 0.15 V) via a multiple annealing scheme, followed by systematic investigation for long-term air stability with time (∼50 days) of MoS2 FETs with (or without) CYTOP encapsulation. The extracted lifetime of the device with CYTOP passivation in air was dramatically improved from 7 to 377 days, and even for the short-term bias stability, the experimental threshold voltage shift, outstandingly well-matched with the stretched exponential function, indicates that the device without passivation has approximately 25% larger the barrier distribution (ΔE(B) = k(B)T(o)) than that of a device with passivation. This work suggests that CYTOP encapsulation can be an efficient method to isolate external gas (O2 and H2O) effects on the electrical performance of FETs, especially with low-dimensional active materials like MoS2.

The authors demonstrate the enhancement mode p-type SnO thin-film transistors (TFTs) using dual gate (DG) structures. The cross-linked polyvinyl alcohol dielectric with a polymethylmethacrylate buffer layer is formed as a top gate (TG) insulator of the DG SnO TFT. The fabricated DG SnO TFT exhibits better electrical performances than the bottom gate (BG) and TG SnO TFTs including higher field-effect mobility and smaller subthreshold slope. In fabricated DG TFTs, the threshold voltage (Vth) of the BG TFT is linearly modulated by the voltage applied to the TG electrode. The BG transfer curve exhibits a depletion mode operation when measured while TG is grounded, but operates in the enhancement mode with a negative Vth (=−0.9 V) when a positive bias of 10 V is applied to the TG electrode. The enhancement mode operation of p-type SnO TFTs can increase the output voltage swing range and decreases the off-stage leakage currents of the complementary logic circuits.