Search Results (10)

In this study, we propose a bidirectional chemical sensor platform based on a reconfigurable ion-sensitive field-effect transistor (R-ISFET) architecture. The device incorporates Ni-silicide Schottky barrier source/drain (S/D) contacts, enabling ambipolar conduction and bidirectional turn-on behavior for both p-type and n-type configurations. Channel polarity is dynamically controlled via the program gate (PG), while the control gate (CG) suppresses leakage current, enhancing operational stability and energy efficiency. A dual-control-gate (DCG) structure enhances capacitive coupling, enabling sensitivity beyond the Nernst limit without external amplification. The extended-gate (EG) architecture physically separates the transistor and sensing regions, improving durability and long-term reliability. Electrical characteristics were evaluated through transfer and output curves, and carrier transport mechanisms were analyzed using band diagrams. Sensor performance—including sensitivity, hysteresis, and drift—was assessed under various pH conditions and external noise up to 5 V_pp (i.e., peak-to-peak voltage). The n-type configuration exhibited high mobility and fast response, while the p-type configuration demonstrated excellent noise immunity and low drift. Both modes showed consistent sensitivity trends, confirming the feasibility of complementary sensing. These results indicate that the proposed R-ISFET sensor enables selective mode switching for high sensitivity and robust operation, offering strong potential for next-generation biosensing and chemical detection. Full article

Organic cocrystals, which are assembled by noncovalent intermolecular interactions, have garnered intense interest due to their remarkable chemicophysical properties and practical applications. One notable feature, namely, the charge transfer (CT) interactions within the cocrystals, not only facilitates the formation of an ordered supramolecular network but also endows them with desirable semiconductor characteristics. Here, we present the intriguing ambipolar CT properties exhibited by nanosheets composed of single cocrystals of C₇₀/ferrocene (C₇₀/Fc). When heated to 150 °C, the initially ambipolar monoclinic C₇₀/Fc nanosheet-based field-effect transistors (FETs) were transformed into n-type face-centered cubic (fcc) C₇₀ nanosheet-based FETs owing to the elimination of Fc. This thermally induced alteration in the crystal structure was accompanied by an irreversible switching of the semiconducting behavior of the device; thus, the device transitions from ambipolar to unipolar. Importantly, the C₇₀/Fc nanosheet-based FETs were also found to be much more thermally stable than the previously reported C₆₀/Fc nanosheet-based FETs. Furthermore, we conducted visible/near-infrared diffuse reflectance and photoemission yield spectroscopies to investigate the crucial role played by Fc in modulating the CT characteristics. This study provides valuable insights into the overall functionality of these nanosheet structures. Full article

Oxygen and hydrogen mobility are among the important characteristics for the operation of solid oxide fuel cells, permselective membranes and many other electrochemical devices. This, along with other characteristics, enables a high-power density in solid oxide fuel cells due to reducing the electrolyte resistance and enabling the electrode processes to not be limited by the electrode-electrolyte-gas phase triple-phase boundary, as well as providing high oxygen or hydrogen permeation fluxes for membranes due to a high ambipolar conductivity. This work focuses on the oxygen and hydrogen diffusion of mixed ionic (oxide ionic or/and protonic)–electronic conducting materials for these devices, and its role in their performance. The main laws of bulk diffusion and surface exchange are highlighted. Isotope exchange techniques allow us to study these processes in detail. Ionic transport properties of conventional and state-of-the-art materials including perovskites, Ruddlesden–Popper phases, fluorites, pyrochlores, composites, etc., are reviewed. Full article

We propose an ambipolar chitosan synaptic transistor that effectively responds to binary neuroplasticity. We fabricated the synaptic transistors by applying a chitosan electric double layer (EDL) to the gate insulator of the excimer laser annealed polycrystalline silicon (poly-Si) thin-film transistor (TFT) with Ni-silicide (NiSi) Schottky-barrier source/drain (S/D) junction. The undoped poly-Si channel and the NiSi S/D contact allowed conduction by electrons and holes, resulting in artificial synaptic behavior in both p-type and n-type regions. A slow polarization reaction by the mobile ions such as anions (CH₃COO⁻ and OH⁻) and cations (H⁺) in the chitosan EDL induced hysteresis window in the transfer characteristics of the ambipolar TFTs. We demonstrated the excitatory post-synaptic current modulations and stable conductance modulation through repetitive potentiation and depression pulse. We expect the proposed ambipolar chitosan synaptic transistor that responds effectively to both positive and negative stimulation signals to provide more complex information process versatility for bio-inspired neuromorphic computing systems. Full article

Owing to the excellent properties of high selectivity, high thermal stability, and low cost, in the past twenty years, mixed protonic-electronic conducting hydrogen separation membranes have received extensive attention. In particular, dual-phase mixed protonic-electronic conducting membranes with high ambipolar conductivity are more attractive because of the high hydrogen permeability. This paper aimed to present a review of research activities on the dual-phase membranes, in which the components, the characteristics, and the performances of different dual-phase membranes are introduced. The key issues that affect the membrane performance such as the elimination of the inter-phase reaction, the combination mode of the phases, the phase ratio, and the membrane configuration were discussed. The current problems and future trends were simply recommended. Full article

A stable doping technique for modifying the conduction behaviour of two-dimensional (2D) nanomaterial-based transistors is imperative for applications based on low-power complementary oxide thin-film transistors. Achieving an ambipolar feature with a controlled threshold voltage in both the p- and n-regimes is crucial for applying MoTe₂-based devices as electronic devices because their native doping states are unipolar. In this study, a simple method to tune the threshold voltage of MoTe₂ field-effect transistors (FETs) was investigated in order to realise an enhancement-mode MoTe₂ thin-film transistor by implementing a facile method to modulate the carrier polarity based on the oxidative properties of MoTe₂ FETs. Annealing in air induced a continuous p-doping effect in the devices without significant electrical degradation. Through a precise control of the duration and temperature of the post-annealing process, the tailoring technique induces hole doping, which results in a remarkable shift in transfer characteristics, thus leading to a charge neutrality point of the devices at zero gate bias. This study demonstrates the considerable potential of air heating as a reliable and economical post-processing method for precisely modifying the threshold voltage and further controlling the doping states of MoTe₂-based FETs for use in logic inverters with 2D semiconductors. Full article

This study proposes a bidirectional chemical sensor platform using ambipolar double-gate ion-sensitive field-effect transistors (ISFET) with microwave-assisted Ni-silicide Schottky-barrier (SB) source and drain (S/D) on a fully depleted silicon-on-insulator (FDSOI) substrate. The microwave-assisted Ni-silicide SB S/D offer bidirectional turn-on characteristics for both p- and n-type channel operations. The p- and n-type operations are characterized by high noise resistance as well as improved mobility and excellent drift performance, respectively. These features enable sensing regardless of the gate voltage polarity, thus contributing to the use of detection channels based on various target substances, such as cells, antigen-antibodies, DNA, and RNA. Additionally, the capacitive coupling effect existing between the top and bottom gates help achieve self-amplified pH sensitivity exceeding the Nernst limit of 59.14 mV/pH without any additional amplification circuitry. The ambipolar FET sensor performance was evaluated for bidirectional electrical characteristics, pH detection in the single-gate and double-gate modes, and reliability in continuous and repetitive operations. Considering the excellent characteristics confirmed through evaluation, the proposed ambipolar chemical sensor platform is expected to be applicable to various fields including biosensors. And through linkage with subsequent studies, various medical applications and precision detector operations for specific markers will be possible. Full article

In this study, the efficient fabrication of nickel silicide (NiSi_x) Schottky barrier thin-film transistors (SB-TFTs) via microwave annealing (MWA) technology is proposed, and complementary metal-oxide-semiconductor (CMOS) inverters are implemented in a simplified process using ambipolar transistor properties. To validate the efficacy of the NiSi_x formation process by MWA, NiSi_x is also prepared via the conventional rapid thermal annealing (RTA) process. The Rs of the MWA NiSi_x decreases with increasing microwave power, and becomes saturated at 600 W, thus showing lower resistance than the 500 °C RTA NiSi_x. Further, SB-diodes formed on n-type and p-type bulk silicon are found to have optimal rectification characteristics at 600 W microwave power, and exhibit superior characteristics to the RTA SB-diodes. Evaluation of the electrical properties of NiSi_x SB-TFTs on excimer-laser-annealed (ELA) poly-Si substrates indicates that the MWA NiSi_x junction exhibits better ambipolar operation and transistor performance, along with improved stability. Furthermore, CMOS inverters, constructed using the ambipolar SB-TFTs, exhibit better voltage transfer characteristics, voltage gains, and dynamic inverting behavior by incorporating the MWA NiSi_x source-and-drain (S/D) junctions. Therefore, MWA is an effective process for silicide formation, and ambipolar SB-TFTs using MWA NiSi_x junctions provide a promising future for CMOS technology. Full article

We present the compact unified charge control model (UCCM) for carbon nanotube field-effect transistors (CNTFETs) to enable the accurate simulation of the DC characteristics and plasmonic terahertz (THz) response in the CNTFETs. Accounting for the ambipolar nature of the carrier transport (n-type and p-type conductivity at positive and negative gate biases, respectively), we use n-type and p-type CNTFET non-linear equivalent circuits connected in parallel, representing the ambipolar conduction in the CNTFETs. This allows us to present a realistic non-linear model that is valid across the entire voltage range and is therefore suitable for the CNTFET design. The important feature of the model is that explicit equations for gate bias, current, mobility, and capacitance with smoothing parameters accurately describe the device operation near the transition from above- to below-threshold regimes, with scalability in device geometry. The DC performance in the proposed compact CNTFET model is validated by the comparison between the SPICE simulation and the experimental DC characteristics. The simulated THz response resulted from the validated CNTFET model is found to be in good agreement with the analytically calculated response and also reveals the bias and power dependent sub-THz response and relatively wide dynamic range for detection that could be suitable for THz detectors. The operation of CNTFET spectrometers in the THz frequency range is further demonstrated using the present model. The simulation exhibits that the CNT-based spectrometers can cover a broad THz frequency band from 0.1 to 3.08 THz. The model that has been incorporated into the circuit simulators enables the accurate assessment of DC performance and THz operation. Therefore, it can be used for the design and performance estimation of the CNTFETs and their integrated circuits operating in the THz regime. Full article

In this study, electrical characteristics of MoTe₂ field-effect transistors (FETs) are investigated as a function of channel thickness. The conductivity type in FETs, fabricated from exfoliated MoTe₂ crystals, switched from p-type to ambipolar to n-type conduction with increasing MoTe₂ channel thickness from 10.6 nm to 56.7 nm. This change in flake-thickness-dependent conducting behavior of MoTe₂ FETs can be attributed to modulation of the Schottky barrier height and related bandgap alignment. Change in polarity as a function of channel thickness variation is also used for ammonia (NH₃) sensing, which confirms the p- and n-type behavior of MoTe₂ devices. Full article