Porous materials as effective chemiresistive gas sensors.

Chemiresistive gas sensors (CGSs) have revolutionized the field of gas sensing by providing a low-power, low-cost, and highly sensitive means of detecting harmful gases. This technology works by measuring changes in the conductivity of materials when they interact with a testing gas. While semiconducting metal oxides and two-dimensional (2D) materials have been used for CGSs, they suffer from poor selectivity to specific analytes in the presence of interfering gases and require high operating temperatures, resulting in high signal-to-noise ratios.

Effects of thermal annealing on analog resistive switching behavior in bilayer HfO/ZnO synaptic devices: the role of ZnO grain boundaries.

The effects of thermal annealing on analog resistive switching behavior in bilayer HfO/ZnO synaptic devices were investigated. The annealed active ZnO layer between the top Pd electrode and the HfO layer exhibited electroforming-free resistive switching. In particular, the switching uniformity, stability, and reliability of the synaptic devices were dramatically improved thermal annealing at 600 °C atomic force microscopy and X-ray diffraction analyses revealed that active ZnO films demonstrated increased grain size upon annealing from 400 °C to 700 °C, whereas the ZnO film thickness and the annealing of the HfO layer in bilayer HfO/ZnO synaptic devices did not profoundly affect the analog switching behavior.

Performance enhancement of HfO-based resistive random-access memory devices using ZnO nanoparticles.

In this study, resistive random-access memory (ReRAM) devices with ZnO nanoparticles (NPs) are suggested to enhance performance and reduce variation in device switching parameters. The ZnO NPs are formed by annealing ZnO prepared via atomic layer deposition on HfO, which is verified using transmission electron microscopy, x-ray diffraction pattern, and atomic force microscopy. The depth profile analysis of x-ray photoelectron spectroscopy shows that oxygen diffuses from HfOto ZnO NPs during annealing.

ZnWO nanorod-colloidal SnO quantum dots core@shell heterostructures: Efficient solar-light-driven photocatalytic degradation of tetracycline.

Zinc tungsten oxide (ZW) and colloidal SnO quantum dots (CS) were synthesized individually by hydrothermal and wet chemical methods. ZW-CS core@shell nanorods were prepared using a sonochemical method for the enhanced photocatalytic activity of tetracycline (TC) degradation. ZW-CS core@shell nanorods were systematically characterized by structural, morphological mapping and optical techniques.

Bottom-Gated ZnO TFT Pressure Sensor with 1D Nanorods.

In this study, a bottom-gated ZnO thin film transistor (TFT) pressure sensor with nanorods (NRs) is suggested. The NRs are formed on a planar channel of the TFT by hydrothermal synthesis for the mediators of pressure amplification. The fabricated devices show enhanced sensitivity by 16~20 times better than that of the thin film structure because NRs have a small pressure transmission area and causes more strain in the underlayered piezoelectric channel material.

Effect of high-pressure D and H annealing on LFN properties in FD-SOI pTFET.

Tunneling field-effect transistors (TFETs) are a promising candidate for the next generation of low-power devices, but their performance is very sensitive to traps near the tunneling junction. This study investigated the effects of high-pressure deuterium (D) annealing and hydrogen (H) annealing on the electrical performance and low-frequency noise (LFN) of a fully depleted silicon-on-insulator p-type TFET. Without high-pressure annealing, the typical noise power spectral density exhibited two Lorentzian spectra that were affected by fast and slow trap sites.

IGZO-decorated ZnO thin films and their application for gas sensing.

In this study, indium-gallium-zinc oxide (IGZO)-decorated ZnO thin films were investigated through the change in IGZO deposition time for the detection of NO gas. The atomic layer deposited ZnO on interdigitated Au electrode alumina substrates are decorated with IGZO by controlling the deposition time. The IGZO (ZnO:GaO:InO = 1:1:1 mol.

Zinc oxide and indium-gallium-zinc-oxide bi-layer synaptic device with highly linear long-term potentiation and depression characteristics.

The electrical properties, resistive switching behavior, and long-term potentiation/depression (LTP/LTD) in a single indium-gallium-zinc-oxide (IGZO) and bi-layer IGZO/ZnO (ZnO: zinc oxide) memristors were investigated for synapse application. The use of the oxide bi-layer memristors, in particular, improved electrical properties such as stability, memristor reliability, and an increase in synaptic weight states. The set voltage of bi-layer IGZO/ZnO memristors was 0.

Physical and Electrical Analysis of Poly-Si Channel Effect on SONOS Flash Memory.

In this study, polycrystalline silicon (poly-Si) is applied to silicon-oxide-nitride-oxide-silicon (SONOS) flash memory as a channel material and the physical and electrical characteristics are analyzed. The results show that the surface roughness of silicon nitride as charge trapping layer (CTL) is enlarged with the number of interface traps and the data retention properties are deteriorated in the device with underlying poly-Si channel which can be serious problem in gate-last 3D NAND flash memory architecture. To improve the memory performance, high pressure deuterium (D) annealing is suggested as a low-temperature process and the program window and threshold voltage shift in data retention mode is compared before and after the D annealing.

High Pressure Deuterium Passivation of Charge Trapping Layer for Nonvolatile Memory Applications.

In this study, the deuterium passivation effect of silicon nitride (SiN) on data retention characteristics is investigated in a Metal-Nitride-Oxide-Silicon (MNOS) memory device. To focus on trap passivation in SiN as a charge trapping layer, deuterium (D) high pressure annealing (HPA) was applied after SiN deposition. Flat band voltage shifts (ΔV) in data retention mode were compared by CV measurement after D HPA, which shows that the memory window decreases but charge loss in retention mode after program is suppressed.

Fluorine-implanted indium-gallium-zinc oxide (IGZO) chemiresistor sensor for high-response NO detection.

Gas sensors fabricated using In-Ga-Zn oxide (IGZO) thin films doped with Fluorine (F) were used to detect nitrogen dioxide (NO) gas. IGZO films with a thickness of 250 nm were deposited onto SiO/Si substrates via radio-frequency magnetron sputtering, followed by F-doping by an ion-implantation procedure with implant energy of 45 keV and a dose of 3 × 10 ions/cm. The NO gas detection performance of the fabricated thin-film sensors was tested at various temperatures and NO concentrations.

Effective Schottky barrier lowering of NiGe/p-Ge(100) using Terbium interlayer structure for high performance p-type MOSFETs.

Ultra-low contact resistance at the interface between NiGe and p-Ge, i.e., NiGe/p-Ge was achieved by introducing terbium (Tb) as an interlayer in forming NiGe using Tb/Ni/TiN structure.

Temperature Dependence of Low Frequency Noise in Silicon on Insulator Tunneling Field Effect Transistor.

In this work, noise mechanism of a tunneling field-effect transistor (TFET) on a silicon-on-insulator substrate was studied as a function of temperature. The results show that the drain current and subthreshold slope increase with increase in temperature. This temperature dependence is likely caused by the generation of greater current flow owing to decreased silicon band gap and leakage.

Improved Sensitivity in Schottky Contacted Two-Dimensional MoS Gas Sensor.

Two-dimensional (2D) transition-metal dichalcogenides have attracted significant attention as gas-sensing materials owing to their superior responsivity at room temperature and their possible application as flexible electronic devices. Especially, reliable responsivity and selectivity for various environmentally harmful gases are the main requirements for the future chemiresistive-type gas sensor applications. In this study, we demonstrate improved sensitivity of a 2D MoS-based gas sensor by controlling the Schottky barrier height.

Investigation of Intra-Nitride Charge Migration Suppression in SONOS Flash Memory.

In order to suppress the intra-nitride charge spreading in 3D Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) flash memory where the charge trapping layer silicon nitride is shared along the cell string, N plasma treated on the silicon nitride is proposed. Experimental results show that the charge loss decreased in the plasma treated device after baking at 300 °C for 2 h. To extract trap density according to the location in the trapping layer, capacitance-voltage analysis was used and N plasma treatment was shown to be effective to restrain the interface trap formation between blocking oxide and silicon nitride.

Investigation of Positive Bias Temperature Instability Characteristics of Fully Depleted Silicon on Insulator Tunneling Field Effect Transistor with High-k Dielectric Gate Stacks.

The positive bias temperature instability (PBTI) characteristics of fully depleted silicon on insulator (FD-SOI) tunneling field effect transistor (TFET) are investigated in comparison with those of metal oxide semiconductor field effect transistor (MOSFET) fabricated with the same technology process. Unlike some of the previously reported studies, in which the PBTI lifetime of TFET is much longer than that of MOSFET, in this study, the PBTI lifetime of TFET is found to be shorter than that of MOSFET. This result is very interesting, because degradation of electrical parameters of TFET is mainly affected by local traps near the source junction rather than global traps in the channel region.

Gate Voltage Dependence of Low Frequency Noise in Tunneling Field Effect Transistors.

In this paper, the dependency of low frequency noise as a function of the gate voltage was examined for tunneling field effect transistors (TFETs). When the level of gate voltage is low, the tunneling width of the TFETs is large. Thus, electrons move via the trap instead of tunneling directly.

Additive effect of poly(4-vinylphenol) gate dielectric in organic thin film transistor at low temperature process.

We fabricated pentacene-based organic thin film transistors (OTFTs) with formulated poly[4-vinylphenol] (PVP) gate dielectrics. The solution of gate dielectrics is prepared by adding methylated poly[melamine-co-formaldehyde] (MMF) and photo-initiator (PI) [1-phenyl-2-hydroxy-2-methylpropane-1-one, Darocur1173@Ciba] to PVP By using a small amount (2.4 wt%) of PI, the cross-linking temperature is lowered to 90 degrees C, which is lower than general thermal curing reaction temperature for the cross-linked PVP (> 180 degrees C).

Novel palladium germanide schottky contact for high performance schottky barrier ge MOSFETs and characterization of its leakage current mechanism.

The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

The effect of thermal annealing on pentacene thin film transistor with micro contact printing.

We used micro contact printing (micro-CP) to fabricate inverted coplanar pentacene thin film transistors (TFTs) with 1-microm channels. The patterning of micro-scale source/drain electrodes without etch process was successfully achieved using Polydimethylsiloxane (PDMS) elastomer stamp. We used the Ag nano particle ink as an electrode material, and the sheet resistance and surface roughness of the Ag electrodes were effectively reduced with the 2-step thermal annealing on a hotplate, which improved the mobility, the on-off ratio, and the subthreshold slope (SS) of the pentacene TFTs.

Thermal endurance and microstructural evolution of PtGe for high-performance nano-scale Ge-on-Si MOSFETS.

The thermal endurance and microstructural evolution of Ni-germanide (NiGe) and Pt-germanide (PtGe) on a Ge-on-Si substrate were compared in this paper. In case of the Ni/TiN structure, the sheet resistance exhibited a stable RTP window of 350 to 600 degrees C, while that of the Pt/TiN structure showed more stable characteristics up to 700 degrees C. Furthermore, after post-germanidation annealing, NiGe exhibited the formation of islands due to the severe agglomeration as well as a prominent grain boundary grooving, which accounts for the sharp increase of the sheet resistance from 550 degrees C, whereas PtGe showed a smooth and continuous surface morphological stability without signs of agglomeration even up to 600 degrees C.

Improvement of heavy dopant doped Ni-silicide using ytterbium interlayer for nano-scale MOSFETS with an ultra shallow junction.

In this paper, a novel Ni silicide with Yb interlayer (Yb/Ni/TiN) on a boron cluster (B18H22) implanted source/drain junction is proposed for the first time, and its thermal stability characteristics are analyzed in depth. The proposed Ni-silicide exhibits a wider RTP temperature window for uniform sheet resistance, surface roughness and better thermal stability than the conventional structure (Ni/TiN). In addition, the cross-sectional profile of the proposed Ni-silicide showed less agglomeration despite the high temperature post-silicidation annealing, and it can be said that the proposed structure was little dependence on the temperature post-silicidation annealing.

Maskless laser direct patterning of PEDOT/PSS layer for soluble process organic thin film transistor.

In this work, we have fabricated TIPS-pentacene TFTs with conductive polymer (3,4-ethylenedioxythiophene):poly(4-stylenesulfonate) (PEDOT:PSS) source/drain electrodes which is patterned by maskless laser direct patterning (LDP). The 5-microm resolution of source and drain patterns with PEDOT:PSS were clearly defined. Furthermore, the OTFTs with 10-microm channel length were successfully achieved by exposing the focused Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser beam onto the spin-coated PEDOT:PSS films and developing with deionized water.