Post-Treatment of Monolayer MoS Field-Effect Transistors with HO Vapor: Alleviation of Remote Channel Doping.

Atomic layer deposition (ALD) of high-k dielectric films on MoS channels can lead to inadvertent remote electron doping of channels owing to nonequilibrium ALD conditions, such as the low temperatures and short purge times required for pinhole-free coating, as well as the weak physical adsorption of ALD precursors on MoS. In this study, we propose the application of a simple and effective HO vapor post-treatment (HO PT) at 100 °C immediately after complete integration of bottom- and top-gate monolayer MoS field-effect transistors (FETs), to address the inadvertent channel doping effect. When HO PT was applied to bottom-gate monolayer MoS FETs with an ALD-AlO passivation layer, the mitigation of channel doping was confirmed through electrical and optical measurements.

Three-Dimensional Surface Treatment of MoS Using BCl Plasma-Derived Radicals.

The realization of next-generation gate-all-around field-effect transistors (FETs) using two-dimensional transition metal dichalcogenide (TMDC) semiconductors necessitates the exploration of a three-dimensional (3D) and damage-free surface treatment method to achieve uniform atomic layer-deposition (ALD) of a high-k dielectric film on the inert surface of a TMDC channel. This study developed a BCl plasma-derived radical treatment for MoS to functionalize MoS surfaces for the subsequent ALD of an ultrathin AlO film. Microstructural verification demonstrated a complete coverage of an approximately 2 nm-thick AlO film on a planar MoS surface, and the applicability of the technique to 3D structures was confirmed using a suspended MoS channel floating from the substrate.

Wafer-Scale Epitaxial Growth of an Atomically Thin Single-Crystal Insulator as a Substrate of Two-Dimensional Material Field-Effect Transistors.

As the electron mobility of two-dimensional (2D) materials is dependent on an insulating substrate, the nonuniform surface charge and morphology of silicon dioxide (SiO) layers degrade the electron mobility of 2D materials. Here, we demonstrate that an atomically thin single-crystal insulating layer of silicon oxynitride (SiON) can be grown epitaxially on a SiC wafer at a wafer scale and find that the electron mobility of graphene field-effect transistors on the SiON layer is 1.5 times higher than that of graphene field-effect transistors on typical SiO films.

Effects of Plasma Damage Removal on Direct Contact Resistance and Hot-Electron-Induced Punch Through (HEIP) of PMOSFETs.

In order to reduce contact resistance of the source/drain region in nanoscale devices, it is essential to overcome the increasing leakage and hot-electron-induced punch through (HEIP) degradation. In this paper, we propose a simple Si soft treatment technique immediately after direct contact (DC) etching to reduce and minimize HEIP degradation. We found by analysis with a transmission electron microscope, that 10 s of treatment reduced the plasma damaged layer by 19%, which resulted in 10.

Characteristics of an Amorphous Carbon Layer as a Diffusion Barrier for an Advanced Copper Interconnect.

The size of the advanced Cu interconnects has been significantly reduced, reaching the current 7.0 nm node technology and below. With the relentless scaling-down of microelectronic devices, the advanced Cu interconnects thus requires an ultrathin and reliable diffusion barrier layer to prevent Cu diffusion into the surrounding dielectric.

Risk factor analysis of postoperative kyphotic change in subaxial cervical alignment after upper cervical fixation.

Objective: Little is known about the risk factors for postoperative subaxial cervical kyphosis following craniovertebral junction (CVJ) fixation. The object of this study was to evaluate postoperative changes in cervical alignment and to identify the risk factors for postoperative kyphotic change in the subaxial cervical spine after CVJ fixation.

Methods: One hundred fifteen patients were retrospectively analyzed for postoperative subaxial kyphosis after CVJ fixation.

P-N Junction Diode Using Plasma Boron-Doped Black Phosphorus for High-Performance Photovoltaic Devices.

This study used a spatially controlled boron-doping technique that enables a p-n junction diode to be realized within a single 2D black phosphorus (BP) nanosheet for high-performance photovoltaic application. The reliability of the BP surface and state-of-the-art 2D p-n heterostructure's gated junctions was obtained using the controllable pulsed-plasma process technique. Chemical and structural analyses of the boron-doped BP were performed using X-ray photoelectron spectroscopy, transmission electron microscopy, and first-principles density functional theory (DFT) calculations, and the electrical characteristics of a field-effect transistor based on the p-n heterostructure were determined.

Novel Conductive Filament Metal-Interlayer-Semiconductor Contact Structure for Ultralow Contact Resistance Achievement.

In the post-Moore era, it is well-known that contact resistance has been a critical issue in determining the performance of complementary metal-oxide-semiconductor (CMOS) reaching physical limits. Conventional Ohmic contact techniques, however, have hindered rather than helped the development of CMOS technology reaching its limits of scaling. Here, a novel conductive filament metal-interlayer-semiconductor (CF-MIS) contact-which achieves ultralow contact resistance by generating CFs and lowering Schottky barrier height (SBH)-is investigated for potential applications in various nanodevices in lieu of conventional Ohmic contacts.

New Insights into Mechanism of Surface Reactions of ZnO Nanorods During Electrons Beam Irradiation.

This study provides new insight into mechanisms of ionic reactions on the surface of ZnO nanorod networks, which could result in enhanced performance in optical or molecular sensors. The current- voltage characteristics of ZnO nanorod network devices exhibit typical nonlinear behavior in air, which implies the formation of a Schottky barrier when metals are used as contacts. The conductance of the device increased significantly in vacuum, which can be explained by the desorption of hydroxyl groups at very low pressure.

Electrical properties and thermal stability in stack structure of HfO/AlO/InSb by atomic layer deposition.

Changes in the electrical properties and thermal stability of HfO grown on AlO-passivated InSb by atomic layer deposition (ALD) were investigated. The deposited HfO on InSb at a temperature of 200 °C was in an amorphous phase with low interfacial defect states. During post-deposition annealing (PDA) at 400 °C, In-Sb bonding was dissociated and diffusion through HfO occurred.

Carrier-Type Modulation and Mobility Improvement of Thin MoTe.

A systematic modulation of the carrier type in molybdenum ditelluride (MoTe ) field-effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O environment (p-type modulation) and benzyl viologen (BV) doping (n-type modulation). Al O capping is then introduced to improve the carrier mobilities and device stability. MoTe is found to be ultrasensitive to O at elevated temperatures (250 °C).

AlO Passivation Effect in HfO·AlO Laminate Structures Grown on InP Substrates.

The passivation effect of an AlO layer on the electrical properties was investigated in HfO-AlO laminate structures grown on indium phosphide (InP) substrate by atomic-layer deposition. The chemical state obtained using high-resolution X-ray photoelectron spectroscopy showed that interfacial reactions were dependent on the presence of the AlO passivation layer and its sequence in the HfO-AlO laminate structures. Because of the interfacial reaction, the AlO/HfO/AlO structure showed the best electrical characteristics.

Evenly transferred single-layered graphene membrane assisted by strong substrate adhesion.

We explored the transfer of a single-layered graphene membrane assisted by substrate adhesion. A relatively larger adhesion force was measured on the SiO substrate compared with its van der Waals contribution, which is expected to result from the additional contribution of the chemical bonding force. Density functional theory calculations verified that the strong adhesion force was indeed accompanied by chemical bonding.

Ultrasensitive Room-Temperature Operable Gas Sensors Using p-Type Na:ZnO Nanoflowers for Diabetes Detection.

Ultrasensitive room-temperature operable gas sensors utilizing the photocatalytic activity of Na-doped p-type ZnO (Na:ZnO) nanoflowers (NFs) are demonstrated as a promising candidate for diabetes detection. The flowerlike Na:ZnO nanoparticles possessing ultrathin hierarchical nanosheets were synthesized by a facile solution route at a low processing temperature of 40 °C. It was found that the Na element acting as a p-type dopant was successfully incorporated in the ZnO lattice.

Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin AlO: Thermal, Ambient, and Mechanical Stabilities.

There is an increasing demand in the flexible electronics industry for highly robust flexible/transparent conductors that can withstand high temperatures and corrosive environments. In this work, outstanding thermal and ambient stability is demonstrated for a highly transparent Ag nanowire electrode with a low electrical resistivity, by encapsulating it with an ultra-thin AlO film (around 5.3 nm) via low-temperature (100 °C) atomic layer deposition.

Chemically Homogeneous and Thermally Robust NiPtSi Film Formed Under a Non-Equilibrium Melting/Quenching Condition.

To synthesize a thermally robust NiPtSi film suitable for ultrashallow junctions in advanced metal-oxide-semiconductor field-effect transistors, we used a continuous laser beam to carry out millisecond annealing (MSA) on a preformed Ni-rich silicide film at a local surface temperature above 1000 °C while heating the substrate to initiate a phase transition. The melting and quenching process by this unique high-temperature MSA process formed a NiPtSi film with homogeneous Pt distribution across the entire film thickness. After additional substantial thermal treatment up to 800 °C, the noble NiPtSi film maintained a low-resistive phase without agglomeration and even exhibited interface flattening with the underlying Si substrate.

Improved electroluminescence of quantum dot light-emitting diodes enabled by a partial ligand exchange with benzenethiol.

In this study, benzenethiol ligands were applied to the surface of CdSe@ZnS core@shell quantum dots (QDs) and their effect on the performance of quantum dot light-emitting diodes (QD-LEDs) was investigated. Conventional long-chained oleic acid (OA) and trioctylphosphine (TOP) capping ligands were partially replaced by short-chained benzenethiol ligands in order to increase the stability of QDs during purification and also improve the electroluminescence performance of QD-LEDs. The quantum yield of the QD solution was increased from 41% to 84% by the benzenethiol ligand exchange.

Trap-induced photoresponse of solution-synthesized MoS2.

We investigated, for the first time, the photoresponse characteristics of solution-synthesized MoS2 phototransistors. The photoresponse of the solution-synthesized MoS2 phototransistor was solely determined by the interactions of the photogenerated charge carriers with the surface adsorbates and the interface trap sites. Instead of contributing to the photocurrent, the illumination-generated electron-hole pairs were captured in the trap sites (surface and interface sites) due to the low carrier mobility of the solution-synthesized MoS2.

MoS2-InGaZnO Heterojunction Phototransistors with Broad Spectral Responsivity.

We introduce an amorphous indium-gallium-zinc-oxide (a-IGZO) heterostructure phototransistor consisting of solution-based synthetic molybdenum disulfide (few-layered MoS2, with a band gap of ∼1.7 eV) and sputter-deposited a-IGZO (with a band gap of ∼3.0 eV) films as a novel sensing element with a broad spectral responsivity.

Structural and Electrical Properties of EOT HfO2 (<1 nm) Grown on InAs by Atomic Layer Deposition and Its Thermal Stability.

We report on changes in the structural, interfacial, and electrical characteristics of sub-1 nm equivalent oxide thickness (EOT) HfO2 grown on InAs by atomic layer deposition. When the HfO2 film was deposited on an InAs substrate at a temperature of 300 °C, the HfO2 was in an amorphous phase with an sharp interface, an EOT of 0.9 nm, and low preexisting interfacial defect states.

Thickness scaling of atomic-layer-deposited HfO2 films and their application to wafer-scale graphene tunnelling transistors.

The downscaling of the capacitance equivalent oxide thickness (CET) of a gate dielectric film with a high dielectric constant, such as atomic layer deposited (ALD) HfO2, is a fundamental challenge in achieving high-performance graphene-based transistors with a low gate leakage current. Here, we assess the application of various surface modification methods on monolayer graphene sheets grown by chemical vapour deposition to obtain a uniform and pinhole-free ALD HfO2 film with a substantially small CET at a wafer scale. The effects of various surface modifications, such as N-methyl-2-pyrrolidone treatment and introduction of sputtered ZnO and e-beam-evaporated Hf seed layers on monolayer graphene, and the subsequent HfO2 film formation under identical ALD process parameters were systematically evaluated.

Composition Control of CuInSe2 Thin Films Using Cu/In Stacked Structure in Coulometric Controlled Electrodeposition Process.

Cu/In bi-metal stacked structures were prepared on Mo coated soda lime glass substrates using electrodeposition method. These metallic precursors were selenized at 550 °C for 60 min to synthesize the CuInSe2 (CIS) thin films in a thermal evaporator chamber with an Se overpressure atmosphere. The composition ratios of CIS thin films were systematically controlled using the coulometric method of the electrodeposition, where the accumulated coulomb of In layers was varied from 1062 to 6375 mC/cm2.

Wafer-scale synthesis of thickness-controllable MoS2 films via solution-processing using a dimethylformamide/n-butylamine/2-aminoethanol solvent system.

The wafer-scale synthesis of two-dimensional molybdenum disulfide (MoS2) films, with high layer-controllability and uniformity, remains a significant challenge in the fields of nano and optoelectronics. Here, we report the highly thickness controllable growth of uniform MoS2 thin films on the wafer-scale via a spin-coating route. Formulation of a dimethylformamide-based MoS2 precursor solution mixed with additional amine- and amino alcohol-based solvents (n-butylamine and 2-aminoethanol) allowed for the formation of a uniform coating of MoS2 thin films over a 2 inch wafer-scale SiO2/Si substrate.