Reducing contact resistance of MoS2-based field effect transistors through uniform interlayer insertion via atomic layer deposition.

Molybdenum disulfide (MoS2), a semiconducting two-dimensional layered transition metal dichalcogenide (2D TMDC), with attractive properties enables the opening of a new electronics era beyond Si. However, the notoriously high contact resistance (RC) regardless of the electrode metal has been a major challenge in the practical applications of MoS2-based electronics. Moreover, it is difficult to lower RC because the conventional doping technique is unsuitable for MoS2 due to its ultrathin nature.

Atomic-Layer-Deposition-Based 2D Transition Metal Chalcogenides: Synthesis, Modulation, and Applications.

Transition metal chalcogenides (TMCs) are a large family of 2D materials with different properties, and are promising candidates for a wide range of applications such as nanoelectronics, sensors, energy conversion, and energy storage. In the research of new materials, the development and investigation of industry-compatible synthesis techniques is of key importance. In this respect, it is important to study 2D TMC materials synthesized by the atomic layer deposition (ALD) technique, which is widely applied in industries.

High-Performance Gas Sensor Using a Large-Area WSSe Alloy for Low-Power Operation Wearable Applications.

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have attracted considerable attention as promising building blocks for a new generation of gas-sensing devices because of their excellent electrical properties, superior response, flexibility, and low-power consumption. Owing to their large surface-to-volume ratio, various 2D TMDCs, such as MoS, MoSe, WS, and WSe, have exhibited excellent gas-sensing characteristics. However, exploration toward the enhancement of TMDC gas-sensing performance has not yet been intensively addressed.

Recovery Improvement for Large-Area Tungsten Diselenide Gas Sensors.

Semiconducting two-dimensional transition-metal dichalcogenides are considered promising gas-sensing materials because of their large surface-to-volume ratio, excellent electrical conductivity, and susceptible surfaces. However, enhancement of the recovery performance has not yet been intensively explored. In this study, a large-area uniform WSe is synthesized for use in a high-performance semiconductor gas sensor.

Low-temperature synthesis of 2D MoS on a plastic substrate for a flexible gas sensor.

The efficient synthesis of two-dimensional molybdenum disulfide (2D MoS2) at low temperatures is essential for use in flexible devices. In this study, 2D MoS2 was grown directly at a low temperature of 200 °C on both hard (SiO2) and soft substrates (polyimide (PI)) using chemical vapor deposition (CVD) with Mo(CO)6 and H2S. We investigated the effect of the growth temperature and Mo concentration on the layered growth by Raman spectroscopy and microscopy.

Enhanced Light Stability of InGaZnO Thin-Film Transistors by Atomic-Layer-Deposited YO with Ozone.

We report the effect of YO passivation by atomic layer deposition (ALD) using various oxidants, such as HO, O plasma, and O, on In-Ga-Zn-O thin-film transistors (IGZO TFTs). A large negative shift in the threshold voltage (V) was observed in the case of the TFT subjected to the HO-ALD YO process; this shift was caused by a donor effect of negatively charged chemisorbed HO molecules. In addition, degradation of the IGZO TFT device performance after the O plasma-ALD YO process (field-effect mobility (μ) = 8.

Catalytic chemical vapor deposition of large-area uniform two-dimensional molybdenum disulfide using sodium chloride.

The effective synthesis of atomically thin molybdenum disulfides (MoS) of high quality and uniformity over a large area is essential for their use in electronic and optical devices. In this work, we synthesize MoS that exhibit a high quality and large area uniformity using chemical vapor deposition (CVD) with volatile S organic compound and NaCl catalysts. In the latter process, the NaCl enhances the growth rate (5 min for synthesis of monolayer MoS) and purity of the synthesized MoS.

Highly stable 2D material (2DM) field-effect transistors (FETs) with wafer-scale multidyad encapsulation.

Field-effect transistors (FETs) composed of 2D materials (2DMs) such as transition-metal dichalcogenide (TMD) materials show unstable electrical characteristics in ambient air due to the high sensitivity of 2DMs to water adsorbates. In this work, in order to demonstrate the long-term retention of electrical characteristics of a TMD FET, a multidyad encapsulation method was applied to a MoS FET and thereby its durability was warranted for one month. It was well known that the multidyad encapsulation method was effective to mitigate high sensitivity to ambient air in light-emitting diodes (LEDs) composed of organic materials.

Effect of AlO Deposition on Performance of Top-Gated Monolayer MoS-Based Field Effect Transistor.

Deposition of high-k dielectrics on two-dimensional MoS is an important process for successful application of the transition-metal dichalcogenides in electronic devices. Here, we show the effect of HO reactant exposure on monolayer (1L) MoS during atomic layer deposition (ALD) of AlO. The results showed that the ALD-AlO caused degradation of the performance of 1L MoS field effect transistors (FETs) owing to the formation of Mo-O bonding and trapping of HO molecules at the AlO/MoS interface.

Self-Limiting Layer Synthesis of Transition Metal Dichalcogenides.

This work reports the self-limiting synthesis of an atomically thin, two dimensional transition metal dichalcogenides (2D TMDCs) in the form of MoS2. The layer controllability and large area uniformity essential for electronic and optical device applications is achieved through atomic layer deposition in what is named self-limiting layer synthesis (SLS); a process in which the number of layers is determined by temperature rather than process cycles due to the chemically inactive nature of 2D MoS2. Through spectroscopic and microscopic investigation it is demonstrated that SLS is capable of producing MoS2 with a wafer-scale (~10 cm) layer-number uniformity of more than 90%, which when used as the active layer in a top-gated field-effect transistor, produces an on/off ratio as high as 10(8).