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Molybdenum disulfide (MoS2) has great potential as a two‐dimensional semiconductor for electronic and optoelectronic application, but its high sensitivity to environmental adsorbents and charge transfer from neighboring dielectrics can lead to device variability and instability. Aluminum oxide (Al2O3) is widely used as an encapsulation layer in (opto)‐electronics, but it leads to detrimental charge transfer n‐doping to MoS2. Here, this work reports a scalable encapsulation approach for MoS2 field‐effect transistors (FETs) where hexagonal boron nitride (h‐BN) monolayers are employed as a barrier layer in‐between each of the Al2O3 and MoS2 interfaces. These devices exhibit a significant reduction of charge transfer, when compared to structures without h‐BN. This benefit of h‐BN in the gate stack is confirmed by ab initio density functional theory calculations. In addition, the devices with h‐BN layers show very low hysteresis even under ambient operating conditions. [ABSTRACT FROM AUTHOR]

Atomically thin (2D) nanoporous membranes are an excellent platform for a broad scope of academic research. Their thickness and intrinsic ion selectivity (demonstrated for example in molybdenum disulfide‐MoS2) make them particularly attractive for single‐molecule biosensing experiments and osmotic energy harvesting membranes. Currently, one of the major challenges associated with the research progress and industrial development of 2D nanopore membrane devices is small‐scale thin‐film growth and small‐area transfer methods. To address these issues, a large‐area protocol including a wafer‐scale monolayer MoS2 synthesis, Si/SiNx substrate fabrication and wafer‐scale material transfer are demonstrated. First, the 7.62 cm wafer‐scale MOCVD growth yielding homogenous monolayer MoS2 films are introduced. Second, a large number of devices are fabricated in one batch by employing the wafer‐scale thin‐film transfer method with high transfer efficiency (>70% device yield). The growth, the transfer quality and cleanliness are investigated using transmission electron microscopy, atomic force microscopy and Raman spectroscopy. Finally, the applicability and robustness of the large‐area protocol is demonstrated by performing a set of double‐stranded DNA translocation experiments through as‐fabricated MoS2 nanopore devices. It is believed that the shown approach will pave the way toward wafer‐scale, high‐throughput use of 2D nanopores in various applications. [ABSTRACT FROM AUTHOR]

In the increasing research field of 2D materials such as graphene, molybdenum disulfide MoS2 has attracted great interest due to the existence of a direct bandgap in monolayer MoS2, which gives the possibility of achieving MoS2 field-effect transistors or optoelectronic devices. We analyzed by THz time-domain spectroscopy (THz-TDS) up to 2 THz and infrared (IR) spectroscopy, CVD-obtained MoS2 using either S or H2S gas as a sulfur precursor, grown on a sapphire substrate. From THz-TDS we obtained the transmittance, conductivity, and attenuation. From IR spectroscopy on the same samples, we deduced the transmittance in the IR frequency range. We observed the coherence of both spectroscopic methods. The advantage of the THz-TDS method is that we can get significant parameters related to the sample quality without the need for depositing any electrical contact or sample preparation. Our results show that at high frequencies MoS2 is even better than graphene as a material for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Favorable mechanical and electrical properties motivate the use of 2D semiconductors in flexible electronic devices. One of the main challenges here is the absence of a practical doping strategy which should provide air‐stable, tunable doping levels in a process with a low thermal budget. Here, it is shown that SU8, an epoxy‐based photoresist, can be used for nondegenerate n‐type doping of monolayer MoS2. The doping level can be finely tuned via low‐temperature annealing. The doping method exhibits good ambient stability. The high degree of mechanical flexibility and low processing temperature also allows the integration of SU8 coating with flexible MoS2 FETs, where it can provide both controllable doping and act as an encapsulation layer. The demonstrated stability of the devices to bending and exposure to water confirms the attractiveness of using SU8 in flexible electronic devices based on 2D semiconductors in a simple, versatile and scalable approach. It is shown that the photoresist SU8 can be used for n‐type doping of monolayer MoS2 with good ambient stability. The doping level can easily be controlled during processing by changing the resist baking time. In addition to doping, the SU8 layer can also act as an encapsulation layer and protect flexible MoS2 transistors from direct submersion in water. [ABSTRACT FROM AUTHOR]

Atomically thin (2D) nanoporous membranes are an excellent platform for a broad scope of academic research. Their thickness and intrinsic ion selectivity (demonstrated for example in molybdenum disulfide‐MoS2) make them particularly attractive for single‐molecule biosensing experiments and osmotic energy harvesting membranes. Currently, one of the major challenges associated with the research progress and industrial development of 2D nanopore membrane devices is small‐scale thin‐film growth and small‐area transfer methods. To address these issues, a large‐area protocol including a wafer‐scale monolayer MoS2 synthesis, Si/SiNx substrate fabrication and wafer‐scale material transfer are demonstrated. First, the 7.62 cm wafer‐scale MOCVD growth yielding homogenous monolayer MoS2 films are introduced. Second, a large number of devices are fabricated in one batch by employing the wafer‐scale thin‐film transfer method with high transfer efficiency (>70% device yield). The growth, the transfer quality and cleanliness are investigated using transmission electron microscopy, atomic force microscopy and Raman spectroscopy. Finally, the applicability and robustness of the large‐area protocol is demonstrated by performing a set of double‐stranded DNA translocation experiments through as‐fabricated MoS2 nanopore devices. It is believed that the shown approach will pave the way toward wafer‐scale, high‐throughput use of 2D nanopores in various applications. [ABSTRACT FROM AUTHOR]

In the increasing research field of 2D materials such as graphene, molybdenum disulfide MoS2 has attracted great interest due to the existence of a direct bandgap in monolayer MoS2, which gives the possibility of achieving MoS2 field-effect transistors or optoelectronic devices. We analyzed by THz time-domain spectroscopy (THz-TDS) up to 2 THz and infrared (IR) spectroscopy, CVD-obtained MoS2 using either S or H2S gas as a sulfur precursor, grown on a sapphire substrate. From THz-TDS we obtained the transmittance, conductivity, and attenuation. From IR spectroscopy on the same samples, we deduced the transmittance in the IR frequency range. We observed the coherence of both spectroscopic methods. The advantage of the THz-TDS method is that we can get significant parameters related to the sample quality without the need for depositing any electrical contact or sample preparation. Our results show that at high frequencies MoS2 is even better than graphene as a material for optoelectronic devices. [ABSTRACT FROM AUTHOR]