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Two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are making impressive strides in a short duration compared to other candidates. However, to unlock their full potential for advanced logic transistors, attention must be given to improving the contacts or interfaces they form. One approach is to interface with a suitable low work function metal contact to allow the surface Fermi level (EF) movement toward intended directions, thereby augmenting the overall electrical performance. In this work, we implement physical characterization to understand the tin (Sn) contact interface on monolayer and bulk molybdenum disulfide (MoS2) via in situ x-ray photoelectron spectroscopy and ex situ atomic force microscopy. A Sn contact exhibited a van der Waals type weak interaction with the MoS2 bulk surface where no reaction between Sn and MoS2 is detected. In contrast, reaction products with Sn—S bonding are detected with a monolayer surface consistent with a covalentlike interface. Band alignment at the interface indicates that Sn deposition induces n-type properties in the bulk substrate, while EF of the monolayer remains pinned. In addition, the thermal stability of Sn on the same substrates is investigated in a sequential ultrahigh vacuum annealing treatment at 100, 200, 300, and 400 °C. Sn sublimated/desorbed from both substrates with increasing temperature, which is more prominent on the bulk substrate after annealing at 400 °C. Additionally, Sn significantly reduced the monolayer substrate and produced detectable interface reaction products at higher annealing temperatures. The findings can be strategized to resolve challenges with contact resistance that the device community is having with TMDs. 

The interface properties and thermal stability of bismuth (Bi) contacts on molybdenum disulfide (MoS2) shed light on their behavior under various deposition conditions and temperatures. The examination involves extensive techniques including X-ray photoelectron spectroscopy, scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). Bi contacts formed a van der Waals interface on MoS2 regardless of deposition conditions, such as ultrahigh vacuum (UHV, 3 × 10–11 mbar) and high vacuum (HV, 4 × 10–6 mbar), while the oxidation on MoS2 has been observed. However, the semimetallic properties of Bi suppress the impact of defect states, including oxidized-MoS2 and vacancies. Notably, the n-type characteristic of Bi/MoS2 remains unaffected, and no significant changes in the local density of states near the conduction band minimum are observed despite the presence of defects detected by STM and STS. As a result, the Fermi level (EF) resides below the conduction band of MoS2. The study also examines the impact of annealing on the contact interface, revealing no interface reaction between Bi and MoS2 up to 300 °C. These findings enhance our understanding of semimetal (Bi) contacts on MoS2, with implications for improving the performance and reliability of electronic devices. 

The concept of chip-to-chip information propagation by spoof surface plasmon polariton (SSPP) metasurface at terahertz frequency has been introduced of late, that promises data transfer with high bandwidth, low crosstalk, and low energy consumption. As the exotic electromagnetic properties of the metasurface derive from its designed geometric pattern and periodicity, any possible variation of fabrication process parameters may affect the design pattern and consequently, the information capacity of SSPP interconnects. In this work, we have investigated the extent of performance degradation of SSPP interconnect with the statistical variation of the geometric pattern of the metasurface. We also described the technique of the design of an appropriate analog circuit so that the loss of signal integrity incurred by the process variation can be recuperated in real-time.