Controlled Low‐Frequency Electrical Noise of Monolayer MoS₂ with Ohmic Contact and Tunable Carrier Concentration

Abstract

and unique band structures. [1] Semiconducting monolayers of the TMDs, such as MoS 2 and WSe 2 , possess a direct band gap and excellent photoresponsivity. [2,3] In addition, single-layer MoS 2 is moderately easy to attain Ohmic contact with various metals [4][5][6][7] and graphene, [8] and the singlelayer MoS 2 field-effect transistors (FETs) show decent performances on the mobility (tens of cm 2 V −1 s −1 ) [9,10] and the on-off current ratio (exceeding 10 8 ) [4,10] at room temperature, suggesting that the monolayer MoS 2 holds greater potential for flexible nanodevices and optoelectronic applications. The huge surface-to-volume ratio of the atomically thin TMDs makes their performances extremely sensitive to the surface and interface conditions. The low-frequency electrical noise of devices often discloses the influences from the surface [11] and the interface conditions and has been widely adopted as a nondestructive tool to study the interface conditions. The subthreshold slope of the FETs and the photo response time of the MoS 2 photodetectors are significantly determined by the interfacial traps. [12] Unlike the thermal noise and shot noise that possess a constant power spectral density, low-frequency noise typically has a 1/f spectrum, and its effect on the accuracy of a device cannot be reduced by increasing the averaging time. [13] Such noise manner causes a critical issue of applications of the TMDs in the signal sensing and processing, [14] and raises numerous interests in investigating the 1/f noise in the TMD-based devices for identifying its origin and for reducing its strength.The first study of low-frequency electrical noise in exfoliated monolayer MoS 2 [15] claimed that the noise has a 1/f spectrum and is mainly explained by fluctuation of the mobility. By contrast, the 1/f noise in the exfoliated MoTe 2[16] with the ambipolar transport behaviors and many other TMD FETs [17][18][19][20] is further described as fluctuation of the carrier density. Finding a clear picture of the possible factors contributing to the 1/f noise, including the external adsorbates on the devices, [15] the defect states at the metal/TMD contacts, [17] and the trappingdetrapping centers in the substrate near the TMD channel, [18,21] remains a challenging issue because of the lack of Ohmic contacts, ideal material quality, and an effective control of the carrier density. Recently, the high-quality chemical-vapor-deposited (CVD) MoS 2 monolayers show the comparable electrical

Van der Waals Contact to 2D Semiconductors with a Switchable Electric Dipole: Achieving Both n‐ and p‐Type Ohmic Contacts to Metals with a Wide Range of Work Functions

“…So, the above simulation results need high‐quality samples without too much defects. This agrees with literature that ideal high‐quality samples play a key role in metal–semiconductor junctions 58…”

High-Vacuum Particulate-Free Deposition of Wafer-Scale Mono-, Bi-, and Trilayer Molybdenum Disulfide with Superior Transport Properties

“…This is smaller than that reported in earlier publications for MoS 2 transistors implemented with the exfoliated or CVD material. 49,53 The latter provides an additional confirmation of the material quality from the device applications' point of view.…”

Considerations for Utilizing Sodium Chloride in Epitaxial Molybdenum Disulfide

“…29,47,48 Finally, we note that most highperformance synthetic MoS 2 FETs are from powder-grown, single-crystalline grains with careful device fabrication process. 29,48 Therefore, future works to remove the antiphase grain boundaries and optimize the device fabrication focusing on large-scale films may lead further improvements on the performance of synthetic 2D films.…”

“…Unlike devices on exfoliated and transferred TMDs, synthetic TMDs on 3D crystalline substrates always exhibit stronger film/substrate coupling such as chalcogen passivating interlayer, charge transfer, and Coulomb screening . This unique coupling is a convoluting factor when trying to understand how dopants impact the threshold voltage, mobility, on/off ratio, and low-frequency noise in as-grown cases. ,, Finally, we note that most high-performance synthetic MoS 2 FETs are from powder-grown, single-crystalline grains with careful device fabrication process. , Therefore, future works to remove the antiphase grain boundaries and optimize the device fabrication focusing on large-scale films may lead further improvements on the performance of synthetic 2D films.…”