Low Variability in Synthetic Monolayer MoS₂ Devices

Abstract

Despite much interest in applications of two-dimensional (2D) fabrics such as MoS, to date most studies have focused on single or few devices. Here we examine the variability of hundreds of transistors from monolayer MoS synthesized by chemical vapor deposition. Ultraclean fabrication yields low surface roughness of ∼3 Å and surprisingly low variability of key device parameters, considering the atomically thin nature of the material. Threshold voltage variation and very low hysteresis suggest variations in charge density and traps as low as ∼10 cm. Three extraction methods (field-effect, Y-function, and effective mobility) independently reveal mobility from 30 to 45 cm/V/s (10th to 90th percentile; highest value ∼48 cm/V/s) across areas >1 cm. Electrical properties are remarkably immune to the presence of bilayer regions, which cause only small conduction band offsets (∼55 meV) measured by scanning Kelvin probe microscopy, an order of magnitude lower than energy variations in Si films of comparable thickness. Data are also used as inputs to Monte Carlo circuit simulations to understand the effects of material variability on circuit variation. These advances address key missing steps required to scale 2D semiconductors into functional systems.

Recommended Methods to Study Resistive Switching Devices

“…The best quality material is normally achieved by mechanical exfoliation, but this leads to small material flakes (typically <10 µm) with uncontrollable thicknesses, [78] and it requires EBL to pattern the electrodes. [7] CVD can be used to grow high quality graphene, [80] molybdenum disulfide (MoS 2 ), [81] molybdenum diselenide (MoSe 2 ), [82] tungsten disulfide (WS 2 ), [83] tungsten selenide (WSe 2 ), [84] and hexagonal boron nitride (h-BN), [85][86][87] among many others. The two most widespread methods to synthesize 2D materials applied to RS devices are chemical vapor deposition (CVD) and liquid-phase exfoliation.…”

“…The two most widespread methods to synthesize 2D materials applied to RS devices are chemical vapor deposition (CVD) and liquid-phase exfoliation. [89][90][91] A solution commonly employed is to synthesize the 2D material on the most suitable substrates (metallic foils for graphene [80] and h-BN [85][86][87] and SiO 2 or sapphire for 2D transition metal dichalcogenides (TMDs) [81][82][83] ) and transfer it on the desired sample using different methods, [92][93][94] being the wet transfer with the assistance of a polymer scaffold the most used by the RS community. The problem is that the temperature used for the growth is typically >700 °C, which prevents growing the 2D material on wafers with existing integrated circuits due to diffusion problems; the maximum temperature allowed for complementary metal-oxidesemiconductor (CMOS) back-end of line integration is typically 450 °C.…”

Engineering thermal and electrical interface properties of phase change memory with monolayer MoS2

“…In addition, the electrical conductivity of undoped MoS2 is orders of magnitude lower than graphene and this 2D layer can effectively be considered an insulator. 21,22 Because of this, cell power-efficiency can be improved even when MoS2 is not precisely patterned.…”

CMOS-compatible batch processing of monolayer MoS2MOSFETs

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Result and discussion Figure 4 shows the DC current-voltage characteristics of a typical MoS2 MOSFET with a gate length of 0.4 μm before passivation. With a saturated drain-source current of 5 μA/μm, a peak transconductance of 2 μS/μm, and an on/off current ratio of 10 5 , the characteristics are comparable to the state-of-art of MOSFETs fabricated on CVD MoS2 [10]. The extrinsic field-effect electron mobility μfe, at approximately 3 cm 2 /V•s, is comparable to the Hall mobility of the present MoS2 as grown [11] and other grown MoS2, giving orders-of-magnitude variation in MoS2 mobility reported in the literature.…”