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. 2018 Jun 28;9(1):2524.
doi: 10.1038/s41467-018-04934-x.

Zero-static power radio-frequency switches based on MoS2 atomristors

Myungsoo Kim  1 , Ruijing Ge  1 , Xiaohan Wu  1 , Xing Lan  2 , Jesse Tice  2 , Jack C Lee  1 , Deji Akinwande  3
Affiliations

Zero-static power radio-frequency switches based on MoS2 atomristors

Myungsoo Kim et al. Nat Commun. .

Abstract

Recently, non-volatile resistance switching or memristor (equivalently, atomristor in atomic layers) effect was discovered in transitional metal dichalcogenides (TMD) vertical devices. Owing to the monolayer-thin transport and high crystalline quality, ON-state resistances below 10 Ω are achievable, making MoS2 atomristors suitable as energy-efficient radio-frequency (RF) switches. MoS2 RF switches afford zero-hold voltage, hence, zero-static power dissipation, overcoming the limitation of transistor and mechanical switches. Furthermore, MoS2 switches are fully electronic and can be integrated on arbitrary substrates unlike phase-change RF switches. High-frequency results reveal that a key figure of merit, the cutoff frequency (fc), is about 10 THz for sub-μm2 switches with favorable scaling that can afford fc above 100 THz for nanoscale devices, exceeding the performance of contemporary switches that suffer from an area-invariant scaling. These results indicate a new electronic application of TMDs as non-volatile switches for communication platforms, including mobile systems, low-power internet-of-things, and THz beam steering.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Device schematics and images with material characterization. a Simplified illustration of the signal transmission and device structure of the RF switches based on monolayer MoS2. b Zoomed-in plan view SEM image of a MoS2 RF switch with lateral area of 1 × 1 μm2. Scale bar, 2 μm. The dashed box in b marks the area covered with MoS2. The inset is a top-view optical image of a fabricated MoS2 RF switch with Au electrodes. Scale bar, 50 μm. c Raman and photoluminescence (inset) spectra of CVD-grown monolayer MoS2
Fig. 2
Fig. 2
DC switching characteristics of MoS2 atomristors. a Representative I–V curve of the bipolar resistance switching effect in a monolayer MoS2 RF switch with lateral area of 0.5 × 0.5 μm2. Step 1: voltage increases from 0 V. At ~1.4 V, the current abruptly increases to compliance current, indicating a transition (SET) from a high-resistance state to a low-resistance state. Step 2: voltage decreases from 2 to 0 V. The device persists in the low-resistive state. Step 3: voltage decreases from 0 to −1 V. At approximately −0.7 V, the current abruptly decreases, indicating a transition (RESET) from LRS to HRS. Step 4: voltage returns back to 0 V. The device persists in HRS until the next cycle. b Representative I–V curve of the bipolar resistance switching effect in a bilayer MoS2 RF switch with lateral area of 0.5 × 0.5 μm2 showing similar switching profile. c The retention measurement of a monolayer MoS2 switch with lateral area of 0.5 × 1 μm2 at room temperature revealing stable operation. The HRS and LRS resistance are determined by measuring the current at a small bias of 0.1 V. d Typical DC cycling of monolayer MoS2 non-volatile resistance switches
Fig. 3
Fig. 3
Radio-frequency characterization of MoS2 RF switches. a, b Experimental S(cattering)-parameter data in both the ON-state (insertion loss) and OFF-state (isolation) of an RF switch based on 0.5 × 0.5 μm2 monolayer MoS2 atomristor. The extracted RON and COFF values are 4.2 Ω and 6.5 fF, respectively. c, d S-parameter insertion loss and isolation data of an RF switch based on 0.5 × 0.5 μm2 bilayer MoS2 atomristor. RON is 5.3 Ω and COFF is 5.4 fF. The dashed lines are derived from an equivalent circuit model
Fig. 4
Fig. 4
Device scaling performance of the RF switches based on MoS2 atomristor. The equivalent lumped element model parameters: a ON-state resistance, b OFF-state capacitance, and c cutoff frequency dependencies on the area. The error bar indicates the standard deviation. The normalized figure of merit, fc ∙ A ~ 1 THz-μm2. While the ON-state resistance is area independent, the OFF-state capacitance is dependent on the lateral area of the device and has a normalized capacitance of ~28 fF/μm2. The lines in the figures are area-scaling guides and the slopes of b, c are based on the statistically averaged capacitance value
Fig. 5
Fig. 5
Signal power handling of MoS2 RF switches. a Representative ON-state P1dB and normalized insertion loss measured at 1 GHz in monolayer MoS2 RF switch with lateral area of 0.25 × 0.5 μm2. b OFF-state power handling measured at 1 GHz in monolayer MoS2 RF switch with lateral area of 0.5 × 0.5 μm2. c Transmission spectrum of an OFF-state monolayer MoS2 RF switch at different RF input powers. The inset shows an equivalent lumped element circuit model including an OFF-state capacitance (~13 fF) in parallel with an OFF-state variable resistance. d OFF-state resistance has an exponentially decreasing dependence on RF input power, which can be modeled as a diode-like voltage-dependent resistance (model line). The error bar indicates the standard deviation
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