Abstract
Fluctuations are ubiquitous in magnetic materials and can cause random telegraph noise. Such noise is of potential use in systems such as spiking neuron devices, random number generators and probability bits. Here we report electrically tunable magnetic fluctuations and random telegraph noise in multilayered vanadium-doped tungsten diselenide (WSe2) using vertical tunnelling heterostructure devices composed of graphene/vanadium-doped WSe2/graphene and magnetoresistance measurements. We identify bistable magnetic states through discrete Gaussian peaks in the random telegraph noise histogram and the 1/f2 features of the noise power spectrum. Three categories of fluctuation are detected: small resistance fluctuations at high temperatures due to intralayer coupling between the magnetic domains; large resistance changes over a wide range of temperatures; and persistent large resistance changes at low temperatures due to magnetic interlayer coupling. We also show that the bistable state and cut-off frequency of the random telegraph noise can be modulated with an electric bias.
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Data availability
Source data are provided with this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.
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Acknowledgements
This work was supported by the Institute for Basic Science (IBS-R011-D1) and Advanced Facility Center for Quantum Technology. P.K. acknowledges partial support from ARO (W911NF-18-1-0366). M.-K.J. was supported by an NRF grant funded by the Korean government (MSIT) (NRF-2022R1A2C4001245) and by Sookmyung Women’s University Research Grants (1-2203-2001).
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L.-A.T.N., J.J. and D.L.D. initiated this work. L.-A.T.N. fabricated and characterized the devices. T.D.N. synthesized the V-WSe2 single crystals. M.-K.J. performed the noise analysis. D.L.D. and Y.H.L. guided the work. L.-A.T.N., P.K., M.-K.J., D.L.D. and Y.H.L. analysed the data. All authors discussed and wrote the manuscript.
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Extended data
Extended Data Fig. 1 In-plane and out-of-plane MR hysteresis of 0.3% V-doped WSe2 for the same bias of 0.85 mV at different temperatures.
Out-of-plane MR hysteresis curve (> 3 T) is much larger than in-plane MR hysteresis curve (~1.5 T) at 2 K. MR hysteresis persists at higher temperatures in out-of-plane direction, whereas it is obscured in in-plane direction. This indicates the easy axis in-plane magnetic order.
Extended Data Fig. 2 In-plane and out-of-plane MR hysteresis of 0.1%, 0.3%, and 0.5% V-doped WSe2 at 2 K.
MR hysteresis is distinctly manifested at 0.3% and 0.5% V, confirming the stable ferromagnetic states. MR hysteresis is obscured at 0.1% V, indicating unstable magnetic states. All samples are the same thickness of ~ 2 nm. The biases of 0.8 V, 0.85 mV, and 0.5 mV are applied for corresponding 0.1%, 0.3%, and 0.5% V-doped WSe2.
Extended Data Fig. 3 RTN signals after FC with out-of-plane and in-plane 1 T magnetic fields.
The data were measured at 30 K with -0.9 V and +0.9 V in device 5.
Extended Data Fig. 4 Complete data on temperature-dependent RTN signals across the Gr/V-WSe2/Gr after FC at -0.9 V in device 1.
Time evolution of RTNs in the high (160–300 K), intermediate (70–140 K), and low temperature regions (2–60 K).
Extended Data Fig. 5 Control of RTNs with bias changes at 2 K after ZFC and FC at 1 T for a given thinner sample of 2 nm-thick 0.1% V-doped WSe2.
Note that the resistance was significantly reduced in an order of kΩ, compared to Fig. 5c with a sample thickness of 5 nm (device 7). The number of jumps increases with increasing biases, similar to the data in Fig. 5c in of device 2, confirming the bias-controlled number of jumps in both ZFC and FC.
Extended Data Fig. 6 Control of RTN signals after ZFC by positive biases in device 2.
The effect was similar to that seen with negative biases (Fig. 5c).
Extended Data Fig. 7 Control of RTN signals by biases at 120 K after FC of 1 T in device 1.
The frequency increased from ~0.1 Hz at -0.85 V to ~1.7 Hz at -0.95 V. The control of device speed becomes slower when applying too high magnetic field during FC that induces too stable magnetic states.
Extended Data Fig. 8
Switching capability of bistable state of parallel and antiparallel states by using two polarities of biases at + 0.9 V and -0.9 V after FC at 1 T and 40 K in device 1.
Extended Data Fig. 9 Representative bitmap image constructed by the obtained RTN data stream in bottom of Fig. 5c (4,096 points).
a, Measured RTNs at 2 K and −0.95 V after ZFC. b, Bitmap image realized by 4 k bits of the generated RTNs as a potential application for true random number generator (top) and corresponding digitized image (Bottom). c, Bitmap images by 40 k bits of the generated RTNs, where the RTN data stream of Extended Data Fig. 9b was stacked by 10 times.
Extended Data Table. 10
RTNs after ZFC at -0.7 V, 300 K with a size of 1×1 µm2 in device 6.
Supplementary information
Supplementary Information
Supplementary Figs. 1–14 and note.
Supplementary Data
Compressed file comprising source data for Supplementary Figs. 1–9, 11 and 13.
Source data
Source Data Fig. 1
Resistance changes with temperature and the identification of giant RTN in a vertical graphene/V-WSe2/graphene device.
Source Data Fig. 2
MR hysteresis in V-doped WSe2 at different V-doping concentrations.
Source Data Fig. 3
Control of RTN by magnetic fields.
Source Data Fig. 4
Temperature-dependent RTN across the vertical graphene/V-WSe2/graphene junction after FC.
Source Data Fig. 5
Control of RTNs across the vertical graphene/V-WSe2/graphene junction by biases after ZFC process.
Source Data Extended Data Fig. 1
In-plane and out-of-plane MR hysteresis of 0.3% V-doped WSe2 for the same bias of 0.85 mV at different temperatures.
Source Data Extended Data Fig. 2
In-plane and out-of-plane MR hysteresis of 0.1%, 0.3% and 0.5% V-doped WSe2 at 2 K.
Source Data Extended Data Fig. 3
RTN signals after FC with out-of-plane and in-plane 1 T magnetic fields.
Source Data Extended Data Fig. 4
Complete data on temperature-dependent RTN signals across the graphene/V-WSe2/graphene after FC at –0.9 V in device 1.
Source Data Extended Data Fig. 5
Control of RTNs with bias changes at 2 K after ZFC and FC at 1 T for a given thinner sample of 2-nm-thick 0.1% V-doped WSe2.
Source Data Extended Data Fig. 6
Control of RTN signals after ZFC by positive biases in device 2.
Source Data Extended Data Fig. 7
Control of RTN signals by biases at 120 K after FC of 1 T in device 1.
Source Data Extended Data Fig. 8
Switching capability of the bistable state of P and AP states by using two polarities of biases at +0.9 and –0.9 V after FC at 1 T and 40 K in device 1.
Source Data Extended Data Fig. 9
Representative bitmap image constructed by the obtained RTN data stream in bottom of Fig. 5c (4,096 points).
Source Data Extended Data Fig. 10
RTNs after ZFC at –0.7 V, 300 K with a size of 1 × 1 µm2 in device 6.
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Nguyen, LA.T., Jiang, J., Nguyen, T.D. et al. Electrically tunable magnetic fluctuations in multilayered vanadium-doped tungsten diselenide. Nat Electron 6, 582–589 (2023). https://doi.org/10.1038/s41928-023-01002-1
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DOI: https://doi.org/10.1038/s41928-023-01002-1