Science - USA (2021-12-10)

performance of Te switches matches well with
those of GST-based PCM cells, which do not
deteriorate severely after series connection with
PCM cells (fig. S15). The intrinsically homoge-
neous composition and BEOL compatibility of
the Te switch not only cut the time-consuming
material-optimization process but also enable
aggressive size downscaling toward sub-10-nm
dimensions for realizing 3D memory chips with
the highest density.

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ACKNOWLEDGMENTS

Funding:Financial support was provided by the National Key

Research and Development Program of China (2017YFB0206101)

and the Strategic Priority Research Program of the Chinese

Academy of Sciences (XDB44010000). M.Z. acknowledges support

by the Hundred Talents Program (Chinese Academy of Sciences)

and Shanghai Rising-Star Program (21QA1410800).Author

contributions:Conceptualization: M.Z. Methodology: M.Z., J.S.,

and S.J. Investigation: J.S., S.J., N.S., Q.G., T.G., and S.L.

Visualization: J.S. and M.Z. Funding acquisition: M.Z., Q.L., and Z.S.

Project administration: M.Z., Q.L., and Z.S. Supervision: M.Z.

Writing–original draft: M.Z. Writing–review & editing: M.Z.,

S.R.E., and R.D.Competing interests:The idea of a Te-based

switch is protected by a Chinese patent (CN202010975902.2) and

an international patent (PCT/CN2020/124585).Data and

materials availability:All data needed to evaluate the conclusions

in this paper are present in the paper or the supplementary

materials.

SUPPLEMENTARY MATERIALS

science.org/doi/10.1126/science.abi6332

Materials and Methods

Figs. S1 to S15

Tables S1 to S3

References ( 44 – 54 )

Movies S1 and S2

20 April 2021; resubmitted 12 August 2021

Accepted 12 October 2021

10.1126/science.abi6332

1394 10 DECEMBER 2021¥VOL 374 ISSUE 6573 science.orgSCIENCE

Fig. 4. Switching mechanism of the Te device obtained through in situ
TEM observations.(A) TEM image of a TiN/Te/TiN nanodevice, resembling the
T-shaped device. Enlarged view and corresponding mappings show that the
nanodevice is a stack of Cu, TiN, Te, TiN, and W layers. (B) DCI-Vcurve of
the Te nanodevice during switching. Critical time steps are also indicated by red
arrows. A tungsten tip (cathode) is touching the nanodevice (anode), as shown
in the inset, and applies the voltage. (CandD) Microstructure of the Te film in the
nanodevice before switching. The Te film has a trigonal structure, identified by the

FFT image (D). (EandF) Microstructure of the Te film after switching.

Spontaneous recrystallization occurs after voltage removal. The recrystallized

Te regrows into the same trigonal structure, yet with a different orientation (F).

(GtoJ) Snapshots of TEM images (from movie S1) during switching. The initial Te

device is in the OFF state with negligible passing current. As time proceeds, the

corresponding currents are found [marked earlier (by red arrows) in (B)]. The Te

film melts as the voltage exceeds 2.5 V [(H) to (J)], and the flow of the liquid

causes a void in this unconfined nanodevice [red arrow in (E)].

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