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Kirill Mitrofanov1 Yuta Saito1 2 Noriyuki Miyata1 Paul Fons1 Alexander Kolobov1 Junji Tominaga1

1, National Institute of Advanced Industrial Science and Technology, Tsukuba, , Japan
2, Cambridge University, Cambridge, , United Kingdom

Interfacial phase-change memory (iPCM) based on chalcogenide superlattice structures was initially proposed as an improvement of conventional phase-change memory providing lower switching energy due to minimization of thermal losses attributed to the switching process [1]. Recently, it was reported that chalcogenide superlattices show some additional effects [2-5], which potentially could broaden the application of iPCM. In the current work, the electrical switching behavior of chalcogenide GeTe/Sb2Te3 superlattice-based iPCM devices was studied at elevated temperature and under external magnetic field.
iPCM devices showed resistance switching between the SET and the RESET states as a result of applying short (100∼500 ns) voltage pulses at room temperature. Switching was characterized also at elevated temperature (up to 200°C) and it was found that at around 150°C an initial RESET state could not be obtained and that the device resistance approached the SET resistance level. Major features of the observed behavior were explained by thermally driven effects in the superlattice structure, similar to chalcogenide alloy case, while some of the observed differences were attributed to the structural peculiarities of the former. The same experiments were repeated with the external magnetic field (0.1∼0.5 T), applied to the devices during switching. While for the room temperature case there were no additional switching effects detected, at ∼160°C both SET and RESET resistances shifted to the new, intermediate level and remained there during further annealing to 200°C and consequent cooling to ∼150°C. This result implies that an external magnetic field at high temperature can lead to a new structural condition of the iPCM superlattice, which, in turn, leads to the appearance of an additional resistance level in the device. The possible mechanism of the observed effect was reported earlier [5]. It was found that such a process also could lead to appearance of additional resistance effects at room temperature and during electrically induced switching.
In conclusion, the effect of an external magnetic field at elevated temperature on the performance of switching of iPCM devices based on GeTe/Sb2Te3 superlattices was found. A combination of the thermal, electric and magnetic field treatment can lead to permanent changes in the structure of the superlattice that may be utilized in a new type of memory.
This work was supported by JST-CREST (JPMJCR14F1). A part of this study was supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
[1] R. E. Simpson et al., Nat. Nanotech., 6, 501-505 (2011).
[2] J. Tominaga et al., Appl. Phys. Lett. 99, 152105 (2011).
[3] J. Tominaga et al., Sci. Technol. Adv. Mater. 16, 014402 (2015).
[4] Y. Saito et al., ACS Appl. Mater. Interfaces, 9, 23918 (2017).
[5] J. Tominaga et al., Adv. Funct. Mater., 27 (40), 1702243 (2017).

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