Conductance switching behavior of GeTe/Sb 2 Te 3 superlattice upon hot-electron injection: a scanning probe microscopy s
- PDF / 434,241 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 18 Downloads / 135 Views
Conductance switching behavior of GeTe/Sb2Te3 superlattice upon hot-electron injection: a scanning probe microscopy study Leonid Bolotov1,2, Yuta Saito1,2, Tetsuya Tada1,2, and Junji Tominaga1,2 1 National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan. 2 CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 3320012, Japan. ABSTRACT Topological (GeTe)/(Sb2Te3) superlattices (SL) are of practical interest for memory applications because of different mechanism of electric conductance switching in the crystalline phase. In the work, electrical switching behavior of individual SL grains was examined employing a multimode scanning probe microscope (MSPM) in a lithography mode at room temperature. Using programmed bias voltage with different amplitude and pulse duration, we observed the position-dependent variations of the switching voltage and the current injection delay for [(GeTe)2 (Sb2Te3)]4 SLs on Si(100). The results shed a light on the role of electric field and hot-electron injection on the SL conductance switching. INTRODUCTION Development of new class of materials for next generation memory cells has been of great importance to achieve energy efficient operation. In particular, interfacial phase-change memory (PCM) topological materials such as (GeTe)/(Sb2Te3) superlattices (SL)[1-5] have been showing huge magnetoresistance,[6] magneto-optical[7] and magnetoelectric behavior[8] essential for memory application. While conventional PCM films experience amorphous-to-crystalline phase transition, [3,9,10] the PCM SL films offer different mechanism of conductance switching which involves Ge atom migration at the interface of the constituent sub-layers.[1,3,11] Therefore, the carrier transport across SL can be controlled by Ge atom displacement caused by voltage pulses.
Fig. 1 (a) Measurement setup. (b) Atomic arrangement in GeTe and Sb2Te3 layers. Topological SL structures has been studied for device applications. [12-14] An activation voltage of ~1.4 V and a total switching power of 50-80 pJ have been reported for 400-nm SL PCM devices consisting of multiple grains of [(GeTe)2 (Sb2Te3)5]8 SLs. However, to optimize
375
the memory performance, detail understanding of the conductance switching in individual SL grains is essential to realize nanoscale multi-level memory cells. Here, we studied electrical switching behavior of individual SL grains employing a multimode scanning probe microscope (MSPM) in a scanning probe lithography (SPL) mode.[15-20] We used programmed bias voltage with different amplitude and duration to elucidate the role of hot-electron injection on the SL conductance switching for [(GeTe)2 (Sb2Te3)]4 SLs prepared in an optimized process. EXPERIMENT Sample structure SL [(GeTe)2 (Sb2Te3)1]4 films were grown on Si(100) substrates in optimized two-step process using an Ar-ion sputtering system.[21] The process included (1) deposition of a 3-nmthick Sb2Te3 seed layer at room temperature and subsequent annealing at 230oC
Data Loading...
