Characterization of Cr-doped Sb₂ Te₃ films and their application to phase-change memory

Abstract

Phase‐change memory (PCM) is regarded as one of the most promising candidates for the next‐generation nonvolatile memory. Its storage medium, phase‐change material, has attracted continuous exploration. Along the traditional GeTe–Sb2Te3 tie line, the binary compound Sb2Te3 is a high‐speed phase‐change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb2Te3, called Cr–Sb2Te3 (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb2Te3 without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST_10.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10‐year data retention is 120.8 °C, which indicates better thermal stability than GST and pure Sb2Te3. PCM cells based on CST_10.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr–Sb2Te3 with suitable composition is a promising novel phase‐change material used for PCM with high speed and good thermal stability performances. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Systematic Study of Ferromagnetism in CrxSb2−xTe3 Topological Insulator Thin Films using Electrical and Optical Techniques

“…A small shift to 530.5 eV in the present case for the sample with the lowest doping concentration ( x = 0.15) can be attributed to surface oxidation (labelled with arrows). Upon increasing the Cr concentration, the peaks shift towards the un-oxidized, pristine value of 528 eV, thus indicating that the doping with Cr prevents further oxidation of Sb 2 Te 3 , consistent with earlier reports 11 , 22 . In other words, Cr atoms are more prone to oxidation compared to the Sb atoms, and upon substitution, the degree of surface oxidation of the sample is reduced.…”

“…This has led to the recent experimental observations of the topological magnetoelectric effect 7 , induction of a magnetic monopole 8 and the quantum anomalous Hall effect (QAHE) 9 . Hence a wide range of potential industrial applications have found their way into the literature such as magnetic sensing 10 , information storage 10 , phase change memories 11 and various spin injectors for spintronic devices 12 . In the quantized version of the anomalous Hall effect (AHE), the topologically protected state has a dissipationless current flowing along the edge of a 2D surface of a magnetically doped TI in the absence of a magnetic field.…”

Giant ultrafast optical nonlinearities of annealed Sb2Te3 layers

“…These results are in very good accordance with previous crystallographic studies of the Sb 2 Te 3 material. 21,[24][25][26] The difference of the peak amplitudes is attributed to the different annealing surfaces. In the case of oven annealing the whole sample surface was annealed, while in the case of laser annealing a surface area of approximately 1 cm 2 was crystallized.…”

Temperature dependence of the ferromagnetic response in CrxSb2-xTe3 topological insulator thin films investigated using terahertz spectroscopy and magneto-transport.

“…This has led to the recent experimental observations of the topological magnetoelectric effect 8 , induction of a magnetic monopole 9 and the quantum anomalous Hall effect (QAHE) 10 . Hence a wide range of potential industrial applications have been demonstrated in literature such as magnetic sensing 11 , information storage 11 , phase change memories 12 and various spin injectors for spintronic devices 13 . In the quantized version of the anomalous Hall effect (AHE), the topologically protected state has a dissipationless current flowing along the edge of a 2D surface of a magnetically doped TI in the absence of a magnetic field.…”