NbTe₄ Phase‐Change Material: Breaking the Phase‐Change Temperature Balance in 2D Van der Waals Transition‐Metal Binary Chalcogenide

Abstract

Abstract2D van der Waals (vdW) transition metal di‐chalcogenides (TMDs) have garnered significant attention in the nonvolatile memory field for their tunable electrical properties, scalability, and potential for phase engineering. However, their complex switching mechanism and complicated fabrication methods pose challenges for mass production. Sputtering is a promising technique for large‐area 2D vdW TMD fabrication, but the high melting point (typically Tm > 1000 °C) of TMDs requires elevated temperatures for good crystallinity. This study focuses on the low‐Tm 2D vdW TM tetra‐chalcogenides and identifies NbTe4 as a promising candidate with an ultra‐low Tm of around 447 °C (onset temperature). As‐grown NbTe4 forms an amorphous phase upon deposition that can be crystallized by annealing at temperatures above 272 °C. The simultaneous presence of a low Tm and a high crystallization temperature Tc can resolve important issues facing current phase‐change memory compounds, such as high Reset energies and poor thermal stability of the amorphous phase. Therefore, NbTe4 holds great promise as a potential solution to these issues.

Phase-change behavior of RuSbTe thin film for photonic applications with amplitude-only modulation

“…The resistivity for the crystalline phase (3.90 × 10 –2 Ωcm) was found to be an order of magnitude larger than that for the amorphous phase (2.86 × 10 –3 Ωcm). This type of resistive change classifies RuSbTe as an inverse resistance change PCM 8 , 16 – 18 . Since the sudden increase in resistance corresponds to the crystallization in inverse resistance change PCMs 8 , 18 , the T x can be approximately 350 °C, which is much higher than GST by 200 °C.…”

“…This type of resistive change classifies RuSbTe as an inverse resistance change PCM 8 , 16 – 18 . Since the sudden increase in resistance corresponds to the crystallization in inverse resistance change PCMs 8 , 18 , the T x can be approximately 350 °C, which is much higher than GST by 200 °C. Such high thermal stability is assumed to originate from the high number of coordination bonds formed in the local structure around Ru in the amorphous phase, as predicted for Ru-doped GeTe 11 .…”

Recent Progress on Phase Engineering of Nanomaterials

“…In the past decades, phase change phenomena have been widely observed in metal oxides, amorphous Si, and chalcogenides ( e.g. , K 2 Bi 8 Se 13 , Sb 2 Te 3 , GeTe, and NbTe 4 ). − …”

“…In 2023, Shuang et al . reported a novel phase change material NbTe 4 with an ultra-low T m (∼447 °C) . In this work, amorphous NbTe 4 thin films were grown by RF sputtering at room temperature.…”

“…Based on the aforementioned advantages, this Sb 2 Te 3 /GeTe-based memory cell could realize the reversible phase change behavior with an ultra-low reset current density of 0.1 MA cm −2 , which is 1−2 orders of magnitude lower than that of conventional phase change memory cells.Besides designing exquisite device structures, synthesizing novel phase change materials with high crystallization temperature (T c ) and low melting temperature (T m ) is crucial to improving the performance of phase change memories. In 2023, Shuang et al reported a novel phase change material NbTe 4 with an ultra-low T m (∼447 °C) 1297. In this work, amorphous NbTe 4 thin films were grown by RF sputtering at room temperature.…”