Density Functional Theory Studies of Nonvolatile Intermediate States of 1T–VTe 2 Film

Le résumé fourni par la source

1T–VTe 2 thin film undergoes three‐step phase transitions (PTs) at ≈135, 240, and 260 K upon heating. Such PT behaviors should come from two intermediate states, which could be applied to memory devices. Such three‐step PTs are difficult to be explained with various known charge density wave (CDW) phases. Our calculations with density functional theory indicated that there exist at least 11 possible metastable states between the low‐temperature ground state and high‐temperature 1T state. All of them are CDW states with weak antiferromagnetism. Double zigzag chains of vanadium atoms in these metastable states are formed along the b crystal direction owing to the emergence of vanadium trimers viewed from the b crystal direction. The three‐step PTs in the previous experimental observations are reconstructive type, which should correspond to low‐temperature ground state R4L4 ( C 2/ m ) → R4R0, L4R0, L0R4, R4R4, and L4L4 ( Cm ) states → L0R0 ( P 2 1 /m ) and L4R4 ( C 2/ m ) states → high‐temperature 1T ( P ‐3 m 1) state. The stability order of R4L4 and L4R4 configurations will undergo a reversal as the amount of electron injection increases.

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