Ultrafast interfacial transformation from 2D- to 3D-bonded structures in layered Ge–Sb–Te thin films and heterostructures

Abstract

Single ns-laser pulse induced phase transition between the vdW-bonded trigonal and the covalently bonded cubic structure of Ge–Sb–Te.

Phase change thin films for non-volatile memory applications

“…charge transport and optical reectivity, in crystalline GST materials. 58,61,[81][82][83] In GST225 phase I the vacancies are randomly distributed and are necessary to stabilize the structure as indicated by a negative formation energy. 65 For example, the creation of vacancies in the Ge 2 Sb 2 Te 4 compound reduces the average number of valence electrons and thus, the occupation of antibonding states.…”

“…9(a) featuring only the cubic GST225(111) and cubic GST(222) reections corresponds to an epitaxial cubic GST thin lm which is characterized by random distribution of vacancies (phase I) and thus no superstructure reections appear. This phase can be obtained in an elegant way by ns-laser crystallization of amorphous GST thin lms deposited on crystalline Si(111) substrates or by laser induced recrystallization of trigonal GST225 thin lms, 83,93 while GST225 phase II can be produced by fs-laser irradiation. 61 The fabrication process of phase I ensures that no vacancy ordering is present, whereas during preparation methods involving thermal annealing on longer timescales partial vacancy ordering might occur.…”

“…14,106,[147][148][149] Recently, a promising approach to study the crystallization capabilities of GST225 has been presented based on interfaceassisted epitaxial recrystallization of GST225 phase I (c-GST225) in epitaxially grown GST225 thin lms. 83 In detail, single ns-laser pulse irradiation of an epitaxial trigonal GST225 (t-GST225) thin lm caused partial melting of the lm followed by ultrafast recrystallization during the cool down process. Fig.…”

Applications of Phase Change Materials in Electrical Regime From Conventional Storage Memory to Novel Neuromorphic Computing

“…The GST225 alloy is well known to exhibit sharp difference on electrical resistivity and optical reflectivity between the crystalline and amorphous states, as verified in Figures 4(a) and 4(b). Such properties variations can be attributed to its structural disorder [33]- [35]. The vacancies in the first metastable phase of GST225 are randomly distributed and enable the structure stability [36].…”

Layer‐Switching Mechanisms in Sb2Te3

“…Instead of unconstrained phase transitions between the amorphous and crystalline state, short-range phase transitions through local rearrangements, such as layer-switching between two-layered crystalline states of GST, are proposed for iPCM. Although this switching mechanism is still under debate, [36][37][38][39][40][41][42][43][44][45][46] layer-switching has been shown to occur in layer-structured GST through swapped bilayers. [47][48][49][50][51] The intermixing of Sb and Te has been proven to be essential for the stabilization of the swapped bilayers.…”