Calorimetric measurements of structural relaxation and glass transition temperatures in sputtered films of amorphous Te alloys used for phase change recording

Abstract

Sputtered amorphous Ge4Sb1Te5, Ge1Sb2Te4, Ge2Sb2Te5, and Ag0.055In0.065Sb0.59Te0.29 thin films were studied by differential scanning calorimetry. Upon continuous heating, heat release due to structural relaxation of the amorphous phase between 0.5 and 1.0 kJ/mol was observed. This value depends on the thermal history of the sample. Preannealing of the amorphous phase revealed the glass transition temperature Tg within 10 K of the crystallization temperature upon continuous heating at 40 K/min.

Young's modulus and residual stress of GeSbTe phase-change thin films

“…The maximum upward static deflection increases with annealing temperature because of the built up of tensile residual stress. ria [15] and Kalb [34]. The measured Young's moduli are lower than reported by Blachowicz et al [28], who found 24.8 (0.06) GPa for the amorphous and 39.5 (0.8) GPa for the crystalline phase.…”

Structural relaxation kinetics for first- and second-order processes: Application to pure amorphous silicon

“…The weak unstructured signal detected at low temperatures is due to structural relaxation whereas the intense sharp peak corresponds to crystallization. Similar thermograms have been measured for other amorphous materials, such as ball milled silicon [3], metallic powders [4] and supercooled alloys [5,6]. The characteristic unstructured signal of structural relaxation is also found in crystalline materials with a high concentration of non-equilibrium point or line defects: cold worked metals [7] and irradiated materials [8].…”

NegativeP−Tslopes characterize phase change processes: Case of the Ge1Sb2TeKalkan1, Sen2, Aitken3 et al. 2011Phys. Rev. B7120View full textAdd to dashboardCite

“…However, amorphous GST (a-GST) thin films crystallize upon laser irradiation into c-GST, a metastable, face-centered cubic (fcc) rocksalt structure with Te atoms occupying one fcc sublattice while Ge/Sb atoms randomly occupy the other [1]. This rocksalt structure is relevant for the phase-change applications and is also formed first upon thermal heating of the amorphous material to ~ 393 K. Further heating to higher temperatures of ~ 453 K eventually transforms the rocksalt structure into the stable hexagonal structure [5][6][7]. It is to be noted that the crystal structure of the c-GST phase is characterized by the presence of a large number of vacancies in the Ge/Sb sublattice, e.g.…”