TY - JOUR
T1 - Glass transition of the phase change material AIST and its impact on crystallization
AU - Pries, Julian
AU - Sehringer, Julia Charlotte
AU - Wei, Shuai
AU - Lucas, Pierre
AU - Wuttig, Matthias
N1 - Funding Information:
The authors acknowledge funding from the Deutsche Forschungsgemeinschaft ( DFG ) via the collaborative research center Nanoswitches ( SFB 917 ). P.L. acknowledges funding from NSF-DMR grant No. 1832817 . S.W. acknowledges the support of the DFG grant No. AOBJ670132 .
Funding Information:
To identify the phase the material crystallizes from, and to obtain the temperature dependence of crystallization, the thermal response of amorphous as-deposited and pre-annealed Ag4In3Sb67Te26 (AIST) films prepared by sputter deposition is characterized using the conventional differential scanning calorimetry (DSC) and ultrafast Flash DSC (FDSC) with heating rates spanning more than six orders of magnitude from 3.3 ? 10?2 K/s to 4.0 ? 104 K/s. The (F)DSC data yields valuable insights on glass dynamics, crystallization kinetics and their different temperature dependencies. The results allow us to reveal the distinction in the crystallization behaviors from the amorphous phase. Pre-annealing produces changes in the crystallization behavior and the nucleation tendency as inferred from fluctuation electron microscopy (FEM). This technique supports the conclusion from (F)DSC that AIST crystallizes from the glassy phases at low heating rates. Finally, these results are also found to be consistent with an estimate of the standard glass transition temperature Tg of AIST derived from an analysis of the enthalpy recovery exotherm.Powders for conventional differential scanning calorimetry (DSC) and ultrafast or flash DSC (FDSC) measurements of the phase change material (PCM) Ag4In3Sb67Te26 are produced from a stoichiometric target by magnetron sputter deposition at a base pressure of 3 ? 10?6 mbar. The composition was confirmed via energy dispersive X-ray spectroscopy (EDS) in a FEI Helios Dual Beam FIB. The excess specific heat capacity Cpexc was obtained in a PerkinElmer Diamond DSC and a Mettler-Toledo Flash DSC 1 by subtracting the crystalline rescan from the initial scan. The as-deposited and pre-annealed AIST samples were measured on the same sensor in FDSC. The melting onset of pure Indium was used to calibrate the temperature at a constant heating ? of the DSC and FDSC measurements. Fluctuation electron microscopy (FEM) was obtained at an FEI Titan G2 80?300 STEM on 30 nm thick AIST samples sputtered directly onto amorphous carbon films supported by copper grids. For both phases at least 1000 diffraction patterns were acquired from which the FEM variance was calculated. For the calibration of the detector for real space and reciprocal space readings a silicon reference was used. The electron beam diameter (probe size) and a divergence angle of 0.35 mrad was obtained to be 1.36 nm (FWHM).The authors acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via the collaborative research center Nanoswitches (SFB 917). P.L. acknowledges funding from NSF-DMR grant No. 1832817. S.W. acknowledges the support of the DFG grant No. AOBJ670132.
Publisher Copyright:
© 2021
PY - 2021/11/1
Y1 - 2021/11/1
N2 - Engineering phase change materials (PCM) to realize superior data storage devices requires a detailed understanding of crystallization kinetics and its temperature dependence. The temperature dependence of crystallization differs distinctly between crystallizing from the glassy phase and the undercooled liquid (UCL). Hence, knowing the phase from which crystallization occurs is necessary for predicting the switching ability. Here, we measure the glassy dynamics and crystallization kinetics using calorimetry for heating rates spanning over six orders of magnitude. Our results show that the prominent PCM (Ag,In)-doped Sb2Te (AIST) exhibits a change from crystallizing from the glassy phase to crystallizing from the UCL at a critical heating rate of 5000 K/s. Above the glass transition, the activation energy of crystallization changes drastically enabling rapid crystallization at elevated temperatures.
AB - Engineering phase change materials (PCM) to realize superior data storage devices requires a detailed understanding of crystallization kinetics and its temperature dependence. The temperature dependence of crystallization differs distinctly between crystallizing from the glassy phase and the undercooled liquid (UCL). Hence, knowing the phase from which crystallization occurs is necessary for predicting the switching ability. Here, we measure the glassy dynamics and crystallization kinetics using calorimetry for heating rates spanning over six orders of magnitude. Our results show that the prominent PCM (Ag,In)-doped Sb2Te (AIST) exhibits a change from crystallizing from the glassy phase to crystallizing from the UCL at a critical heating rate of 5000 K/s. Above the glass transition, the activation energy of crystallization changes drastically enabling rapid crystallization at elevated temperatures.
KW - Crystallization kinetics
KW - Glass transition temperature
KW - Metavalent bonding
KW - Phase change materials
KW - Structural relaxation
KW - Ultrafast differential scanning calorimetry (FDSC)
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U2 - 10.1016/j.mssp.2021.105990
DO - 10.1016/j.mssp.2021.105990
M3 - Article
AN - SCOPUS:85107996222
SN - 1369-8001
VL - 134
JO - Materials Science in Semiconductor Processing
JF - Materials Science in Semiconductor Processing
M1 - 105990
ER -