Research output: Contribution to Journal/Magazine › Journal article › peer-review
Nanomechanical morphology of amorphous, transition, and crystalline domains in phase change memory thin films. / Bosse, Jim; Grishin, Ilja; Huey, Bryan et al.
In: Applied Surface Science, Vol. 314, 30.09.2014, p. 151-157.Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Nanomechanical morphology of amorphous, transition, and crystalline domains in phase change memory thin films
AU - Bosse, Jim
AU - Grishin, Ilja
AU - Huey, Bryan
AU - Kolosov, Oleg
PY - 2014/9/30
Y1 - 2014/9/30
N2 - In the search for phase change materials (PCM) that may rival traditional random access memory, a complete understanding of the amorphous to crystalline phase transition is required. For the well-known Ge2Sb2Te5 (GST) and GeTe (GT) chalcogenides, which display nucleation and growth dominated crystallization kinetics, respectively, this work explores the nanomechanical morphology of amorphous and crystalline phases in 50 nm thin films. Subjecting these PCM specimens to a lateral thermal gradient spanning the crystallization temperature allows for a detailed morphological investigation. Surface and depth-dependent analyses of the resulting amorphous, transition and crystalline regions are achieved with shallow angle cross-sections, uniquely implemented with beam exit Ar ion polishing. To resolve the distinct phases, ultrasonic force microscopy (UFM) with simultaneous topography is implemented revealing a relative stiffness contrast between the amorphous and crystalline phases of 14% for the free film surface and 20% for the cross-sectioned surface. Nucleation is observed to occur preferentially at the PCM-substrate and free film interface for both GST and GT, while fine subsurface structures are found to be sputtering direction dependent. Combining surface and cross-section nanomechanical mapping in this manner allows 3D analysis of microstructure and defects with nanoscale lateral and depth resolution, applicable to a wide range of materials characterization studies where the detection of subtle variations in elastic modulus or stiffness are required.
AB - In the search for phase change materials (PCM) that may rival traditional random access memory, a complete understanding of the amorphous to crystalline phase transition is required. For the well-known Ge2Sb2Te5 (GST) and GeTe (GT) chalcogenides, which display nucleation and growth dominated crystallization kinetics, respectively, this work explores the nanomechanical morphology of amorphous and crystalline phases in 50 nm thin films. Subjecting these PCM specimens to a lateral thermal gradient spanning the crystallization temperature allows for a detailed morphological investigation. Surface and depth-dependent analyses of the resulting amorphous, transition and crystalline regions are achieved with shallow angle cross-sections, uniquely implemented with beam exit Ar ion polishing. To resolve the distinct phases, ultrasonic force microscopy (UFM) with simultaneous topography is implemented revealing a relative stiffness contrast between the amorphous and crystalline phases of 14% for the free film surface and 20% for the cross-sectioned surface. Nucleation is observed to occur preferentially at the PCM-substrate and free film interface for both GST and GT, while fine subsurface structures are found to be sputtering direction dependent. Combining surface and cross-section nanomechanical mapping in this manner allows 3D analysis of microstructure and defects with nanoscale lateral and depth resolution, applicable to a wide range of materials characterization studies where the detection of subtle variations in elastic modulus or stiffness are required.
KW - Phase Change Memory
KW - AFM
KW - UFM
KW - Chalcogenide
KW - Morphology
KW - Stiffness
KW - Cross-section
U2 - 10.1016/j.apsusc.2014.06.135
DO - 10.1016/j.apsusc.2014.06.135
M3 - Journal article
VL - 314
SP - 151
EP - 157
JO - Applied Surface Science
JF - Applied Surface Science
SN - 0169-4332
ER -