Publications

TEM Studies of Segregation in a Ge–Sb–Te Alloy During Heating

Singh, Manish K.; Ghosh, Chanchal; Tripathi, Shalini; Kotula, Paul G.; Bakan, Gokhan; Silva, Helena; Carter, C.B.

Phase-change materials are important for optical and electronic computing memory. Ge–Sb–Te (GST) is one of the important phase-change materials and has been studied extensively for fast, reversible, and non-volatile electronic phase-change memory. GST exhibits structural transformations from amorphous to metastable fcc at ~150 ℃ and fcc to hcp at ~300 ℃. The investigation of the structural, microstructural, and microchemical changes with high-temporal resolution during heating is crucial to gain insights on the changes that materials undergo during phase transformations. The as-deposited GST film has amorphous island morphology which transform to the metastable fcc phase at ~130 ℃. The second-phase transformation, from fcc to hexagonal, is observed at ~170 ℃. While the as-deposited amorphous islands show a homogeneous distribution of Ge, Sb and Te, these islands boundaries become Ge-rich after heating. Morphological and structural evolutions were captured during heating inside an aberration corrected environmental TEM equipped with a high-speed camera under a low-dose conditions to minimize beam-induced changes in the samples. Microchemical studies were carried out employing ChemiSTEM technique in probe-corrected mode with a monochromated beam.