An amorphous chalcogenide Ge2Sb2Te5 film is most commonly used for phase-change data storage, in which its small volume is switched between amorphous and crystalline states by local heating with short laser or current pulses. A speed of amorphous-to-crystalline phase transformation in Ge2Sb2Te5 and Ag0.1(Ge2Sb2Te5)0.9 films has been evaluated on a nanosecond time scale using a 658-nm laser beam. The focused laser beam with a diameter <10 μm was illuminated in the power (P) and pulse duration (t) ranges of 1–17 mW and 10–460 ns, respectively, with subsequent detection of the response signals reflected from the film surface. We also evaluated the material characteristics, such as optical absorption and energy gap, crystalline phases, and sheet resistance of as-deposited and annealed films. The experiments showed that the crystallization speed of the Ge2Sb2Te5 film is largely improved by adding Ag. For example, the threshold pulse durations (tT) for Ge2Sb2Te5 and Ag0.1(Ge2Sb2Te5)0.9 films are approximately 70 and 30 ns for P=7 mW. In addition, the sheet resistance in the amorphous state of the Ag0.1(Ge2Sb2Te5)0.9 film is approximately ten times that of the Ge2Sb2Te5 film. This improvement can lead to a low programming current in electronic operation. To understand the ultrafast crystallization in the amorphous Ag0.1(Ge2Sb2Te5)0.9 film, we suggest heat confinement by electron hopping.
Crystallization properties of thermally deposited amorphous Alx(Ge2Sb2Te5)1−x (x=0.06 and 0.10) films were investigated. The crystallization was performed by both macroscopic thermal annealing and nanopulse laser illumination (λ=658 nm and beam diameter <2 μm). The Al0.10(Ge2Sb2Te5)0.90 film exhibited a very stable one-step phase transition from amorphous→face-centered cubic (fcc) in the annealing temperature range of 100–300 °C. The Al0.10(Ge2Sb2Te5)0.90 film had a higher sheet resistances (RS) in both the amorphous and crystalline phases compared to the Ge2Sb2Te5 film, resulting in lower set and reset programming currents in the phase-change random-access memory. The crystallization speed (v) of the amorphous films was quantitatively and qualitatively evaluated through the analysis of the surface images and the nanopulse reflection-response curves. Conclusively, the Al atom added into Ge2Sb2Te5 serves as a center for suppression of the fcc-to-hexagonal phase transition and the v-value was largely improved by the proper addition of Al, e.g., v[Al0.10(Ge2Sb2Te5)0.90]>v[Ge2Sb2Te5]. Additionally, the improved v was believed to result from improvements in both the nucleation and growth processes.
Rhabdoid tumor of the kidney (RTK) is a rare malignancy in infancy. Central nervous system involvement in RTK is already known. However, solitary spinal metastasis in RTK has been hardly reported. The authors report a case of metastatic RTK to spine causing paraplegia in an 8-month-old girl. Since the patient was young, the diagnosis of spine metastasis was delayed until paraplegia was seen after radical nephrectomy. Thorough neurological examination should be performed for early diagnosis of spinal metastasis in young patients with RTK. If there are any abnormal signs in neurologic examination, magnetic resonance images of brain and spine are recommended.
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