Search

Crystallization determines the programming speed of phase‐change memory devices; while, the nucleation phenomenon of many phase‐change materials (PCMs) is not entirely understood, especially concerning the atomic structures and dynamic behaviors of the subcritical nuclei. This is undoubtedly an insurmountable challenge for scandium antimony telluride (ScxSb2Te3) PCM as its subnanosecond‐crystallization nature impedes the real‐time observation of the transient nucleation process. To solve the puzzle, atomic probe tomography and transmission electron microscopy are employed to circumvent the technical difficulties; for the first time, the atomistic information of the heterogeneous nuclei in ScxSb2Te3 is unveiled, such as enriched Sc ≈ 25 at% in core composition, ≈1.0 nm in geometric size, and ≈1023–1024 m−3 in spatial density. The unique nanoscale chemical inhomogeneity ensures the unusual stabilities and dynamics of the early‐stage nuclei, reinforcing them to survive the melt‐quenching action and greatly suppressing the nucleating randomness, thereby facilitating simultaneous and prompt crystal growth throughout the amorphous phase to achieve ultrafast crystallization. The present study offers a new insight into the nonclassical pathways, which will improve understanding and promote better regulation of the nucleation phenomenon in functional materials. [ABSTRACT FROM AUTHOR]

The scandium doped antimony tellurides (ScxSb2Te3), as promising phase-change memory materials, possess the merits of ultrafast crystallization speed and ultralow resistance drift, of the amorphous phases, ensuring the development of cache-type universal memory and high-accuracy computing chip. There is keenness to further explore the annealing effect in the crystalline ScxSb2Te3 phases to seek a potential metal–insulator transition (MIT) in electrical conduction, by which more intermediate resistance states of superior stability can be generated to enhance the programming contrast and accuracy. In this work, we have identified the metastable rock salt ScxSb2Te3 as an Anderson-type insulator and verified that the MIT occurs in its stable rhombohedral grains when lattice vacancies are highly ordered into the van der Waals-like gaps. The Sc dopant can exert profound influence on retarding the vacancy-ordering procedure, even completely prohibiting the MIT for the Sc-rich compounds. Our work suggests that tuning Sc content in ScxSb2Te3 alloys provides a simple route to engineer the material microstructures and electrical properties for the desired memory and computing performances. [ABSTRACT FROM AUTHOR]

Cu0.10(Ge2Sb2Te5)0.90 is proposed for low power consumption phase change memory (PCM). The thermal stability of Ge2Sb2Te5 is increased by 10at% Cu doping, with the crystallization temperature and data retention increased from 163°C to 202°C and from 87°C to 134°C, respectively. The electric operation results have proved the low power consumption and good cycling ability (>104), which may result from the low melting point (486°C) and the negligible phase separation in Cu0.10(Ge2Sb2Te5)0.90. The good thermal stability, low T m and good cycling phase change ability have made Cu0.10(Ge2Sb2Te5)0.90 a promising candidate for the low power consumption PCM application. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effect of hydrogen peroxide on anti-infection and reducing postoperative drainage in multi-segmental lumbar surgery., Methods: A clinical data of 510 patients with multi-segmental lumbar degenerative diseases who were treated with surgery between January 2017 and January 2018 was retrospectively analyzed. In study group, the incisions of 230 cases were washed with hydrogen peroxide before suture. In control group, the incisions of 280 cases were washed with normal saline before suture. There was no significant difference in gender, age, lesion type, disease duration, operative segment, and other clinical data between the two groups ( P >0.05). The operation time, intraoperative blood loss, postoperative drainage volume, and postoperative incidence of infection were recorded and compared between the two groups. The Centers for Disease Control and Prevention (CDC) standard was used to evaluate infection, which was divided into superficial infection and deep infection., Results: All operations completed successfully. There was no significant difference in operation time and intraoperative blood loss between the two groups ( P >0.05). The postoperative drainage volume in the study group was significantly less than that in the control group ( t =-2.990, P =0.005). A total of 13 patients developed infection after operation, including 10 cases of superficial infection (2 cases in the study group and 8 cases in the control group) with the infection time of (7.3±1.5) days, and 3 cases of deep infection (all in the control group) with the infection time of (16.6±3.1) days. The incidences of superficial and deep infections in the study group were lower than those in the control group, but there was no significant difference between the two groups ( χ 2 =2.595, P =0.123; P =0.256). All the superficial infections were Staphylococcus aureus infection and recovered after active dressing change. Among the patients with deep infections, 2 cases were infected by Staphylococcus aureus and 1 case was infected by Escherichia coli ; and the incisions healed after being washed and sutured thoroughly, and active dressing change., Conclusion: The incidence of postoperative infection and postoperative drainage volume can be reduced by washing the incision with hydrogen peroxide in multi-segmental lumbar surgery.

Objective: To compare the effectiveness and screw planting accuracy of percutaneous reduction and internal fixation with robot and traditional fluoroscopy-assisted in the treatment of single-level thoracolumbar fractures without neurological symptoms., Methods: The clinical data of 58 patients with single-level thoracolumbar fractures without neurological symptoms between December 2016 and January 2018 were retrospectively analysed. According to different surgical methods, the patients were divided into group A (28 cases underwent robot-assisted percutaneous reduction and internal fixation) and group B (30 cases underwent fluoroscopy-assisted percutaneous reduction and internal fixation). There was no neurological symptoms, other fractures or organ injuries in the two groups. There was no significant difference in general data of age, gender, fracture location, AO classification, time from injury to surgery, and preoperative vertebral anterior height ratio, sagittal Cobb angle, visual analogue scale (VAS) score, and Oswestry disability index (ODI) score between the two groups ( P >0.05). The screw placement time, operation time, intraoperative blood loss, intraoperative fluoroscopy frequency, hospitalization time, operation cost, postoperative complications, VAS score, ODI score, anterior vertebral height ratio, and sagittal Cobb angle before operation, at 3 days, 6 months after operation, and at last follow-up were recorded and compared between the two groups. The accuracy of the pedicle screw placement was evaluated by Neo's criteria., Results: The screw placement time, operation time, and intraoperative fluoroscopy frequency of group A were significantly less than those of group B, and the operation cost was significantly higher than that of group B ( P <0.05). But there was no significant difference in intraoperative blood loss and hospitalization time between the two groups ( P >0.05). Both groups were followed up 12-24 months, with an average of 15.2 months. The accuracy rate of screw placement in groups A and B was 93.75% (150/160) and 84.71% (144/170), respectively, and the difference was significant ( χ 2 =5.820, P =0.008). Except for 1 case of postoperative superficial infection in group A and wound healing after dressing change, there was no complication such as neurovascular injury, screw loosening and fracture in both groups, and there was no significant difference in the incidence of complications between the two groups ( χ 2 =0.625, P =0.547). The anterior vertebral height ratio, sagittal Cobb angle, VAS score, and ODI score of the two groups were significantly improved ( P <0.05); there was no significant difference between the two groups at all time points after operation ( P >0.05)., Conclusion: The spinal robot and traditional fluoroscopy-assisted percutaneous reduction and internal fixation can both achieve satisfactory effectiveness in the treatment of single-level thoracolumbar fractures without neurological symptoms. However, the former has higher accuracy, fewer fluoroscopy times, shorter time of screw placement, and lower technical requirements for the operator. It has wide application potential.

Phase change memory (PCM) is a promising nonvolatile memory to reform current commercial computing system. Inhibiting face-centered cubic (f-) to hexagonal (h-) phase transition of Ge 2 Sb 2 Te 5 (GST) thin film is essential for realizing high-density, high-speed, and low-power PCM. Although the atomic configurations of f- and h-lattices of GST alloy and the transition mechanisms have been extensively studied, the real transition process should be more complex than previous explanations, e.g. vacancy-ordering model for f-to-h transition. In this study, dynamic crystallization procedure of GST thin film was directly characterized by in situ heating transmission electron microscopy. We reveal that the equilibrium to h-phase is more like an abnormal grain growth process driven by surface energy anisotropy. More specifically, [0001]-oriented h-grains with the lowest surface energy grow much faster by consuming surrounding small grains, no matter what the crystallographic reconfigurations would be on the frontier grain-growth boundaries. We argue the widely accepted vacancy-ordering mechanism may not be indispensable for the large-scale f-to-h grain growth procedure. The real-time observations in this work contribute to a more comprehensive understanding of the crystallization behavior of GST thin film and can be essential for guiding its optimization to achieve high-performance PCM applications.