RESUMEN
HfO2-ZrO2 ferroelectric films have recently gained considerable attention from integrated circuit researchers due to their excellent ferroelectric properties over a wide doping range and low deposition temperature. In this work, different HfO2-ZrO2 superlattice (SL) FE films with varying periodicity of HfO2 (5 cycles)-ZrO2 (5 cycles) (SL5), HfO2 (10 cycles)-ZrO2 (10 cycles) (SL10), and HfO2 (15 cycles)-ZrO2 (15 cycles) (SL15) were studied systematically. The HfZrOx (HZO) alloy was used as a comparison device. The SL5 film demonstrated improved ferroelectric properties compared to the HZO film, with the 2 times remnant polarization (2Pr) values increasing from 41.4 to 48.6 µC/cm2 at an applied voltage of 3 V/10 kHz. Furthermore, the first-order reversal curve diagrams of different SL and HZO capacitors at different states (initial, wake-up, fatigue, and recovery) were measured. The SL capacitors were found to effectively suppress the diffusion of defects during P-V cycling, resulting in improved fatigue stability characteristics and fatigue recovery capability compared to the HZO capacitor. Moreover, an improved switching speed of the SL films compared to the HZO capacitor was concluded based on the inhomogeneous field mechanism (IFM) model. These results indicate that the SL structure has a high potential in future high-speed ferroelectric memory applications with excellent stability and recovery capability.
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Background: Gangliocytoma is an uncommon disease. In this report, we report a patient who was admitted to the hospital with a mediastinal tumor which is giant rarely. Case Description: A 30-year-old male patient was found to have a mediastinal mass 2 weeks ago during a routine examination. The patient occasionally had chest pain before 1 month. Computed tomography of the chest showed a mass occupying the posterior mediastinum and located anterior to the spine, above the diaphragm. The mass is removed by thoracoscopic surgery. In the surgical field of view, the tumor was loosely adhered to the surrounding organs and was freed by blunt-sharp combination Histologically confirmed mediastinal gangliocytoma with a size of 9.5 cm × 6.0 cm × 3.0 cm. The surgery was successful, and the patient's symptoms were completely relieved after the surgery. The patient underwent chest X-ray review at the 6th month after discharge, and no recurrence was found. Conclusions: Gangliocytomas are rare tumors of the peripheral nervous system. However, most of these tumors are retroperitoneal and are more common in children and young adults. Ganglioneuromas arise from neural crest cells. Most of these tumors are asymptomatic, but some may develop high blood pressure and flushing. Surgery is the best way to treat such tumors, and attention should be paid to protecting the normal tissue around the tumor during surgery to prevent postoperative complications.
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The traditional Haber-Bosch method of ammonia (NH3) synthesis has low production efficiency and can lead to greenhouse gas emission due to high temperature and pressure dependent reactions. Hence, the nitrogen reduction reaction (NRR) in a mild environment has been developed. However, the inert NîN triple bond and the competition with the hydrogen evolution reaction (HER) limit its wide application. In order to find an effective way of reducing N2 into NH3, in this work, PC6 monolayers with good electro-optical properties and eight transition metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn) are chosen to construct PC6-TM3 and PC6-TM4 single cluster catalysts (SCCs), which are proved to have low overpotential, multiple active-sites and superior activity. The thermodynamic stability, N2 adsorption, reaction paths, selectivity for the NRR and catalytic mechanism are systematically investigated. (PC6-Co3, PC6-Fe4)/(PC6-V3, PC6-Cr3)/(PC6-V4, PC6-Mn4) prefer to adsorb N2 rather than H in the end-on/side-on I/side-on III mode. PC6-Fe4 and PC6-Cr3 are finally screened out which have excellent catalytic activity with an overpotential of -0.46 V and -0.26 V in the consecutive path of side-on III and I modes, respectively. Moreover, both of them have 100% faradaic efficiency and present high selectivity for the NRR. The catalytic mechanism is elucidated by discussing the electronic properties of PC6-Cr3, where the back-donation behaviors of Cr atoms play an important role during the formation of NH3. This research may provide theoretical guidance for finding potential NRR catalysts with excellent performance and high selectivity.
RESUMEN
Nowadays, the electrocatalytic nitrogen reduction reaction (NRR) still faces great challenges. It's significant to design the electrocatalysts with excellent activity and high selectivity. Herein, the 28 single atom catalysts of transition metal atoms anchored on defective silicene (TM@D-silicene) are designed for electrocatalytic ammonia synthesis under ambient conditions. Two independent screening schemes are proposed to screen the potential SAC candidate. The criteria of Ebin < 0 eV, ΔG*N2< -0.1 eV, ΔG*H > ΔG*N2, and the lowest ΔG*NNH in scheme I, as well as ΔG*N2< -0.1 eV, smaller G*NNH and larger G*NH2 in scheme II are utilized in the screening procedure. Finally, Cr@D-silicene is picked out since it performs well in the aspects of N2 adsorption, selectivity and catalytic activity of NRR. Moreover, the electronic properties are systematically investigated to clarify why the Cr@D-silicene is qualified for NRR from the perspective of the strong interaction between N2 and Cr, the continuous activation of the N2 molecule, charge transfer and distribution. This work provides a new idea for electrocatalytic ammonia synthesis by using single-atom catalysts.
