Enhanced polarization switching characteristics of HfO2 ultrathin films via acceptor-donor co-doping.

In the realm of ferroelectric memories, HfO2-based ferroelectrics stand out because of their exceptional CMOS compatibility and scalability. Nevertheless, their switchable polarization and switching speed are not on par with those of perovskite ferroelectrics. It is widely acknowledged that defects play a crucial role in stabilizing the metastable polar phase of HfO2. Simultaneously, defects also pin the domain walls and impede the switching process, ultimately rendering the sluggish switching of HfO2. Herein, we present an effective strategy involving acceptor-donor co-doping to effectively tackle this dilemma. Remarkably enhanced ferroelectricity and the fastest switching process ever reported among HfO2 polar devices are observed in La3+-Ta5+ co-doped HfO2 ultrathin films. Moreover, robust macro-electrical characteristics of co-doped films persist even at a thickness as low as 3 nm, expanding potential applications of HfO2 in ultrathin devices. Our systematic investigations further demonstrate that synergistic effects of uniform microstructure and smaller switching barrier introduced by co-doping ensure the enhanced ferroelectricity and shortened switching time. The co-doping strategy offers an effective avenue to control the defect state and improve the ferroelectric properties of HfO2 films.

Three-dimensional ultrafast charge-density-wave dynamics in CuTe.

Charge density waves (CDWs) involved with electronic and phononic subsystems simultaneously are a common quantum state in solid-state physics, especially in low-dimensional materials. However, CDW phase dynamics in various dimensions are yet to be studied, and their phase transition mechanism is currently moot. Here we show that using the distinct temperature evolution of orientation-dependent ultrafast electron and phonon dynamics, different dimensional CDW phases are verified in CuTe. When the temperature decreases, the shrinking of c-axis length accompanied with the appearance of interchain and interlayer interactions causes the quantum fluctuations (QF) of the CDW phase until 220 K. At T < 220 K, the CDWs on the different ab-planes are finally locked with each other in anti-phase to form a CDW phase along the c-axis. This study shows the dimension evolution of CDW phases in one CDW system and their stabilized mechanisms in different temperature regimes.

Enhanced Exchange Bias in Epitaxial High-Entropy Oxide Heterostructures.

High-entropy oxides (HEOs) have gained significant interest in recent years due to their unique structural characteristics and potential to tailor functional properties. However, the electronic structure of the HEOs currently remains vastly unknown. In this work, combining magnetometry measurements, scanning transmission electron microscopy, and element-specific X-ray absorption spectroscopy, the electronic structure and magnetic properties of the perovskite-HEO La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 epitaxial thin films are systemically studied. It is found that enhanced magnetic frustration emerges from competing exchange interactions of the five transition-metal cations with energetically favorable half-filled/full-filled electron configurations, resulting in an unprecedented large vertical exchange bias effect in the single-crystalline films. Furthermore, our findings demonstrate that the La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 layer with a thickness down to 1 nm can be used as a pinning layer and strongly coupled with a ferromagnetic La0.7Sr0.3MnO3 layer, leading to a notable exchange bias and coercivity enhancement in a cooling field as small as 5 Oe. Our studies not only provide invaluable insight into the electronic structure of HEOs but also pave the way for a new era of large bias materials for spintronics devices.

Finger-powered agglutination lab chip with CMOS image sensing for rapid point-of-care diagnosis applications.

Agglutination is an antigen-antibody reaction with visible expression of aggregation of the antigens and their corresponding antibodies. Applications extend to the identification of acute bacterial infection, hemagglutination, such as blood grouping, and diagnostic immunology. Our finger-powered agglutination lab chip with external CMOS image sensing was developed to support a platform for inexpensive, rapid point-of-care (POC) testing applications related to agglutination effects. In this paper, blood grouping (ABO and Rh grouping) was utilized to demonstrate the function of our finger-powered agglutination lab chip with CMOS image sensing. Blood antibodies were preloaded into the antibody reaction chamber in the lab chip. The blood sample was pushed through the antibody reaction chamber using finger-powered pressure actuation to initiate a hemagglutination reaction to identify the blood type at the on-chip detection area using our homemade CMOS image sensing mini-system. Finger-powered actuation without the need for external electrical pumping is excellent for low-cost POC applications, but the pumping liquid volume per finger push is hard to control. In our finger-powered agglutination lab chip with CMOS image sensing, we minimized the effects of different finger push depths and achieved robust performance for the test results with different push depths. The driving sample volume per finger push is about 0.79 mm3. For different chips and different pushes, the driven sample volume per finger push was observed to vary in the range of 0.64 to 1.18 mm3. The red blood cells were separated from the plasma on-chip after the whole blood sample was finger pumped and before the red blood cells reached the antibody chamber via an embedded plasma-separation membrane. Our homemade CMOS image mini-system robustly read and identified the agglutination results on our agglutination lab chip.

[Repair of old injury of knee medial collateral ligament by a combination of dynamic and static stability].

OBJECTIVE: To observe the effectiveness of the combination of dynamic and static stability in the treatment of old knee medial collateral ligament injury. METHODS: Between March 2004 and June 2008, 26 cases of old knee medial collateral ligament injury were treated, including 19 males and 7 females with a mean age of 38 years (range, 21-48 years). Injury was caused by traffic accident in 6 cases, by sprains in 12 cases, by falling from height in 8 cases. The location was left knee in 15 cases and right knee in 11 cases. Of them, 24 patients showed the positive result of knee valgus test, 2 cases showed slightly relaxed knee tendon. The knee X-ray films of valgus stress position showed that the medial joint space differences between both knees were 3-5 mm in 2 cases and 5-12 mm in 24 cases. The injuries included avulsion of the medial femoral condyle starting point in 19 cases, central laceration in 6 cases, and tibial point laceration concomitant meniscus injury in 1 case. The time from injury to hospitalization was 3-14 months (mean, 6.4 months). Gracilis muscle was used to repair knee medial collateral ligament and the sartorius muscle transfer to reconstruct the medial rotation of knee stability function. RESULTS: All incisions healed by first intention. No joint infection, deep vein thrombosis, or other postoperative complications occurred. Twenty-six cases were followed up 12-58 months with an average of 30 months. The results of knee valgus stress test were negative with no joint tenderness. At 3 months after operation, the knee X-ray films of valgus stress position showed the medial joint space differences between both knees were less than 1 mm. According to the modified Lysholm-Scale score, the results were excellent in 18 cases, good in 7 cases, and fair in 1 case with an excellent and good rate of 96% at last follow-up. CONCLUSION: A combination of dynamic and static stability in repairing old knee medial collateral ligament injury is easy-to-operate and has the advantages to perform the operation in the same incision, so it can avoid the shortcomings of single repair method and achieve better effectiveness.