Search

The purpose of this study is to investigate the indirect effects on the properties of ZrO2 films deposited by atomic layer deposition (ALD) when an Mg-Ca alloy is modified through equal-channel angular pressing (ECAP) following extrusion. The study aims to understand how the increase in CaO content in the native oxide layer of the Mg-Ca alloy influences the crystallinity and defect density of the ZrO2 film. Consequently, the corrosion protection performance of the ZrO2 film is enhanced by 1.2 to 1.5 times. A reduction in the anti-scratch property of the ZrO2 film was also observed, with a critical load reduction of 34 μN. This research provides a detailed analysis of the modifications induced by ECAP on the as-extruded Mg-Ca alloy and its subsequent impact on the properties of the ZrO2 film. [ABSTRACT FROM AUTHOR]

In this study, platinum (Pt) and tungsten (W), two materials with dissimilar coefficients of thermal expansion (CTE) and work functions (WF), are used as the top electrode (TE) and the bottom electrode (BE) in metal/ferroelectric/metal (MFM) structures to explore the ferroelectricity of hafnium zirconium oxide (HZO) with a thickness less than 10 nm. The electrical measurements indicate that a higher CTE mismatch between HZO and TE/BE is beneficial for enhancing the ferroelectric properties of nanoscale HZO thin films. The different WFs of TE and BE generate a built-in electric field in the HZO layer, leading to shifts in the hysteresis loops and the capacitance–voltage characteristics. The structural characterizations reveal that the preferred formation of the orthorhombic phase in HZO is dominated by the W BE. The device in which W is used as the TE and BE (the W/HZO/W MFM structure) presents the optimal ferroelectric performance of a high remanent polarization (2 P r = 55.2 μ C cm−2). The presence of tungsten oxide (WO x ) at the W/HZO interfaces, as revealed by high-resolution transmission microscopy, is also responsible for the enhancement of ferroelectric properties. This study demonstrates the significant effects of different CTEs and WFs of TE and BE on the properties of ferroelectric HZO thin films. [ABSTRACT FROM AUTHOR]

Atomic layer engineering is investigated to tailor the morphotropic phase boundary (MPB) between antiferroelectric, ferroelectric, and paraelectric phases. By increasing the HfO2 seeding layer with only 2 monolayers, the overlying ZrO2 layer experiences the dramatic phase transition across the MPB. Conspicuous ferroelectric properties including record‐high remanent polarization (2Pr ≈ 60 µC cm−2), wake‐up‐free operation, and high compatibility with advanced semiconductor technology nodes, are achieved in the sub‐6 nm thin film. The prominent antiferroelectric to ferroelectric phase transformation is ascribed to the in‐plane tensile stress introduced into ZrO2 by the HfO2 seeding layer. Based on the high‐resolution and high‐contrast images of surface grains extracted precisely by helium ion microscopy, the evolution of the MPB between tetragonal, orthorhombic, and monoclinic phases with grain size is demonstrated for the first time. The result indicates that a decrease in the average grain size drives the crystallization from the tetragonal to polar orthorhombic phases. [ABSTRACT FROM AUTHOR]

In recent years, aluminum matrix composites (AMCs) have attracted attention due to their promising properties. However, the presence of ceramic particles in the aluminum matrix renders AMCs a high corrosion rate and makes it challenging to use traditional corrosion protection methods. In this study, atomic layer deposition (ALD) techniques were used to deposit HfO2, ZrO2, TiO2, and Al2O3 thin films on AMC reinforced with 20 vol.% SiC particles. Our results indicate that the presence of micro-cracks between the Al matrix and SiC particles leads to severe micro-crack-induced corrosion in Al-SiC composites. The ALD-deposited films effectively enhance the corrosion resistance of these composites by mitigating this micro-crack-induced corrosion. Among these four atomic-layer deposited films, the HfO2 film exhibits the most effective reduction in the corrosion current density of Al-SiC composites in a 1.5 wt% NaCl solution from 1.27 × 10−6 A/cm2 to 5.89 × 10−11 A/cm2. The electrochemical impedance spectroscopy (EIS) investigation shows that HfO2 deposited on Al-SiC composites has the largest Rp value of 2.0 × 1016. The HfO2 film on Al-SiC composites also exhibits effective inhibition of pitting corrosion, remaining at grade 10 even after 96 h of a salt spray test. [ABSTRACT FROM AUTHOR]

In this article, aluminum nitride (AlN) resistive random access memory (RRAM) devices are fabricated and investigated. To improve the resistive switching performance, the atomic layer annealing (ALA) technique, which is an energy transfer process by the in situ plasma treatment introduced into atomic layer deposition, was used to modulate the film quality of the AlN switching layer with a thickness of only 3.3 nm. The ALA treatment is capable of tailoring nitrogen vacancies in the AlN layer with monolayer accuracy, leading to a decrease in the operating voltage and an improvement in uniformity of the resistive switching characteristics. In addition, the AlN RRAM devices exhibit pulse endurance over 104 cycles and retention of more than 106 s at 125 °C. The result demonstrates that the resistive switching properties of RRAMs can be controlled by the precise atomic layer engineering of each monolayer. [ABSTRACT FROM AUTHOR]

For cardiopulmonary bypass, the polyvinyl chloride (PVC) circuit which can initiate the activation of platelets and the coagulation cascade after blood cell contacting is the possible detrimental effect. Surface coating of the PVC tubing system can be an effective approach to enhance circuit's hemocompatibility. In this study, aluminum oxide (Al2O3) thin films were deposited through thermal atomic layer deposition (T‐ALD) or plasma‐enhanced ALD (PE‐ALD) on PVC samples, and the anticoagulation of the Al2O3‐coated PVC samples was demonstrated. The results revealed that Al2O3 deposition through ALD increased surface roughness, whereas T‐ALD had a relative hydrophilicity compared with blank PVC and PE‐ALD. Whole blood immersion tests showed that blood clots formed on blank PVC and that a large amount of red blood cells was found on PE‐ALD substrates, whereas less blood cells were noted in T‐ALD samples. Both T‐ALD and PE‐ALD Al2O3 films did not cause activation of blood cells, as evidenced in CD3+/CD4+/CD8+, CD61+/CD62P+, and CD45+/CD42b+ populations. Analysis of serum coagulation factors showed that a lower amount of prothrombin was absorbed on T‐ALD Al2O3 samples than that on blank PVC. For albumin and fibrinogen immersion tests, immunostaining and scanning electron microscopy further revealed that a thin albumin layer was absorbed on T‐ALD Al2O3 substrates but not on PVC samples. This study revealed that deposition of Al2O3 films by T‐ALD can improve anticoagulation of the PVC tubing system. [ABSTRACT FROM AUTHOR]

The thickness scaling of the ferroelectric (FE) hafnium zirconium oxide (HZO) down to sub-10 nm is essential in non-volatile memory devices. In this study, high remnant polarization (Pr), low thermal budget, low operation voltage, and high endurance are demonstrated in the FE HZO thin films with thickness shrinkage from 10 to 3 nm. Due to the in-plane tensile stress induced by the TiN capping layer and the initial island growth on the platinum bottom electrode, record-high Pr ∼24.8 μC cm−2 is realized in the 6 nm HZO layer. Good ferroelectricity with Pr ∼10.8 μC cm−2 and low saturation voltage (∼0.7 V) is also achieved in the 3 nm HZO thin film. The wake-up effect is insignificant as the HZO thickness is greater than 5 nm, while an obvious wake-up effect is observed in sub-5 nm HZO thin films. This result can be ascribed to the increasing stability of the tetragonal phase with a decrease of the HZO thickness as supported by the dielectric constant measurement. The dielectric breakdown strength of the HZO layers was evaluated by the time-zero dielectric breakdown test. The dielectric breakdown strength increases rapidly with a decrease of the HZO thickness, which leads to a significant endurance improvement with ∼1011 electric field cycling without breakdown in the 3 nm HZO thin film. The favorable FE properties demonstrated in the sub-5 nm HZO thin films provide a promising approach in future FE non-volatile memory applications. [ABSTRACT FROM AUTHOR]

The performance enhancements of Si junctionless transistors (JLTs) with a short gate length (LG) below 10 nm by a pronounced ferroelectric (FE) gate dielectric were demonstrated for the first time. A TiN gate with LG = ∼8 nm was defined by helium ion beam lithography (HIBL) using hydrogen silsesquioxane as a resist. As compared with the paraelectric HfO2 gate oxide, the FE Hf0.5Zr0.5O2 gate dielectric leads to a suppression of the off-state current (IOFF) by ∼2 orders of magnitude and a reduction of the minimum subthreshold swing (SS) to ∼33 mV dec−1, along with an enhancement of the on/off ratio in the reverse-sweep direction in JLTs with LG = ∼8 nm. JLTs with a long LG = 5 μm were also investigated for comparison, revealing a decrease of IOFF by ∼25× and the sub-60 mV dec−1 SS across ∼3 orders of drain current (ID) under a large drain voltage (VD = 0.5 V) operation during the reverse sweep in FE JLTs. A time domain analysis indicated that the transient negative capacitance (TNC) effect takes place in the FE gate dielectric. A physical model was proposed to account for the TNC effect and the sub-60 mV dec−1 SS based on the capacitance increase during the FE polarization switching. This study also demonstrates for the first time the fabrication of nanoelectronic devices with a sub-10 nm critical dimension by using the HIBL technique with a damage-free dose. [ABSTRACT FROM AUTHOR]

Antiferroelectric (AFE) HfO2/ZrO2-based thin films have recently emerged as a potential candidate for high-performance energy storage capacitors in miniaturized power electronics. However, the materials suffer from the issues of the trade-off between energy storage density (ESD) and efficiency, as well as the difficulty in scaling up of the film thickness. In this study, an AFE TiO2/ZrO2/TiO2 stacked structure is proposed to overcome these difficulties. The compressive chemical pressure arising from the interdiffusion of TiO2/ZrO2 layers leads to a reduction of the hysteresis and thus a high ESD and a low energy loss. Hence the TiO2/ZrO2/TiO2 single-stacked AFE capacitor demonstrates a record-high ESD of 94 J cm−3 and a high efficiency of 80%, along with a high maximum power density of 5 × 1010 W kg−1. The degradation of the energy storage performance as the film thickness increases is alleviated by the TiO2/ZrO2/TiO2 multi-stacked structure, which presents a high ESD of 80 J cm−3 and efficiency of 82% with the thickness scaled up to 48 nm. This improvement is attributed to the enhancement of breakdown strength due to the barrier effect of interfaces on electrical treeing. Furthermore, the capacitors also exhibit an excellent endurance up to 1010 operation cycles. With a combination of high ESD, high efficiency, high power density, and scalability, the TiO2/ZrO2/TiO2 stacked structures show promising prospects for supercapacitor applications. [ABSTRACT FROM AUTHOR]