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In this study, a novel yet general strategy is proposed and demonstrated to enhance the energy storage density (ESD) of dielectric capacitors by introducing a built-in electric field in the dielectric layer, which increases the applied electric field required to polarize the dielectric. By using the top and bottom electrodes of different work functions, a built-in electric field is created in the antiferroelectric layer, which leads to an increase in the critical fields for the antiferroelectric-ferroelectric phase transition and thus the enhancement of ESD. Accordingly, the TiO 2 /ZrO 2 /TiO 2 antiferroelectric capacitor with asymmetric electrodes demonstrates an ultra-high ESD of 114.5 J cm−3, which is improved by ~21% compared to the antiferroelectric capacitor without a built-in field, along with high efficiency of 76%. The achieved ESD is record-high among the HfO 2 /ZrO 2 -based lead-free antiferroelectric thin-film capacitors. The result indicates that engineering the built-in electric field can be an effective and promising approach to increasing the ESD for electrostatic supercapacitors. [Display omitted] • A novel yet general strategy to enhance energy storage density (ESD) in dielectrics by built-in field engineering is proposed and theoretically derived. • Built-in field of opposite direction causes increase of applied electric field and thus increment of ESD. • The strategy is demonstrated on an antiferroelectric supercapacitor by asymmetric electrodes and work functions, revealing 21% improvement in ESD. • A record-high ESD of 114.5 J cm− 3 among Hf/ZrO 2 -based antiferroelectrics is achieved, along with outstanding efficiency and endurance. [ABSTRACT FROM AUTHOR]

The commercial ZK60 (Mg-5.7 wt%Zn-0.6 wt%Zr) magnesium alloy was used to investigate the effects of organic solvents along with CNTs and graphene on hydrogen absorption characteristics. The ZK60 alloy was plastically deformed via equal channel angular pressing using route B A at 300 °C and processed for 12 passes. The mechanically removed chips of deformed ZK60 alloy were milled with 5 wt% graphene or 5 wt% CNTs along with organic solvents (toluene and cyclohexane) in a high energy ball mill at 1725 rpm for 20 h. The kinetics and hydrogen storage were measured using Sievert's apparatus for five cycles at different absorption/desorption temperatures. At 320 °C/320 °C absorption/desorption temperature, the maximum hydrogen absorption with 5 wt% CNTs and 5 wt% graphene was 7.13 wt% and 7.28 wt%, respectively, reaching more than 98% within 10 min. The additions of CNTs and graphene could significantly reduce the hydrogenation temperature because the hydrogen storage and kinetics at 280 °C/280 °C were very close to 320 °C/320 °C. At 320 °C/320 °C absorption/desorption temperature, the maximum hydrogen absorption of 5 wt% CNTs or 5 wt% graphene with the addition of 1 ml toluene was about 6.5 wt%, and the hydrogen absorption with the addition of 2 ml toluene was reduced to 5.5 wt%. The addition of 2 ml cyclohexane along with CNTs and graphene had maximum hydrogen absorption of 6.3 wt% and 6.9 wt%, respectively, after five cycles of hydrogen absorption/desorption at 320 °C/320 °C. At the same absorption/desorption temperature, the number of cycles had no obvious effect on hydrogen storage and kinetics, indicating the absorbed hydrogen was completely released during the desorption process. • ZK60 alloy was ball milled with CNTs and graphene along with different concentrations of organic additives. • Additions of CNTs and graphene along with toluene & cyclohexane can significantly reduce the hydrogenation temperature. • Toluene and cyclohexane addition with CNTs and graphene has enhanced hydrogenation efficiency. • Maximum hydrogen capacities with CNTs and graphene are higher than 7 wt% at 320 °C/320 °C de/hydrogenation temperature. [ABSTRACT FROM AUTHOR]

The in-situ atomic layer doping technique was used to precisely control the Hf incorporation into the thin TiN interlayer for tailoring the effective work function (EWF) of the Pt/Ti x Hf y N bilayer metal gate stack. An analysis of the capacitance-voltage characteristics revealed the variation of the flatband voltage with the equivalent oxide thickness of the gate oxide, giving the EWF of the Pt/Ti x Hf y N bilayer metal gate stack. Instead of the EWF (~5.7 eV) of the single-layer Pt gate electrode, the EWF of the Pt/Ti x Hf y N bilayer metal gate stacks is tunable with the range from 4.54 eV to 5.17 eV by the insertion of the thin TiN interlayer and the Hf incorporation. The result indicates that the in-situ atomic layer doping technique is an effective approach to modulating the electrical properties of metal gate in future MOS devices. [ABSTRACT FROM AUTHOR]

The commercial ZK60 magnesium alloy was used to investigate hydrogen absorption performance. The ZK60 alloy was severely deformed via differential speed rolling with differential speeds of 6:3 and 9:3. High energy ball milling was used to blend deformed ZK60 powder with 5 wt% activated carbon(C), 0.5 wt% silver (Ag), 0.5 wt%palladium (Pd), and 1 wt% zirconium (Zr) for 20h at 1725 rpm. Hydrogen absorption characteristics at different low temperatures and number of cycles were analyzed using Sievert's apparatus with hydrogen supplied with H2S impurities. The microstructure of the powder was analyzed field emission scanning electron microscope (FESEM). The hydrogen absorption capacity increases with the temperature rise, and maximum capacity(6.02 wt%) was observed in 5C1Zr deformed at 9:3DSR at 200 °C after five cycles. Hydrogen absorption capacity increases after each hydrogenation cycle in 5C0.5Ag and 5C1Zr but remains the same in 5C0.5Pd. The increase in H2S concentration decreases the hydrogen capacity, and increase in the number of cycles further deteriorates absorption capacity when the differential speed ratio is 6:3. The H2S concentration variation has almost no effect at the differential speed of 9:3. The maximum hydrogen absorption kinetics (74.7%) in 10min was observed in 5C1Zr. A more refined dendritic microstructure was observed in ZK60 alloy deformed with a differential speed ratio of 9:3. [ABSTRACT FROM AUTHOR]

Using ZK60 commercial magnesium alloy as hydrogen storage material, the effects of equal channel angular extrusion (ECAP) passes and different weight percentages of additives (activated carbon, vanadium and titanium) on hydrogen absorption characteristics were studied. ECAPed ZK60 with additives was prepared by high-energy ball milling for 20 h.The rate of hydrogenation was measured at different temperatures for five cycles using a Sievert's apparatus. The results reveal that hydrogen absorption increased to 5.3 wt% after 12 passes of ECAP in monolithic ZK60. The 12-pass ECAPed ZK60 along with the addition of 5 wt% activated carbon, and 2 wt% vanadium has improved hydrogenation to 6.7 wt% at 350 °C. The hydrogen absorption capacity is increased after each cycle for most ECAPed ZK60 samples, except that doped with 10 wt% activated carbon and 2 wt% titanium in which hydrogen absorption capacity is significantly reduced from 5.6 wt% to 3.2 wt% after the first cycle at 300°C. • ZK60 was deformed using ECAP and ball milled with Vanadium, Activated carbon and Titanium. • Hydrogenation capacities was analyzed using Sieverts apparatus. • Hydrogenation capacities increase with the increase in number of passes. • 12 passed ECAPed ZK60 with 5 wt% activated carbon and 2 wt% Vanadium has maximum hydrogen capacity. [ABSTRACT FROM AUTHOR]

• HiPIMS was used to produce NiO film with enhanced p-type optoelectronic performance. • The high ionization rate of HiPIMS holds promise to elevate Ni3+ content. • The optimal conductivity of 50 S·cm−1 with a high hole concentration is realized. High power impulse magnetron sputtering (HiPIMS) technology has attracted lots of attention due to its high target ionization rate. This characteristic is desirable in preparing metal compounds with complex valence states. In the current work, NiO films were deposited by HiPIMS and direct current magnetron sputtering (DCMS) at various oxygen flow ratios. The films' structural and optoelectronic properties were investigated. The results show that, thanks to the enhanced Ni3+ ion density formed during the HiPIMS deposition process, more nickel vacancies are formed in the film leading to the film's carrier concentration improving significantly. NiO films deposited by HiPIMS possess much better p-type conductivity than the films deposited by DCMS. Additionally, with oxygen flow ratio increase, more interstitial oxygen can be introduced, which can also enhance the film's p-type electrical conductivity. However, these defects reduce the film's transmittance. [ABSTRACT FROM AUTHOR]

Herein, intrinsic p-type conductivity of NiO films were enhanced by high power impulse magnetron sputtering (HiPIMS) technology, where more charged Ni3+ ions are created during the deposition process. The formation of Ni3+ ions are advantageous for strengthening the p-type conductivity of NiO films. As the pulse off-time increases from 0 μs to 3000 μs, Ni3+ concentration improves greatly, indicating the amount of Ni vacancies as well as the hole concentration significantly enhances. It confirms that HiPIMS is a preferential technology for preparing NiO films with high p-type conductivity. Especially, when pulse off-time reaches 3000 μs, a high carrier concentration of 2.86 × 1021 cm−3 and a relatively low electrical resistivity about 0.07 Ω·cm are achieved. [ABSTRACT FROM AUTHOR]

Sub-10 nm high-K gate dielectrics are of critical importance in two-dimensional transition metal dichalcogenides (TMDs) transistors. However, the chemical inertness of TMDs gives rise to a lot of pinholes in gate dielectrics, resulting in large gate leakage current. In this study, sub-10 nm, uniform and pinhole-free Al 2 O 3 high-K gate dielectrics on MoS 2 were achieved by atomic layer deposition without surface functionalization, in which an ultrathin Al 2 O 3 layer prepared with a short purge time at a low temperature of 80 °C offers the nucleation cites for the deposition of the overlaying oxide at a higher temperature. Conductive atomic force microscopy reveals the significant suppression of gate leakage current in the sub-10 nm Al 2 O 3 gate dielectrics with the low-temperature nucleation layer. Raman and X-ray photoelectron spectroscopies indicate that no oxidation occurred during the deposition of the low-temperature Al 2 O 3 nucleation layer on MoS 2 . With the high-quality sub-10 nm Al 2 O 3 high-K gate dielectrics, low hysteresis and subthreshold swing were demonstrated on the normally-off top-gated MoS 2 transistors. [ABSTRACT FROM AUTHOR]

In the recent decade, there is a growing interest in Hf 0.5 Zr 0.5 O 2 (HZO) thin films owing to their well-behaved ferroelectricity and high compatibility with semiconductor integrated circuit technology. The ferroelectric properties of HZO are highly pertinent to the wake-up effect, which has been reported to be associated with the monoclinic (m-), orthorhombic (o-), and tetragonal (t-) phases. However, it is very challenging to distinguish the o- and t- phases by conventional X-ray diffraction. In this study, the HZO thin films with and without the need for the wake-up process to enhance the ferroelectricity were prepared, and the precession electron diffraction (PED) phase mapping technique was utilized to identify the crystalline phases in the HZO layers. The PED characterization reveals the correlation between the phase transformation and the wake-up effect in HZO. The absence of the t-phase is responsible for the wake-up-free property in the ferroelectric HZO thin film. The wake-up-free and pronounced ferroelectricity of the nanoscale HZO thin film in this study may bring a practical impact on a variety of ferroelectric applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Ferroelectric (FE) Hf 0.5 Zr 0.5 O 2 (HZO) is treated with atomic layer annealing (ALA). • The ALA process upon HfO 2 monolayer induces superior crystalline and FE properties. • Insignificant wake-up effect is achieved in HZO thin films without post annealing. In recent years, ferroelectric hafnium zirconium oxide (Hf 0.5 Zr 0.5 O 2 , HZO) has emerged as a promising candidate for nonvolatile memory and energy storage devices. A low thermal budget technique for achieving sub-10 nm HZO thin films with pronounced ferroelectricity is highly demanded for ferroelectric applications such as advanced semiconductor technology nodes. In this paper, the atomic layer annealing (ALA) technique, which is the in situ He/Ar plasma treatment incorporated into the atomic layer deposition cycle, is demonstrated to achieve the transformation from amorphous to orthorhombic phase in sub-10 nm HZO layers without the need of any high-temperature post annealing. As compared with the ALA process conducted on each ZrO 2 monolayer, the ALA treatment performed on each HfO 2 monolayer is much preferred in terms of superior crystallinity and ferroelectric properties of the HZO thin films. Hence a high remanent polarization together with a nearly wake-up-free property are accomplished in the HZO layer. The study demonstrates ALA is an effective technique to realize the atomic tailoring of crystalline quality and ferroelectric/dielectric characteristics of nanoscale thin films at a low temperature, which is very favorable in a variety of applications including biomedical, wearable, and nanoelectronic devices, in which a low thermal budget process is required. [ABSTRACT FROM AUTHOR]

Abstract: We report the structural and electrical characteristics of hafnium oxide (HfO2) gate dielectrics treated by remote NH3 plasma under various radio-frequency (RF) powers at a low temperature. Significant increase of effective dielectric constant (k eff), decrease of capacitance equivalent thickness (CET), reduction in leakage current density, and suppression of the interfacial layer thickness were observed with the increase of the RF power in the remote NH3 plasma treatment. The effects of hydrogen passivation and depassivation on the HfO2/Si interface due to the remote NH3 plasma treatment were also observed by the variation of photoluminescence (PL) intensity, indicating that the PL measurement is applicable to probe the interfacial properties. An ultrathin interfacial layer (∼0.3nm), a high k eff, (20.9), a low leakage current density (9×10−6 A/cm2), and a low CET (1.9nm) in the nitrided HfO2 film were achieved, demonstrating that the nitridation process using remote NH3 plasma under a high RF power at a low temperature is a promising way to improve in electrical properties of high-K gate dielectrics. [Copyright &y& Elsevier]

Abstract: Commercial alloy ZK60 (Mg-6 wt%Zn-0.8 wt% Zr) was used as a hydrogen-storage material to study the effect of cold rolling, ball milling, and plus graphite additives on hydrogen-storage characteristics, hydrogen absorption–desorption behavior, and the related microstructural change of the alloy. Experimental results showed that cold-rolled alloy could not be activated easily. Even after ball milling for 20h and hydrogen absorption–desorption cycling for 10 times, no saturated hydrogen absorption was observed for cold-rolled alloy. In contrast, alloys with 5 wt% graphite additives could be easily activated after the first hydrogen absorption–desorption cycle, and a saturated hydrogen absorption of 6.9 wt% was obtained after absorption–desorption cycling for five times. A hydrogen absorption of 5.52 wt%, equivalent to 80% of the saturated absorption amount, was measured in 5min, showing a hydrogen absorption rate of 1.104 wt%/min. The sample reached saturation in 30min. [Copyright &y& Elsevier]

Abstract: Lithium manganese oxides have been deposited by radio frequency magnetron sputter deposition with relatively lower annealing temperatures and then post-treated with a radio frequency (rf) driven oxygen plasma. Following oxygen plasma irradiation, the film properties were modified, and the performance of the thin film cathode has been enhanced. The electrochemical properties of the treated thin-film cathodes were characterized and compared. The results showed that the samples with moderate plasma treatment also maintained good cyclic properties as cycled at a wide range potential window of 2.0 V–4.5 V. Its electrochemical properties were significantly improved by this process, even though the films were prepared under low annealing temperature. [Copyright &y& Elsevier]

• TiO 2 film was deposited on surface of Ni50Ti50 substrate using atomic layer deposition techniques. • TiO 2 film thickness, surface roughness, corrosion resistance and biocompatibility were investigated. • TiO 2 film thickness is directly proportional with number of ALD cycles. • The maximum corrosion resistance, excellent surface morphology and Cell proliferation was achieved after 200 ALD cycles. NiTi shape memory alloys (SMAs) have been widely applied in biomedical fields due to their excellent shape memory effect, super-elasticity, and biocompatibility. In this study, the plasma- enhanced atomic layer deposition was applied to deposit TiO 2 film on the surface of Ni50Ti50 substrate. The characterization and surface properties of TiO 2 film, bending strain test, corrosion resistance, nickel release and in vitro biocompatibility were studied to evaluate the performance of ALD-TiO 2 film. The results show that the ALD-TiO 2 film is uniform and exhibits an amorphous structure. The ALD-TiO 2 films are less hydrophilic than the Ni50Ti50 substrate. As the deposition cycle increases, the water contact angle of ALD-TiO 2 film only changes slightly. The ALD-TiO 2 film exhibits an adequate adhesion to the Ni50Ti50 substrate and can withstand proper bending strain. ALD-TiO 2 film can effectively inhibit the release of nickel ions. After being immersed in the simulated body fluid for 30 days, the amount of nickel ions released decreases from 60 ppb for Ni50Ti50 substrate to 20–20 ppb for Ni50Ti50 with 200-cycle ALD-TiO 2 film. Meanwhile, Ni50Ti50 with ALD-TiO 2 films have better corrosion resistance than the Ni50Ti50 substrate. In vitro biocompatibility reveals that the ALD-TiO 2 film can enhance cell adhesion, promote cell proliferation and reduce cytotoxicity. After 5 days of culture, the 200-cycle ALD-TiO 2 film can enhance the cell proliferation by 2.7 times and reduce the cytotoxicity from 48% for Ni50Ti50 substrate to 37% for Ni50Ti50 with 200-cycle ALD-TiO 2 film. These results indicate that the TiO 2 films deposited by PE-ALD technique can effectively improve the biocompatibility of NiTi SMAs. [ABSTRACT FROM AUTHOR]

• The heating depth of atomic layer annealing (ALA) is less than 5 atomic layers. • The ALA-treated AlN layer is a high-quality epilayer with a low FWHM ~150 arcsec. • The film density of AlN is increased by ~11% by the ALA technique. • The dielectric constant of AlN is increased by ~35% by the ALA technique. • The leakage current is reduced by ~2 orders of magnitude by the ALA technique. • The threading dislocation density is suppressed by one order of magnitude by ALA. Conventional annealing techniques face tremendous challenges in nanoscale fabrication. For example, the heating depth of conventional annealing techniques is much greater than the critical dimension of nanoscale devices, resulting in excessive thermal budget and so degradation of device performance. In this study, the atomic layer annealing (ALA) technique of a sub-nanometer heating depth is demonstrated. ALA is an in-situ plasma treatment applied in the process of atomic layer deposition (ALD), resulting in delivery of energy to the surface of as-deposited thin films from the plasma. The ALA treatment introduced into each ALD cycle leads to significant enhancement of crystallinity, film density, and dielectric constant, as well as considerable suppression of leakage current and threading dislocation densities, of the AlN layer. These improvements of the AlN properties was degraded significantly with an increase of the cycle spacing of the ALA treatment in the ALD process, indicating the heating depth of the ALA technique is below 5 atomic layers. The result indicates that the ALA process of precise sub-nanometer heating depth plays a critical role to achieve high-quality nanoscale materials and devices. [ABSTRACT FROM AUTHOR]

A layer-by-layer, in-situ H 2 plasma treatment in each cycle of atomic layer deposition, referred to as "atomic layer hydrogen bombardment" (ALHB), is applied to improve electrical properties of ZrO 2 high-k gate dielectrics. The H 2 plasma bombardment facilitates the adatom migration due to energy delivery to each as-deposited monolayer from the H 2 plasma. In addition, the H 2 plasma treatment contributes to the removal of precursor ligands for the release of steric hindrance. Hence the ALHB treatment leads to film densification and suppression of oxygen vacancies of ZrO 2 , as evidenced by X-ray reflectivity and X-ray photoelectron spectroscopy characterizations. As a result, ~90% decrease of gate leakage current is achieved in the ZrO 2 high-k gate dielectrics with capacitance equivalent thicknesses of ~1.3 nm and ~0.6 nm in metal-insulator-semiconductor and metal-insulator-metal capacitors, respectively. The results manifest that the ALHB treatment is a promising technique to enhance dielectric and electrical characteristics of nanoscale thin films, for further progress of advanced devices such as sensors, solar cells, memories, and nanoelectronics. Image 1 • To improve the gate dielectrics, atomic layer hydrogen bombardment (ALHB) is applied. • ALHB leads to the densification of films and the suppression of oxygen vacancies. • ~90% decrease of the leakage current is achieved in ZrO 2 MIM capacitors with a low CET ~0.6 nm. [ABSTRACT FROM AUTHOR]