In Situ Formation of Polycyclic Aromatic Hydrocarbons as an Artificial Hybrid Layer for Lithium Metal Anodes.

Nonuniform Li deposition causes dendrites and low Coulombic efficiency (CE), seriously hindering the practical applications of Li metal. Herein, we developed an artificial solid-state interphase (SEI) with planar polycyclic aromatic hydrocarbons (PAHs) on the surface of Li metal anodes by a facile in situ formation technology. The resultant dihydroxyviolanthron (DHV) layers serve as the protective layer to stabilize the SEI. In addition, the oxygen-containing functional groups in the soft and conformal SEI film can regulate the diffusion and transport of Li ions to homogenize the deposition of Li metal. The artificial SEI significantly improves the CEs and shows superior cyclability of over 1000 h at 4 mAh cm-2. The LiFePO4/Li cell (2.8 mAh cm-2) enables a long cyclability for 300 cycles and high CEs of 99.8%. This work offers a new strategy to inhibit Li dendrite growth and enlightens the design on stable SEI for metal anodes.

Growth Mechanism, Ambient Stability, and Charge Trapping Ability of Ti-Based Maleic Acid Hybrid Films by Molecular Layer Deposition.

Ti-based maleic acid (MA) hybrid films were successfully fabricated by molecular layer deposition (MLD) using organic precursor MA and inorganic precursor TiCl4. The effect of deposition temperature on the growth rate, composition, and bonding mode of hybrid thin films has been investigated systematically. With increasing temperature from 140 to 280 °C, the growth rate decreases from 1.42 to 0.16 Å per MLD cycle with basically unchanged composition ratio of C:O:Ti in the films. Fourier transform infrared spectra indicate that all hybrid films show preference for bidentate bonding mode. Further analyses of X-ray photoelectron spectroscopy and in situ quartz crystal microbalance elucidate that as-deposited MLD Ti-MA hybrid films consist of inorganic Ti-O-Ti units and organic-inorganic Ti-MA units. In addition, the density functional theory calculation was performed to investigate the possible reaction mechanism of the TiCl4-MA MLD process, which is well consistent with experimental results. More importantly, upon comparison with the TiCl4-fumaric acid MLD system, it is demonstrated that the cis- and trans-configurations of butenedioic acid influence the MLD growth, bonding mode, stability, and charging ability of MLD hybrid films. Ti-MA hybrid films exhibit better stability and charging ability than Ti-FA hybrid films, benefiting from the inorganic Ti-O-Ti units in the hybrid films.

Photocatalytic activity and photocorrosion of atomic layer deposited ZnO ultrathin films for the degradation of methylene blue.

ZnO ultrathin films with varied thicknesses of 7-70 nm were prepared at 200 °C on Si and fused quartz substrates by atomic layer deposition (ALD). The impact of film thickness and annealing temperature on the crystallinity, morphology, optical bandgap, and photocatalytic properties of ZnO in the degradation of methylene blue (MB) dye under UV light irradiation (λ = 365 nm) has been investigated deeply. The as-deposited 28 nm thick ZnO ultrathin film exhibits highest photocatalytic activity, ascribed to the smallest band gap of 3.21 eV and proper thickness. The photocorrosion effect of ALD ZnO ultrathin films during photocatalytic process is observed. The presence of MB significantly accelerates the dissolution of ZnO ultrathin films. The possible photoetching mechanism of ZnO in MB solution is proposed.

[Relationship of alcohol drinking and tea consumption with the risk of nasopharynx cancer among Chinese population: a meta-analysis].

OBJECTIVE: To evaluate the relationship and strength of association for alcohol drinking and tea consumption with the riskS of nasopharynx cancer among Chinese population so as to provide control rationales for nasopharynx cancer in China. METHODS: A systematic search of 3 Chinese electronic databases (CNKI, VIP, Wanfang) and 3 English databases (Pubmed, ScienceDirect and SpringerLink) up to March 2013 was performed. Two reviewers independently conducted the literature search, examined eligibility and performed data extraction and quality evaluations. Pooled odd ratio (OR) value and 95%CI value were calculated with random-effects model weighted with inverse of variances. RESULTS: A total of 14 studies (including 3 cohort and 11 case-control) involving 6559 cases of nasopharynx cancer and 10 567 controls from 6 provinces were included. The pooled OR between alcohol drinking and risks of nasopharynx cancer was 1.12 (95%CI: 0.98-1.26; I(2) = 44.5%, P = 0.037). Compared with the non-drinkers, the risks of nasopharynx cancer for regular drinkers and occasional drinkers were 1.18 (95%CI: 1.00-1.38; I(2) = 0.0%, P = 0.578) and 0.76 (95%CI: 0.65-0.89; I(2) = 33.4%, P = 0.212). And the association of tea consumption with the risks of nasopharynx cancer was 0.53 (95%CI: 0.43-0.60; I(2) = 17.9%, P = 0.301). CONCLUSIONS: In China, occasional alcohol drinking may decrease the risks of nasopharynx cancer while regular drinking elevates the risks. And there is significantly protective effect for tea consumption on the risks of nasopharynx cancer.

Electrochemical Resistive Switching in Nanoporous Hybrid Films by One-Step Molecular Layer Deposition.

An organic-inorganic hybrid resistive random-access memory based on a nanoporous zinc-based hydroquinone (Zn-HQ) thin film has been constructed with a Pt/Zn-HQ/Ag sandwich structure. The porous Zn-HQ functional layer was directly fabricated by a one-step molecular layer deposition. These Pt/Zn-HQ/Ag devices show a typical electroforming-free bipolar resistive switching characteristic with lower operation voltages and higher on/off ratio above 102. Our nanoporous hybrid devices can also realize multilevel storage capability and exhibit excellent endurance/retention properties. The connection and disconnection of Ag conductive filaments in nanoporous Zn-HQ thin film follow the electrochemical metallization mechanism. Our computational simulations confirm that the existence of nanopores in Zn-HQ thin films facilitates the Ag filament formation, contributing to the high performance of our hybrid devices.

Growth behavior of Ir metal formed by atomic layer deposition in the nanopores of anodic aluminum oxide.

The conformal coating or surface modification in high aspect ratio nanostructures is a tough challenge using traditional physical/chemical vapor deposition, especially for metal deposition. In this work, the growth behavior of iridium (Ir) metal formed by atomic layer deposition (ALD) in anodic aluminum oxide (AAO) templates was explored deeply. It is found that the surface hydrophilicity is crucial for the nucleation of ALD Ir. An in situ ALD Al2O3 layer with an ultra-hydrophilic surface can greatly promote the nucleation of ALD Ir in AAO nanopores. The effect of the Ir precursor pulse time, diameter, and length of AAO nanopores on the infiltration depth of ALD Ir was investigated systematically. The results show that the infiltration depth of ALD Ir in AAO nanopores is in proportion to the pore diameter and the square root of the Ir precursor pulse time, which follows a diffusion-limited model. Furthermore, the Ir precursor pulse time to obtain conformal Ir coating throughout all the AAO channels is in proportion to the square of the aspect ratio of AAO templates. In addition, the conformal Ir deposition in AAO nanopores is also related to the Ir precursor purge time and the O2 partial pressure. Insufficient Ir purge time could cause a CVD-like reaction, leading to the reduction of the infiltration depth in AAO. Higher O2 partial pressure can facilitate Ir nucleation with more Ir precursor consumption at the entrance of nanopores, decreasing the infiltration depth in AAO nanopores, so appropriate O2 partial pressure should be chosen for ALD Ir in high aspect ratio materials. Above all, our research is valuable for surface modification or coating of metal by ALD in high aspect ratio nanostructures for 3D microelectronics, nano-fabrication, catalysis and energy fields.

Realizing the enhanced cyclability of a cactus-like NiCo2O4 nanocrystal anode fabricated by molecular layer deposition.

Lithium-ion batteries with conversion-type anode electrodes have attracted increasing interest in providing higher energy storage density than those with commercial intercalation-type electrodes. However, conversion-type materials exhibit severe structural instability and capacity fade during cycling. In this work, a molecular layer deposition (MLD)-derived conductive Al2O3/carbon layer was employed to stabilize the structure of the cactus-like NiCo2O4 nanocrystal (NC) anode. The conductive Al2O3/carbon network and cactus-like NiCo2O4 NCs are beneficial for fast Li+/e- transport. Moreover, the Al2O3/carbon buffer-layer can prevent the NiCo2O4 NCs from agglomeration and form a steady solid electrolyte interphase (SEI), thus hampering the penetration of the electrolyte. Owing to these advantages, the assembled NiCo2O4@Al2O3/carbon half battery shows a high reversible capacity (931.2 mA h g-1 at 2 A g-1) and long-term stability of 290 mA h g-1 at 5 A g-1 over 500 cycles. Quantitative analyses further reveal the fast kinetics and the capacitance-battery dual model mechanism in the 3D core-shell structures. The design and introduction of MLD-derived hybrid coating may open a new way to conversion-type and alloy-type anode materials beyond NiCo2O4 to achieve high cyclability.

Tailoring Stress and Ion-Transport Kinetics via a Molecular Layer Deposition-Induced Artificial Solid Electrolyte Interphase for Durable Silicon Composite Anodes.

Silicon is considered as a blooming candidate material for next-generation lithium-ion batteries due to its low electrochemical potential and high theoretical capacity. However, its commercialization has been impeded by the poor cycling issue associated with severe volume changes (∼380%) upon (de)lithiation. Herein, an organic-inorganic hybrid film of titanicone via molecular layer deposition (MLD) is proposed as an artificial solid electrolyte interphase (SEI) layer for Si anodes. This rigid-soft titanicone coating with Young's modulus of 21 GPa can effectively relieve stress concentration during the lithiation process, guaranteeing the stability of the mechanical structure of a Si nanoparticles (NPs)@titanicone electrode. Benefiting from the long-strand (Ti-O-benzene-O-Ti-) unit design, the optimized Si NPs@70 cycle titanicone anode delivers a high Li+ diffusion coefficient and a low Li+ diffusion barrier, as revealed by galvanostatic intermittent titration (GITT) investigations and density functional theory (DFT) simulations, respectively. Ultimately, the Si NPs@70 cycle titanicone electrode shows high initial Coulombic efficiency (84%), long cycling stability (957 mAh g-1 after 450 cycles at 1 A g-1), a stable SEI layer, and good rate performances. The molecular-scale design of the titanicone-protected Si anodes may bring in new opportunities to realize the next-generation lithium-ion batteries as well as other rechargeable batteries.

[Anti-tumor efficacy of interventional chemotherapy with liposomal doxorubicin for hepatic metastasis of pancreatic cancer in nude mouse model].

OBJECTIVE: To investigate the anti-tumor effect of interventional chemotherapy with liposome doxorubicin for hepatic metastasis of pancreatic tumor in nude mice. METHODS: After the establishment of hepatic metastatic model of pancreatic tumor, the nude mice received various formulations via a spleen injection to imitate the interventional chemotherapy. In each of two following experiments, 42 nude mice were randomly divided into 6 groups. They received liposomal doxorubicin (including high, intermittent and low-dose), free doxorubicin, gemcitabine plus cisplatin and control respectively. In the first experiment, the doses were 6, 3, 1.5, 3, 3 mg/kg and 100 µl 10% glucose for each group respectively. And in the second experiment, 9, 6, 3, 6, 6 mg/kg, and 100 µl 10% glucose respectively. The efficacies of interventional injection of liposomal doxorubicin with different doses were examined in terms of tumor growth retardation for the hepatic metastatic foci of pancreatic tumor. RESULTS: In the first experiment, the difference of median hepatic tumor volume was significant among the three groups of mice receiving liposomal doxorubicin with incremental doses in a dose-dependent manner [high dose: (3 ± 1) mm(3), middle dose: (55 ± 18) mm(3), low dose: (90 ± 23) mm(3), P < 0.05]. The liposomal doxorubicin led to a substantial delay of tumor growth as compared to the free drug or gemcitabine plus cisplatin at the same dose (both P < 0.05). In addition, all animals were well-tolerated with no obvious acute toxicity. In the second experiment, significant difference was obtained for the mice injected with different doses of liposomal doxorubicin [(11 ± 4) mm(3), (13 ± 4) mm(3), (50 ± 18) mm(3), P < 0.05]. It was correlated with tumor growth delay. The mice administered with either 9 mg/kg or 6 mg/kg were more efficacious to retard tumor growth than those given 3 mg/kg (P < 0.05). Despite its enhanced effectiveness as compared to mice in gemcitabine plus cisplatin group (P < 0.05), the liposomal doxorubicin at a dose of 6 mg/kg resulted in a marginally delayed tumor growth compared to those of free doxorubicin at the same dose (P > 0.05). No evident acute toxic response was observed for each group of mice receiving liposomal doxorubicin. In contrast, approximately half of the animals receiving either free doxorubicin or gemcitabine plus cisplatin died of toxic responses. CONCLUSION: Liposomal doxorubicin may be a potential interventional chemotherapeutic agent for hepatic metastasis of pancreatic tumor because of improved anti-tumor efficacy and reduced toxicity in comparison to free doxorubicin and gemcitabine plus cisplatin.

Titanicone-derived TiO2 quantum dot@carbon encapsulated ZnO nanorod anodes for stable lithium storage.

To address the issues of large volume expansion and low electrical conductivity of ZnO anode nanomaterials during lithium ion battery operation, herein we engineered a rod-like ZnO anode with robust and conductive TiO2 quantum dot (QD)@carbon coating derived from molecular layer deposited titanicone, in which the TiO2 QDs are well confined inside the carbon layer. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) confirm the formation of TiO2 QDs and carbonization of fumaric acid in hybrid films after annealing in H2 atmosphere at 700 °C. Benefiting from a unique protective layer design, the prepared TiO2 QD@carbon@ZnO nanorod (NR) anodes display outstanding cycling performance with a discharge capacity of 1154 mA h g-1 after 100 cycles and 70% capacity retention, along with a high rate capacity of 470 mA h g-1 for 500 cycles at 2 A g-1. Moreover, our work demonstrates an innovative and promising approach toward a robust and conductive metal oxide QD@carbon nanocomposite layer for electrode materials in the future.

Co-Pt bimetallic nanoparticles with tunable magnetic and electrocatalytic properties prepared by atomic layer deposition.

Co-Pt bimetallic nanoparticles with adjustable composition and particle size were prepared by the combination of atomic layer deposition and H2 post-deposition annealing. The structure, magnetic and electrocatalytic properties of Co-Pt bimetallic nanoparticles can be facilely tuned by controlling the composition.

Enhanced visible light photocatalytic activity of Fe2O3 modified TiO2 prepared by atomic layer deposition.

In this work, commercial anatase TiO2 powders were modified using ultrathin Fe2O3 layer by atomic layer deposition (ALD). The ultrathin Fe2O3 coating having small bandgap of 2.20 eV can increase the visible light absorption of TiO2 supports, at the meantime, Fe2O3/TiO2 heterojunction can effectively improve the lifetime of photogenerated electron-hole pairs. Results of ALD Fe2O3 modified TiO2 catalyst, therefore, showed great visible light driven catalytic degradation of methyl orange compared to pristine TiO2. A 400 cycles of ALD Fe2O3 (~ 2.6 nm) coated TiO2 powders exhibit the highest degradation efficiency of 97.4% in 90 min, much higher than pristine TiO2 powders of only 12.5%. Moreover, an ultrathin ALD Al2O3 (~ 2 nm) was able to improve the stability of Fe2O3-TiO2 catalyst. These results demonstrate that ALD surface modification with ultrathin coating is an extremely powerful route for the applications in constructing efficient and stable photocatalysts.

Atomic layer deposition of ZnO/TiO2 nanolaminates as ultra-long life anode material for lithium-ion batteries.

In this work, we designed ZnO/TiO2 nanolaminates by atomic layer deposition (ALD) as anode material for lithium ion batteries. ZnO/TiO2 nanolaminates were fabricated on copper foil by depositing unit of 26 cycles ZnO/26 cycles TiO2 repeatedly using ALD. ZnO/TiO2 nanolaminates are much more stable than pristine ZnO films during electrochemical cycling process. Therefore, ZnO/TiO2 nanolaminates exhibit excellent lithium storage performance with an improved cycling performance and superior rate capability compared to pristine ZnO films. Moreover, coulombic efficiency (CE) of ZnO/TiO2 nanolaminates is above 99%, which is much higher than the value of pristine ZnO films. Excellent ultralong-life performance is gained for ZnO/TiO2 nanolaminates, retaining a reversible capacity of ~667 mAh g-1 within cut-off voltage of 0.05-2.5 V after 1200 cycles of charge-discharge at 500 mA g-1. Constructing nanolaminates structures via ALD might open up new opportunities for improving the performance of anode materials with large volume expansion in lithium ion batteries.

Comparison of chemical stability and corrosion resistance of group IV metal oxide films formed by thermal and plasma-enhanced atomic layer deposition.

The wide applications of ultrathin group IV metal oxide films (TiO2, ZrO2 and HfO2) probably expose materials to potentially reactive etchants and solvents, appealing for extraordinary chemical stability and corrosion resistance property. In this paper, TiO2 ultrathin films were deposited on Si at 200 °C while ZrO2 and HfO2 were grown at 250 °C to fit their growth temperature window, by thermal atomic layer deposition (TALD) and plasma-enhanced ALD (PEALD). A variety of chemical liquid media including 1 mol/L H2SO4, 1 mol/L HCl, 1 mol/L KOH, 1 mol/L KCl, and 18 MΩ deionized water were used to test and compare chemical stability of all these as-deposited group IV metal oxides thin films, as well as post-annealed samples at various temperatures. Among these metal oxides, TALD/PEALD HfO2 ultrathin films exhibit the best chemical stability and anti-corrosion property without any change in thickness after long time immersion into acidic, alkaline and neutral solutions. As-deposited TALD ZrO2 ultrathin films have slow etch rate of 1.06 nm/day in 1 mol/L HCl, however other PEALD ZrO2 ultrathin films and annealed TALD ones show better anti-acid stability, indicating the role of introduction of plasma O2 in PEALD and post-thermal treatment. As-deposited TiO2 ultrathin films by TALD and PEALD are found to be etched slowly in acidic solutions, but the PEALD can decrease the etching rate of TiO2 by ~41%. After post-annealing, TiO2 ultrathin films have satisfactory corrosion resistance, which is ascribed to the crystallization transition from amorphous to anatase phase and the formation of 5% Si-doped TiO2 ultrathin layers on sample surfaces, i.e. Ti-silicate. ZrO2, and TiO2 ultrathin films show excellent corrosion endurance property in basic and neutral solutions. Simultaneously, 304 stainless steel coated with PEALD-HfO2 is found to have a lower corrosion rate than that with TALD-HfO2 by means of electrochemical measurement. The pre-treatment of plasma H2 to 304 stainless steel can effectively reduce interfacial impurities and porosity of overlayers with significantly enhanced corrosion endurance. Above all, the chemical stability and anti-corrosion properties of IV group metal oxide coatings can be improved by using PEALD technique, post-annealing process and plasma H2 pre-treatment to substrates.

Fabrication and Characterization of ZnO Nano-Clips by the Polyol-Mediated Process.

ZnO nano-clips with better monodispersion were prepared successfully using zinc acetate hydrate (Zn(OAc)2·nH2O) as Zn source and ethylene glycol (EG) as solvent by a simple solution-based route-polyol process. The effect of solution concentration on the formation of ZnO nano-clips has been investigated deeply. We first prove that the 0.01 M Zn(OAc)2·nH2O can react with EG without added water or alkaline, producing ZnO nano-clips with polycrystalline wurtzite structure at 170 °C. As-synthesized ZnO nano-clips contain a lot of aggregated nanocrystals (~ 5 to 15 nm) with high specific surface area of 88 m2/g. The shapes of ZnO nano-clips basically keep constant with improved crystallinity after annealing at 400-600 °C. The lower solution concentration and slight amount of H2O play a decisive role in ZnO nano-clip formation. When the solution concentration is ≤ 0.0125 M, the complexing and polymerization reactions between Zn(OAc)2·nH2O and EG predominate, mainly elaborating ZnO nano-clips. When the solution concentration is ≥ 0.015 M, the alcoholysis and polycondensation reactions of Zn(OAc)2·nH2O and EG become dominant, leading to ZnO particle formation with spherical and elliptical shapes. The possible growth mechanism based on a competition between complexing and alcoholysis of Zn(OAc)2·nH2O and EG has been proposed.

TiOxNy Modified TiO2 Powders Prepared by Plasma Enhanced Atomic Layer Deposition for Highly Visible Light Photocatalysis.

In this work, TiN film deposited by plasma enhanced atomic layer deposition (PEALD) is adopted to modify the commercial anatase TiO2 powders. A series of analyses indicate that the surface modification of 20, 50 and 100 cycles of TiN by PEALD does not change the morphology, crystal size, lattice parameters, and surface area of TiO2 nano powders, but forms an ultrathin amorphous layer of nitrogen doped TiO2 (TiOxNy) on the powder surfaces. This ultrathin TiOxNy can facilitate the absorption of TiO2 in visible light spectrum. As a result, TiOxNy coated TiO2 powders exhibit excellent photocatalytic degradation towards methyl orange under the visible light with good photocatalytic stability compared to pristine TiO2 powders. TiOxNy (100 cycles PEALD TiN) coated TiO2 powders exhibit the excellent photocatalytic activity with the degradation efficiency of 96.5% in 2 hours, much higher than that of pristine TiO2 powder of only 4.4%. These results clearly demonstrate that only an ultrathin surface modification layer can dramatically improve the visible light photocatalytic activity of commercial TiO2 powders. Therefore, this surface modification using ALD is an extremely promising route to prepare visible light active photocatalysts.

[Morphological research on brain development and expression of vital cytokines in brain of human 6-8 week old embryo aborted for unexpected cause].

OBJECTIVE: To clarify the changes in cell proliferation, differentiation, apoptosis and in the expression of vital cytokines during development of 6-8 week old embryo, and hence provide the evidence for identifying the mechanisms of cell proliferation, differentiation, apoptosis during early developing human embryonic brain. METHODS: Human aborted embryos were obtained with the consents signed by the pregnant women with unexpected abortions in gestation of 6-8 weeks. The histochemical SABC method and TUNEL Staining were employed to this research project. RESULTS: At 6 weeks, two telencephalons, diencephalon, mesencephalon, metencephalon, and myelencephalon have been formed, and from week 6 to 8, every cerebral vesicle has had three layer cells including germinal layer (GL), intermediate layer ( IL ), and marginal zone (MZ). At 6-7 weeks, TUNEL-labeled cells and PCNA-, Bcl-2-, Bax-, Fas-, Fas-L-, Rb- and P53-positive cells were all observed in the GL and IL of the five brain regions, positive deposition appeared in nuclei. At week 8, Fas- and Rb-positive cells were observed in the IL of the five brain regions, positive deposition appeared in cytoplasm and cell processes, and no changes in the distributions of TUNEL-labeled cells and positive cells regarding the other five factors. The expressions of the cytokines were in agreement with the occurrence of the neuronal proliferation and apoptosis temporally and in space. CONCLUSION: During development in early embryo brain, neural precursor cell proliferation and apoptosis occur simultaneously. Fas, FasL and Bax may be involved in the induction of cell apoptosis. Bcl-2 probably prevents the cell apoptosis and provides a survival signal for cells. Rb and P53 may play a critical role in monitoring and maintaining the normal neural precursor cell to proliferation and differentiation.

Interfacial, Electrical, and Band Alignment Characteristics of HfO2/Ge Stacks with In Situ-Formed SiO2 Interlayer by Plasma-Enhanced Atomic Layer Deposition.

In situ-formed SiO2 was introduced into HfO2 gate dielectrics on Ge substrate as interlayer by plasma-enhanced atomic layer deposition (PEALD). The interfacial, electrical, and band alignment characteristics of the HfO2/SiO2 high-k gate dielectric stacks on Ge have been well investigated. It has been demonstrated that Si-O-Ge interlayer is formed on Ge surface during the in situ PEALD SiO2 deposition process. This interlayer shows fantastic thermal stability during annealing without obvious Hf-silicates formation. In addition, it can also suppress the GeO2 degradation. The electrical measurements show that capacitance equivalent thickness of 1.53 nm and a leakage current density of 2.1 × 10-3 A/cm2 at gate bias of Vfb + 1 V was obtained for the annealed sample. The conduction (valence) band offsets at the HfO2/SiO2/Ge interface with and without PDA are found to be 2.24 (2.69) and 2.48 (2.45) eV, respectively. These results indicate that in situ PEALD SiO2 may be a promising interfacial control layer for the realization of high-quality Ge-based transistor devices. Moreover, it can be demonstrated that PEALD is a much more powerful technology for ultrathin interfacial control layer deposition than MOCVD.

Photocatalytic Properties of Co3O4-Coated TiO2 Powders Prepared by Plasma-Enhanced Atomic Layer Deposition.

Co3O4-coated commercial TiO2 powders (P25) p-n junction photocatalysts were prepared by plasma-enhanced atomic layer deposition (PEALD) technique. The structure, morphology, bandgap, and photocatalytic properties under ultraviolet light were investigated systematically. Although the deposition of Co3O4 does not change the anatase structure and crystallite size of P25 powders, the ultraviolet photocatalytic activity has been improved evidently. For the Co3O4-coated P25 powders, the trace Co ions exist as Co3O4 nanoparticles attached to TiO2 powder surface instead of the occupation of Ti4+ position in TiO2 lattice. The Co3O4-coated P25 powders exhibit enhanced photocatalytic degradation efficiency of almost 100% for methylene blue in 1.5 h under ultraviolet light, compared with P25 of 80%. The Mott-Schottky plots of photocatalyst powders confirm the p-n heterojunction formation in Co3O4-TiO2 nanocomposite materials, which is beneficial to increase the efficiency of photogenerated electron-hole separation. In addition, the Co3O4 coating also promotes the adsorption of organic dyes of methylene blue on P25 powders.

Atomic Layer Deposited Oxide-Based Nanocomposite Structures with Embedded CoPtx Nanocrystals for Resistive Random Access Memory Applications.

Al2O3- or HfO2-based nanocomposite structures with embedded CoPtx nanocrystals (NCs) on TiN-coated Si substrates have been prepared by combination of thermal atomic layer deposition (ALD) and plasma-enhanced ALD for resistive random access memory (RRAM) applications. The impact of CoPtx NCs and their average size/density on the resistive switching properties has been explored. Compared to the control sample without CoPtx NCs, ALD-derived Pt/oxide/100 cycle-CoPtx NCs/TiN/SiO2/Si exhibits a typical bipolar, reliable, and reproducible resistive switching behavior, such as sharp distribution of RRAM parameters, smaller set/reset voltages, stable resistance ratio (≥102) of OFF/ON states, better switching endurance up to 104 cycles, and longer data retention over 105 s. The possible resistive switching mechanism based on nanocomposite structures of oxide/CoPtx NCs has been proposed. The dominant conduction mechanisms in low- and high-resistance states of oxide-based device units with embedded CoPtx NCs are Ohmic behavior and space-charge-limited current, respectively. The insertion of CoPtx NCs can effectively improve the formation of conducting filaments due to the CoPtx NC-enhanced electric field intensity. Besides excellent resistive switching performances, the nanocomposite structures also simultaneously present ferromagnetic property. This work provides a flexible pathway by combining PEALD and TALD compatible with state-of-the-art Si-based technology for multifunctional electronic devices applications containing RRAM.