Native Ti Research Articles

Engineering the PEM Water Electrolysis Anode for Better Interfacial Electrical Conductivity

In pursuing cost-effective green hydrogen production via proton exchange membrane water electrolysis (PEMWE), the high expense of the iridium (Ir)-based oxygen evolution reaction (OER) catalysts poses a significant challenge. To overcome this issue, researchers have focused on developing active OER catalysts and catalyst layers (CLs) with minimum uses of Ir. However, they frequently encountered performance problems at the single-cell level that originate not only from the kinetic polarization but also from the ohmic polarization. In this aspect, we have focused on identifying the reasons for the poor performance of low IrOx-loaded anodes, with loadings as low as 0.10 mg cm-2. We pinpoint the cause of the poor performance of the low loaded anodes to an electron transport problem within the native oxide on the Ti porous transport layer (PTL). Our analysis, grounded in the metal-insulator band model, reveals that the primary factors contributing to electron conductivity loss in the Ti oxide are the upward band bending induced by the Schottky contact with high work function IrOx and by the pinch-off effect from the extensive ionomer contact. Based on the above understanding, we propose an anode CL composed of a one-dimensional iridium catalyst, fabricated by electrospinning and calcination processes. Our nanofiber-based CL effectively mitigates the electron transport problem of the native Ti oxide. This improvement stems from the low work function of the Ir nanofiber catalyst and the highly porous structure that reduces the ionomer contact with the Ti oxide. Furthermore, the highly porous nature of the nanofiber-based CL enhances two-phase mass transport, facilitating the high current operation. These findings underscore the critical role of the CL/PTL interface of the PEMWE anode and present the necessity of a well-structured CL to achieve efficient and cost-effective water electrolysis.

Regulation of TiO2 nanotubes on titanium implants to orchestrate osteo/angio-genesis and osteo-immunomodulation for boosted osseointegration

The bio-inertness of titanium (Ti) and accompanying severe inflammation can extremely inhibit the coupled osteogenesis-angiogenesis regulation and result in an undesirable osseointegration of peri-implant during the implantation process. Herein, three types of TiO2 nanotubes (TNT) were prepared on native Ti substrate using an anodic oxidation approach, including TNT with a diameter of 30 nm (TNT-30), 70 nm (TNT-70), or 110 nm (TNT-110). Among the four substrates, TNT-70 was the most prominent to induce the differentiation of macrophages to the pro-healing M2 phenotype via significant down-regulation of pro-inflammation genes (CD86, iNOS, CD11c) and cytokines (TNF-α, IL-6), as well as up-regulation of anti-inflammation genes (CD206, Arg-1, IL-10) and cytokines (TGF-β, IL-10). Furthermore, TNT-70 could stimulate the osteogenic potential of mesenchymal stem cells (MSCs) and the angiogenic ability of human umbilical vein endothelial cells (HUVECs) via multiple paracrine signaling. In vivo experiments suggested that TNT-70 significantly relieved early inflammatory response around the implant, facilitated coupled osteogenesis and angiogenesis, and effectively promoted the osseointegration of peri-implant. This study provided a reference for fabricating surface topography on Ti implant for improving osseointegration and relieving associated excessive inflammatory response.

Screening and analysis of key genes in the biological behavior of bone mesenchymal stem cells seeded on gradient nanostructured titanium compared with native pure Ti.

Titanium (Ti) and Ti-based alloy materials are ideal brackets that restore bone defect, and the mechanism of related genes inducing bone mesenchymal stem cells (BMSCs) to osteogenic differentiation is currently a hot research topic. In order to screen key genes of BMSCs during the osteogenic expression process, we acquired data sets (GSE37237 and GSE84500) which were in the database Gene Expression Omnibus (GEO). Investigations on differentially expressed genes (DEGs) and their enrichment of functions were conducted. We constructed relative protein-protein interaction (PPI) network by using Search Tool for the Retrieval of Interacting Genes (STRING) and visualized the expression of DEGs with Cytoscape. A total of 279 DEGs were discerned, which could be divided into 177 down regulated genes and 102 up regulated genes. In addition, the DEGs' enrichment and pathways included regulation of actin cytoskeleton, inflammatory mediator regulation of transient receptor potential (TRP) channels, peroxisome proliferator-activated receptors (PPAR) pathway, cell cycle, Rheumatoid arthritis, mitogen-activated protein kinases (MAPK) signaling pathway and Ras signaling pathway ect. It showed that 10 notable up regulated genes were mainly in AMP-activated protein kinase (AMPK) pathway. Then we used a technology named surface mechanical attrition treatment (SMAT) to prepare gradient nanostructured (GNS) surface Ti and seeded well-growing BMSCs on the surface of SMAT Ti and native pure Ti. Cell Counting Kits-8 (CCK-8), apoptosis experiment, immunofluorescence technology and staining experiments for alka-line phosphatase (ALP) and alizarin red staining (ARS) were used to research the proliferation, adhesion and differentiation ability of BMSCs seeded on SMAT Ti compared with native pure Ti. We used quantitative real-time PCR (qRT-PCR) technology so as to verify the expression of the most significant 5 genes. In summary, these results indicated novel point of views into candidate genes and potential mechanism for the further study of BMSCs' behaviors seeded on SMAT Ti.

Fabrication of copper ions-substituted hydroxyapatite coating on titanium substrates for antibacterial and osteogenic applications

The aim of this study was to enhance the antibacterial property and osteogenic ability of copper ions-substituted hydroxyapatite (HA-Cu)-based titanium dioxide nanotubes (TNT) implants. The morphology and crystal structure of HA-Cu nanoparticles were characterized by transmission electron microscope (TEM) and X-ray diffraction (XRD). Morphologies and hydrophilic property of Ti, TNT, TNT-HA, and TNT-HA-Cu were evaluated by scanning electron microscope (SEM) and water contact angle (WCA) measurement. Antibacterial assays confirmed that the TNT-HA-Cu presented strong antibacterial abilities against E. coli (82.3%) and S. aureus (87.0%) compared with native Ti substrates. Cellular experiments indicated that TNT-HA-Cu was biocompatible and could induce osteogenesis by stimulating osteoblasts adhesion, proliferation, differentiation, and up-regulating the expression of osteogenic-related genes. The HA-Cu modified TNT substrates were an effective approach of designing both antibacterial and osteogenic Ti-based implants in the orthopedic field.

Two new minerals, badengzhuite, TiP, and zhiqinite, TiSi<sub>2</sub>, from the Cr-11 chromitite orebody, Luobusa ophiolite, Tibet, China: is this evidence for super-reduced mantle-derived fluids?

Abstract. Titanium minerals enclosed in corundum separated from the Cr-11 orebody include native Ti, zamboite (FeTiSi2), osbornite (TiN)-khamrabaevite (TiC) solid solutions, and jingsuiite (TiB2), as well as the new minerals badengzhuite (TiP) and zhiqinite (TiSi2) and two potentially new minerals, Ti11(Si,P)10 and Ti10(Si,P,□)7, where □ indicates a vacancy. These minerals together constitute a spheroid 20 µm across inferred to have crystallized from a droplet of Ti–Si–P intermetallic melt. Energy-dispersive spectroscopy and three-dimensional electron diffraction were applied to characterize the two new minerals. Badengzhuite has a primitive hexagonal cell with a=3.49(7) Å, c=11.70(23) Å, V=124(4) Å3, and crystallizes in space group P63∕mmc (Z=4). It is isostructural with synthetic TiP. Two EDX (energy dispersive X-ray spectroscopy) analyses of badengzhuite gave 60.56 wt %Ti and 39.44 wt % P and 62.74 wt % Ti and 37.26 wt % P from which an empirical formula of Ti1.020P0.980 was calculated on the basis of two atoms (ideally TiP). Zhiqinite has a primitive orthorhombic cell with a=8.18(16) Å, b=4.85(10) Å, c=8.42(17) Å, V=334(12) Å3, and crystallizes in space group Fddd (Z=8). It is isostructural with synthetic TiSi2 (C54 type). Four EDX analyses of zhiqinite gave 39.58–44.79 wt % Ti and 55.21–60.42 wt % Si, from which an empirical formula of Ti0.905Si2.095 was calculated on the basis of three atoms (ideally TiSi2). We suggest that interaction of mantle-derived CH4 + H2 fluids with basaltic magmas in the shallow lithosphere (depths of ∼ 30–100 km) under conditions more reducing than 6 log units below the oxygen fugacities corresponding to the iron–wüstite buffer resulted in precipitation of corundum that entrapped intermetallic melts, some of which crystallized to ultra-reduced Ti–P–Si phases. Experimental work on the Ti–Si and Ti–P systems indicates that the minerals enclosed in corundum could have crystallized from the alloy melt at the lowest temperature accessible on the liquidus. It has been alleged that these ultra-reduced phases are anthropogenic contaminants inadvertently introduced with fused alumina abrasive during preparation of mineral separates. Nonetheless, we conclude that the differences between the ultra-reduced minerals in the separates and the ultra-reduced phases in fused alumina are more convincing evidence for these minerals having a natural origin than the similarities between them are evidence for an anthropogenic origin.

Fabrication of magnesium/zinc-metal organic framework on titanium implants to inhibit bacterial infection and promote bone regeneration

The residual bacteria in the second revision surgery caused by infection would further lead to the failure of the implantation. Pathogenic bacteria adhesion to an implant surface not only interfere the functions of bone-formation related cells, but also activate the host immune system, thus resulting in inflammation and osteogenesis inhibition. Thus, to fabricate multifunctional (antibacterial, anti-inflammation and pro-osteogenesis) titanium implants is essential to address this issue. In this work, hybrid magnesium/zinc-metal organic framework (Mg/Zn-MOF74) coating was constructed on alkali-heat treated titanium (AT) surface. The hybrid Mg/Zn-MOF74 coating displayed good stability and its stability was related to the content of Zn2+. The MOF74-modified samples were sensitive to bacterial acid microenvironment and displayed strong antibacterial ability against both Escherichia coli and Staphylococcus aureus due to the degradation of MOF74 coating, leading to alkaline microenvironment (about pH 8.0) and degradation products (2,5-dihydroxyterephthalic acid and Zn2+). The coating also showed good early anti-inflammatory property to native Ti substrates. In vivo results further verified that AT-Mg/Zn3 implants had high antibacterial and anti-inflammatory properties at early stage of implantation, and greatly improved new bone formation around implants both at non-infected and infected femur sites.

The fabrication and in vitro properties of antibacterial polydopamine-LL-37-POPC coatings on micro-arc oxidized titanium.

Bacterial infection commonly occurs in clinical settings when the procedure involves a medical implant. Thus, the fabrication of antimicrobial medical materials has attracted much attention in recent years. To improve the antibacterial properties of titanium (Ti)-based biomedical materials, surface microporous structures, with antimicrobial peptide coatings, were employed in this study. Native Ti substrates were endowed with a certain level of antibacterial activity after treatment with the micro-arc oxidation (MAO). A multilayer consisting of polydopamine, cationic antimicrobial peptides LL-37, and phospholipid (POPC) was coated onto MAO substrates, leading to antibacterial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria. The combination of polydopamine-LL-37-POPC was found to alleviate the burst release of LL-37 in the initial phase. This multilayer coated onto microporous Ti substrates also showed favorable cytocompatibility to both mesenchymal stem cells (MSCs) and osteoblasts. These findings illustrate a novel strategy for the development of antibacterial Ti-based implants.

Exploring a novel ceramic (Ti,W)3SiC2 for interconnect of intermediate temperature solid oxide fuel cell

A solid solution (Ti,W)3SiC2 possessing good oxidation resistance and low area-specific resistance (ASR) after oxidation has been synthesized by an in-situ hot pressing process. The oxidation rate constant at 800 °C in air is 6.29 × 10−14 g2 cm−4 s−1 for (Ti,W)3SiC2. The formed single-layer oxide is composed of W doped rutile TiO2 and amorphous SiO2. SiO2 is evenly inlaid in the communicative body frame of TiO2. W doped in TiO2 mainly exists as W6+. W doping not only hinders the outward diffusion of Ti by decreasing the concentration of native Ti interstitials in TiO2, but also restrains the inward diffusion of oxygen by decreasing the concentration of O vacancies. Furthermore, W dopant in TiO2 enhances the electrical conductivity of TiO2 by increasing the concentration of semi-free electron. Therefore, the low ASR of (Ti,W)3SiC2 after oxidation owes to high electrical conductivity of TiO2 as well as the reduced thickness of oxide scale. All the results render (Ti1-xWx)3SiC2 promising as interconnects for the intermediate temperature solid oxide fuel cell.

Native target chemistry during reactive dc magnetron sputtering studied by ex-situ x-ray photoelectron spectroscopy

We report x-ray photoelectron spectroscopy (XPS) analysis of native Ti target surface chemistry during magnetron sputtering in an Ar/N2 atmosphere. To avoid air exposure, the target is capped immediately after sputtering with a few-nm-thick Al overlayers; hence, information about the chemical state of target elements as a function of N2 partial pressure pN2 is preserved. Contrary to previous reports, which assume stoichiometric TiN formation, we present direct evidence, based on core-level XPS spectra and TRIDYN simulations, that the target surface is covered by TiNx with x varying in a wide range, from 0.27 to 1.18, depending on pN2. This has far-reaching consequences both for modelling of the reactive sputtering process and for everyday thin film growth where detailed knowledge of the target state is crucial.

Synergistic interactions of blood-borne immune cells, fibroblasts and extracellular matrix drive repair in an in vitro peri-implant wound healing model.

Low correlations of cell culture data with clinical outcomes pose major medical challenges with costly consequences. While the majority of biomaterials are tested using in vitro cell monocultures, the importance of synergistic interactions between different cell types on paracrine signalling has recently been highlighted. In this proof-of-concept study, we asked whether the first contact of surfaces with whole human blood could steer the tissue healing response. This hypothesis was tested using alkali-treatment of rough titanium (Ti) surfaces since they have clinically been shown to improve early implant integration and stability, yet blood-free in vitro cell cultures poorly correlated with in vivo tissue healing. We show that alkali-treatment, compared to native Ti surfaces, increased blood clot thickness, including platelet adhesion. Strikingly, blood clots with entrapped blood cells in synergistic interactions with fibroblasts, but not fibroblasts alone, upregulated the secretion of major factors associated with fast healing. This includes matrix metalloproteinases (MMPs) to break down extracellular matrix and the growth factor VEGF, known for its angiogenic potential. Consequently, in vitro test platforms, which consider whole blood-implant interactions, might be superior in predicting wound healing in response to biomaterial properties.

Material Tailoring of Ti–V–Fe–Zr for Improving Sorption Behaviour Employing Off Stoichiometric Concentration of Native Element Ti

Material Tailoring of Ti–V–Fe–Zr for Improving Sorption Behaviour Employing Off Stoichiometric Concentration of Native Element Ti

SILICIDE SPHERULES FROM PERMIAN SEDIMENTS OF THE FORE-SUDETIC MONOCLINE (SW POLAND)

The presence of Fe-silicides, extremely rare mineral phases were documented in the Permian Cu-bearing ore formation in the Fore-Sudetic Monocline (Polkowice-Sieroszowice and Rudna mines, SW Poland). It is a first report of their occurrence within rocks of Late Palaeozoic age. The Fe-Si alloys forme spherules of various structure and chemical composition. The silicide spherules were found in the flotation concentrates prepared from the copper ore. Their composition varies from FeSi (fersilicite) to Fe2Si3 or Fe4Si9. A dominant constituent is Fe5Si3 (xifengite) with admixtures of P, Ti, Cr and Mn. Native Si and Ti were detected in the marginal part of spherules. The current knowledge do not permit to determine unequivocally whether the Fe-silicide spherules formed as a result of Permian cosmic dust or constitute terrestrial magmatic material of ultramafic character transported into a sedimentary basin from the adjacent terrain.

Quantitative theory of the oxygen vacancy and carrier self-trapping in bulk TiO2

Standard approximations of density functional theory often fail for defects in transition metal oxides. Despite its significance in applications and decades of research, the oxygen vacancy in TiO${}_{2}$ is also poorly understood from the theory point of view. The Heyd-Scuseria-Ernzerhof functional (HSE06) provides a total energy that is a linear function of the occupation number (as it should be for the exact functional) also in TiO${}_{2}$. This allows reproduction of the measured infrared absorption, photoluminescence, and thermal ionization data within \ensuremath{\sim}0.1 eV. From our calculations, a consistent and quantitative interpretation of the conflicting experiments emerges. Electron self-trapping in rutile makes the properties of the vacancy concentration dependent. In oxidized samples the vacancies are passivated by native Ti${}^{3+}$/Ti${}^{4+}$ traps. This explains why electrons localized to the vacancy could only be observed after illumination at very low temperature in magnetic resonance experiments. In strongly reduced samples, electrons may stay localized in the vacancy and even the neutral state gives rise to two vertical electronic transitions (at 0.8 and 1.2 eV). The situation is much simpler in anatase, where only holes are self-trapped by O${}^{2\ensuremath{-}}$/O${}^{1\ensuremath{-}}$ transitions. The oxygen vacancy is a shallower donor in anatase than in rutile.

Electrochemical investigation of chromium nanocarbide coated Ti–6Al–4V and Co–Cr–Mo alloy substrates

This study investigated the electrochemical behavior of chromium nano-carbide cermet coating applied on Ti–6Al–4V and Co–Cr–Mo alloys for potential application as wear and corrosion resistant bearing surfaces. The cermet coating consisted of a highly heterogeneous combination of carbides embedded in a metal matrix. The main factors studied were the effect of substrate (Ti–6Al–4V vs. Co–Cr–Mo), solution conditions (physiological vs. 1 M H 2O 2 of pH 2), time of immersion (1 vs. 24 h) and post coating treatments (passivation and gamma sterilization). The coatings were produced with high velocity oxygen fuel (HVOF) thermal spray technique at atmospheric conditions to a thickness of 250 μm then ground and polished to a finished thickness of 100 μm and gamma sterilized. Native Ti–6Al–4V and Co–Cr–Mo alloys were used as controls. The corrosion behavior was evaluated using potentiodynamic polarization, mechanical abrasion and electrochemical impedance spectroscopy under physiologically representative test solution conditions (phosphate buffered saline, pH 7.4, 37 °C) as well as harsh corrosion environments (pH ∼ 2, 1 M H 2O 2, T = 65 °C). Severe environmental conditions were used to assess how susceptible coatings are to conditions that derive from possible crevice-like environments, and the presence of inflammatory species like H 2O 2. SEM analysis was performed on the coating surface and cross-section. The results show that the corrosion current values of the coatings (0.4–4 μA/cm 2) were in a range similar to Co–Cr–Mo alloy. The heterogeneous microstructure of the coating influenced the corrosion performance. It was observed that the coating impedances for all groups decreased significantly in aggressive environments compared with neutral and also dropped over exposure time. The low frequency impedances of coatings were lower than controls. Among the coated samples, passivated nanocarbide coating on Co–Cr–Mo alloy displayed the least corrosion resistance. However, all the coated materials demonstrated higher corrosion resistance to mechanical abrasion compared to the native alloys.

Origin of native sulfur ball from the Kueishantao hydrothermal field offshore northeast Taiwan: Evidence from trace and rare earth element composition

We first report the trace and rare earth element compositions of native sulfur ball with sulfur contents varying from 97.08 wt.% to 99.85 wt.% from the Kueishantao hydrothermal field, off NE Taiwan. We then discuss the sources of trace and rare earth elements incorporated into the native sulfur ball during formation. Comparison of our results with native sulfur from crater lakes and other volcanic areas shows the sulfur content of native sulfur ball from the Kueishantao hydrothermal field is very high, and that the rare earth element (REE) and trace element constituents of the native sulfur balls are very low (∑REE < 35 ppb). In the native sulfur ball, V, Cr, Co, Ni, Nb, Rb, Cs, Ba, Pb, Th, U, Al, Ti and REE are mostly derived from andesite; Mg, K and Mn are mostly derived from seawater; and Fe, Cu, Zn and Ni are partly derived from magma. Based on the sulfur contents, trace and rare earth element compositions, and local environment, we suggest that the growth of the native sulfur ball is significantly slower than that of native sulfur chimneys, which results in the relatively higher contents of trace and rare earth element contents in the native sulfur ball than in the native sulfur chimneys from the Kueishantao hydrothermal field. Finally, we suggest a “glue pudding” growth model for understanding the origin of the native sulfur ball in the Kueishantao hydrothermal field, whereby the native sulfur ball forms from a mixture of oxygenated seawater and acidic, low-temperature hydrothermal fluid with H 2S and SO 2 gases, and is subsequently shaped by tidal and/or bottom currents.

Zinc-ion implanted and deposited titanium surfaces reduce adhesion of Streptococccus mutans

While titanium (Ti) is a commonly used dental implant material with advantageous biocompatible and mechanical properties, native Ti surfaces do not have the ability to prevent bacterial colonization. The objective of this study was to evaluate the chemical composition and bacterial adhesive properties of zinc (Zn) ion implanted and deposited Ti surfaces (Zn–PIIID–Ti) as potential dental implant materials. Surfaces of pure Ti (cp–Ti) were modified with increasing concentrations of Zn using plasma immersion ion implantation and deposition (PIIID), and elemental surface compositions were characterized by X-ray photoelectron spectrometry (XPS). To evaluate bacterial responses, Streptococcus mutans were seeded onto the modifiedTi surfaces for 48 h and subsequently observed by scanning electron microscopy. Relative numbers of bacteria on each surface were assessed by collecting the adhered bacteria, reculturing and counting colony forming units after 48 h on bacterial grade plates. Ti, oxygen and carbon elements were detected on all surfaces by XPS. Increased Zn signals were detected on Zn–PIIID–Ti surfaces, correlating with an increase of Zn-deposition time. Substantial numbers of S. mutans adhered to cp–Ti samples, whereas bacterial adhesion on Zn–PIIID–Ti surfaces signficantly decreased as the Zn concentration increased ( p < 0.01). In conclusion, PIIID can successfully introduce Zn onto a Ti surface, forming a modified surface layer bearing Zn ions that consequently deter adhesion of S. mutans, a common bacterium in the oral environment.

Metal-saturated peridotite in the mantle wedge inferred from metal-bearing peridotite xenoliths from Avacha volcano, Kamchatka

Lithospheric mantle is inferred to be more oxidized than the asthenosphere, and mantle-wedge peridotites are characterized by high oxidation state relative to abyssal and continental peridotites due to addition of slab-derived fluids or melts. We found metals (native Ni, Fe silicides, native Fe and possible native Ti) from otherwise oxidized sub-arc mantle peridotite xenoliths from Avacha volcano, Kamchatka. This is contrary to the consensus and experimental results that the metals are stable only in deeper parts of the mantle (> 250 km). The metals from Avacha are different in chemistry and petrography from those in serpentinized peridotites. The Avacha metals are characteristically out of chemical equilibrium between individual grains as well as with surrounding peridotite minerals. This indicates their independent formation from different fluids. Some of the Avacha metals form inclusion trails with fluids and pyroxenes, leading to the inference that very local metal saturation resulted from rapid supply (‘flashing’) of reducing fluids from deeper levels. The fluids, possibly rich in H 2, are formed by serpentinization at the cold base of the mantle wedge just above the slab, and they reduce overlying peridotites. We propose a metal-saturated peridotite layer, underlying the main oxidized portion, within the mantle wedge beneath the volcanic front to fore-arc region.

TISSUE INTEGRATION OF IMPLANTED POLYPROPYLENE MESHES IN TWO POSITIONS IN A RABBIT ABDOMINAL MODEL

The objective of the study was to describe the morp hological changes of implanted polypropylene meshes in two positions at the level of abdominal w alls in rabbits. Two abdominal wall defects in 10 r abbits were reconstructed with polypropylene (D-tek) mesh. Five rabbits were sacrificed on days 30 and 60 for evaluation of morphological changes of explants. At sacrifice, all implant areas were photographed and was mentioned the presence of adhesions, infection, or signs of rejection. The entire abdominal wall was t hen harvested and divided, each containing the implant, the interface between implant and native host ti ssue, then explants were cut for histopathology exams.

Reduction of Pd catalytic particle size by a double activation process

We have used a double activation method to reduce the size of Pd catalytic particles commonly used as an activation layer for electroless Cu deposition. The method produces Pd particles with sizes reduced by a factor of 4 and density increased by a factor of 10 compared to the single activation method. The first activation and the Pd etching process in the double activation removes the native Ti oxide on TiN surface and largely increase the nucleation sites for Pd. With more nucleation sites, nucleation events outrun ripening events throughout the deposition time range. However, excessive etching of Pd and the underlying TiN layer could lead to rougher electroless Cu films. Secondary ion mass spectrometry data show that the double activation step does not increase the net amount of Pd deposited on TiN surface; it only changes its particle size and density. Electroless Cu deposited on a doubly Pd activated surface has a larger grain size and appears to have a lower resistivity.

Synchrotron radiation x-ray photoelectron spectroscopy study on the interface chemistry of high-k PrxAl2−xO3 (x=0–2) dielectrics on TiN for dynamic random access memory applications

Engineered dielectrics combined with compatible metal electrodes are important materials science approaches to scale three-dimensional trench dynamic random access memory (DRAM) cells. Highly insulating dielectrics with high dielectric constants were engineered in this study on TiN metal electrodes by partly substituting Al in the wide band gap insulator Al2O3 by Pr cations. High quality PrAlO3 metal-insulator-metal capacitors were processed with a dielectric constant of 19, three times higher than in the case of Al2O3 reference cells. As a parasitic low dielectric constant interface layer between PrAlO3 and TiN limits the total performance gain, a systematic nondestructive synchrotron x-ray photoelectron spectroscopy study on the interface chemistry of PrxAl2−xO3 (x=0–2) dielectrics on TiN layers was applied to unveil its chemical origin. The interface layer results from the decreasing chemical reactivity of PrxAl2−xO3 dielectrics with increasing Pr content x to reduce native Ti oxide compounds present on unprotected TiN films. Accordingly, PrAlO3 based DRAM capacitors require strict control of the surface chemistry of the TiN electrode, a parameter furthermore of importance to engineer the band offsets of PrxAl2−xO3∕TiN heterojunctions.