Hf Metal Research Articles

General Regularities and Differences of Nanostructured Coatings Based on Nitrides of Zr, Ti, Hf, V, Nb Metals and Their Combinations

Using the vacuum-arc source with the HF discharge, nano-structured hard and super-hard coatings based on Ti-Hf-N(Fe), Ti-Hf-Si-N, Ti-Zr-Si-N, and (Ti, Zr, Hf, Nb, V)N of 1.2µm to 2.5µm thickness were manufactured. The coatings were studied using the proton micro-beam µ-PIXE, RBS, SIMS, SEM with EDS, XRD, and tested for adhesion resistance, wear, and nano-hardness. It was found that a concentration of Ti, Zr, Hf, V, and Nb metals as well as a bias potential applied to a substrate and residual pressure in a chamber (N or Ar/N) affected the formation regularities of solid solutions and quasi-amorphous phases based on a-Si3N4. Hardness of the resulting coatings reached 48GPa to 52GPa, their elastic modulus was 420GPa to 535GPa. The friction coefficient was 0.12 to 0.2, and temperature resistance was as high as 1300oC.[1] Coating structures varied from a columnar to a nanosized one. Grain sizes of the phases of the solid solutions were from 4nm to 10nm or 12nm. Those of a-Si3N4 inter-layer were from 0.8nm to 1.2nm.

Zirconium on Benthic Foraminiferal Tests in the Arctic: A Plausible Shield towards Ocean Acidification

Foraminiferal samples from Kongsfjorden (Arctic Ocean) were analysed for elemental ratios using Energy Dispersive spectrometry (EDS), along with sediment organic carbon, grain size and trace metals (Zr and Hf). EDS results on benthic foraminifera N. labradorica tests surface indicated presence of zirconium (Zr), whereas other foraminiferal species like Elphidium excavatum, Cassidulina reniforme and Quinqueloculina stalkeri were devoid of any Zr traces. Both foraminiferal analysis (EDS) as well as sediment analysis (ICP-MS) indicated highest Zr percentage at the inner fjord station 4. Concentration of Zr showed opposite trend to salinity, temperature and organic carbon indicating that the source of Zr is through weathering of continental zircon. Zr showed close association with Hafnium (Hf) and the average Zr/Hf ratio within Kongsfjorden was 43. Benthic foraminiferal shells did not show any signs of dissolution. As Zr is resistant to any acid corrosion; it could possibly be protecting the foraminifera from dissolution. Hence, in the present study we conducted lab experiment on the benthic foraminifera from outer/ inner fjord by pH manipulation, to identify the possible effects on benthic foraminiferal tests in absence/presence of zirconium coating towards dissolution. Interestingly, at pH 6 foraminifera from inner fjord having Zr coating (as evidenced by EDS) did not show any dissolution, whereas outer fjord ones which are devoid of Zr shielding showed dissolution. These preliminary results indicate that with the continuing increase in atmospheric CO 2 it may be interesting to study the test structure of Zr encrusted foraminiferal tests in Kongsfjorden.

Synthesis, Characterization, and Materials Chemistry of Group 4 Silylimides

This paper focuses on the development of potential single source precursors for M-N-Si (M = Ti, Zr or Hf) thin films. The titanium, zirconium, and hafnium silylimides (Me(2)N)(2)MNSiR(1)R(2)R(3) [R(1) = R(2) = R(3) = Ph, M = Ti(1), Zr (2), Hf (3); R(1) = R(2) = R(3) = Et, M = Ti (4), Zr (5), Hf (6); R(1) = R(2) = Me, R(3) = (t)Bu, M = Ti (7), Zr (8), Hf (9); R(1) = R(2) = R(3) = NMe(2), M = Ti (10), Zr (11), Hf (12)] have been synthesized by the reaction of M(NMe(2))(4) and R(3)R(2)R(1)SiNH(2). All compounds are notably sensitive to air and moisture. Compounds 1, 2, 4, and 7-10 have been structurally characterized, and all are dimeric, with the general formula [M(NMe(2))(2)(μ-NSiR(3))](2), in which the μ(2)-NSiR(3) groups bridges two four-coordinate metal centers. The hafnium compound 3 possesses the same basic dimeric structure but shows additional incorporation of liberated HNMe(2) bonded to one metal. Compounds 11 and 12 are also both dimeric but also incorporate additional μ(2)-NMe(2) groups, which bridge Si and either Zr or Hf metal centers in the solid state. The Zr and Hf metal centers are both five-coordinated in these species. Aerosol-assisted CVD (AA-CVD) using 4-7 and 9-12 as precursors generates amorphous films containing M, N, Si, C, and O; the films are dominated by MO(2) with smaller contributions from MN, MC and MSiON based on XPS binding energies.

Metal Electrode Contact Cleaning in Small Dimension Phase Change Memory

It is necessary to be studied attributes for controlling interface resistance especially in dash type small metal contact for high performance phase change memory cell. In this study, we will discuss about the metal electrode interface cleaning by using SC1, HF cleanings and NH3 plasma treatment. On electrode metal surface, SC1, HF cleanings and NH3 plasma combined treatment is most effective for the interface ohmic condition. Cross sectional view TEM data shows that the interface unknown substances were not seen. This is because SC1, HF cleaning and plasma treatment removes the metal residue acting as a lift off agent and reduces metal oxide complexes during in annealing process.

Fabrication of High-k/Ge Stacks with High Quality GeO2 Interlayer

Successful fabrication process of high-k/Ge with GeO2 interlayer has been proposed. Low temperature oxidation of Ge substrate gave rise to no GeO desorption at GeO2/Ge interface, that maintains the interface property to be good except a large VFB shift. Deposition of component metals of high-k material on the GeO2/Ge structure was effective to improve the VFB shift with low temperature annealing. Therefore, low temperature oxidation annealing of metal on GeO2/Ge structure has been expected to fabricate high-k/GeO2/Ge with good interface property. In case of Al2O3/GeO2/Ge, this prediction has been proved. In case of HfO2/GeO2/Ge, however, during the thermal treatment the Hf metal diffuse into Ge substrate which causes the formation of the hillocks. The good characteristic was obtained by preventing the hillocks being formed.

Thermodynamic properties of the kagome lattice in herbertsmithite

Strongly correlated Fermi systems are among the most intriguing and fundamental systems in physics, whose realization in some compounds is still to be discovered. We show that herbertsmithite ZnCu_3(OH)_6Cl_2 can be viewed as a strongly correlated Fermi system whose low temperature thermodynamic in magnetic fields is defined by a quantum critical spin liquid. Our calculations of its thermodynamic properties are in good agreement with recent experimental facts and allow us to reveal their scaling behavior which strongly resembles that observed in HF metals and 2D 3He.

Characteristics of Hafnium Silicate Films Deposited on Si by Atomic Layer Deposition Process

We investigated the effects of annealing (i.e., temperature and time) on the characteristics of hafnium silicate () films deposited on a Si substrate by atomic layer deposition process (ALD). We found that the post deposition annealing under oxidizing ambient causes the oxidation of residual Hf metal components, resulting in the improvement of electrical characteristics (e.g., hysteresis window and leakage current are decreased). In addition, we observed the annealing temperature is more important than the annealing time for post deposition annealing. Based on these observations, we suggest that post deposition annealing under oxidizing ambient is necessary to improve the electrical characteristics of films deposited by ALD. However, the annealing temperature has to be carefully controlled to minimize the regrowth of interfacial oxide, which degrades the value of equivalent oxide thickness.

Porous anodic alumina on galvanically grown PtSi layer for application in template-assisted Si nanowire growth

We report on the fabrication and morphology/structural characterization of a porous anodic alumina (PAA)/PtSi nano-template for use as matrix in template-assisted Si nanowire growth on a Si substrate. The PtSi layer was formed by electroless deposition from an aqueous solution containing the metal salt and HF, while the PAA membrane by anodizing an Al film deposited on the PtSi layer. The morphology and structure of the PtSi layer and of the alumina membrane on top were studied by Scanning and High Resolution Transmission Electron Microscopies (SEM, HRTEM). Cross sectional HRTEM images combined with electron diffraction (ED) were used to characterize the different interfaces between Si, PtSi and porous anodic alumina.

저온 Osub2어닐링 공정을 통한 HfSixOy의 전기적 특성 개선

We investigated the effects of low temperature () annealing on the characteristics of hafnium silicate () films deposited on a Si substrate by atomic layer deposition (ALD). We found that the post deposition annealing under oxidizing ambient causes the oxidation of residual Hf metal components, resulting in the improvement of electrical characteristics such as flat band voltage shift () by hysteresis without oxide capacitance reduction. We suggest that post deposition annealing under oxidizing ambient is necessary to improve the electrical characteristics of films deposited by ALD.

Improvement of bias stability of indium zinc oxide thin film transistors by the incorporation of hafnium fabricated by radio-frequency magnetron sputtering

We report on the fabrication and performance of amorphous oxide thin film transistors with indium zinc oxide (In 2O 3:ZnO = 1:1 mol%) and various ratios of hafnium-doped indium zinc oxide (IZO:HfO 2 = 2:0, 0.3, 0.7, and 1.1 mol%) deposited at the same deposition conditions for semiconductor channel layer. The carrier concentration ( N cp) of the HIZO films was further decreased from 7.08 × 10 17 to 5.0 × 10 16 cm − 3 . This indicates that Hf metal cations effectively suppress carrier generation due to the high electron negativity (1.3) of Hf. In addition, we compared bias instability of both devices after bias temperature stress (BTS) test under on-current state at V DS of 10 V and I DS of 3 μA at 60 °C for 420 min. It was found that the Hf metal cations could be effectively incorporated in the IZO thin films as a suppressor against both the oxygen deficiencies and the carrier generation in the ZnO-based system.

Structural and thermodynamic aspects of the dissociation of cyclopentadienyl rings from homoleptic cyclopentadienyl early transition metal, cerium, and thorium derivatives

Homoleptic cyclopentadienyl derivatives of the early transition metals and lanthanides that have been synthesized include Cp 4M (M = Ti, Zr, Ce, Hf, Th), Cp 3M (M = Sc, Y, most lanthanides, Ti, Zr, Hf, Th), and Cp 2M (M = Ti, V). Density functional theory shows that the Cp 4M structures with unusual S 4 symmetry are saddle points for the d-block metals Ti, Zr, Hf but genuine minima for the f-block metals Ce and Th. The true equilibrium Cp 4M geometries have C 1 symmetry with two η 5-Cp rings and two η 1-Cp rings for M = Ti and Hf but three η 5-Cp rings and one η 1-Cp ring for M = Zr. The dissociation energies for Cp 4M → Cp 3M + Cp are substantial and in the order Ti < Ce < Zr ∼ Hf < Th, roughly consistent with the observed relative stabilities of the +4 and +3 oxidation states of these metals. The C 3 h structures with all η 5-Cp rings are genuine minima for most of the Cp 3M compounds except for Cp 3Ti, which has a C s symmetry minimum with two η 5-Cp rings and one η 2-Cp ring, and Cp 3V, which has two η 5-Cp rings and one η 1-Cp ring. The dissociation energies for Cp 3M → Cp 2M + Cp are in the order V < Ti < Sc < Y < La, consistent with the relative stabilities of the +2 and +3 oxidation states of these metals.

Geochemistry of trace metals and Pb isotopes of sediments from the lowermost Xiangjiang River, Hunan Province (P. R. China): implications on sources of trace metals

This paper reports a geochemical study of trace metals and Pb isotopes of sediments from the lowermost Xiangjiang River, Hunan province (P. R. China). Trace metals Ba, Bi, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Cd, Sn, Sb, Pb, Tl, Th, U, Zr, Hf, Nb and Ta were analyzed using ICP-MS, and Pb isotopes of the bulk sediments were measured by MC-ICP-MS. The results show that trace metals Cd, Bi, Sn, Sc, Cr, Mn, Co, Ni, Cu, Zn, Sb, Pb and Tl are enriched in the sediments. Among these metals, Cd, Bi and Sn are extremely highly enriched (EF values >40), metals Zn, Sn, Sb and Pb significantly highly (5 < EF < 20), and metals Sc, Cr, Mn, Co, Ni, Cu and Tl moderately highly (2 < EF < 5) enriched in the river sediments. All these metals, however, are moderately enriched in the lake sediments. Geochemical results of trace metals Th, Sc, Co, Cr, Zr, Hf and La, and Pb isotopes suggest that metals in the river sediments are of multi-sources, including both natural and anthropogenic sources. Metals of the natural sources might be contributed mostly from weathering of the Indosinian granites (GR) and Palaeozoic sandstones (PL), and metals of anthropogenic sources were contributed from Pb–Zn ore deposits distributed in upper river areas. Metals in the lake sediments consist of the anthropogenic proportions, which were contributed from automobile exhausts and coal dusts. Thus, heavy-metal contamination for the river sediments is attributed to the exploitation and utilization (e.g., mining, smelting, and refining) of Pb–Zn ore mineral resources in the upper river areas, and this for the lake sediments was caused by automobile exhausts and coal combustion. Metals Bi, Cd, Pb, Sn and Sb have anthropogenic proportion of higher than 90%, with natural contribution less than 10%. Metals Mn and Zn consist of anthropogenic proportion of 60–85%, with natural proportion higher than 15%. Metals Sc, Cr, Co, Cu, Tl, Th, U and Ta have anthropogenic proportion of 30–70%, with natural contribution higher than 30%. Metals Ba, V and Mo might be contributed mostly from natural process.

Ab-initio analysis of stability of ω-phase in Ti, Zr and Hf under high pressure

The unusual occurrence of ω phase (a three atom simple hexagonal structure) prior to β (bcc) phase under high pressure in group IV transition metals Ti, Zr and Hf has been analyzed through first principles electronic band structure calculations. The analysis of band structure of ω and β phases in the w stability regime suggest that the opening of band gap at the Fermi level in ω phase lowers the total energy of this phase relative to β, and stabilizes the ω phase. Additionally, the extension of band gap near Fermi level is largest in Ti followed by Hf and then Zr suggesting that ω phase is most stable in Ti and least in Zr, in line with the experimental observations. Further, the density of states of ∼ 0.33, 0.4 and 0.5, respectively at Fermi energy for ω phase relative to β phase in Ti, Hf and Zr indicates that the lowering in energy for ω is highest in Ti and lowest in Zr.

Atomic parameter model for the solid solubilities in binary transition metal based alloys

Based on the same method by us which describes the solid solubilities of the binary nontransition metal based alloys, the solid solubilities at room temperature in 1380 binary alloys which are based on the 23 transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Zr, Nb, Mo, Ru, Rh, Pd, La, Hf, Ta, W, Re, Os, Ir and Pt) of the fourth, fifth and sixth long periods have been studied in this paper. It has been found that the soluble elements can be separated from the insoluble elements by an ellipse equation (x−m)2/c2+(y−n)2/d2 = 1, by using a criterion of 0.5at% solubility at room temperature for every host element. The results show that the overall reliability for the ellipse equation is up to 90% for the 1380 alloys, which indicates the theoretical results are very good in agreement with the experimental data. The parameters m, n, c and d in the ellipse equation can be explained by the appropriate parameters for every host metal.

Purification of Hafnium by Hydrogen Plasma Arc Melting

Purification of two kinds of Hf metal, a high-purity Hf (HP-Hf) with 99.7 mass% and a low-purity Hf (LP-Hf) with 98 mass%, by hydrogen plasma arc melting (HPAM) has been carried out and the removal behavior of various impurity elements has been examined. Many metallic impurities (Fe, Al, Cr, Cu, Mn, Sn, Ti etc.) in the melted Hf, with higher vapor pressures than that of Hf, were removed to the very low levels by vaporization during HPAM and their removal rates increased with the hydrogen content of plasma arc. Then, the purity (except for Zr, O, N and C) of LP-Hf and HP-Hf were improved to nearly 99.998% and above 99.999%, respectively, after 60 min of 20%H2+Ar plasma arc melting. For the removal of Fe, Al, Cu and Ti from Hf, the refining effect of HPAM under atmospheric pressure was found to be superior to that of EBM under high vacuum. Therefore, HPAM has been confirmed to be a very useful method for the purification of Hf and the dissociated and activated hydrogen atoms formed in the high temperature plasma arc must play an important role for the unique refining process of HPAM.

A crystal chemical approach to superconductivity. I. A bond-valence sum analysis of inorganic compounds

A crystal-chemical approach to superconduc- tivity is described that is intended to complement the cor- responding physical approach. The former approach takes into account the distinction between the stoichiometric va- lence ( stoich V) and the structural valence ( struct V) which is represented by the bond-valence sums (BVS). Through calculations of BVS values from crystal-structure data de- termined at ambient temperature and pressure it has been found that in chalcogenides und pnictides of the transition metals Fe, Co, Ni, Mn, Hf, and Zr the atoms of the poten- tial superconducting units yield values of |BVS| ¼ | struct V| � 1.11 � | stoich V|, whereas the atoms of the charge reser- voirs have in general values of | struct V| < 1.11 � | stoich V|. In corresponding compounds which contain the same ele- ments but are not becoming superconducting, nearly all atoms are found to have | struct V| < 1.11 � | stoich V|. For atoms of oxocuprates that are not becoming superconduct- ing and for atoms of the charge reservoirs of oxocuprates that become superconducting, the relation | struct V| < 1.11 � | stoich V| seems also to be fulfilled, with the exception of Ba. However, in several oxocuprates the relation | struct V| ¼ 1.11 � | stoich V| for the atoms that become superconduct- ing units is violated. These violations seem to indicate that in oxocuprates it is the local bond-valence distribution rather than the bond-valence sums that is essential for superconductivity. The present analysis can possibly be used to predict, by a simple consideration of ambient-T, P structures, whether a compound can become an unconven- tional superconductor at low T, under high P and/or by doping, or not.

Effects of O2 Ambient on Structural, Optical and Electrical Properties of Hafnium Oxide Thin Films Prepared by E-Beam Evaporation

In this paper, thin HfO2 films were grown by using E-beam evaporation technique in vacuum and O2 ambient, respectively. Effects of O2 ambient on structural, optical and electrical properties of the HfO2 films were investigated by deploying x-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, I-V and C-V characteristics. Results show that the O2 ambient deposited HfO2 films exhibited excellent structural, optical and electrical properties as compared with vacuum ambient HfO2 films, which especially performs a low content of metal Hf, a high transmittance, a low leakage current and a high dielectric constant.

Initiation of a passivated interface between hafnium oxide and In(Ga)As( 1)−(4×2)

Hafnium oxide interfaces were studied on two related group III rich semiconductor surfaces, InAs(0 0 1)-(4x2) and In(0.53)Ga(0.47)As(0 0 1)-(4x2), via two different methods: reactive oxidation of deposited Hf metal and electron beam deposition of HfO(2). The interfaces were investigated with scanning tunneling microscopy and spectroscopy (STS). Single Hf atom chemisorption sites were identified that are resistant to oxidation by O(2), but Hf islands are reactive to O(2). After e(-) beam deposition of <<1 ML of HfO(2), single chemisorption sites were identified. At low coverage (<1 ML), the n-type and p-type HfO(2)/InGaAs(0 0 1)-(4x2) interfaces show p-type character in STS, which is typical of clean InGaAs(0 0 1)-(4x2). After annealing below 200 degrees C, full coverage HfO(2)/InGaAs(0 0 1)-(4x2) (1-3 ML) has the surface Fermi level shifted toward the conduction band minimum for n-type InGaAs, but near the valence band maximum for p-type InGaAs. This is consistent with the HfO(2)/InGaAs(0 0 1)-(4x2) interface being at least partially unpinned, i.e., a low density of states in the band gap. The partially unpinned interface results from the modest strength of the bonding between HfO(2) and InGaAs(0 0 1)-(4x2) that prevents substrate atom disruption. The fortuitous structure of HfO(2) on InAs(0 0 1)-(4x2) and InGaAs(0 0 1)-(4x2) allows for the elimination of the partially filled dangling bonds on the surface, which are usually responsible for Fermi level pinning.

ChemInform Abstract: Interatomic Distances in the Stable and Metastable bcc and Omega Structures of the Transition Metals: Analysis of Experimental and Theoretical Trends and Correlations with Pauling′s Bond Lengths.

Abstract The name omega (Ω) phase refers to a high-pressure modification of the transition metals (TMs) Ti, Zr, and Hf. In alloys of Ti, Zr and Hf with other TMs, the Ω phase can be formed and retained metastably at room temperature by quenching the bcc structure, which is usually the stable high-temperature phase in these alloy systems. As a part of a long-term research program on the structural and bonding properties of TM phases, we present in this paper a detailed analysis of the shortest interatomic distances (SIDs) of the stable and metastable bcc and Ω structures of the 3d, 4d and 5d TMs, as well as the connections between these and the single-bond length D(1) entering into Pauling’s classical bond length vs. bond number relation (BLBNR). The analysis involves an extensive database including experimental data, very recent ab initio calculations, and new predictions based on the BLBNR for the bcc phase of the TMs. Our results lend support to early suggestions by Jamieson of the existence of a correlation between D(1) and the SID of the Ω phase of Ti and Zr. We also find that, for most TMs, D(1) and the SID of the Ω structure differ by less than about 2%, which implies that the Jamieson correlation might be considered as a reasonably accurate first approximation in estimating IDs and lattice parameters for unknown Ω phases of the TMs.

ChemInform Abstract: Thermoelectric Properties of Ternary Transition Metal Antimonides

Novel compounds T6MBi2, where T=Zr, Hf; M=Fe, Co, Ni, were synthesised by arc melting elemental combinations. Isotypism of these compounds with the ordered Fe2P-type was established from Rietveld X-ray powder data. Physical properties (electrical resistivity and thermoelectric power) were investigated for a series of ternary transition metal compounds with stoichiometries such as TM1−xX and T6MX2, where T is an electropositive transition metal (Zr, Hf and Nb), M is a metal from the iron group (Fe, Co, Ni) and X is Sb or Bi. Resistivities reveal a general metallic behaviour except for ZrCoSb and NbFeSb which are characterized by variable range hopping conductivity in a substantial temperature region. Thermoelectric power of these materials does not exceed 100 μV K−1.