Nm Of Ti Research Articles

CO2 detection using In and Ti doped SnO2 nanostructures: Comparative analysis of gas sensing properties

This research explores the gas-sensing characteristics of undoped SnO2, as well as indium (In:SnO2) and titanium (Ti:SnO2) doped SnO2 nanostructures, which were synthesized using a homogeneous precipitation technique. Structural analyses indicate the presence of a tetragonal rutile phase with a preferred orientation along the (110) plane, with both doped samples showing shifts towards higher angles. Raman spectroscopy confirms the vibrational modes associated with SnO2 in both the pure and In: SnO2 samples, while the Ti: SnO2 sample reveals vibrational modes corresponding to both SnO2 and TiO2. Fourier-transform infrared (FTIR) spectroscopy indicates shifts in the O-Sn-O and Sn-O bonds in the doped samples, suggesting the effects of doping. X-ray photoelectron spectroscopy (XPS) results imply a combination of SnO and SnO2 phases in the undoped SnO2, while In: SnO2 samples display In-O bonding and the presence of metallic indium, and Ti: SnO2 shows Ti-O bonding. Scanning electron microscopy (SEM) images show agglomerated particles in the pure and In-doped samples, whereas the Ti-doped samples exhibit a flake-like structure. Transmission electron microscopy (TEM) analysis verifies the integration of dopants into the SnO2 crystal lattice, with average crystallite sizes measured at 44.46 nm for undoped, 34.06 nm for In: SnO2, and 42.63 nm for Ti: SnO2. Gas-sensing experiments for CO2 detection reveal that In: SnO2 demonstrates the most significant sensing response. These results underscore the impact of doping on the structural, morphological, and gas-sensing attributes of SnO2 nanostructures, offering important insights for the advancement of efficient carbon dioxide sensors.

In Situ Measurement of Hydrogen Absorption into Copper-Coated Titanium Using Neutron Reflectometry and Electrochemical Impedance Spectroscopy

We set out to investigate the possibility that a small amount of hydrogen, generated by sulfide-driven corrosion or radiolytic processes, might be absorbed into the copper coating proposed for use as corrosion protection for the used nuclear fuel containers (UFCs) to be stored in a deep geological repository (DGR) in Canada. Hydrogen absorption may have the potential to alter the mechanical properties of the copper coating. This contribution discusses our initial study, using in situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS), of hydrogen absorption into a 50-nm layer of copper coated onto 4 nm of Ti on a Si single-crystal substrate. In situ NR-EIS experiments detected no increase in the hydrogen content within the copper layer of the copper-titanium thin film following 55 h of polarization in deoxygenated 0.1 M NaCl solution at pH 9, at potentials ranging from −444 mV/SCE to −1300 mV/SCE (detection limit ~2 at.%). However, these NR results showed that hydrogen can be absorbed into copper when the latter is cathodically polarized below about ─900 mV/SCE, which is the experimentally measured potential threshold for the hydrogen evolution reaction (HER) under these conditions. Although hydrogen did not accumulate in the outer Cu layer, our experiments revealed that the absorbed hydrogen quickly traversed the Cu layer to concentrate in the underlying titanium layer, which favours absorbed hydrogen. This observation is consistent with hydrogen uptake measured using inert gas fusion analysis on oxygen-free, phosphorus-doped (OFP) copper, which showed that in the absence of hydrogen recombination inhibitors (e.g., As(III)), only a small increase of 22 wt. ppm hydrogen was absorbed into the copper after 24 h at E = −1300 mV/SCE, and no increase in absorbed hydrogen occurred at potentials of −1100 mV/SCE or more positive. The initial absorption efficiency for electrolytically produced hydrogen atoms at the copper surface was determined to be 3.2%, suggesting that there may be an upper limit for hydrogen uptake by the copper coating of the UFC, although studies on 3 mm copper-coated steel samples representative of UFC materials will be required to confirm that. This result supports the prediction that hydrogen absorption is unlikely to lead to any failure of the copper barrier within a proposed DGR, in which it will not be possible to achieve such negative electrochemical potentials. Intended future research using in situ NR-EIS to study hydrogen absorption during the corrosion of copper thin films by HS⁻ ions and further studies on hydrogen absorption into 3-mm-thick copper-coated steel samples will help to validate these conclusions.

Ultrathin stable Ohmic contacts for high-temperature operation of β-Ga2O3 devices

Beta gallium oxide (β-Ga2O3) shows significant promise in high-temperature, high-power, and sensing electronics applications. However, long-term stable metallization layers for Ohmic contacts at high temperatures present unique thermodynamic challenges. The current most common Ohmic contact design based on 20 nm of Ti has been repeatedly demonstrated to fail at even moderately elevated temperatures (300–400 °C) due to a combination of nonstoichiometric Ti/Ga2O3 interfacial reactions and kinetically favored Ti diffusion processes. Here, we demonstrate stable Ohmic contacts for Ga2O3 devices operating up to 500–600 °C using ultrathin Ti layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the 5 nm Ti/100 nm Au contact stack is designed to fully oxidize while forming an Ohmic contact, thereby limiting both thermodynamic and kinetic instability. This novel contact design strategy results in an epitaxial conductive anatase titanium oxide interface layer that enables low-resistance Ohmic contacts that are stable both under long-term continuous operation (>500 h) at 600 °C in vacuum (≤10−4 Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550 °C in flowing N2. This stable Ohmic contact design will accelerate the development of high-temperature devices by enabling research focus to shift toward rectifying interfaces and other interfacial layers.

Hydrogen Absorption into Copper-Coated Titanium Measured by In Situ Neutron Reflectometry and Electrochemical Impedance Spectroscopy

One concern regarding the used nuclear fuel containers proposed for use in a Canadian deep geological repository (DGR) is the possibility that a small amount of hydrogen might be absorbed into their copper coating, potentially altering its mechanical properties. Reported herein is a study of hydrogen absorption into 50 nm of copper, coated on 4 nm of Ti using in situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). NR results show that hydrogen is absorbed when the copper is cathodically polarized below the threshold for the hydrogen evolution reaction (HER), but that the hydrogen concentrates in the underlying titanium layer rather than concentrating in the copper coating. The hydrogen concentration in titanium rapidly rose when the HER was initiated and was observed to reach a steady state at TiH1.5. Over the course of 55h of cathodic polarization, the concentration of hydrogen in the copper remained below the NR detection limit (2 at %). The portion of hydrogen atoms produced that diffused through the copper layer was initially 3.2%, suggesting a possible upper limit for hydrogen uptake by the copper coating of the UFC, although definitive conclusions can only be drawn from studies on 3 mm copper-coated steel samples.

Optical and electrochemical properties of pure and Ti-doped CdO nanoparticles for device applications

Cadmium oxide (CdO) is one among the transparent conducting oxides which is famous for its various applications in optoelectronics, gas sensors, and electrochemical sensors, etc. The present work therefore reports the synthesis and structural, optical, and electrochemical properties of pure CdO and Ti doped CdO nanoparticles which were synthesized using simple sol–gel method. The structural analysis of the prepared samples was done by using x-ray diffraction (XRD) technique. The XRD peaks revealed the existence of crystalline structure of the samples. The average crystallite sizes of the samples were calculated by considering the intense peaks observed in the XRD spectrum and they were found to be 59.45 nm and 55.25 nm for pure CdO and Ti doped CdO nanoparticles respectively. The absorption and transmission spectra of synthesized nanoparticles were recorded in the UV–VIS-NIR region. Using the absorption and transmission spectra, the optical band gap of pure CdO and Ti doped CdO were estimated as 2.14 eV and 2.99 eV respectively, using Tauc plot method. The Urbach energies were calculated, and they were found to be 1059 meV and 679 meV for the pure and Ti doped CdO nanoparticles. The optical conductivity, real and imaginary part of dielectric constant, dielectric loss tangent were also investigated using UV–VIS-NIR spectral data for the possible application in opto-electronic devices. The electrochemical performance of the samples was investigated using cyclic voltammetry (CV) technique. The specific capacitance and diffusion coefficients were calculated using the recorded cyclic voltammogram. The results of CV data showed that the maximum specific capacitance was occurred to be 390F/g at the rate 25 mV/s and 219F/g at the rate 50 mV/s for the pure and Ti-doped CdO nanomaterials respectively. The outcome of the present study provided an useful information for the possibilities of these materials in the device applications.

Enhanced optical properties and light-to-heat conversion performance of Ti3C2/[BMIM]BF4 nanofluids based direct absorption solar collector

A solar-thermal utilization heat transfer fluid with excellent light-to-heat conversion performance and good thermal reliability at high temperature is highly desirable for direct absorption solar collector (DASC). To obtain IL-based nanofluids as suitable HTFs for medium-high temperature DASCs, GO, MWCN and Ti 3 C 2 were selected as nanoadditives, respectively. The result shows that the light-to-heat conversion efficiency of Ti 3 C 2 /[BMIM]BF 4 nanofluid is 20% and 29% higher than that of GO/[BMIM]BF 4 nanofluid and MWCN/[BMIM]BF 4 nanofluid, respectively, after irradiation for 1000 s, due to the excellent optical absorption performance of Ti 3 C 2 . Furthermore, the effects of mass fractions of Ti 3 C 2 , solar concentrations and DASCs heights on the light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids are investigated systematically. The light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids rapidly increase with the increase of mass ratios of Ti 3 C 2 owing to the outstanding broad-spectrum absorption properties (250–2100 nm) of Ti 3 C 2 . Moreover, the light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids in DASCs increase with the increase of solar concentrations and DASCs heights. Additionally, the light-to-heat conversion efficiency of 0.04 wt% Ti 3 C 2 /[BMIM]BF 4 nanofluid is 2.7 times that of the pure ionic liquid at solar concentration C = 2.5, DASCs height H = 2.5 cm and 6500 s of irradiation. The obtained high-performance Ti 3 C 2 /[BMIM]BF 4 nanofluids show great potential application as advanced heat transfer fluids (HTFs) for DASCs. • Ti 3 C 2 /[BMIM]BF 4 nanofluid had excellent stability and optical property. • Performances of various nanofluids based DASCs were studied by experiments. • Optical properties significantly affected the temperature distribution. • Efficiency of nanofluid with Ti 3 C 2 is higher than that with GO and MWCN. • Efficiency of 0.04 wt% Ti 3 C 2 /[BMIM]BF 4 nanofluid is 2.7 times that of the pure IL.

Effect of Ti/V ratio on thermodynamics and kinetics of MC in γ/α matrices of Ti–V microalloyed steels

Through the solubility product theory of the ternary secondary phase, classical nucleation theory, and Ostwald ripening theory, a model was established to describe the thermodynamics and kinetics of (Ti, V)C precipitates in austenite/ferrite (γ/α) matrices. The model was used to calculate the volume fraction, precipitation–temperature–time (PTT) curve, and nucleation rate–temperature (NrT) curve of MC (M = Ti, V) precipitates in γ/α matrices in Ti–V microalloyed steels with various Ti/V ratios, which is verified by hardness tester, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The calculations indicate that, by decreasing Ti/V ratio from Ti4V0 steel to Ti0V4 steel, the complete-dissolution temperature decreases monotonically from 1226 to 830 °C, and the equilibrium volume fraction of MC precipitated from austenite decreases from 0.333% to 0.091% at 900 °C. Moreover, the maximum nucleation temperature of MC precipitated from α matrix decreases from 748 to 605 °C and the fastest precipitation temperature decreases from 844 to 675 °C as Ti/V ratio decreases. PTT and NrT diagrams of MC precipitated from α matrices in different Ti–V microalloyed steels all exhibit C-shaped and inverse C-shaped curves. In addition, both theoretical calculation and experimental results show that when tempered at 600 °C for 100 h, Ti2V2 steel shows the largest hardness value of 312 HV among the three steels tested because it has a larger volume fraction (0.364%), a larger precipitate density (1689 μm−2), and the smallest average size (8.4 nm) of (Ti, V)C precipitates. The theoretical calculations are consistent with experimental results, which indicates that the thermodynamics and kinetics model for (Ti, V)C precipitates is reliable and accurate.

The Effect of the Metal Phase on the Compressive and Tensile Stresses Reduction in the Superhard Nitride Coatings

The influence of the compressive and tensile stresses forming in the nanostructured Ti–Al–N coatings during deposition on their physical-mechanical properties was studied. The modifying influence of metal components (Ni and Cu) introduction into Ti–Al–N coatings, which do not interact with nitrogen and have limited solubility with the nitride phase, was also under research. Coatings were deposited on WC–(6 wt.%)Co carbide cutting inserts with an arc-PVD method using a cathodic vacuum arc evaporation apparatus. The introduction of Ni and Cu to the composition leads to the reduction of nitride phases grain size in both investigated coatings from 120 to 10–12 nm for Ti–Al–Cu–N and to 15–18 nm for Ti–Al–Ni–N. Thus, the hardness increases from 29 to 43 and 51 GPa for the mentioned above coatings, respectively. Meanwhile, Ti–Al–Cu–N and Ti–Al–Ni–N coatings are characterized by tensile stresses about 0.12–0.32 MPa against the much higher value of compressive stresses in Ti–Al–N coatings (4.29–5.31 GPa). The modification of Ti–Al–N coatings also leads to the changing of their destruction mechanism during the scratch-test. The critical loads characterizing the emergence of the first cracks in the coatings and complete abrasion of the coating (Lc1 and Lc3) were determined. They had the value of 20; 22 N (Lc1) and 64; 57 N (Lc3) for Ti–Al–Ni–N; Ti–Al–Cu–N coatings, respectively. The Lc1 parameter for Ti–Al–N coatings was much lower and was equal to 11 N. Along with those, Ti–Al–N coatings destructed according to the adhesion mechanism when the critical load was 35 N. In addition, the decreasing level of compressive stresses in Ti–Al–Cu–N and Ti–Al–Ni–N coatings as compared to that in the Ti–Al–N coating, their crack resistance during multi-cycle shock-dynamic impact test was significantly higher. The results can indicate that high hardness and crack resistance of the coatings is to a greater extent determined by coatings nanostructuring, not the stresses value. In addition, it confirms the possibility to obtain coatings with low stresses value while maintaining their superhardness.

Interactions of Ti and its oxides with selected surfaces: Si(100), HOPG(0001) and graphene/4H-SiC(0001)

The paper presents an interaction of Ti/Ti-oxides with: Si(100), HOPG(0001) and graphene/4H-SiC(0001) substrates. A thin layer (~3 nm) of Ti was deposited by means of DC sputtering technique on all the considered substrates. XPS, AFM and Raman spectroscopy were applied to find out the differences in interaction of Ti/Ti-oxides with selected substrates under UHV annealing. In the case of Si(100), substrate, apart from the expected TiO2, the presence of TiSi2 and TiSiOx components and the easiest reduction towards Ti2O3 was observed under UHV annealing. The sample exhibited also substantial evolution of surface morphology without the change of surface roughness which was attributed to formation of TiSi2 and TiSiOx components. This was in contrast with HOPG substrate where an annealing-induced agglomeration of the deposited material increased the surface roughness substantially. However, in the case of Ti/Ti-oxides deposited on graphene/4H-SiC(0001), UHV annealing caused no noticeable change of surface morphology. Agglomerates were not formed which was attributed to degradation of graphene (confirmed by Raman spectra) and supressing van der Waals' interactions responsible for easy surface diffusion. The differences in morphology were also discussed in the context of the surface energy of selected substrates.

IBA investigation on the effect of Ti-Mo interdiffusion on the D concentration in TiDx/Mo films

Ion Beam Analysis (IBA) which combines Rutherford backscattering (RBS), D(3He,p)4He nuclear reaction analysis (NRA) and chemical etching, is employed to detect the depth profiles of deuterium, titanium and molybdenum in metal hydride films (TiDx/Mo). Using this analysis technique, not only the depth resolutions of better than 70 nm for both Ti and Mo were achieved, but also there is no change in D content after the etching. Both secondary ion mass spectrometer (SIMS) and grazing incidence X-ray diffraction (GIXRD) have been also used to analyze the effect of Ti-Mo interdiffusion on the D concentration.

On the use of AES data analysis to determine local enrichments of conversion coating elements at intermetallic particles on rolled Al

In this paper, the behaviour of the industrial applied Ti/Zr conversion coating (CC) pretreatment on rolled automotive aluminium samples (AA5182) is analysed. Due to its nanometre lateral and depth resolution, Auger electron spectroscopy (AES) is used to analyse the CC distribution at surface cathodic intermetallic particles. As a result of its high surface sensitivity, the AES technique is very susceptible to differences in the top contamination layer thickness. It is demonstrated that AES point measurements performed on aluminium model samples coated with 1.5 and 3 nm of Ti (oxide) layer cannot differentiate the two‐layer thicknesses if a difference in the top contamination thickness is not taken into account. A data analysis methodology is introduced, based on the ratio of normalized peak areas (enrichment ratios), to eliminate the effect of the contamination layer thickness. The experimental validation of the methodology is performed on the model samples, demonstrating errors of 2% on the enrichment ratios on similar samples with different contamination layer thicknesses, while the conventional spectra quantification results in errors of 49%. The methodology is also theoretically substantiated within certain constraints. By the use of the AES methodology, an enriched Ti and Zr deposition is confirmed at the cathodic intermetallic particles at the surface of the industrial no‐rinse CC sprayed automotive aluminium sheet samples.

Interface dynamics in ohmic contact optimization on AlGaN/GaN heterostructure by the formation of TiN

We illustrate a systematic approach to reduce the ohmic contact resistance on AlGaN/GaN heterostructure. We have optimized the ohmic contact resistance by varying the thickness of AlGaN barrier layer, Ti layer, Al/Ti ratio, and temperature. We have observed nonlinear dependency on various process conditions. Careful observations on performed experiments bring out the interface dynamics of the metal and semiconductor layers. We have demonstrated a very low typical contact resistance of 0.06 Ω.mm for AlGaN barrier thickness of 13 nm, Ti/Al/Ni/Au of 12/150/40/50 nm, and annealed at 775 °C. The minimum contact resistance is found to be 0.05 Ω mm when measured across devices. This RC value is appropriate for high power RF applications of AlGaN/GaN based high electron mobility transistors. This value of the contact resistance is the lowest among the values reported on AlGaN/GaN heterostructure using alloyed contacts. A lower thickness AlGaN barrier can help to reduce the thermal budget for achieving low ohmic contact resistance. This is achieved at lower critical thickness for Ti which is dependent on the AlGaN barrier thickness. It is also observed that Ti:Al ratio should be increasingly larger for decreasing thickness of Ti. This trend is observed till 7 nm of Ti.

Photochemistry of dithiophosphinate Ni(S2P(i-Bu)2)2 complex in CCl4. Transient species and TD-DFT calculations

Femtosecond spectroscopy and nanosecond laser flash photolysis were used to study the photophysical and photochemical transformations of the bis-diisobutyl-dithiophosphinate Ni(II) complex (Ni(S2P(i-Bu)2)2 = Ni(dtpi)2, where dtpi− ≡ −S2P(i-Bu)2) in CCl4 solutions. The radiation of second harmonic (405 nm) of Ti:Sapphire laser transfers the Ni(dtpi)2 complex to an excited 1LMCT state. Its decay in CCl4 is described by three exponents with time constants 0.58, 2.0 and ˜150 ps. The first process apparently involves the fast transitions from 1LMCT state to 3LMCT due to the intersystem crossing (ISC) and then to lower-lying "hot" 3LF (Ligand Field) state. The second time constant, most likely, corresponds to the vibrational cooling of this "hot" 3LF state. And the third slow process is the transition from 3LF state to ground state (1GS).The quantum yield of photochemical transformation under the 405 irradiation is close to zero, so the study of photochemistry was performed with a nanosecond flash photolysis at 308 nm. In this case an electron transfer from the excited Ni(dtpi)2 complex to a solvent molecule leads to the appearance of primary intermediate, the [ClNi(dtpi)(dtpi)] complex, in which a dtpi radical is coordinated with a nickel ion via one sulfur atom. In the fast reaction with Ni(dtpi)2, this complex forms a long-lived dimer ClNi(dtpi)(dtpi)[Ni(dtpi)2]. This intermediate for a few hundred microseconds decays in the reaction of recombination with the formation of (dtpi)2 disulphide and unstable ClNi(dtpi) complex. The insoluble NiCl2 salt falled in CCl4 as the sediment due to the reaction of two ClNi(dtpi) complexes. The quantum chemical calculations allowed to determine the geometry of the intermediate complexes arising in the photochemistry of Ni(S2P(i-Bu)2)2 complex.

Corrosion of Platinum Nanocoatings Thin Films Deposited by Sputtering Deposition Method for Medical Applications

Platinum (Pt.) thin films have been deposited by Magnetron Sputtering Deposition method with 25 nm and 50 nm thickness by used power RF for deposited 5 nm Titanium (Ti) firstly then used DC for deposited Platinum (Pt) on Ni-Cr alloy substrate. SEM/EDX and Ellipsometry Spectroscopy have been used to investigate the morphology, element analysis, nanothickness and roughness of the thin films respectively. Electrochemical corrosion tests have been used to analyze the localized corrosion resistance by used cyclic polarization, Tafel extrapolation and open circuit potential (o.c.p) methods on artificial saliva solution at 37 ±1 oC. The results show the ability to deposit 5 nm of Ti before deposited of Pt. film to improve the adhesive of the films, nanostructure morphology of the Pt. film without defect or microcracks, nanocoatings thickness of Pt. film, and high localized corrosion resistance in artificial saliva corrosive media.

A novel ferritic steel family hardened by intermetallic compound G-phase

In this paper, G-phase precipitation and the resulting hardening effect on Fe-20Cr-3Ni-1Mn-3Si ferritic alloys by the addition of Ti, Nb, Ta and Zr were individually studied by electron microscopy and atom probe tomography, combined with thermodynamic and first principle calculations. The high resolution scanning electron and transmission electron microscopy observations confirmed that four kinds of Ni16M6Si7 (M=Ti, Nb, Ta and Zr) G-phase particles were distributed uniformly in the matrix of the four alloys aged at 560–860 °C. The 3D-APT results revealed the formation of the four different nanoscale precipitates, with the highest number density (6.05 × 1023 m−3) and smallest radius (1.64 ± 0.45 nm) in the Ti added alloy. The nanoscale sized precipitates stability (~3 nm for Ti added alloy; ~5 nm for Nb added alloy and Zr added alloy; ~25 nm for Ta added alloy) was attributed to their particular cube-cube orientation relationships, which led to a very low interfacial energy. The effects of the G-phase on precipitation hardening and quasi steady-state deformation resistance were examined. The 560 °C-aging hardening experiments suggested a rapid precipitation process of the nano-particles. The peak hardness values of the four alloys are in the descending order: Ti ˃˃ Nb > Ta ˃˃ Zr. The 660 °C quasi steady-state deformation experiments showed threshold stresses of 110 and 140 MPa in cases of the Nb and Ti added alloys, which were higher than that of the previously reported B2-NiAl strengthened steels and commercial heat-resistant steels. By using the formation of nanoscale G-phase precipitates, a new ferritic steel family with very high strength and creep resistance has been proposed. Further alloy optimization is in progress.

Bilayer Dielectrics for RRAM Devices

Non-volatile resistive random-access memory (RRAM) devices are currently being investigated as a low power, high density and high-speed alternative DRAM (1). A transition metal oxide dielectric layer is typically used as an insulating layer in a metal-insulator-metal (MIM) structure. To reduce the large variability of switching parameters and high operation current in these RRAM devices, bilayer dielectric structures are being explored. In this work we have used several different bilayer structures using different dielectrics. In each device the bottom electrode (BE) was 10nm Ti/50nmTiN followed by 1nm Al2O3. The second dielectric layer or the switching layer was a 7-nm HfO2 (R3), HfZrO2 (R4 with Hf:Zr%=50%) or HfAlO2 (R1 with Hf:Al%= 3%) followed by the top electrode (TE) constituting of 8nm Ti/6nm ALD TiN+50nm PVD TiN. In some cases, the top electrode was varied to 2nm ALD TiN/8nm Ti/6nm ALD TiN+50nm PVD TiN (R5) by adding a 2nm ALD TiN layer prior to 8nm Ti. Some devices with HfZrO2 (R2) were subjected to a post deposition anneal (PDA) at 700oC for 60 s. In all cases, to enhance the switching characteristics on the top electrode 8 nm Ti was used as the cap layer material except in the case of R5 where 2nm of ALD TiN was deposited prior to 8 nm of Ti. The use of thin dielectric layer of 1nm Al2O3 was to suppress the sneak-path problem (3) in the low resistance state (RON). Comparing the variation of switching layer, it was observed that the device with 1nm Al2O3/7nm HfAlO2 (R1) provided the superior average Roff/Ron values and both set and reset power compared to HfO2 (R3), and HfZrO2 (R4) devices. When the HfZrO2 (R4) devices were compared with the identical device with PDA (R2) Ron increased and Roff decreased for the PDA device, reducing the Roff/Ron value. Variation of cap layer to TiN instead of Ti also showed similar Roff/Ronbehavior. D. Ielmini, Semicond. Sci. Technol. Vol. 31, 063002, 2016.Xiaorong Chen and Jie Feng, Appl. Phys. A, vol. 120, 67 2015U. Chand, K-C. Huang, C-Y. Huang, and T-Y. Tseng, IEEE Trans. on Electron Devices, vol. 62(11), 3665, 2015

REGULARITIES OF FORMATION AND DEGRADATION OF THE MICROSTRUCTURE AND PROPERTIES OF NEW ULTRAFINE-GRAINED LOW-MODULUS Ti–Nb–Mo–Zr ALLOYS

Regularities of the formation of ultrafine-grained (UFG) and submicrocrystalline (SMC) structures in new nickel-free low-modulus Ti–Nb–Mo–Zr titanium β alloys under the action of plastic deformation were studied. Temperature-time ranges of the development of dynamic recrystallization processes under the simultaneous action of temperature and plastic deformation were determined. The recrystallization diagram of II type of the Ti–28Nb–8Mo–12Zr alloy was constructed and analyzed. It was shown using scanning electron microscopy and electron backscatter diffraction method that the UFG structure with an average grain size of no more than 7 μm and high fraction of high-angle grain boundaries is formed in the investigated alloys as a result of longitudinal rolling followed by annealing for quenching. It was found that the formation of the UFG structure leads to a significant increase in the strength and plastic characteristics of these alloys. The regularities of the formation of UFG and SMC structures in the titanium β alloys Ti–28Nb–8Mo–12Zr and VT30 widely used in industry under the action of plastic deformation by the helical rolling method were studied. It was shown that the helical rolling of the VT30 alloy leads to the formation of the homogeneous UFG state as opposite to the developed Ti–28Nb–8Mo–12Zr β alloy where this method causes structure softening with micropores and microcracks formed in the central region. It is possible to form a nanostructured state with an average grain size of about 100 nm in Ti–Nb–Mo–Zr titanium β alloys using high-pressure torsion method.

Ti:Pt:Au:Ni thin-film CVD diamond sensor ability for charged particle detection

This work demonstrates the development of diamond sensors with reliable contacts using a new metallization formula, which can operate under high-pressure gas environment. The metallization was created using thin film layers of titanium, platinum, gold and nickel deposited on a single crystal electronic grade CVD diamond chip. The contacts were 2 mm in diameter with thickness of 50/5/20/150 nm of Ti:Pt:Au:Ni. The optimum operating voltage of the sensor was determined from the current-voltage measurements. The sensor was calibrated with 239Pu and 241Am alpha radiation sources at 300 V. The energy resolution of the Ti:Pt:Au:Ni diamond sensor was determined to be 7.6% at 5.2 MeV of 239Pu and 2.2% at 5.48 MeV of 241Am. The high-pressure gas loading environment under which this sensor was used is discussed. Specifically, experimental observations are described using hydrogen loading of nickel as a means of initiating low energy nuclear reactions. No neutrons, electrons, ions or other ionizing radiations were observed in these experiments.

Electropolishing valve metals with a sulfuric acid-methanol electrolyte at low temperature

This study reports the electropolishing of Ti and Nb metals using a fluoride-free electrolyte of sulfuric acid and methanol at low temperature (−70 °C) without prior treatment. A fluoride-free electrolyte provides a less hazardous and more environmentally friendly option for electropolishing procedure. Experimental studies are presented on electropolishing with sulfuric acid electrolyte, which provides high quality macro- and micro-smoothing of the metal surfaces. Optimal conditions yielded leveling and brightening of the surface of Ti and Nb metals beyond that by the currently utilized electropolishing procedures with fluoride-containing electrolytes. The root mean square roughness (Rq) from atomic force microscopy analysis was 1.64 and 0.49 nm for Ti and Nb, respectively. Lower temperature experiments led to noticeable kinetic effects, indicated by a dramatic drop in current densities and the expansion of the steady-state current density plateau in anodic polarization curves. In addition, the voltage range of the current plateau expanded with increasing acid concentration. Surface characterization of Ti and Nb metals after polishing provided evidence of salt film formation. In addition, these metals were used as substrates in the formation of nanostructured metal oxides. The overall quality of the electropolishing led to a dramatic improvement in the uniformity of the nanostructures.

Tuning excitation laser wavelength for secondary resonance in low-intensity phase-selective laser-induced breakdown spectroscopy for in-situ analytical measurement of nanoaerosols

In recent years, a novel low-intensity phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique has been developed for unique elemental-composition identification of aerosolized nanoparticles, where only the solid-phase nanoparticles break down, forming nanoplasmas, without any surrounding gas-phase breakdown. Additional work has demonstrated that PS-LIBS emissions can be greatly enhanced with secondary resonant excitation by matching the excitation laser wavelength with an atomic transition line in the formed nanoplasma, thereby achieving low limits of detection. In this work, a tunable dye laser is employed to investigate the effects of excitation wavelength and irradiance on in-situ PS-LIBS measurements of TiO2 nanoaerosols. The enhancement factor by resonant excitation can be 220 times greater than that for non-resonant cases under similar conditions. Moreover, the emitted spectra are unique for the selected resonant transition lines for a given element, suggesting the potential to make precise phase-selective and analyte-selective measurements of nanoparticles in a multicomponent multiphase system. The enhancement factor by resonant excitation is highly sensitive to excitation laser wavelength, with narrow excitation spectral windows, i.e., 0.012 to 0.023nm (FWHM, full width at half maximum) for Ti (I) neutral atomic lines, and 0.051 to 0.139nm (FWHM) for Ti (II) single-ionized atomic lines. Boltzmann analysis of the emission intensities, temporal response of emissions, and emission dependence on excitation irradiance are investigated to understand aspects of the generated nanoplasmas such as temperature, local thermodynamic equilibrium (LTE), and excitation mechanism.