Sputtering Of Niobium Research Articles

Application of Sims Depth Profiling to Ceramic Materials

ABSTRACTDepth profiling is becoming a common method of determining composition gradients for those research facilities that have access to SIMS. The problems with this procedure are briefly discussed but well referenced for those interested in using the technique. Spectra for application of depth profiling to a tantalum pentoxide layer on tantalum, silicon implanted in silica, preferential sputtering of niobium and surface treated lithium alumina silicate glass are presented.

Substrate heating rates for planar and cylindrical-post magnetron sputtering sources

Substrate heating energies per atom deposited are reported for planar magnetron sputtering of aluminum, chromium, nickel, copper, molybdenum, indium, tantalum, tungsten and platinum in argon as well as for aluminum and chromium sputtered in O 2. Data are also reported for cylindrical magnetron sputtering of niobium, silver, tantalum, tungsten and Pb-Sn in argon as well as for molybdenum sputtered in neon, argon, krypton and xenon. The planar and cylindrical magnetron heating rates were comparable. The heating energies for argon sputtering ranged from 10–15 eV per deposited atom for the light metals to almost 100 eV atom -1 for tantalum and tungsten. The implied reactive sputtering heating energies were about 500 eV molecule -1 for Cr 2O 3 and 1150 eV molecule -1 for Al 2O 3. Special experiments were conducted to examine the contributions to the substrate heating of plasma species and ion neutralization and reflection at the cathode. The data indicate that charged plasma species do not contribute significantly to the heating but that neutralized and reflected ions play a significant role in the planar as well as the cylindrical cases despite the differences in cathode geometry.

Superconducting properties of reactively sputtered NbCN thin films

Niobium Carbonitride thin films have been prepared by rf reactive sputtering of niobium in ar argon, reactive-gas (RG) atmosphere where the RG is a mixture of cyanogen and nitrogen. Film composition ranged from Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.03\leq \times \leq0.5</tex> ) as determined by Auger analysis, the carbon content roughly tracking the cyanogen partial pressure. Composition and substrate temperature were systematically varied and the resultant films studied by measurements of x-ray structure, resistivity, superconducting transition temperature T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> , and critical magnetic fields. We have found systematic preferential orientation of the crystallites in these films depending upon substrate temperature ana RG to argon ratio. Increasing either quantity causes the crystallites to reorient from the

Non-epitaxial and epitaxial growth of A15 Nb 3Si by sputtering

The sputtering of niobium and silicon with low energy argon and krypton ions onto a silica glass substrate at 550–600 °C from an Nb-Si target containing 73–80 at.% Nb produces deposits of a b.c.c. niobium solid solution of silicon and A15 Nb 3Si with a lattice parameter a 0 of 518–519 pm and a superconducting transition temperature T c of 5.3–7.55 K. If niobium and silicon are sputtered onto epitaxially effective A15 Ti 3Au substrates, higher temperatures (640–670 °C) can be used. A well-crystallized A15 Nb 3Si structure is thus produced for which a 0 = 509 pm, the theoretically required value and T c = 9.4 K.

Experiments on sputtering of niobium by 14–16 MeV protons and Monte Carlo calculations for proton and neutron sputtering

The sputtering of niobium with 14 MeV neutrons is simulated by 14–16 MeV protons. The targets are cold-rolled niobium foils of 240 μm thickness as prepared by the ANL and PNL (Round Robin samples). The sputtered Nb atoms are collected on Si wafers in forward and backward direction, and then detected by RBS analysis with 300 keV He +, using special features for background suppression. The sputtering yields measured are in the range of 10 −5-10 −4 atoms/proton. A theoretical analysis and comparison of neutron and proton effects is carried out with the realistic Monte Carlo code TRIM, using the Molière repulsive potential and Lindhard-Scharff electronic stopping. The recoil production is based on improved cross sections for elastic scattering and nuclear reactions. The results are the following sputtering yields: neutrons 0.6 × 10 −5 forward, 0.03 × 10 −5 backward; protons 1.5 × 10 −5 forward, 0.9 × 10 −5 backward. The low forward-to-backward ratio for protons, 1.6, is due to the large number of low-energy recoils from Coulomb interactions, starting nearly perpendicular to the proton motion and contributing equally to forward and backward sputtering.

Fast-neutron sputtering of niobium

Fast-neutron sputtering of niobium

Sputtering of niobium by energetic neutrons and protons: a round-robin experiment

Sputtering of niobium by energetic neutrons and protons: a round-robin experiment

Sputtering of niobium by energetic neutrons and protons: A round-robin experiment

This paper presents the results of a round-robin neutron-sputtering experiment in which six independent research groups have participated. Targets of cold-rolled niobium prepared by two standard techniques were used by all participants. Three participating groups used (d,t) neutrons of about 14.8 MeV, one group used (d,Be) neutrons produced by 40-MeV deutrons on a thick Be target, and two groups used 16-MeV protons in transmission. The emission of micrometer-sized particles was observed by two groups and not observed by the other four. This particle emission was observed by two of the groups who used (d,t) neutrons in their irradiations. Chunk emission was observed for only one of the two standardized target types used in the round robin. The round-robin results support the concept that the neutron-sputtering yield of Nb, including atomic and chunk emission, has an estimated probable value no larger than 10−4 atoms per neutron. However, sputtering yields in the range 1.4×10−5 to ≲2.6×10−3 are reported here. The probable value for the sputtering yield was found to be independent of the two target preparations and the method of analysis, whether or not chunks were observed during analysis.

Simulation experiments for the sputtering of niobium by 14 MeV neutrons

Simulation experiments for the sputtering of niobium by 14 MeV neutrons are conducted at the Berlin Cyclotron with protons of 11 to 20 MeV which pass through a sandwich of niobium target foils and silicon catcher disks. The stack is assembled in an UHV chamber and is irradiated to doses of 0.7 to 1.4 × 10 18 p/cm 2. The sputtered material is detected by RBS, taking advantage of Si background reduction by the 〈111〉 channeling effect and by electronic pile-up rejection. The measured sputter ratios are in the forward direction (1.0–2.4) × 10 −4 for the first irradiation and (1.0–2.5) × 10 −5 for a second (subsequent) irradiation; in the backward direction sputter ratios are found to be considerably lower, between several 10 −6 (limit of detection) and 2.8 × 10 −5 (maximum). The emission of radioactive recoils is also observed through 7 spectrometry of targets and collectors.

Simulation experiments for the sputtering of niobium by 14 MeV neutrons

Simulation experiments for the sputtering of niobium by 14 MeV neutrons are conducted at the Berlin Cyclotron with protons of 11 to 20 MeV which pass through a sandwich of niobium target foils and silicon catcher disks. The stack is assembled in an UHV chamber and is irradiated to doses of 0.7 to 1.4 × 1018 p/cm2. The sputtered material is detected by RBS, taking advantage of Si background reduction by the 〈111〉 channeling effect and by electronic pile-up rejection. The measured sputter ratios are in the forward direction (1.0–2.4) × 10−4 for the first irradiation and (1.0–2.5) × 10−5 for a second (subsequent) irradiation; in the backward direction sputter ratios are found to be considerably lower, between several 10−6 (limit of detection) and 2.8 × 10−5 (maximum). The emission of radioactive recoils is also observed through 7 spectrometry of targets and collectors. Des expériences de simulation pour la pulvérisation du niobium par des neutrons de 14 MeV ont été effectuées au Cyclotron de Berlin avec des protons de 11 à 20 MeV qui passent à travers un sandwich de feuilles de niobium servant de cibles et de disques de silicium agissant comme capteurs. Ce faisceau est assemblé dans une chambre UHV et est irradié à des doses de 0,7 à 1,4 × 1018 p/cm2. Le matériau pulvérisé est détecté par RBS, en tirant avantage de la réduction du spectre de fond du Si par l'effet de canalisation suivant les directions 〈111〉 et par le rejet électronique. Les rapports de pulvérisation mesurés sont dans la direction en avant égaux à (1–2,4) × 10−4 pour la première irradiation et (1−2,5) × 10−5 pour une seconde irradiation ultérieure. Dans la direction opposée les rapports de pulvérisation sont considérablement plus faibles, compris entre 10−6 (limite de détection) et 2,8 × 10−5 (maximum). L'émission de reculs radioactifs est également observé à l'aide de la spectrométrie γ des cibles et des collecteurs. Simulationsexperimente für die Oberflächenzerstäubung von Niob mit 14-MeV-Neutronen wurden am Berliner Kompaktzyklotron mit 11 bis 20 MeV-Protonen durchgeführt. Ein Sandwich von Nb-Targetfolien und Si-Fängerscheiben wurde in einer UHV-Kammer zu Dosen von 0,7 und 1,4 × 1018p/cm2 bestrahlt. Das zerstäubte Niob wurde durch Rutherford-Rückstreuung nachgewiesen, wobei der von der Si-Scheibe herrührende Untergrung durch 〈111〉-Channelling und elektronische pile-up-Unterdrückung wesentlich reduziert wurde. Die gemessenen Zerstäubungsausbeuten betrugen in Vorwärtsrichtung 1,0 bis 2,4 × 10−4 bei der ersten Bestrahlung und 1,0 bis 2,5 × 10−5 bei der zweiten (Wiederholungs-) Bestrahlung; in Rückwärtsrichtung wurden wesentlich niedrigere Zerstäubungsausbeuten gefunden, nämlich einige 10−6 (Nachweisgrenze) bis 2,8 × 10−5 (Höchstwert). Der Austritt radioaktiver Rückstosskerne wurde ermittelt durch γ-Spektrometric von Nb-Targets und Fängerscheiben.

14.1-MeV neutron sputtering of polycrystalline and monocrystalline niobium with different surface microstructures

14.1-MeV neutron sputtering of polycrystalline and monocrystalline niobium with different surface microstructures

Birefringent waveguides prepared by reactive sputtering of niobium in O_2–N_2 mixtures

Birefringent waveguides prepared by reactive sputtering of niobium in O_2–N_2 mixtures

A method of utilizing lithium-induced nuclear reactions in the determination of carbon, nitrogen, and oxygen in thin films

A method of analysis of oxygen, nitrogen, and carbon in thin samples involves the detection of charged particles from nuclear reactions induced by a 7-MeV lithium-6 beam. The particle detection with a telescope counter near 0° takes full advantage of high exothermic reactions. The sensitivity is of the order of 10−3 μg/cm2. A preliminary study of the contaminants introduced during the sputtering of niobium is presented.

Cathode sputtering of niobium and its alloys in a helium glow discharge

Cathode sputtering of niobium and its alloys in a helium glow discharge

Propriétés et structure des couches minces de nitrure de niobium élaborées par pulvérisation cathodique réactive. II. Etude cristallographique par microscopie et diffraction électroniques

Niobium nitride superconductors have been obtained by cathodic sputtering of niobium in nitrogen followed by deposition on amorphous carbon substrates. This report relates to their examination by transmission electron microscopy and diffraction. In the N/Nb ratio range from 0 to 1.5 this fabrication process leads to thin films of crystallite size 30–300 Å. Depending on the N/Nb ratio, the material is either monophase (α-solid solution or δ-superconductor phase) or biphase (niobium and δ-phase). The position and intensity of diffraction rays show that the α-solid solution and δ-phase composition range cannot be described by an equilibrium phase diagram. All thin films were heat-treated at 600, 800 and 900 °C in the electron microscope; if stable at room temperature, their structure changes when temperature increases. If the N Nb ratio > 1 , the δ-phase which appears exhibits a Nb lacunar structure. The diffraction ray position of this structure fluctuates on either side of the theoretical value. Heat treatment at 800 °C in the microscope brings back the usual diffraction ray order, possibly because an atomic rearrangment due to migration of lacuna occurs leading to a nearly stoichiometric δ-phase.

Superconductivity transition temperatures of rf reactively sputtered NbN Films

Niobium nitride films of a thickness ranging from 500 to 3000 Å have been deposited by reactive rf sputtering of niobium in a nitrogen/argon atmosphere. A water-cooled substrate holder was used. The partial pressure of nitrogen was varied systematically between 0 and 10−3 Torr at two different argon pressures. Generally, the substrate was set on anode potential but in some cases a bias voltage was applied. The experiments showed that the transition temperature was strongly dependent upon the partial pressures of nitrogen and argon. In the sputtering experiments without bias very steep transition curves were obtained. The highest transition temperature was Tc = 14.5 K. The structures of films were examined by x-ray and TEM transmission methods. The investigations made evident that rf sputtering is a method by which high transition temperatures can be obtained, even at high residual gas pressures and unheated substrates.

Sputtering of Niobium by Niobium, Hydrogen, Deuterium, and Helium Ions in the 10- to 80-keV Energy Range

Sputtering coefficients of niobium for bombardment by Nb, H, D, and He ions in the 10- to 80-keV range have been measured and compared with theory. The light-ion measurements were obtained by sputtering through a thin film (600 Å) of niobium deposited on a zirconium substrate. Penetration of the film was observed by the appearance of substrate ions in the mass spectrum of sputtered ions from the target.

Superconductive Films Made by Protected Sputtering of Tantalum or Niobium

Electrodes of the material to be sputtered are placed one above the other in a 0.1 to 0.2 mm Hg Ar atmosphere. Substrates for the deposited layers are placed on the lower electrode. An asymmetric alternating current first causes the Ar to sputter the upper electrode with a current density J = 0.5 ma/cm2, which causes a thin layer to be deposited on the substrate; next, the current reverses and Ar bombards the substrate and thin deposited layer with J = 0.1 ma/cm2, thus driving out impurities from the deposited layer. This method circumvents the strong gettering action of sputtered Ta and Nb. The superconducting properties of the films formed by this process are discussed.