Sputtering Of Compound Target Research Articles

Influence of oxide matrix on electron transport in (FeCoZr)x(Al2O3)1-x nanocomposite films

Electron transport in (Fe0.45Co0.45Zr0.10)x(Al2O3)1-x granular nanocomposites (NCs) produced by the ion-beam sputtering of compound target was studied in the temperature range of 2–300 K. Conductivity of the films synthesized in the inert (Ar) atmosphere is determined below percolation threshold by the thermally activated electron tunneling over metallic granules at low temperatures and replaced by the Mott variable range hopping (VRH) with increasing temperature. Introduction of oxygen to the sputtering chamber suppresses VRH leading to retention of the thermally activated tunneling in the whole studied temperature range for the metallic phase atomic concentrations up to х = 0.62. The model of thermally activated tunneling over metallic granules gives an excellent agreement with experimental data when alumina matrix permittivity is considered as increasing with concentration of the metallic phase fraction in the films, which is due to increase in number of localized electronic states. The established influence of the sputtering atmosphere on the electron transport in nanocomposites is explained by reduction of concentration of the defects in matrix when oxygen is added to the sputtering atmosphere.

High visible light photocatalytic activity of nitrogen-doped ZnO thin films deposited by HiPIMS

Reactive High Power Impulse Magnetron Sputtering (HiPIMS) of a pure Zn target in Ar/N2/O2 gas mixture was used to synthesize ZnOxNy thin films with nitrogen content and optical band-gap energy values ranging over 0–6.2at.% and 3.34–1.67eV, respectively. The fine control of the nitrogen content in the deposited ZnOxNy thin films composition was possible through the stabilization of the reactive HiPIMS discharge in the transition region, between the metallic and compound target sputtering modes. Various analytical techniques such as AFM, XPS, XRD, UV–Vis and Raman spectroscopy have been employed to characterize the properties of the deposited thin films. The photocatalytic activity, light excitation efficiency and life time of photo-generated charge carriers in the ZnOxNy films were investigated by photo-electrochemical and photo-current measurements during visible light on/off irradiation cycles. The as-deposited films showed poor visible-light photocatalytic activity and photo-current response. Post-deposition annealing of the films in nitrogen atmosphere resulted in a slight enhancement of crystalline order. However, the thermal treatment improved considerably the film photocatalytic activity and stability for water splitting under visible light irradiation. The optimum photo-current response and photocatalytic activity have been obtained for the annealed ZnOxNy films with a nitrogen content of 3.4at.% (photon-to-current efficiency up to 33% at λ=370nm and 0.5V biasing potential vs. Ag/AgCl). Increasing the nitrogen content above this value, in spite of lowering the energy band-gap, worsened the visible light photocatalytic activity of the films due to deterioration of the crystalline order.

Tuning the band gap and nitrogen content of ZnOxNy thin films deposited by reactive HiPIMS

We show that it is possible to manipulate the stoichiometry and composition of the thin films deposited by reactive high power impulse magnetron sputtering (HiPIMS) by the design of the discharge pulsing scheme. This is illustrated for the case of the short-pulse HiPIMS of a pure Zn target in Ar/N2/O2 mixture gas (low content of O2), where the variation of the discharge pulsing frequency has led to depositions of crystalline ZnOxNy thin films with the nitrogen content and optical band gap values ranging from 0 to 6.2at.% and from 3.34 to 1.67eV, respectively. The fine control of nitrogen content in the deposited ZnOxNy thin films was obtained by the use of smooth transitions of the reactive HiPIMS discharge between the compound and metallic target sputtering modes. Thus, the yield of the sputtered metal atoms was controlled by the discharge pulsing frequency from low values, in the compound target sputtering mode, to large values, in the metallic target sputtering mode. The controlled amount of metal atoms in the gas phase and the limited amount of oxygen in the deposition chamber determined depositions of films with variable content of nitrogen.

Deposition of vanadium carbide thin films using compound target sputtering and their field emission

Vanadium carbide (VC) thin films were deposited on silicon substrates by direct sputtering of a VC target in an argon atmosphere. The structure, composition, and electrical properties of the films were investigated as functions of deposition conditions. The crystallographic structure of the film was strongly related to the argon pressure. VC films with (111) preferred orientation were formed at 2.0 Pa regardless of the substrate temperature examined, while amorphous films were obtained at the lowest pressure of 0.5 Pa. It was shown that carbon segregation within the film was difficult to avoid, but could be suppressed to some degree. To make a full understanding of the compositional variation in compound target sputtering process, deposition of chromium carbide thin films was also performed. Some common mechanisms involved in compound target sputtering process were discussed. Field emission measurements revealed that the VC film is a good electron emitter.

Molecular dynamics study of Al and Ni 3Al sputtering by Al clusters bombardment

The sputtering of Al and Ni 3Al (1 0 0) surfaces induced by impact of Al ions and Al N clusters ( N=2,4,6,9,13,55) with energies of 100 and 500 eV/atom is studied at atomic scale by means of classical molecular dynamics (MD). The MD code we used implements many-body tight binding potential splined to ZBL at short distances. Special attention has been paid to model dense cascades: we used quite big computation cells with lateral periodic and damped boundary conditions. In addition, long simulation times (10–25 ps) and representative statistics (up to 1000 runs per each case) were considered. The total sputtering yields, energy and time spectrums of sputtered particles, as well as preferential sputtering of compound target were analyzed, both in the linear and non-linear regimes. The significant “cluster enhancement” of sputtering yield was found for cluster sizes N⩾13. In parallel, we estimated collision cascade features depending on cluster size in order to interpret the nature of observed non-linear effects.

Nickel aluminide thin film fabrication via ion beam sputtering of compound targets

We report recent results from our use of Kaufman-type ion beam sputtering to fabricate boron-doped nickel aluminide thin films on substrates of Si, NaCl, and polycarbonate resin plastic. Compound targets of boron-doped Ni 3Al were bombarded with ≈1 keV Ar ions to form films having thicknesses up to 2000 Å and areas of approximately 2.5 cm × 2.5 cm. Films with Ni/Al ratios similar to the target have been produced on NaCl and Si as determined by instrumental neutron activation analysis. Grazing incidence X-ray diffraction scans show the (111) plane of Ni 3Al for films grown on NaCl or Si substrates. Monte Carlo simulations of the compound target sputtering process, taking into account primary ion energy, target surface binding energy, beam-target angle and anisotropy of sputtered species, are compared with film composition as determined by INAA. Results from these measurements comprise complementary data for investigating boron distributions in the films via neutron depth profiling.