Ti Metal Target Research Articles

Microstructruture of Heteroepitaxially Grown TiO2 Films by Magnetron Sputtering

ABSTRACTTitanium dioxide (TiO2) films were deposited on (a) non-alkali glass, (b) MgO (100) and (c) SrTiO3 (100) single crystals by rf reactive magnetron sputtering using a Ti metal target. X-ray diffraction and a pole figure analysis revealed that TiO2 films on the (a) were anatase polycrystals with <101> preferred orientation, whereas heteroepitaxial growth of anatase TiO2 was observed on the (b) and the (c) substrates. FE-SEM analyses on the crystal habit of the firm surfaces showed that the substrate temperature during the deposition (Ts) heavily affected the microstructure and surface morphology of the heteroepitaxially grown films, which could be clearly explained in terms of “Thornton's zone model” or “epitaxial growth model of 2-dimensional ledge or kink modes” considering the normalized Ts by the phase transition temperature from anatase to rutile.

Adhesion and hardness of compositionally gradient TiO2/Ti/TiN, ZrO2/Zr/ZrN, and TiO2/Ti/Zr/ZrN coatings

A technique using compositionally gradient interlayers has been applied to TiO2/Ti/TiN, ZrO2/Zr/ZrN, and TiO2/Ti/Zr/ZrN multi-compositional coatings to enhance the adhesion of hard coatings to substrate. The coatings were prepared by dc reactive magnetron sputtering using a combination of a Zr or a Ti metal target and a pure Ar, an Ar-O2 mixture, or an Ar-N2 mixture discharge gas, onto a borosilicate glass substrate. Adhesion of coatings to the substrate was estimated by a scratch method. The hardness of coatings was measured by a nano-indentation method. Without an interface, ZrN coatings showed a very poor adhesion. By using glass/ZrO2/Zr or glass/TiO2/Ti compositionally gradient interface layers, the adhesion strength of ZrN coatings was enhanced to the adhesion strength almost equal to or higher than those of TiO2 or ZrO2 single layer coatings. From the results of internal stress evaluation, it was found that a high internal stress causes a poor adhesion of ZrN coatings. Hardness of coatings with a ZrN overlayer were 20 to 35 GPa and larger than those of coatings with a TiN overlayer. The increase in the hardness by inserting a compositionally gradient interface was observed in ZrO2/Zr/ZrN and TiO2/Ti/Zr/ZrN systems.

Synthesis and characterization of highly textured polycrystalline AlN/TiN superlattice coatings

AlN/TiN multilayer coatings were synthesized by sputtering Al and Ti metal targets simultaneously in an Ar+N2 plasma using a dual-cathode unbalanced dc magnetron sputtering system. Two different power sources, rf and pulsed-dc, were employed for substrate bias. It was found that under a critical thickness for the AlN layer, the AlN/TiN coating with the AlN layers below a critical thickness exhibit a highly textured [111]-oriented superlattice structure. However, the rf-biased films have poor mechanical properties. Transmission electron microscopy (TEM) studies of the rf-biased films show columnar structure of large grains with weak links (amorphous-like material) between different columnar grains. In the pulsed-dc-biased films, however, we noticed a twofold increase in hardness, when the bilayer thickness is under ∼5 nm. The increase of the hardness coincides with the structure phase transition from a randomly oriented polycrystalline AlN/TiN thin film to a highly [111]-textured AlN/TiN thin film. X-ray diffraction and TEM studies indicate that in the highly [111]-textured multilayer films, AlN is in a nanostabilized cubic form. The critical thickness for AlN to form a nanostabilized cubic structure along [111] is less than about 2.5 nm. TEM studies on the highly textured films deposited with pulsed-dc bias showed a coherent growth of an AlN/TiN layered structure across the film and highly dense grain boundaries, which was achieved by using the low-energy ion bombardment induced by the pulsed-dc bias. The high hardness value of the coating with small bilayer thickness deposited with pulsed-dc bias is not only due to the formation of the nanometer-scale multilayer structure and nanometer-stabilized cubic form of AlN, but also due to the strongly bonded high-angle grain boundaries between different columnar grains.

Hardness enhancement by compositionally modulated structure of Ti/TiN multilayer films

In this article results of an investigation into effects of multilayer structures of compositionally modulated Ti/TiN films on their hardness is presented. Compositionally modulated Ti/TiN multilayer films were deposited onto borosilicate glass substrates by a reactive gas flow rate modulation magnetron sputtering method using a combination of a Ti metal target and an Ar–N2 mixture discharge gas. In this method, a N2 gas flow rate was changed by a computer-controlled mass flow controller to produce films with a varying composition distribution. The film hardness was measured by nanoindentation. The film composition depth profiles were estimated by Auger electron spectroscopy and x-ray photoelectron spectroscopy. A TiN single layer film was also deposited to compare its hardness with those of the Ti/TiN multilayer films. Modulation periods examined in this study were 10, 15, 20, and 40 nm. It was found that the film with a modulation period of 20 nm showed a maximum hardness of 29 GPa and that the films with modulation periods of 15 and 40 nm yielded a higher hardness value than that of the single layer TiN film of 15 GPa. The results obtained in this study indicate that the hardness of compositionally modulated Ti/TiN multilayer films strongly depend on modulation frequency.

Preparation and Properties of (Pb, Ca)TiO3 Thin Films by Multiple-Cathode Sputtering

(Pb, Ca)TiO3 (PCT) thin films were fabricated by multiple-cathode RF-magnetron sputtering, using PbO, CaTiO3 and Ti metal targets. PCT films deposited on Pt/Ti/SiO2/Si and Pt/MgO at the substrate temperature from 460° C to 540° C had perovskite structures. The relationship between the substrate temperature and the film properties were investigated. The remanent polarization, dielectric constant and leakage current of the 200-nm-thick PCT(Ca/Ti=0.30) thin films deposited on Pt/Ti/SiO2/Si at 460° C and on Pt/MgO at 500° C were 22.5 µ C/cm2 225 and on the order of 10-7 A/cm2 (at a field of 250 kV/cm), 41 µ C/cm2, 174 and on the order of 10-7 A/cm2 (at a field of 250 kV/cm), respectively.

MODELLING OF MULTI-ION-BEAM REACTIVE COSPUTTERING OF METAL OXIDE THIN FILMS (Ⅱ)——NUMERICAL CALCULATION AND RESULTS DISCUSSION

The numerical calculation for the model of a multi-ion-beam reactive cosputtering (MI-BRECS) system which we presented very recently in a related paper has been carried out with the parameters adopted in our experiments to prepare PbTiO3 thin films by using Pb and Ti metal targets and MIBRECS technique. The relationships among the sputtered ratio Ri of each target, the partial pressure p of reactive gas in the deposition chamber, and the coverage ratioes Zsmi, Zsli, and Zshi of the simple substances and oxide compounds of Pb and Ti on the substrate surface, with the total reactive gas flux Q and the densities Ji of the sputtering ion beam (both of which can be adjusted independently) are obtained respectively. The calculated results reveal the hysteresis effect which is an essential characteristics in a reactive sputtering, and show that there is a coupling and interaction among the processing parameters in ion beam reactive cosputtering. The relations among the atom ratio and the chemical valences of the elements in prepared thin films with the controllable processing parameters in ion beam reactive cosputtering are obtained, and the method to control and adjust a MIBRECS system for stable reactive cosputtering process is pointed out. The obtained results a-gree with our experiments.

Matrix effects of secondary neutrals: Laser postionization investigations of particles sputtered from clean and oxidized metals.

The striking discrepancy between yields of secondary neutral metal atoms previously observed using nonresonant multiphoton ionization of the sputtered secondary flux and laser-induced fluorescence can be explained by performing measurements using resonant postionization of the secondary atoms. The secondary flux from Ti and Cr metal targets under ion-beam bombardment has been investigated for increasing oxygen partial background pressure from ${10}^{\mathrm{\ensuremath{-}}10}$ up to ${10}^{\mathrm{\ensuremath{-}}6}$ mbar. The existence of matrix effects for sputtered neutrals has been verified.

Pressure Dependence of C–V Curve for Ferroelectric PbTiO3 Thin Films Prepared by RF Multi‐target Magnetron Sputtering

AbstractLead titanate thin films were prepared in‐situ by RF magnetron sputtering method in the substrate temperature region of 550 °C ˜ 650 °C using Ti and Pb metal targets and oxygen gas. The films deposited at 650 °C for 60 min – when the applied power to the Ti and Pb target and deposition pressure were 200 W, 40 W, and 1.8 × 10−2 Torr, respectively — had stoichiometric composition ratio and shown X‐ray diffraction patterns of tetragonal structure like that of the powder.For the application to the piezoelectric field effect transistor (PI‐FET), the substrate of SiO2 (50 nm)/p‐Si(100) was used. Leakage current density of the thin film was 7 × 10−8 A/cm2 at 100 kV/cm, dielectric breakdown voltage was 1.8 MV/cm, and so it showed high insulator characteristics. Capacitance‐voltage curve was measured as a function of pressure. The variation width of the capacitance was 6.5 pF at bias voltage of –4 volts, and the value increased linearly according to the pressure up to about 6 kgf/cm2, and was saturated at the pressure of 8 kgf/cm2.

Electrical properties of strontium titanate thin films by multi-ion-beam reactive sputtering technique

Thin films of SrTiO3 were deposited by multi-ion-beam reactive sputtering technique using SrO and Ti-metal targets. The dielectric behavior of the films deposited on Pt-coated Si substrates showed thickness dependence. A dielectric constant of 219 at 100 KHz was found for 1.2 μm thick films. A charge storage density of about 15 fC/μm2 and leakage current density of 106 μA/cm2 at an electric field of 0.17 MV/cm were obtained for 0.3 μm films. The probable interface layers present between film and silicon substrate, in the case of metal-insulator-silicon configuration, appear to influence the electrical behavior. Preliminary analysis showed that the conduction of the films in high field region was bulk-limited Poole–Frenkel emission mechanisms.