Reactive Ion Plating Research Articles

Fabrication of electrically conductive metal oxide coatings by reactive ion plating

Electrically conductive metal oxide (ceramic) coatings produced by reactive ion plating are being investigated at USA-CERL for potential application in cathodic protection systems. Ceramic materials are advantageous because of their very low dissolution rates (typically less than 1 g/A/yr in 3.5% NaCl solution) and ease of fabrication. Among the ceramic anode materials currently under investigation are two systems: (1) a mixture of titanium oxide and ruthenium oxide and (2) a mixture of titanium oxides ‘‘doped’’ with niobium, each ion plated on niobium substrates. The mixed oxide coatings were fabricated by a reactive ion plating process involving oxygen and dual electron beam evaporation sources. An enhanced plasma was used to increase reactivity. X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy have been used for characterization of the microstructure, crystallography, and elemental composition of the coating.

Oscillator strength of small-polaron absorption in WOx (x≤3) electrochromic thin films

The oscillator strength of small-polaron absorption is studied for various thin films of tungsten oxide, WOx (x≤3), prepared by rf reactive magnetron sputtering, reactive ion plating, and vacuum evaporation. The oscillator strength greatly varies depending on the procedure of film preparation and treatment. For WOx films prepared by vacuum evaporation, the effective oscillator strength decreases down to 0.04 by annealing in air at 200 °C and increases up to 0.24 by annealing in air at 400 °C. The film deposited by reactive ion plating at an rf power of 300 W exhibits a large effective oscillator strength of 0.31. Concerning the film prepared by rf reactive magnetron sputtering, the oscillator strength drastically increases with an increase in rf power. For the film deposited at an rf power of 1000 W, an effective oscillator strength of 0.51 is obtained, which is five times greater than that of the film prepared by vacuum evaporation. X-ray diffraction and XPS measurements reveal that the oscillator strength is affected by the two factors, that is, crystallinity and oxygen content of the film. It is concluded that the enhancement of oscillator strength occurs through crystallization of the film from its amorphous state and a lack of oxygen in the film. Using a configuration coordinate diagram, the mechanism of the oscillator strength enhancement is discussed in terms of a delocalization of polaron wave function.

Structural Investigation of Ti-N Films

ABSTRACTTi-N films were deposited by reactive ion plating on various substrates. The N/Ti-ratio was systematically varied in order to produce films of varying structure and properties from pure titanium to overstoichiometric TiN. Broad diffraction peaks typical of PVD Ti-N films were found. Metastable ct-titanium was observed over a wide range up to about 50 at. % N. No marked differences in the phase composition or in the crystallographic texture could be found in the films deposited on the various substrates. The hardness of the films was observed to increase with increasing nitrogen content, reaching a maximum around 35 – 40 at. % N corresponding to a mixed ε-Ti2N and δ-TiN structure. Extended annealing at 773 K did not result in any major phase transformations. After annealing at 1173 K, α-Ti could no longer be found in nitrogen-rich films. Also ε-Ti2 N transformed to δ-TiN after annealing at 1173 K for 2 h.

Deposition of transparent conducting indium tin oxide thin films by reactive ion plating

The deposition of transparent conducting indium tin oxide thin films by reactive ion plating is described. The films were prepared by evaporating indium and tin from a resistance-heated vapour source in an oxygen atmosphere. The glass substrates were heated in situ during the deposition. Electrical resistivities of 2 × 10 -4 ω cm were obtained, and the average visible transmittance was 85% with values in excess of 90% being achieved at a wavelength of 0.50 μm.

Reactive ion plating of TiO 2

TiO 2 films have been produced from a variety of sources utilising various ion assisted techniques to provide surface energy. It was found that reactive rf bias ion plating using electron beam evaporated titanium metal could give films of refractive index of close to 2.5 and equivalent to those made by conventional reactive evaporation onto substrates at elevated temperatures. Neutralised ion beam and oxygen plasma guns were not so successful, as was the use of sources of TiO 2 and TiO. Reactive planar magnetron sputtering of titanium metal could be equally successful if the source was operated in the metal sputtering mode, this could be achieved with sufficient stability with the use of a pulsed flow of the oxy gen supply.

反応性イオンプレーティング法による炭化チタン皮膜の性質

Film characteristics-film composition, orientation, resistance, etc.-depend on the reaction condition of the reactive ion plating of TiC using CH4 and C2H2 gases as reactants with partially ionized Ti vapor. TiC film plated on steel substrate had a high Hv hardness of 3200Hv at C2H2 gas partial pressure of 0.13Pa, bias voltage of 1kV, ionization current of 700mA, and a distance between ion source and substrate of 8cm. The temperature of the substrate influenced the hardness and phase of the TiC in the film produced by ion plating using CH4 gas as a reactant. The phase of the TiC of the plated film using CH4 gas on the substrate increased at higher temperatures and temperatures higher than 500°C were more effective in obtaining hard TiC films.

反応性イオンプレーティングによる窒化インジウム薄膜の作製とその物性

InN, one of the less-studied III-V compound semiconductors, has pontential applications in visible-light opto-electronic devices and high-efficiency solar cells because of its direct energy gap of 1.9eV. InN polycrys talline films were synthesized by rf reactive ion plating; indium was evaporated in a nitrogen rf glow discharge. The plasma process using rf glow discharge resulted in the low-temperature synthesis of InN. Gas pressure and rf power greatly affected the preparation of the InN films, which were successfully prepared at a pressure of 13Pa and rf power of 100W. The deposition rate was 10-20nm/min. The film structure was evaluated by X-ray diffraction, RHEED and TED, and the oriented growth of the InN films was observed. InN single crystals were also observed on NaCl (100) surfaces. The chemical composition was determined by AES. The electrical, optical, chemical and electrochemical properties of the InN films prepared were also investigated. InN films showed n-type conduction and a dark red color. The InN film was found to show the electrochromic effect. The metal-nitride semiconductor has joined the group of electrochromic materials. The InN film electrode showed the particular photoelectrochemical behavior. Therefore, InN is a material of great interest.

Dielectric and AC conduction properties of ion plated aluminium nitride thin films

Aluminium nitride thin films were deposited by a reactive ion plating technique in a vacuum of 3*10-3 Torr. The composition of the film was analysed by IR spectrum. Thin film capacitors were formed as an Al-aluminium nitride-Al structure. The annealing characteristics of these structures have been studied at 420K. The frequency and temperature dependence of capacitance and tan delta have been studied in the audio frequency range 500 Hz-30 kHz and the results have been discussed. The dependence of AC conduction on frequency has been explained on the basis of the hopping conduction mechanism.

Adhesion studies of ion-plated TiN on steel

Abstract A previous study has shown that the scratch test for the measurement of adhesion can be used to assess the load-bearing capacity of a hard coating/steel substrate composite material. In the present work we extend the previous study to include TiN coated onto three types of steel by reactive ion plating. The mode of coating removal is studied and the critical load for the onset of removal is measured. The results are interpreted as showing that the load-bearing capacity varies with the coating thickness for a given steel substrate. Comparison with previous work indicates that the load-bearing capacity (adhesion) of the present samples corresponds well to that of the previously studied chemically vapour-deposited coatings.

Deposition of conducting and transparent thin films of indium tin oxide by reactive ion plating

Transparent and conductive films of indium tin oxide on glass substrates were obtained by reactive ion plating. The indium and tin were separately evaporated in oxygen from a resistance-heated vapour source. In this way we were able to modify the proportions of indium and tin contained in the films. These proportions were indirectly determined by controlling the rate of evaporation of these two metals by spectroscopic analysis of the light emitted in the discharge. The substrates were heated in situ during the deposition cycle, and thus all annealing was avoided. The growth rates of the films were between 4 and 6 μm h -1. The electrical resistivity was 10 -5 Ωm. The transparency of a film 0.5 μm thick was greater than 85% in the visible region.

Sputtering of silicon carbide coatings by low-energy hydrogen ions

Abstract Various types of silicon carbide coatings made by reactive ion-plating have been bombarded with a 3.0 keV H+3 ion beam at temperatures around 500°C. The sputtering yield in stoichiometric samples (i.e. Si : C = 1 : 1) at 500°C was 1.15 × 10 −2 atoms/H+. As the stoichiometry deviates from this point, the sputtering yield has larger values. The temperature dependence of the sputtering yield in stoichiometric samples was negligible below 600°C. No surface topography changes occurred in stoichiometric samples even at a high fluence of 2 × 10 20 H + /cm 2 , while severe erosion took place in non-stoichiometric samples. By Auger electron spectroscopy (AES), carbon exists on the surface in the form of carbide in stoichiometric SiC before and after bombardment, while it exists in the form of graphite in carbon rich samples, which suggests that the bound state of carbon in the form of carbide should correspond to the low sputtering yield in stoichiometric SiC coatings. The surface stoichiometry changes due to hydrogen bombardment were observed by AES, where the carbon population increases in stoichiometric SiC, while it decreases in carbon rich samples, which was supported as well by the results from electron probe X-ray microanalysis.

Composition and conductivity of fluorine-doped conducting indium oxide films prepared by reactive ion plating

Fluorine-doped transparent conducting oxide films were produced by the reactive ion plating of indium onto glass substrates at room temperature. The electrical properties of these films depended on the content of fluorine, which was introduced into the films as a gaseous dopant from an O 2-fluorocarbon r.f. discharge. The effect of annealing the films in air was also studied in order to elucidate the mechanisms responsible for the electrical conduction. Satisfactory films were fabricated by evaporating indium from boron nitride-titanium diboride evaporation sources.

Reactive Ion Plating of Ceramic Coatings for Wear Reduction in Metal Forming

SummaryIn forming processes a major cause of die wear is abrasion. To prevent such wear the optimum solution is to use pure ceramic coatings. These can be deposited by Chemical Vapour Deposition (CVD), though that technique utilises high process temperatures which soften die steels. This paper gives details of a new method for producing ceramic coatings at comparatively low temperatures, known as reactive ion plating. The technique involves evaporating a metal, such as titanium, in a reactive gas, to produce for example titanium nitride. Information is provided about the equipment and processes used in the technique. Details are given of tests carried out on coatings, including a repeated plane strain compression test devised to assess the wear resistance in a typical industrial forming operation. Titanium nitride coatings have been produced with hardness over 2700 HV and these have been shown in tests to provide considerable protection to bulk metal forming tools.

ZnO Piezoelectric Films Formed by RF Reactive Ion Plating

Highly oriented ZnO films were synthesized successfully on glass, fused quartz, silicon and sapphire substrates with high reproducibility by RF reactive ion plating. Metal zinc was evaporated from an alumina crucible in an RF discharge of oxygen gas at a pressure of 10-4 Torr (10-2 Pa). The piezoelectrical properties of the ZnO films for the surface acoustic wave (SAW) device were evaluated by electrical measurements. The high coupling factor (k) of the ZnO films was measured at between 0.08 and 0.09. The SAW TV-PIF filters fabricated by the ion plated ZnO films were found to be excellent.

Deposition of Ti-N compounds by thermionically assisted triode reactive ion plating

Details are given of the influence of the ion current density on the properties of Ti-N compounds deposited at low temperatures (<600°C) by a thermionically assisted triode reactive ion-plating technique. As the chamber pressure increases, greater specimen currents are necessary, both to prevent the deposition of powdery TiN and also to ensure reaction for the formation of Ti 2N and TiN at lower partial pressures of nitrogen. The ionization efficiency, being related to both pressure and current density, is suggested as a suitable parameter for defining optimum conditions. An ionization efficiency of about 0.3% is identified as the minimum required for the deposition of cohesive TiN, whilst values above this improve the densification and the hardness.

Reactive ion plating (RIP) with auxiliary discharge and the influence of the deposition conditions on the formation and properties of TiN films

In this paper we attempt to analyse the processes of reactive evaporation, activated reactive evaporation and reactive ion plating on the basis of earlier theoretical studies. Our initial results concerning the dependence of phase formation on the deposition rate and working gas pressure in reactive evaporation and ion plating indicate that the proposed ideas can in principle be applied and this was also shown analytically by the dependence of the microhardness of TiN films on the pressure. At low partial pressure of nitrogen TiN x films with a stoichiometric coefficient x near unity are not formed. These near-stoichiometric films are of low hardness. The decrease of microhardness with increasing nitrogen pressure ( p 624 × 10 -2 Pa) can be explained by physical effects, such as the inclusion and scattering of gas. Initial studies on the wear properties of such films have indicated their potential in technological applications.

Formation of transparent heat mirrors by ion plating onto ambient temperature substrates

Transparent conducting oxide films were produced by the reactive ion plating of indium onto glass and plastic substrates at room temperature. The electrical properties of these films were sufficient, with high values of electrical mobility and carrier density, to give a sharp plasma reflectance edge in the near infrared. These properties are ideally suited for the production of the visibly transmitting, IR-reflecting surfaces needed for heat mirror applications. Optimum properties were achieved with careful control of the gas mixture and the amount of substrate bias acquired by the substrate from the radio frequency used for the discharge. Satisfactory films were made using evaporation or planar magnetron-sputtering sources.

Reactive ion plating of metal oxides onto insulating substrates

SnO 2 and In 2O 3 films were produced by evaporation and by magnetron sputtering of the elements in an atmosphere containing oxygen. The insulating substrate of glass or plastic was water cooled and made one electrode of an r.f. discharge in the gas. The optical and electrical properties of the films indicated that the energy of the bombarding ions, measured by the d.c. standing voltage that developed on the substrate due to r.f. discharge, gave properties that had only previously been obtained using substrate temperatures of 450°C and above. The SnO 2 films were insulating. The In 2O 3 films were conducting, a minimum value of the sheet resistivity ( 187 Ω □ being achieved with evaporated films at a bias of −400 V and a value of 630 Ω □ being obtained with sputtered films at a bias of −160 V with a 30 vol.% O 2−70 vol.% Ar gas mixture. All films were about 80 nm thick. The ultraviolet absorption edge position proved to be related to the refractive index and the conductivity. Hall effect measurements gave a carrier concentration of 4 × 10 25 m −3 with a mobility of 1.9 × 10 −3 m 2 V −1 s −1 for the best sputtered film.

Physical vapor deposition of chromium and titanium nitrides by the hollow cathode discharge process

The reactive ion plating of chromium and titanium nitrides was performed by using the hollow cathode discharge (HCD) process. The hardness of the deposit on the substrate as a function of temperature, of applied bias voltage to the substrate and of the partial pressure of nitrogen gas was investigated. A flow of 30 cm 3 (STP) min −1 of argon gas for sustaining the discharge at a level of 1.5 × 10 −3 Torr was introduced into the chamber through the electron beam gun, which was made of tantalum tubing of 4 mm inner diameter with a thickness of 0.5 mm and 80 mm in length. The rate of deposition was approximately 0.27 μm min −1 for CrN, and 0.18 μm min −1 for titanium nitrides when hydrogen was bled in. The HCD electron beam did not make a local evaporation crater in the chromium. An investigation of the deposition of chromium and titanium nitrides at a pressure of 0.1–10 m Torr was carried out. Chromium nitride deposited on a stainless steel substrate had a hardness VHN of about 2200 kg mm −2 and a dark gray color, and it did not change much with a change in substrate temperature from 300 to 500 °C and even with a change in nitrogen partial pressure from 4 × 10 −4 to 6 × 10 −3 Torr. Titanium nitride deposited on this substrate showed a pretty golden color with a hardness VHN of 2000 kg mm −2; it was readily prepared in the pressure range 0.4–2 m Torr. The deposition rate for titanium nitride was greatly improved by bleeding in hydrogen with the nitrogen and argon: it was 0.08 μm min −1 without bleeding and 0.18 μm min −1 with hydrogen.

Silicon Nitride Coatings on Molybdenum by RF Reactive Ion Plating

Rf reactive ion plating technique has been applied to the preparation of protective silicon nitride coating on molybdenum. All the deposits prepared at deposition temperature of less than 1000°C were amorphous. Silicon in deposits was found to be present as nitride by Auger electron spectroscopic, infrared absorption spectroscopic, and x‐ray diffraction analyses. Nearly stoichiometric silicon nitride deposits were obtained at a deposition rate of as high as 1 μm/min. Several factors affecting the stoichiometry of the silicon nitride were discussed. Oxidation test of the coated specimens showed that the silicon nitride layer obtained under optimum conditions protected the molybdenum substrate from oxidation in Ar‐1% gas mixtures up to approximately 1200°C. Typical pitting corrosion was observed in the coating film at the higher temperatures.