Activated Reactive Evaporation Research Articles

Activated reactive evaporation of hydrogenated amorphous silicon

Activated Reactive Evaporation (ARE) has been used to synthesize the plasma conditions present in glow discharge decomposition of silane. This allows hydrogentated amorphous silicon to be deposited at high rates (up to 0.5 um/min has been achieved). It is shown that the addition of negative r.f. bias on the substrate improves the film quality. Doping can be achieved by the addition of diborate for p-type and phosphine for n-type films.

Friction and wear properties of TiC–Al2O3 composite and Al2O3/TiC layered coatings

The measurement of wear, the coefficient of static and dynamic friction and the hardness of TiC–Al2O3, and Al2O3/TiC coatings deposited on stainless steel and TiC precoated stainless steel substrates are reported. The results of the studies are compared with similar studies on TiC coatings deposited by the activated reactive evaporation (ARE) process. It has been found that the wear in both types of TiC–Al2O3 and Al2O3/TiC coatings is a sum total of abrasive and adhesive contributions. The values of the coefficients of friction are higher compared to stainless steel TiC ARE wear couple.

Pretreatment effects on the morphology and properties of aluminum oxide thermally grown on NiCoCrAlY

This report is part of the investigation on thin film temperature sensors for turbine blade applications. The effect of pretreatments on the morphology and properties of aluminum oxide thermally grown from NiCoCrAlY was investigated. The goal was to optimize process steps to produce a highly adherent, continuous, and insulating aluminum oxide. Two pretreatments were carried out, one in vacuum (∼10−4 Torr) at 1350 K for 5 h, and the other consisting of deposition of a 1 μm thick Al2O3 film by ARE (activated reactive evaporation). Samples were subsequently oxidized thermally at 1000 °C for 50 h at 0.5 Torr oxygen pressure. The two pretreatments were carried out on electron-beam evaporation NiCoCrAlY, ∼120 μm thick, deposited on a superalloy turbine blade substrate. The results showed that the thermally grown oxide was significantly different in microstructure, surface topography and in its adherence to the NiCoCrAlY for the two pretreatments. Optimum results were obtained by combining the two pretreatments to produce an adherent, continuous, and insulating oxide film on the NiCoCrAlY coated superalloy substrate.

Temperature dependence of residual stress in TiC coated Mo

The effects of fabrication temperature and heat treatment on the residual stress in TiC coated Mo have been studied by using X-ray diffractometry. TiC coatings on Mo single crystal substrates with (100) and (111) surfaces were carried out with the Activated Reactive Evaporation (ARE) method. It was found that all Mo substrates measured show tensile residual stresses, and their values decrease as the fabrication temperature increases from 300 to 700°C. On the other hand, TiC films measured showed compressive residual stresses, for both TiC/Mo(100) and TiC/Mo(111) specimens. These compressive stresses also decreased with increasing the fabrication temperature. The residual stresses measured were higher in TiC/Mo(100) than in TiC/Mo(111). It was found that the compressive stresses in as-grown TiC films change to the tensile stresses after annaling at 1700°C for 30 min. The preferred orientations of TiC films were observed to depend on the fabrication temperature. However, no epitaxial growth of TiC films was found as far as the present experiment was concerned.

Preparation of [formula omitted] thin films by activated reactive evaporation technique

Thin films of cuprous sulphide (Cu 2S) have been deposited for the first time by a novel Activated Reactive Evaporation (ARE) technique. These films have been deposited as a function of various deposition conditions such as partial pressure of hydrogen sulphide gas, substrate temperature and copper evaporation rate. The microstructure of the films have been characterized by optical microscopy, transmission electron microscopy and electron diffraction. Electrical and optical characterization has also been carried out. Films deposited using, a H 2S partial pressure in the range from 10 −2 to 8 × 10 −4 Torr . a substrate temperature at or near room temperature and a copper evaporation rate of about 200 Å/min, were found to consist of pure chalcocite (Cu 2S). Electrical and optical measurements of the pure Cu 2S films indicated that these films were p-type with carrier concentrations of 1–7 × 10 20/ cm 3 and typical mobility values of 1–3 cm 2/V s. Mobilities as high as 8 cm 2/v s were measured on some samples. The optical determination of the band gap gave a value of E g ≈ 1.2 eV . Preliminary investigation of the Cu 2S/CdS heterojunctions were also carried out usin ARE deposited Cu 2S films on CdS films prepared by direct evaporation.

High rate deposition of hafnium nitride by activated reactive evaporation (ARE)

Cemented carbide inserts are being successfully coated with HfN using the chemical vapor deposition process. Their machining performance is much better than that of uncoated tools. To coat high speed steels with HfN at low deposition temperatures and high rates, we have to resort to physical vapor deposition processes. This paper is concerned with the synthesis of HfN by the activated reactive evaporation (ARE) process and characterization of the deposits. Hafnium was evaporated from an electron beam source in the presence of the reactive gas, nitrogen, the vapor species being activated in the ARE process. The evaporation rate of the metal, reactive gas pressure, deposition temperature and the substrate material were the experimental variables. On stainless steel and high speed steel substrates HfN could be deposited, whereas on tantalum substrates, only mixtures of hafnium, Hf 3N 2, Hf 4N 3 and HfN could be deposited. The microhardness of the deposits varied from 1850 to 2420 KHN.

Enhanced ARE apparatus and TiN synthesis

To apply the activated reactive evaporation (ARE) process to coatings for telecommunication components, the deposition rate must be less than 0.1 μm/min. To accomplish this slow rate, an electron emitting electrode was attached to the ARE apparatus. Electrons emitted from the electrode ’’enhanced’’ the ARE process. In the enhanced ARE process, the generation of plasma and evaporation of metal can be controlled independently. Therefore, the deposition rate can be controlled widely, and resistance heating and laser heating can be used for evaporation instead of electron beam heating. The enhanced ARE process was tested by synthesizing titanium nitride. Since N2 gas pressure can be varied widely in the enhanced ARE process, the chemical composition of the Ti–N films is more easily controlled than with the ARE process. Ti2N film synthesized by the enhanced ARE process showed a maximum hardness of Hv:2824 kg/mm2.

An auger analysis of substrate-layer interactions in the chemical vapor deposition and activated reactive evaporation of TiC

A formalism for quantitative Auger analysis is developed to account for “matrix effects” and peak shape changes in WCTiCTa(Nb)CCo materials by including shape factors and a linear term in the inverse sensitivity factors of carbide single crystals and binary carbide alloys. Atomic concentration profiles are then obtained for carbon, titanium, W+Ta(Nb) and cobalt across the interface between WCTiC Ta(Nb)CCo substrates and TiC coatings deposited by chemical vapor deposition (CVD) and activated reactive evaporation (ARE). Phase compositions of the near- surface region of the substrate estimated from the atomic concentrations indicate that the concentration of carbon dissolved in the binder phase drops from approximately 28 at.% prior to deposition to approximately 10 at.% after the deposition by both processes of TiC coatings about 5 μm thick. The amount of binder phase near the CVD substrate surface was found to be approximately twice as great as that near the ARE substrate surface, probably because of significant transport of cobalt at the higher temperatures used for CVD.

Synthesis of TiC–Ni cermets by the activated reactive evaporation process

This investigation is concerned with the deposition of TiC–Ni cermets using the activated reactive evaporation (ARE) process. A Ti–10 Ni alloy rod was evaporated from an electron beam source in the presence of acetylene (C2H2), the vapor species being activated or partially ionized using the ARE proc microhardness, x-ray fluorescence, x-ray imaging for different elements on an electron microprobe analyzer, optical microscopy, and electron microscopy. It has been shown that TiC–Ni cermets can be deposited by the ARE technique, and they are quite hard. When the deposition was made on Ta substrates at high temperatures, it was observed that Ni diffuses into Ta and forms an intermetallic phase near the interface between the substrate and the deposit.

Synthesis and characterization of yttrium oxide (Y2O3) deposits

The synthesis of yttrium oxide (Y2O3) was accomplished by evaporating elemental yttrium in the presence of oxygen. High-rate physical vapor deposition was employed using both the reactive evaporation (RE) and activated reactive evaporation (ARE) processes. The ARE process resulted in a higher Y2O3/Y ratio for two reasons—more complete reaction and fewer globules of Y being ejected from the molten pool and landing on the deposit surface. The microstructure and mechanical properties of the deposit produced varied with the deposition temperature in accordance with the structural zone model of Movchan and Demchishin. Over a deposition temperature range of 121° to 721 °C, the surface energy, as determined by Hertzian fracture, varied from 645 erg/cm2 to 515 erg/cm2, and the microhardness varied from 320 kg/mm2 to 502 kg/mm2.

Synthesis of dispersion-strengthened alloys by the activated reactive evaporation process from a single rod-fed electron beam source

Oxide-dispersion-strengthened alloys have better high-temperature properties but poorer low-temperature strength compared to Ni-base super alloys. Relative to these alloys, dispersion-strengthened alloys of titanium carbide dispersed in a Ni-base alloy matrix have been found to have good low- as well as high-temperature strength. This investigation was concerned with the synthesis of dispersion-strengthened alloys of TiC particles in a Ni matrix using the activated reactive evaporation (ARE) process. A Ni–Ti alloy rod was evaporated from an electron beam source in the presence of C2H2, all of the vapor species being activated or partially ionized using the ARE process. The deposits were characterized by x-ray diffraction, electron microprobe analysis, microhardness, and transmission electron miscroscopy of carbon replicas. It was established that Ni–TiC dispersion-strengthened alloys were produced by ARE process. The microhardness of the alloys decreased when annealed at high temperatures due to particle coarsening.

Synthesis of various oxides in the Ti−O system by reactive evaporation and activated reactive evaporation techniques

Many metal−gas systems exhibit several equilibrium compound phases of significantly different properties. The Ti−O system has the compounds TiO, Ti2O3, Ti3O5, and TiO2. Some of these exhibit phase transformations with change in temperature. This investigation deals with the synthesis and high rate deposition of these compounds using the reactive evaporation (RE) and activated reactive evaporation (ARE) processes. Ti is evaporated from a rod−fed eb source in the presence of a partial pressure of O2. Both the metal and gas atoms are activated or partially ionized. It was found that the various oxides are synthesized and deposited as predicted by the equilibrium diagram with the higher oxides produced with increasing partial pressures of oxygen. Higher oxides were produced with the ARE process than with the RE process at a constant oxygen pressure, thus demonstrating the higher efficiency of the ARE process. It was also shown that the TiO2 (rutile phase) can be deposited at temperatures as low as 450°C.