Reactive Evaporation Process Research Articles

The synthesis of cubic BN films using a hot cathode plasma discharge in a parallel magnetic field

A method of synthesizing cubic boron nitride (c-BN) films by the activated reactive evaporation process was investigated. A special feature of the gas activation process is that a hot cathode plasma discharge in a parallel magnetic field is used. A conventional type of ion plating apparatus, with an electron beam gun for the evaporation of boron, was used to synthesize c-BN films on a single-crystal silicon plate. A stoichiometric boron nitride film was obtained by reacting boron vapour with high density nitrogen ions, prepared using a hot cathode plasma discharge in a parallel magnetic field around the substrate. Argon gas was mixed with the reactant nitrogen gas to enhance BN formation. An r.f. bias potential was applied to the substrate in order to obtain the cubic BN phase. The optimum value of the total gas pressure in the evaporation chamber was in the range 2.6 × 10 -2-1.1 × 10 -1 Pa. The structures of the films obtained were characterized using IR absorption spectroscopy and X-ray diffraction analysis.

Corrosion properties of TiC films prepared by activated reactive evaporation

Potentiodynamic measurements were used to test the corrosion properties of titanium carbide (TiC) films. The films were deposited by the activated reactive evaporation process which consists of electron beam evaporating titanium at a rate of 0.22 g min -1 in the presence of a d.c. discharge of C 2H 2. Pressure was maintained at 1 × 10 -3 Torr during deposition. The films were deposited onto quartz substrates held at 400 °C. By growing films on an insulating substrate the inherent corrosion properties of TiC films without any substrate contribution can be evaluated. The thickness and grain size of the films, which had a slight (111) texture, were 4 μm and 2 - 3 μm respectively. The TiC films were highly corrosion resistant. Activity in the polarization curve was obtained only in a strong electrolyte (1 M HCl). Neither sulphuric nor perchloric acid could activate the film. The passivation potential and critical current density (current density at the passivation potential) in 1 M HCl were 710 mV ( vs. the saturated calomel electrode (SCE)) and 60 μA cm -2 respectively. The passive potential and passive current density were 900 mV (SCE) and 20 μA cm -2 respectively. The passive potential range was 900 mV up to at least 6000 mV (SCE). The oxygen overpotential was high (more than 5000 mV) for the TiC film and comparable with that for titanium.

Optical properties of activated reactive evaporated TiO 2 films

This paper discusses the optical properties of single-layer TiO 2 films deposited using an activated reactive evaporation process. The combined effects of substrate temperature (in the range 70–200 °C) and discharge currents (0–400 mA) on refractive index, extinction coefficient and packing density of these films are investigated. Significant changes in refractive index values have been observed with increases in substrate temperature and discharge current. The change in refractive index is correlated with the variation in packing density. The variation in extinction coefficient was reduced using the combined effects of substrate temperature and discharge currents. A comparison with films deposited in neutral oxygen has also been made.

傾斜組成制御によるｃ‐ＢＮ薄膜付着力の向上

The authors have investigated that a cubic boron nitride (c-BN) film with stoichiometric composition can be synthesized on a Si wafer by the use of hot cathode plasma discharged within a parallel magnetic field in an activated reactive evaporation process. The c-BN film prepared by this method, however, initially did not show good adhesion because of the internal stress within the film. Thus, in an effort to obtain good adhesion of the film, the effect of gradual control in N content across the film thickness on the adhesion was examined in expectation that the internal stress can be reduced. The results show that it is possible to deposit, with good adhesion, a c-BN film onto a Si wafer by providing a multilayer film structure, i.e., the one comprising a thin B layer, a gradually controlled BN one and a c-BN one.

Investigation of the evaporation process conditions on the optical constants of zirconia films

Deposition parameters required for producing zirconia films for use in optical multilayer systems by electronbeam gun evaporation of zirconia and zirconium starting materials were investigated. The optical constants were determined as a function of distance, partial pressure of oxygen, and angle of incidence. The direct and reactive evaporation processes yielded ZrO(2) films with refractive indices of 2.08 and 2.14, respectively, for vapor incident on the substrate at normal incidence.

Superconducting films grown i n s i t u by the activated reactive evaporation process

The low-pressure activated reactive evaporation process was used successfully to grow superconducting thin films that were uniform in thickness, free of cracks, voids, spits, and other source-related defects, and with mirror-like surface smoothness. These are important considerations for the practical use of these materials in thin-film form. No post-deposition annealing was carried out. Tc (0) for films on yttria-stabilized zirconia (YSZ) substrates is close to 80 K, and the (001) preferred orientation was observed with higher deposition temperatures in the range 550–650 °C. Films on silicon and sapphire substrates were adversely affected by interdiffusion, showing a Tc (0) of 56 and 72 K, respectively.

Fabrication of devices using vacuum deposited a–Si

The long-term objective of this work is to produce a stable, efficient amorphous Si (a-Si) solar cell by a safe and inexpensive method. A process of reactive evaporation in a silane ambient was developed. This technique permits the fabrication of "intrinsic-like" a-Si:H. p-Type and n-type samples (carrier type was confirmed by Seebeck measurements) were prepared by the coevaporation of boron or reactive evaporation in a phosphorus ambient. The intrinsic-like samples have a room temperature conductivity of about 2 × 10−12 S cm−1, high temperature activation energies of 0.9 eV, and optical bandgaps near 1.8 eV. An all-amorphous Si:H pin diode was fabricated using this reactive evaporation process. The device consists of a tantalum contact, 20 – 40 nm of phosphorus doped a-Si:H, 300 – 400 nm of undoped a-Si:H, 20 – 40 nm of boron doped a-Si:H, and another tantalum contact.

YBa/sub 2/Cu/sub 3/O/sub 7/ thin films grown by high pressure reactive evaporation and high pressure reactive sputtering

A high-pressure reactive evaporation process and a high-pressure reactive sputtering process have been developed for the growth of high-quality thin films of YBa/sub 2/Cu/sub 3/O/sub 7/. Both techniques, when used with heated substrates, are effective in the formation of the 123 phase in situ during the film growth. With reactive evaporation only a cooldown anneal in a higher-pressure oxygen ambient is necessary to obtain good superconducting properties. For the reactive sputtering process, a brief, postgrowth, rapid thermal anneal step is required for best results. Fully epitaxial growth has been achieved with single-crystal MgO substrates. The resultant films, which can be quite smooth and uniform, have been patterned to micron and submicron dimensions, and the transport properties of these microstructures have been examined. >

Auger electron spectroscopy and Rutherford backscattering spectroscopy studies of TiN and TiC coatings prepared by the activated reactive evaporation process

Auger electron spectroscopy and Rutherford backscattering spectroscopy studies of TiN and TiC coatings prepared by the activated reactive evaporation process

Plasma diagnostic studies of the activated reactive evaporation process

Plasma volume reactions play an important role in the deposition of films by plasma-assisted processes. We have applied several techniques to the analysis of the plasma volume in the activated reactive evaporation process. Neutral mass spectrometry, plasma mass spectrometry and optical emission spectroscopy (OES) were used to examine the nature and relative concentrations of neutral, excited neutral and ionized species present in the process.Initial experiments involved evaporating titanium in the presence of CH4 and C2H2 gases. Results of plasma mass spectrometry and OES indicate several differences between the species observed depending on the reactive gas used and the evaporation rate used. These results have been used to explain possible reaction paths for TiC compound formation as well as to correlate the dependence of film properties on the deposition conditions.

Production of YBa2Cu3O7−y superconducting thin films i n s i t u by high-pressure reactive evaporation and rapid thermal annealing

A high-pressure reactive evaporation process has been used to produce smooth YBa2Cu3O7−y high Tc superconducting films without the necessity of a post-deposition oven anneal cycle. Augmented in some cases by rapid thermal annealing, the process has yielded films with zero resistance transition temperatures above 80 K, and critical current densities above 106 A/cm2 at 4.2 K on both cubic zirconia and SrTiO3 substrates.

Auger electron spectroscopy and Rutherford backscattering spectroscopy studies of TiN and TiC coatings prepared by the activated reactive evaporation process

TiN x and TiC x films were deposited by the activated reactive evaporation process under different process conditions. The films were studied by Auger electron spectroscopy and Rutherford backscattering spectroscopy (RBS); standards were used for both techniques. The RBS techniques showed low sensitivity to carbon and nitrogen when 1.8 MeV He + ions were used. The sensitivity was enhanced by using 1.5 MeV H + ions, but the resulting non-Rutherford scattering necessitated the use of standards although RBS is potentially a standardless method. A correlation was found between the chemical composition of TiN x and TiC x films and the partial pressures of N 2 and C 2H 2 respectively.

Detailed characterization of TiC and TiN coatings prepared by the activated reactive evaporation process

The objective is to investigate the relationship between the composition, microstructure, and microhardness of TiC and TiN coatings prepared over a range of process parameters using the activated reactive evaporation process. The composition was measured by Auger electron spectroscopy. The phase relationships and preferred orientation were obtained by x-ray diffraction analysis. Microhardness and adhesion of the coatings were measured. The results show that the microhardness depends on the composition/stoichiometry, phases present, the preferred orientation, and possibly the grain size in the case of single-phase coatings.

In-Situ Production of Superconducting YBa2Cu3O7-y Thin Films by High Pressure Reactive Evaporation with Rapid Thermal Annealing

ABSTRACTA high pressure reactive evaporation process has been established that can produce highly oriented YBa2Cu3O7-y high Tc films without the necessity of an extended post-deposition oven anneal cycle. The process is based on the electron beam co-evaporation of the metals Y, Ba and Cu onto heated (600–750 C) substrates in an oxygen partial pressure of 10-3 Torr. In general the films are superconducting when examined directly after termination of the growth process. However a brief rapid thermal anneal step in oxygen, which can be done either in-situ in the growth chamber or elsewhere, is often effective in further improving the superconducting transition. Highly oriented film growth has been obtained on both strontium titanate and yttria-stabilized cubic zirconia substrates. The best films that have been produced thus far with this technique on the cubic zirconia substrates have Tc (zero resistance) = 83 K, transition width ΔTc = 2 K, and room temperature resistivity (ρRT) = 0.5 mQ-cm. Similar results, with somewhat higher values of Tc, have been obtained on SrTiO3. On both substrates the critical current density at 4.2 K is in excess of 106 A/cm2.

Highly conducting transparent undoped indium oxide films deposited below 100°C by activated reactive evaporation

Highly transparent and conducting undoped indium oxide films have been obtained with a resistivity of ≈;4 × 10−1 Ωcm, a carrier density of ≈; × 1020 cm−3 and a mobility of ≈;18 cm2 V−1−1 at a substrate temperature <70° C and a deposition rate of ≈;8 A/s by an activated reactive evaporation process. The stability of electrical and optical properties at room temperature in the open air is reasonable for a film optimized for conductivity. The optical bandgap of these films is ≈;3.3 eV, lower than that of a high temperature deposited tin doped indium oxide film. It is found that undoped indium oxide films with the best conductivity cannot be obtained if a threshold temperature of ≈;200° C is exceeded either during deposition or during post deposition vacuum anneals. However, highly conductive tin doped indium oxide can be easily obtained at high temperature (T ≈; 400° C) by activated reactive evaporation. It is also noted that highly conductive tin doped indium oxide films are more difficult to make at the lower end of the temperature range unless certain precautions are taken.

Transport properties of thin film TiS 2 produced by are

Titanium disulfide has been made by the Activated Reactive Evaporation process. Its electrical conductivity and electrochemical behavior are similar to that of bulk TiS 2, but its lithium diffusivity is lower and depends on the lithium content of the cathode.

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.

Effect of gas species and partial pressure on chromium thin film adhesion

Vacuum evaporated chromium thin films on glass substrates were evaluated for adhesion by the scratch test as a function of partial pressures of Ar, H2, CH4, O2, CO, and CO2 deliberately introduced during chromium deposition. Partial pressures examined ranged from 0.67 to 13.3 mPa. Initial adhesion results suggest a reactive evaporation process of chromium with O2, CO, and CO2 backfills and are in agreement with the theory of an oxide layer formation causing increased initial adhesion. Gas/chromium atom impingement ratios corresponding to noticeably improved adhesion are reported. Time dependent adhesion results reveal a distinction in adhesion behavior between films deposited in O2, CO, and CO2 backfills and those deposited in Ar, CH4, and H2 backfills. Possible mechanisms for this behavior are discussed.

Residual stress in coated low-Z films of TiC and TiN: III. PVD coated films

Physical vapor deposition (PVD) is an attractive method of in-situ deposition for future controlled nuclear fusion reactors since it can prepare various low-Z ceramic films at much lower deposition temperatures. This paper is concerned with the properties of a titanium carbide coating on molybdenum by the activated reactive evaporation process (ARE), a technique known as PVD. Residual stress in films which might affect the adherence of the film were examined with particular reference to the deposition temperature. All films prepared in this study were found to have a compressive stress and its value decreased from 4.76 × 10 10 to 6.77 × 10 9 dyn/cm 2 as the deposition temperature was raised from 300 to 700°C. A discussion was given on the relatively high value of stress measured in PVD-TiC coatings. Problems in applying a PVD to the in-situ coating technique were also discussed.

Improvement in tool life of coated high speed steel drills using the activated reactive evaporation process

Type M-10 high speed steel drills of diameter 0.25 in were coated with TiC and TiN using the activated reactive evaporation process. The coated drills were tested by drilling holes into plates of AISI 4150 steel of thickness 1 in at a hardness level of 300 HB. The speed used was 900 rev min -1 and the feed rate was 0.007 in rev -1. For comparison, uncoated and the standard black-oxide-coated drills were also tested using the same conditions. The average number of holes to failure was seven for uncoated drills, 33 for black-oxide-coated drills and 141 for the TiC- and TiN- coated drills. These results show that the TiC- and TiN-coated drills have tool lives of 20 times that of uncoated drills and 4.2 times that of black-oxide-coated drills under these test conditions. Torque and thrust measurements were made during the drilling test of same steel plates at 770 rev min -1 and a feed rate of 0.008 in rev -1 at Lockheed Company of California, Burbank. The TiC- and TiN-coated drills showed 15%-18% less thrust, 10%-23% less torque and eight to ten times the tool life of uncoated drills under these conditions. They also showed 15%-18% less thrust and 2.5 to three times the tool life in relation to the black-oxide-coated drills.