Many thermal control applications require thin film coatings that emit or absorb strongly at near infrared and infrared wavelengths. One of the primary applications for these coatings is thermal control for surfaces and structures of spacecraft, which are exposed to solar radiation during at least 60% of their orbit, causing wide temperature fluctuations. Another recent application for this type of coating is infrared emissive imaging employing a fiber optic infrared scene projector. While single layer coatings can provide high emissivity in a broad wavelength band, multilayer coatings can be used to obtain higher emissivities over a narrow wavelength band. This band can be tuned to a specific range of temperatures and wavelengths. Coatings developed for thermal control have a reflective base layer, either ZrN or a refractory metal boride or silicide. These materials have increased durability compared to metal layers. The multilayer coating deposited over the based layer consists of an A1203/SiO2 stack with high emittance at 300 K (9.8 μm), and solar reflectance near 0.6. Multilayer tuned infrared absorber/emitter coatings are applied to fiber optic infrared scene projectors. The coatings consists of a three layer Si3N4/Cr/Si3N4 absorber tuned at the 1.06 μtm laser wavelength, and a six layer Cr/dielectric/Cr/dielectric/Cr/dielectric coating which emits strongly in either the 3 - 5 jim or the 8 - 12 μm infrared wavelength bands. Absorption bands of the coatings are independently tunable. All coatings are deposited by reactive DC and RF magnetron sputtering onto 2.5-in fiber optic faceplates. Either Si3N4, Si, or ZnS thin film dielectric materials were used in the emitter coatings. With an input laser power of 15 W, the coatings emit at a black body temperature 529 K, which compared well with predicted performance.

Thin films of TiC, VC and NbC have been deposited on MgO(001) by co-evaporation of C 60 and the metal. The metal induced a decomposition of the C60 cage and a subsequent carbide formation at 100 °C. Epitaxial TiC films were easily obtained at 250 °C, while higher deposition temperatures were required for epitaxial growth of VC(400 °C) and NbC(500 °C). The films grew with the relation MeC(001)//MgO(00 1) and MeC[ 100]//MgO[ 100]. It was also possible to deposit TiC/NbC/MgO polycrystalline multilayers and TiC/VC/MgO superlattices structures by a sequential evaporation of the metals.

W/Si and Mo/Si multilayers with 20 periods (doublelayer spacing d = 24nm) were deposited on silicon substrates using (remote-) plasma-enhanced MOCVD. The substrate temperature was below 200°C, which is necessary to avoid interdiffusion of the layers. The layer thickness and growth was controlled by an in situ soft x-ray reflectivity measurement. The characterisation of the multilayers showed an excellent growth of the silicon layers, while the metal layers are rough with embedded crystallites.

In order to use a flip chip method for bonding the Si chip directly to an organic substrate, compatible under bump metallization (UBM) must be available. Conventional schemes with a copper-based solderable layer are not well compatible with the high-tin solders (such as eutectic Pb-Sn) used with organic substrates. This is due to the rapid reaction between Sn and Cu which depletes the UBM of copper. Ni-based schemes exhibit slower reaction with the solder and have been identified by the semiconductor industry as preferable replacements to Cu-based UBM's. However, Ni-containing metallurgies are often associated with high stresses, which results in poor practical adhesion between the silicon chip and the metallization, leading to interfacial failure during fabrication or service. In this research, several nickel-containing UBM schemes are studied experimentally. Stress measurements are made for each metallization before patterning of UBM pads. An optimal Ni concentration for the UBM is suggested based on the results from this study.

The multiple cracking progress in thin SiOx films deposited on polyethylene terephthalate (PET) substrates during tensile tests were investigated. Five kinds of specimens with different SiOx film thicknesses of 43, 67, 90, 120 and 320 nm were prepared. With the appropriate estimation of the residual strain in the film, the crack onset stress was found to be nearly proportional to the minus one-half power of the thickness. After the cracking is sufficiently developed, on the other hand, thinner specimens showed higher crack density than thicker ones. In order to predict the multiple cracking progress, stress distributions in the cracked films were calculated both by the elastic-plastic finite element analysis and modified shear lag analysis. The prediction, under the assumption of the unique stress criterion, explained reasonably well the multiple cracking progress obtained in the experiments.

Ion Assisted Evaporation and Magnetron Sputtering are the two most important Physical Vapor Deposition processes used for optical coatings today. Each has advantages and limitations, and each is best for different coating applications. This paper provides a brief but comprehensive comparison of the two. Starting with introductory process descriptions, the paper compares Ion Assist and Sputtering feature-by-feature and ranks them in scorecard fashion. Features examined include: adatom energetics, reactivity, materials compatibility, thickness uniformity, deposition rate, substrate temperature, durability, environmental stability, refractive indices, absorption, scatter, mechanical stress control, and scalability (chamber and substrate size). The comparison is illustrated with examples from the author's twenty-four years of optical coating experience at three companies, with more than forty coating chambers (small, medium and very large), in research, development and production coating environments.

The tungsten and vanadium oxides are well known to be usable as solid lubricants at elevated temperatures. Such metal-oxides are interesting for tribological insets at atmospheric conditions because of their “oxidation stability”. This paper reports about investigations made to find stable process windows for the deposition of tungsten and vanadium oxides in a reactive d.c. mode by the MSIP-PVD-process. One focus of the study is on the metal oxide-phases generated in the MSIP-process under various conditions and their mechanical and metallographic properties. Coatings were deposited, developed and analyzed by standard testing methods such as SEM, microhardness (nanoindentation), XRD and scratch testing to characterize the mechanical and structural properties. Stable process windows will be presented for the reactive mode as well as the influence of different process parameters to the microstructure and the material properties. It will be shown that it is possible to deposit vanadium-oxides despite contamination effects in wide ranges by adapting the gas-flow. Process failure was determined at 15 - 18 % oxygen partial pressure for reactively deposited tungsten oxides.

Titanium-aluminum alloys are proved to be a viable candidate material in the field of structural coatings due to their high temperature creep and oxidation resistance in addition to being a lightweight material. In the present paper, we study the effect of applied power on the mechanical properties and surface chemistry of dc-magnetron sputtered Ti3AI thin films. While SEM and XRD investigate the structure and morphology of the deposited films, XPS and AES proved to be an essential tool for studying the surface chemistry and detailed chemical bonding information of the Ti3AI thin films. Glancing angle XPS and Auger depth profiling were carried out to study the chemistry at a few layers beneath the surface to monitor the changes in the stoichiometry of Ti3AI films. Microhardness measurements indicate an increase in the thin film hardness with increased sputtering power. These data were further compared to thin films deposited under liquid N2 temperatures.

Chromia thin films were deposited onto substrates of Ni and Ni-20Cr by gaseous fuel combustion chemical vapor deposition. The chemical precursor utilized to achieve chromia films was aqueous 0.27M chromium nitrate, and the depositions took place within the flame at temperatures between 200 and 550°C. Amorphous coatings were deposited between 200 and 375°C, whereas crystalline coatings of chromia (eskolaite) were deposited between 400 and 550°C. The eskolaite deposition rate was approximately five times faster than the amorphous chromia. Chromia coatings containing 2 wt% yttria were also formed. The deposition temperature necessary to form crystalline chromia/yttria coatings was slightly higher (∼50°C) than those containing chromia only. The ability of the various coatings to provide oxidation protection was characterized using thermogravimetric analysis (TGA). The eskolaite coatings that are at least 1 im thick reduce the oxidation mass gain/area of Ni-20Cr by nearly a factor of ten and the parabolic constant by an order of magnitude, whereas the amorphous chromia coatings that are 0.6 μm thick do not demonstrate such an improvement. Yttria-doped chromia coatings further reduce the parabolic constant by two orders of magnitude, consistent with expectation. Characterization of the coatings was accomplished using a variety of techniques, including SEM, TEM, EDS, and XRD.

The stoichiometric composition and oxidation rates ( wet or dry ) of plasma enhanced chemical vapor deposited (PECVD) silicon carbide (SiC) films are effected by the deposition conditions of trimethylsilane (3MS) and carrier gas. We report the oxidation kinetics of SiC thin films deposited in a modified commercial PECVD reactor. A standard horizontal atmospheric furnace in the temperature range of 925–1100°C was used in the oxidation. Oxidized films were measured optically by commercially available interferometer and ellipsometer tools in addition to mechanically using a commercially available profilometer. Activation energies of the parabolic rates were in the range of 20.93 to 335.26 kJ/mol.

Pulsed Laser Deposition (PLD) allows the ablation of nonconductive and high melting point target materials and the preparation of films with complex composition. High energy impact leads to melting and evaporation of the target material in a single step. In case of mullite ablation, the flux of the metal components is stoichiometric. Under reduced pressure the oxygen content in the layers decreases. However, after a short oxidation treatment, the formation of mullite in the coating is completed, as confirmed by IR spectroscopy and XRD investigations. For a commercial Si-SiC precoated C/C material, the effectiveness of additional PLD mullite layers as outer oxidation protection is tested in the temperature range 773 K < T < 1873 K. Mullite coatings with a thickness of 2.5 pm improve the oxidation behaviour significantly. Because of SiO2 formation at the mullite-SiC interface, all samples exhibited a mass increase upon oxidation. For oxidation durations of three days, only amorphous SiO2 is formed at the mullite-SiC interface. The inward diffusion of oxygen across the outer mullite-containing layer controls the kinetics of the reaction, as was deduced from 18O diffusivity measurements in PLD mullite layers. At temperatures close to the eutectic temperature (1860 K), mullite can seal defects. The calculated oxidation rates resulting from the diffusion parameters in SiO2 and mullite are close to the thermogravimetric data.

There is a need in the optics community for highly reflective mirrors that do not degrade in harsh environments. While silver can be a highly efficient reflector of visible light, it suffers from poor resistance to corrosive atmospheric gases. Here, we investigate a durable silver coating scheme, in which silver is sputter deposited between very thin layers of nichrome nitride. Excellent corrosion resistance is achieved with a silicon nitride overcoat. Samples were exposed to a variety of atmospheres and it was found that the nichrome nitride dramatically increased corrosion resistance when compared to bare silver or silicon nitride coated silver. Similar results were found when electrochemical impedance spectroscopy was used to evaluate samples. The enhanced corrosion resistance is achieved even when the thickness of the nichrome nilTide adhesion layer is too thin to be considered continuous.

Plasma Assisted Chemical Vapour Deposition (PACVD) deposited films of Boron Phosphide (BP) are known to be very effective in protecting the 8-11.5μm band IR substrate materials germaniurn and zinc sulphide from solid and liquid particle erosion encountered in high speed flight. This paper describes the results obtained by protecting the 3-5μm band substrate material silicon and the 8-11.5μm band substrate material zinc selenide. In addition, results are presented which show that germanium can be very effectively protected from the corrosive effects of salt fog.

A new approach to deposition of thin films for thermal barrier applications is described. During electron beam evaporation, the extreme shadowing effect that is present at highly oblique incidence is employed to introduce porosity into thin films of zirconia. Using controlled substrate motion a solid capping layer may be applied to these porous films. By depositing layers of porous material and capping in an alternating fashion a new structure is produced which warrants evaluation as an improved thermal barrier coating.

Aluminum acetylacetonate and water vapor were used to deposit an amorphous A1203 seal coating on Si and CeO2-stabilized ZrO2 (CSZ) produced by air plasma spray. The A1203 coating prepared at ∼500°C was ∼2.5μm thick, uniform, and non-porous. The crystallization and adhesion characteristics of the A1203 coating were examined by thermally annealing the A12 03- coated Si and CSZ substrates in air. The amorphous coating crystallized to metastable A1203 phases within 20 hours at temperatures as low as 700°C. The coating on Si spalled upon annealing whereas the coating on CSZ did not spall, but microcracked extensively due to the significant volume shrinkage associated with crystallization.

Efforts to increase efficiency of energy conversion devices have required their operation at ever higher temperatures. This will force the substitution of highertemperature structural ceramics for lower temperature materials, largely metals. Yet, many of these ceramics will require protection from high temperature corrosion caused by combustion gases, atmospheric contaminants, or the operating medium. This paper discusses examples of the initial development of such coatings and materials for potential application in combustion, aluminum smelting, and other harsh environments.

Understanding the role of gas-phase reactions is an important step in the development of useful CVD process models. In this article, we review the general types of gas-phase reactions that can occur and discuss quantum-chemistry techniques for predicting their thermochemistry and kinetics. We also describe the use of high-temperature flow reactors to measure gas-phase reaction kinetics. Coupling these theoretical and experimental methods is a powerful approach to the characterization of CVD precursor chemistry. We illustrate this in a discussion of the reaction between BC13 and NH3, which is important in the deposition of hexagonal boron nitride coatings.

We demonstrate a novel approach to improving the step coverage of thin films made by chemical vapor deposition (CVD). Titanium nitride (TiN) films were deposited by atmospheric pressure CVD using tetrakis(diethylamido)titanium vapor (TDEAT) and ammonia gas (NH3) carried in nitrogen gas. Trimethylamine (NMe3) gas was added during some of the depositions. The substrates were patterned silicon wafers having holes with aspect ratio of 3.5 through a silicon dioxide layer. We discovered that the step coverage was significantly increased for TiN films made with NMe3. At 320 °C, the step coverage was increased from 70% to nearly 100%. Within the range of deposition temperatures used in our study, 320 °C to 370 °C, the amount of improvement increased as the deposition temperature decreased. The trimethylamine did not increase the resistivity or the impurity levels in the films, but it did reduce the growth rate slightly. We suggest that the trimethylamine adsorbs onto the surface, temporarily blocking some of the sites on which growth could take place. Thus the effective sticking coefficients for the precursors are decreased, and the step coverage is increased.

The codeposition of alumina, silica, and aluminosilicates from mixtures of silicon tetrachloride, aluminum trichloride, carbon dioxide, and hydrogen is investigated in this study. Chemical vapor deposition experiments are carried out in a hot-wall reactor of tubular geometry coupled with an electronic microbalance. In order to elucidate some aspects of the codeposition process, the deposition of pure alumina and pure silica from mixtures of silicon tetrachloride and aluminum trichloride, respectively, with CO2 and H2, is also investigated. Among the most interesting findings of our study is that the presence of AIC13 has a catalytic effect on the incorporation of silica in the deposit, leading to codeposition rates that are higher than the deposition rates that are obtained when only one of the two chlorides (SiCI4 or A1C13) is present in the feed

A new model, based on irreversible reactions, is used to describe surface kinetics in copper Chemical Vapour Deposition. The mechanism proposed includes a reduction reaction with hydrogen parallel to the well-known disproportionation reaction of Cu(hfac)VTMS. This reduction reaction, not easily modelled by Langmuir-Hinshelwood-type models, appears to be important only at sufficiently high hydrogen partial pressures. The rate constants of the precursor adsorption reaction and the disproportionation reaction are low, probably caused by the dissociation included in these reactions.