The evolution of the vacuum coating industry is reviewed. Vacuum science progressed slowly until the late nineteenth century due to an incomplete understanding of vacuum and lack of applications. Edison's invention of the light bulb launched the vacuum industry and increased developmentof improved vacuum systems. The thin film optical coating industry arose from the needs of the German and U.S. military efforts during World War II. The author presents his experience in thin film coating from 1939 to the present.

A unique aspect of the Ionized Cluster Beam (ICB) thin film deposition method is that material is deposited as ionized,accelerated atom clusters. Results of one laboratory suggest that a wide range of beneficial film formation effects can be attributed to the clusters, reported to average 1000 atoms in size. We present two cluster measurement methods here to investigate these claims. In the first, the depositing beam passes through an ionizer, a slit and an electrostatic deflection field. An undeflected neutral deposit and an ionized deflection deposit form on a single crystal silicon substrate. The ratio of atom flux to charge flux in the deflected deposit is equal to the number of atoms per singly charged cluster. In the second method, a low amplitude 10 KHz signal modulates the electrostatic deflection field. The phase shift between the modulation voltage and the measured substrate current yields particle velocity from which mass can be obtained. We have confirmed the presence of small, three atom gold clusters.

Reactive Low-Voltage Ion Plating (RLVIP) is a plasma-assisted evaporation process that produces anorganic oxide- and nitride films with a closed microstructure. in order to better understand the process and the resulting film properties a BALZERS PPM 400 Plasmamonitor, a combination of a quadrupole mass filter and an energy selective ion optics, has been used to study the relative abundancies and energy distributions of the ions impinging on the growing film in the RLVIP process. The device is discussed and preliminary results are presented: The plasma is anisotropic. Surprisingly it contains ions with higher energies than expected from the self-bias potential.

Because of the improvement of several thin film properties and the relative ease of transference into a production environment, reactive low voltage ion plating (RLVIP) has found its way into industry at several optics and thin film manufacturers. In this review of recent accomplishments achieved with this process at our laboratory as well as at other institutions we will first recall the underlying principles of operation and some of the improved properties typical of thin films made by RLVIP. Then follow examples of applications exploiting these significant improvements, including coatings for surface smoothing, antireflection coatings for the 2 - 5 pm wavelengths range, non-shifting edge filters and thin film polarizers, narrow band reflectors (laser protection filters), and laser mirrors. The paper concludes with a brief account of the advantages - and disadvantages - of this process compared with conventional electron beam evaporation and deposition processes employing a directed ion beam.

For the next generation of fusion lasers reflecting mirrors with laser damage thresholds of at least 40 J/cm2 for 1 0 ns laser pulses at 1 .064 pm are needed. Up to now, no deposition technique has been developed to produce such mirrors. Best R&D-values realized today are around 30 J/cm2 for e-beam evaporated mirrors. R&D on conventional e-beam coating processes over the last 1 0 years has come up with marginal improvements in laser damage thresholds only. However, new technologies, like PICVD (Plasma-Impulse CVD) developed for the fabrication of ultra-low loss fiber preforms, seem to offer the potential to solve this problem. First results have been reported already [1-3]. It is well known that fused silica produced by CVD processes can have laser damage thresholds as high as 80 J/cm2. However, the thickness of a single deposited film is in the pm-range for most of the CVD-processes used for preform manufacturing; since interference optics need films in the ; /4n range (where n is the refractive index of the dielectric material) the use of preform-fabrication processes for the purpose of interference mirror fabrication is limited to a few plasma based CVD technologies, namely PCVD (Plasma-CVD, Philips [4]; PICVD, SCHOTT [5]). Especially PICVD is a very powerful technology to fabricate thin film multilayers for interference mirrors, because this technique is able to produce films down to monolayer thickness with nearly perfect stoichiometry and morphology. In first and preliminary experiments the usual deposition in a circular tube at high temperatures has been used for simplicity. However, to produce large area high quality laser mirrors this principle know-how has to be transfered from circular to planar geometry. Experiments showed, that there may be some limitations with respect to the homogeneity of a planar deposition using microwave excitation for the plasma. Therefore experiments have been performed in parallel with both RF and microwave excitation for comparison. In the following we will restrict ourselves to the description and discussions of the planar processes; the principle and details of the PICVD-process are described elsewhere [5] while RF-plasma technology is a well known process.

Thin films of titanium, zirconium, and hafnium nitride have been fabricated by reactive cathodic arc deposition from elemental targets in a nitrogen ambient. The optical constants n and k of these films have been measured ellipsometrically from 0.40 to 0.70 m. Refiectances have been measured from 0.40 to 16 jim. Electrical properties have been evaluated using sheet resistance and Hall mobility measurements. Values for cathodic arc TiN films are compared with data for TiN films fabricated by reactive RF bias sputtering from a titanium target in an argon/nitrogen medium. Measured film properties are correlated with deposition parameters and qualitative studies of microstructure and surface topography.

A hollow cathode electron/ion source with permanent-magnet-field was introduced to assist depositing oxidemetal optical coatings. The refractive index ,absoption and scatter of as -deposited layers arediscussed. It wasfound that the optical loss (absoption and scatter) decreased under proper depositing conditions. The optirnumevaporating parameters were obtained through orthogonal experiments.

Effects of ion assisted deposition on the propertes of Ti02, Zr02 and 5102 optical coatings were investigated. Substrates were bombarded with different ions--- oxygen ions , argon ions , and the mixture ions of oxygen-argon during deposition. The refractive indices, optical absorptions and laser-induced damage thresholds (LIDT) measurments of these films are reported.

The windows of modern automobiles are growing larger and larger. The larger the window, the greater its angle of inclination. This causes some problems for the passengers and their compartment. One well-known problem is the heat irradiation into the car. For a long time green tinted glass has been used to solve this problem. Some coatings have been developed to solve this heat problem. But with greater angles of window inclination a new problem appears: the visible light transmittance decreases. At an angle of 70° the transmittance through the windshield is only 50% from the driver's viewpoint. The only way to solve this problem is by special antireflection coating. First tests with such coatings have shown that it is possible to achieve both the right optical function and the necessary hardness.

To protect the soft surface of organic CR 39 ophthalmic lenses we built up a parallel plate reactor and developed a Plasma Enhanced Chemical Vapor Deposition (PECVD) process for Si02 protection films. Beside high transmission in the VIS-range we obtained refractive indices between n=1.46 and n=l.49 depending on the process parameters at layer- thicknesses of 2,5 jnn to 5 jmt. Deposition rates up to 30 A/s and thickness uniformities of 10 % were achieved. The mechanical properties of these layers were tested with different methodes and gave better results compared with other technologies like ion-assisted deposition or lacquering.

Optically variable thin film coatings have been prepared on rolls of polyester film by depositing thin multi-layers in a vacuum roll coater. Such coatings can be removed from the polyester film and ground into optically variable pigments for printing inks. Various printing inks including gravure, flexographic, and Intaglio inks have been prepared from these pigments, and printed images using these inks have been obtained from commercial printing presses. These optically variable systems have been used on various security documents to prevent counterfeiting with color copiers. Unique colors, color shifting effects, and other optical properties have been obtained by combining non-optically variable pigment and dyes with this light interference pigment. The merits of this new ink relative to other optically variable systems are color uniformity, print quality, its ready use on existing printing presses, and high security.

Some interference filter with antireflecting, antistatic and contrast enhancing effects were investigated both by computer simulations and experimentally. The aim was to prepare such coatings for TV cathode ray tubes and display devices on large scale by magnetron sputteritig. To avoid large values of the thicknesses of the individual films ( high preparation cost) and to achieve the antistatic and contrast enhancing effect an electrical conducting and light absorbing layer is embedded between insulating, non-absorbing films. For the mechanical durability a hard material as TiN, ZrN or HfN was taken into account. Good results were obtained with TiN. As an example, the obtained total thickness of a three layer filter with a light ref lectance lower or equal 0.4 % and a light transmission of 30 % was about 100 mu. The sheet resistivity for this filter is of about 300 Ohm. For a conventional dielectric filter with the same antireflecting result the total thickness is usually of about 250 nm. Finally, two, three and five layer filters were successfully prepared on an industrial sputtering coater.

A new system has been developed.for DC reactive magnetron sputtering. This system features enhanced oxidation rates and near metallic sputtering conditions. It is particularly well adapted for coating complex multilayer films and for depositing uniform thickness films on small to moderate size planar and nonplanar substrates.

A write-once optical data storage media has been developed which is suitable for tape formats. The recording layer is a metal alloy system which is sputter deposited onto polymeric substrates as a single-layer thin film. The media are manufactured using a continuous sheet process, where the reflectivity of the film at 840nm can be selectively varied between 30 and 70%. These films have been characterized for laser write sensitivity, optical properties, surface chemistry, and environmental stability. An abrasion resistant hard overcoat is applied directly onto the active surface in a second vacuum deposition step. The media performance has been found to be compatible with direct hard-overcoats with no degradation in write sensitivity.

A write-once optical data storage media has been developed which is suitable for tape formats. The recording layer is a metal alloy system which is sputter deposited onto polymeric substrates as a single-layer thin film. The media are manufactured using a continuous sheet process, where the reflectivity of the film at 840nm can be selectively varied between 30 and 70%. These films have been characterized for laser write sensitivity, optical properties, surface chemistry, and environmental stability. An abrasion resistant hard overcoat is applied directly onto the active surface in a second vacuum deposition step. The media performance has been found to be compatible with direct hard-overcoats with no degradation in write sensitivity.

Static sputter processes for the mass production of 5.25" magneto-optical data storage media have been developed. Such single disk processes require a discontinuous operation of circular magnetron cathodes in nonreactive and reactive gas atmospheres. Magnetron field configurations based on specially shaped rotating magnet patterns allow to meet high uniformity criteria for optical and magnetic properties of the individual layers using 210 mm targets and an integrated inner/outer diameter disk masking. The processes have been integrated into avery compact 'circular path coater' which realizes a throughput of 180 disks/hour. Experimental results of the process development for SiN and TbEeCo thin films are presented.

The Kodak 2 .5m Ion Figuring System (IFS), intended for the final figuring of large optics using a directed inert neutralized ion beam, has been installed and is operational. Process development and production implementation efforts are currently underway. Thermal heating effects due to exposure to the ion beam removal function are discussed. Details of processing and results from an ion figuring correction of a 0.Sm lightweighted optic are presented.

Electrochromics are reviewed in this paper. Known and new electrochromic materials are summarized and properties of electrochromic device elements and classical and new type of electrochromic devices are given herein. Requirements of the electrochromic glasses are studied depending on the application area, and processmateria1-requireinent relationships are examined. Potential car applications and futuristic cars with electrochromics are also reviewed.

Prussian blue (PB) and viologen materials color by electrode oxidation and reduction reactions, respectively; therefore, it may be possible for these materials to function in a complementary fashion in an electrochromic optical filter. The soluble viologen compounds deposit as a colored film during the cathodic reaction and go back into solution when the current is reversed for the erase cycle. Prussian blue, in contrast, is prepared as a permanent film that can be switched back and forth from the colorless to the blue form. In this study we have determined some of the major factors leading to longterm cycle stability for viologen and Prussian blue films. The pH of the tlectrolyte is a major factor in the film stability for Prussian blue. Life-times in excess of 100,000 cycles were easily achieved for Prussian blue films in solutions of pH =2. In contrast, none of the films tested in neutral solutions showed a lifetime exceeding several hundred cycles. For viologen materials, major factors affecting cycle lifetimes are the molecular structure of the viologen along with the electrolyte and solvent compositions. The use of several mixed electrolytes such as KNO3IK2SO4 as well as the use of mixed solvents can greatly increase the cycle stability of some viologen compounds. In fact, the failure mechanism for viologen films can be completely defeated by the appropriate viologen/electrolyte/solvent selection. The complementary behavior of Prussian blue and viologen films will be investigated at electrolyte and solvent compositions favorable for cycle stability.

Silver mercury tetraiodide (Ag,HgI ) is a well known thermochromic pigment that changes color from yellow to ornge at 50 C. The compound is also a fast ion conductor above its phase transition temperature. We synthesized a number of analogues of this compound in which the silver was replaced by cadmium, lead, thallium(I), copper(I), indium(I), gold(I), lithium, cesium and rubidium to determine the range of color transitions and the correlation of electrical conductivity with optical and thermal activity. This paper also reports on continued research to assess the possibility of using these pigments in architectural coatings.

Magneto-optic elements are important in applications requiring frequency shifters. Certain applications require the incorporation of magneto-optic layers into a multilayer optical stack. This paper is concerned with the development of design methodology for maximizing magnetooptical effects. To aid in this developmental process, the well-known concept of thin film Herpin equivalent structures is extended into magneto-optics; specifically, the magneto- optical analog of Herpin equivalents is derived for a thin magneto-optic layer sandwiched between a symmetric pair of dielectric films. The magneto-optic configuration selected is that of the Transverse Kerr effect; that is, the magneto-optic layer magnetization lies in the plane of the film and is in a direction perpendicular to the plane of incidence. For this geometry, magneto-optic effects manifest themselves only for the p (in-plane) polarization. As part of the derivation process, reflectance and transmittance expressions are derived for a symmetric three-element film configuration. It is shown that the magneto-optic effects only manifest themselves in reflection; in other words, the transmitted electric field does not contain a magnetization dependent term. Additionally, as the direction of propagation of the light wave is reversed (with the electric field incident on the three layer structure from the back surface), the magneto-optic signal changes sign, indicating non-reciprocity of the coupling between the light waves and thin film magnetization. It is also shown that the magnitude of magneto-optic effects depends only on three terms: (a) the reduced magneto-optic coefficient of thin film material; (b) the phase thickness of the magneto-optic layer; and (c) the transmittance of the three layer structure.

Thin films of cadmium selenide were prepared for the first time by a selective plating technique on conducting glass and titanium substrates. The films were characterised bymeans of x-ray diffraction, scanning electron microscopy, optical absorption, photoconductivity, and photoelectrochemical (PEC) studies.

A survey of experimental methods and data for thin-film thermal conductivity and heat capacity is given. Simple microscopic theory is provided as a basis for understanding the very small values of thin-film thermal conductivity observed. Interfacial resistance effects, including some conjecture on origins, as well as applications of thermal property data are discussed. The needs for future development of this important area of investigation are summarized, and some suggestions for emphasis are provIded.

Studies were made of the origins of defects in multilayer coatings used as high reflectors in the infrared, with the aim of reducing the numbers of defects and increasing the laser-damage threshold for the coatings. Clean-room conditions were found to be essential for cleaning and coating low-defect substrates. The levels ofsurface and subsurface defects on the substrate were the most important parameters in determining defects on a completed coating. Although the initial chromium film on the silicon substrate appeared to contribute many defects, it was actually making visible submicron defects that were already on the substrates. When the vacuum coating system was operated under clean conditions, the multilayer coatings added few defects to ones already present. Defect densities were reduced by a factor of 100 during the course of the study, resulting in a significant improvement in the laser-damage threshold of the coatings.

Thin films that are used primarily for their optical, electronic, magnetic and chemical properties are not generally considered to be structural elements. Nonetheless, when thin films are auached to substrates, they are often found to support very high stresses which can cause both deformation and fracture to occur. Thus, the mechanical properties of thin films on substrates are of technological importance. In particular, the mechanical properties of optical thin films must be sufficient to insure their mechanical integrity and dimensional stability over the lifetime of the device in which they are used. The origins and consequences of internal stresses in thin films and variations in strength and stiffness from those expected of bulk materials are discussed. Two measurement techniques are presented. In the first, curvatures induced in a substrate by stresses in an attached thin film are measured to determine those stresses. The second technique involves determining the hardness and elastic modulus of a thin film while it is attached to a substrate using a depth-sensing indentation device.

Dense, water-free magnesium and calcium fluoride films were produced by Reactive Ion Beam Sputtering (RIBS). These films were found to J.e fluorine deficient because of a preferential sputtering of fluorine at the target This deficiency was eliminated by the addition of a fluorinecontaining gas (carbon tetrafluoride) to the coating chamber gases during deposition of the films. The chemical composition and density of the films were measured with Rutherford backscattering spectrometry. The relationship between film composition and optical properties was investigated. The results indicate that the fluorine deficiency can be eliminated without compromising either the density or environmental durability.

Thin-film silicon carbide (SiCi) and germanium carbon (Ge,Ci) alloy coatings with low Üifrared optical absorption have been fabricated by DC- and RF-reactive magnetron sputtering. The optical and mechanical properties of the coatings depend on composition determined by deposition conditions. The refractive index and optical absorption coefficient of SiCi. alloys were varied from those of amorphous Si to those near diamond-like carbon (DLC) by increasing C content. The band edge shifted below 1.2 eV with C content as high as 0.8. The useful range of the SiCi coatings was extended to wavelengths as low as 1 jim. The useful transparency range of GeCi coatings is from 3 to 12 jim. The refractive index of GeCi coatings was varied from 4.2 of amorphous Ge to near 3.4 by increasing x from 0 to 0.5. The optical absorption coefficient was a complex function of composition and C-H, Ge-H, and Ge-C bonding. Mechanical stress in both materials was generally moderate, and increased with increasing C content for the GeC alloys and decreased with increasing C for the SiC alloys. The wide range of optical properties obtainable for both coating types makes them useful in many types of multilayer designs. Abrasion-resistant infrared (IR) multispectral antireflection coatings on zinc sulfide (ZnS) were demonstrated using Geij•9C and DLC layers.

We have developed a new method of analyzing surfaces and thin films based on time-of-flight analysis of backscauered particles. The technique employs ions with incident energies from a few tens of keY up to about 500 keY. It combines the quantitative prowess of Rutherford backscattering spectrometry with increased surface sensitivity, increased depth resolution and reduced target damage. Several probe species have been used successfully for analyses with He and Li at 250 keY and C2 at 500 keY being particularly useful because of the range of cross sections and resolutions for depth profiling that they offer. This paper describes the technique and presents studies of the composition of beryllium surfaces for mirror applications and of He indiced erosion of CaF2 and MgF2 films on Be substrates, simulating the exposure of optical coatings to one type of radiation found in Earth orbit

Multilayer-overcoated, high-reflector mirrors in sizes up to 30" x 50" areproduced on a continuous coating line. A fully-automatic, highly-accurate scanning reflectometer has been built as part of the process-control system for the continuous coating line. The reflectometer covers a spectral range of 380 to 800 nm and a range of incidence angles of 15° to 6O. The s- and the p-polariation components of reflectance are scanned separately. The reflectance measurements are absolute and are not referenced to a calibrated standard reflector. The absolute measurement accuracy is This paper describes the optical system used in the reflectometer.

A computer-controlled spectrometer has been built for measuring high-reflectance mirrors in the visible region (380 800 nm). The instrument is designed to scan high-reflectance mirrors (greater than 50%) on a surface up to 32 x 50 in. Plots of complete reflectance scans are available in minutes and are used for process control. The reflectometer can be set to any desired incidence angle in the range of 15 to 60° and four different polarization modes can be selected: P, S, P&S, and No Polarization. The instrument incorporates several techniques in order to perform as an absolute system with an overall accuracy of better than 1% . The optical system features double-bounce reflection, a special integrating-sphere light source, a double-stage monochromator, and a high-uniformity, 9-stage, side-on photomultiplier tube. This paper will focus on the electronics, controls and computer system used in the reflectometer.

The chemical composition, refractive index, texture thermal stability and microstructure of the films, by evaporating T102 mixed with elements of TaO5, YO3, and Mo , at the substrates with temperature of room, 180°c and 250° c, were investigated. The results showed that chemical composition of the films is different corresponding to not only that of materials and substrate temperature but also the manufacturing device. Both thermal stability with respect to crystalline temperature and rnicrostructure were different due to both the substrate temperature and chemical composition of the films/or coating materials.

A method is presented for nionitoring Taultilayer structures with nonquarter wavelength thickness. This method is similar to the conventional turning point method, except that the irronitoring wavelength selected by adniittance diagram will be changed with layers. Results are given for the use of this method in depositing Antireflectance coatings (ARC.)

Planar Waveguides were fabricated from three polyimide samples differing significantly in terms of their precursor and curing chemistry. The samples were selected from the groups of non-photosensitive preimidized, photosensitive preimidized and photosensitive polyamic ester precursor based polyimides. We observed significant differences in the waveguiding characteristics of these films which demonstrate the critical role of precursor chemistry on the optical properties. Curing conditions such as heating rate and bake duration also affected the optical properties. A scattering loss of less than 0.7 dB/cm was measured for waveguides fabricated from the photosensitive preimidized samples. On the other hand the photosensitive polyamic ester bas,ed samples registered a loss of greater than 1.5 dB/cm. In general the scattering loss increased with the bake temperature. The magnitude of the increase was much higher for the photosensitive polyamic ester based samples. UV exposure also affected the waveguiding characteristics and caused formation of scattering centers as evidenced by the increase in the scattering losses associated with these waveguides. Planar waveguides based on photosensitive preimidized precursor, retained excellent lightguiding properties even after high processing temperatures (Optical losses in these waveguides remained below 1.0 dB/cm after a 300 °C bake).

Mode concentration and propagation constants in Te thin film structures are readily obtained from a transverse resonant method without explicit knowledge of the dispersion relationship from Maxwell's equations. Losses involved, best method of coupling a light beam into a Te thin-film waveguide, non linear Te-X-junctions, bends co and contradirectional coupling, second order harmonic generation (SHG) in a Te Waveguide structure, are briefly discussed. Finally the measured optimized detection characteristics of Te/Si thin film device and the proposed theory of the detection mechanism yield to consider Te thin-films as a potenthlly improved room temperature pulsed C02 laser detector.

The electrochromic behavior of all solid state devices (ASSDs) is connected with deposition methods and process techniques for production. Cathodically and anodically colored electrochromic materials and solid state electrolytes are compared and the influence of films prepared by reactive evaporation and reactive sputtering is described. In addition, the general electrochemical behavior of films is discussed, whiéh are produced by chemical vapor deposition, dip coating, electrodeposition and anodic oxidation.