Coatings Technology Handbook Episode 1 Part 9 docx

30 -10 Coatings Technology Handbook, Third Edition 30.7.2 Magnetic Some high-performance magnetic data storage media are deposited via sputtering. Cobalt alloys such as cobalt–chromium and, to a lesser extent, nickel, iron, and samarium alloys are typically used. 30.7.3 Optical Thin metal and dielectric coatings are used to construct mirrors, antireflection coatings, light valves, laser optics, and lens coatings, and to provide architectural energy control and optical data storage. 30.7.4 Mechanical Hard coatings such as titanium carbide, nitride, and carbon produce wear-resistant coatings for cutting tools. Molybdenum sulfide serves as a solid lubricant. 30.7.5 Chemical Thin film coatings can be used to provide high-temperature environmental corrosion resistance for aerospace and engine parts, catalyst surfaces, gas barrier layers, and lightweight battery components. 30.7.6 Decorative Titanium nitride is deposited on watch bands and jewelry as a hard gold-colored coating. Metals are deposited for weight reduction in automotive and decorative graphics applications. 30.8 Additional Resources The following professional societies include sections dealing with sputtered coatings: American Vacuum Society (offers short courses in sputtering and coatings), Society of Vacuum Coaters, Electrochemical Society, and Materials Research Society. Journals that cover developments in sputtered coatings include Journal of Vacuum Science and Technology , Thin Solid Films , Journal of Applied Physics , Vacuum, Progress in Surface Science , and the Journal of the Electrochemical Society. Bibliography Bunshah, R. F. et al., Deposition Technologies for Films and Coatings. Park Ridge, NJ: Noyes Publications, 1982. Chapman, B., Glow Discharge Processes, Sputtering and Plasma Etching. New York: Wiley, 1980. Coutts, T. J., Active and Passive Thin Film Devices. New York: Academic Press, 1978. Maissel, L. I. and R. Glang, Handbook of Thin Film Technology. New York: McGraw-Hill, 1970. Vossen, J. L. and W. Kern, Thin Film Processes. New York: Academic Press, 1978. DK4036_book.fm Page 10 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 31 -1 31 Vapor Deposition Coating Technologies 31.1 Introduction 31- 1 31.2 Physical Vapor Deposition 31- 3 31.3 Chemical Vapor Deposition 31- 16 31.4 Decorative and Barrier Coatings 31- 22 31.5 Conclusions 31- 28 References 31- 28 31.1 Introduction For over 25 years, the thermal evaporation of aluminum onto thin polymeric webs, such as polyester (PET) and polypropylene (PP), has generated large volumes of barrier packing films, decorative films, capacitor films, and some window films. The experience of wide web handling was combined with deposition technologies, such as electron beam evaporation, magnetron sputtering, and plasma-enhanced chemical vapor deposition, to create a large number of new, exciting, coating materials, including oxides and nitrides of most elements. More particularly, combinations of these coating layers into a complex coating stack led to new products, such as low emissivity, solar heat reflecting, architectural glazing films, electrochromic devices, and high-performance optical reflectors. With these technologies, unique coating characteristics can be realized, e.g., transparent electrodes, flexible glassy barriers for moisture and gases, and amorphous soft magnetic materials for security devices. To build highly functional components with vacuum-coated webs, severe quality standards should be in use today. 1 Many different characteristics are important for further functionality after coating, e.g., mechanical tensile strengths, Young’s modulus, surface finish, optical clarity (e.g., transparency haze), and resistance to corrosion and UV irradiation. Many special additional surface treatments have also materials that have been used industrially to date. Recently, the technical availability of low-cost SiO 2 and A1 2 O 3 coatings has created very interesting coating stack building blocks. 2 Since 1980, tool coatings formed by physical vapor deposition (PVD) technologies have become a reality, and an industry has evolved around PVD tool coatings based on the work of the early pioneers in this field. 3–6 Lindas Pranevicius Vytautas Magnus University DK4036_C031.fm Page 1 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC Thermal Evaporation • Electron Beam Evaporation • Sputter Arc Deposition Thermal Chemical Vapor Deposition • Plasma-Enhanced Deposition in Plasma • Reactive Sputter Deposition • Cathodic Chemical Vapor Deposition (PECVD) Decorative Coatings • Barrier Coatings employed for the flexible substrates used for vacuum coating. Table 31.1 gives a survey of most substrates become indispensable in attaining necessary product performance. Table 31.2 lists most of the coating Vapor Deposition Coating Technologies 31 -5 sibility of deposition at relatively low substrate temperatures. The major roles of the plasma in various plasma-assisted processes are related to activation and enhancement of the reactions that are necessary for deposition compound films, and modification of the growth kinetics and, hence, modification of the structure and morphology of the deposits. Due to the above consideration, plasma is used in a variety of physical and chemical vapor deposition processes. The most commonly used techniques for plasma-assisted PVD are as follows: (1) sputtering, including direct current (dc), radio frequency (rf), triode, or magnetron geometries and reactive sputtering using dc, rf, triode, or magnetron sources; and (2) activated reactive evaporation. The presence of the plasma in the source–substrate space significantly affects the processes occurring at each of these steps in film deposition, which are generation of species, transport from source to substrate, and film growth on the substrate. Moreover, the effect of the plasma on the above three steps differs significantly between various processes. Such differences are manifest in terms of the types and concentrations of the metastable species, ionized species, and energetic neutrals that, in turn, influence the reaction paths or steps involved in the overall reaction of film formation and the physical location of these reaction sites. Moreover, it should be noted that the ionizing probability is maximum for electrons in the range of 50 to 60 eV and decreases with further increase in energy. It is, therefore, advantageous to have low-energy electrons for ionization of the gas and vapor species. 31.2.3.1 Diode Plasmas The dc-diode plasma device is the simplest form of a plasma used for sputtering and sputter deposition. The system consists of a cathode, an anode, a dc power supply, and an enclosure. The interrelation between gas density, electrode spacing, and applied voltage needed for the breakdown of the gas and the formation of plasma is given by Paschen curves. 17 Only a tiny fraction (about 0.01%) of the gas atoms are ionized — the majority are neutral. The electrons in the plasma are relatively hot, with a Maxwellian energy distribution and an equivalent thermal temperature of 10,000 to 50,000 K. The electron temper- ature is usually described with energy units (eV), where 1 eV is about 11,600 K. Because the plasma is conductive, there is virtually no potential gradient with the plasma itself. All of the electric fields occur at the edge of the plasma in a region called a sheath. Due to the large proportion of neutral gas atoms to ions, the ions are in thermal equilibrium with the gas atoms (through collisions) and are only at a temperature in the range of 100 to 1000 ° C. And due to the much higher electron temperature and lower mass, the electrons move rapidly around the plasma. This last effect results in the appearance of several different potentials within the system. The plasma potential is the apparent voltage on the bulk of the plasma away from the sheath. The floating potential is the potential reached by an electrically isolated object immersed in the plasma. It is also the potential (on any surface, conductive or not) at which the arriving ion and electron fluxes are equal. The floating potential is always the negative of the plasma potential, typically by a factor 3 times the electron temperature. For objects floating electrically in the plasma, the energy is usually less than 20 eV and causes little sputtering. For a surface such as the cathode, the ion energy is equal to the difference between the plasma potential (a few more volts positive than the anode) and the cathode voltage. These energies can be several hundreds of eV and will cause significant sputtering of the cathode surface. Therefore, a sample to be coated with a thin film of sputtered atoms could be located on the anode surface or virtually anywhere within the chamber. Dc-diode plasmas are characterized by low etching and deposition rates. The reason for the low rates is a low plasma density due to a cross for electron-impact ionization that is fairly small. Therefore, to get a high plasma density and, hence, a high ion bombardment rate, the gas pressure must be increased to pressures near 133 Pa. In addition, the voltages needed for moderate currents are fairly high, several kV. The resultant sputtered atoms are rapidly scattered by the background gas, and the net deposition rate on a sample surface is fairly low. DK4036_C031.fm Page 5 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC 31 -6 Coatings Technology Handbook, Third Edition Dc-diode sputtering is also constrained by the requirement that the electrodes must be metallic conductors. If one of the electrodes is insulating, it charges rapidly, and additional current is suppressed. This effect can occur if a reactive gas, such as oxygen or nitrogen, is introduced into the plasma, resulting in the oxidations of metal surfaces on the electrodes. Therefore, dc-diode sputtering is not an appropriate technology for the deposition of most compounds and dielectrics. By operating the plasma diode with an ac potential, rather than dc, these problems can be overcome (Figure 31.1). At the most commonly used frequency of 13.6 MHz, there is little voltage drop across the insulating electrode or layer. The electrodes will not charge up, and therefore, it is possible to sputter dielectrics or reactively sputter metals. There is an additional degree of ionization with an rf-powered plasma due to additional energy transmitted to the plasma electrons at the oscillating sheath. The net result is a higher plasma density, compared to dc-powered plasmas, and the ability to operate at lower system pressures (0.5 to 120 mPa). The cathode of a typical rf-diode system is usually powered through an impedance-matching device known as matchbox. The function of the matchbox is to maximize the power flow from the rf generator, which has an output impedance of 50 ohms, to the plasma, which has a complex impedance usually in the 1000 ohm range. A series capacitor is included in the matchbox to allow the formation of a dc bias on the cathode. This occurs due to the higher electron mobility and results in a negative dc potential on the powered electrode of up to one-half applied rf peak-to-peak voltage. The ions in the plasma that are accelerated to the cathode are too massive to respond to the 13.6 MHz fields and respond only to the dc bias. The most common application of rf-diode sputtering is for the deposition of dielectric films. Often, the sample surface is biased slightly during the deposition to provide some level of ion bombardment that results in changes to the density and microstructure of the films and some degree of resputtering that leads to increased planarization. 31.2.3.2 Magnetically Enhanced Plasmas Electrons in a magnetic field are subjected to Lawrence force, which in a homogeneous magnetic field perpendicular to the electron motion would cause the electron to move in a circular path with radius, known as the Larmor radius. In the direction of the magnetic field, there is no net magnetic force, so the electrons are unconfined. The net result is that electrons tend to spiral along magnetic field liners in a helical path. By constraining the electron to this motion, the effective path length of the electron is increased significantly, and hence, the probability of an ionizing electron–atom collision is increased. For FIGURE 31.1 The rf excitation system: R a and R c — anode and cathode sheath resistances; R p — plasma resistance; C a and C c — the geometric sheath capacitances. Plasma Cathode Sheath Anode Sheath Cathode Anode R p R a C a D a R c C c D c rf rf DK4036_C031.fm Page 6 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC Vapor Deposition Coating Technologies 31 -7 a given applied power, then, the effect of the magnetic field is to reduce the plasma impedance, resulting in higher discharge currents at lower voltages. The increased density also allows significant reductions in the background pressure, such that the magnetically enhanced plasmas can operate at pressures as low as the 10 –2 Pa range. Magnetrons are the most common form of magnetically enhanced plasmas. In the device, a magnetic field is configured to be parallel to the surface of the cathode. There is a resulting electron drift, caused by the cross-product of the electric and magnetic fields (known as an E-cross–B-drift) that tends to trap electrons close to the cathode surface. The drift motion is directional, and in a magnetron it is configured to close on itself. A common example of this is shown in Figure 31.2, for a circular geometry, and is called a circular planar magnetron. In this case, the magnetic field is configured to be radial pole and a perimeter, or ring magnetic pole. The magnetron device, which is defined as having a closed-loop E × B drift path for the secondary electrons, has been developed in a number of geometries. 18 Perhaps the most common alternative is to use a rectangular configuration, known as a “racetrack” magnetron (Figure 31.3). This geometry has some intrinsic advantages for the automated handling of parts. FIGURE 31.2 Circular planar magnetron showing an expanded view of the pole-piece configuration. Water cooling is not shown, but it typically occupies the volume between the cathode and the back of the pole-piece assembly. FIGURE 31.3 A rectangular or racetrack magnetron. S N Cathode Magnetic Field Lines E × B Drift Path N S Magnetic Pole Piece Assembly Cathode E × B Drift Path DK4036_C031.fm Page 7 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC 31 -8 Coatings Technology Handbook, Third Edition Magnetron plasmas have a unique feature in that the secondary electrons are strongly constrained to the region near the cathode surface. This causes dense plasma to form near the cathode in the region of the drift loop. The dense plasma results in very high levels of ion bombardment of the cathode surface and, hence, high rates of sputtering. The high-rate ion bombardment is localized on the cathode directly under the E × B path. The resultant sputter emission of atoms is also localized, which means that deposition uniformity is usually not good. Therefore, for most deposition systems, it will be necessary to either move the sample or alter the magnetron location to attain good deposition uniformity. In addition, the erosion of the cathode is also localized, which results in poor utilization of the cathode material, as deep grooves are eroded into the cathode surface in the vicinity of the E × B drift path. The wide grooves are called the “etch track” and are characteristic of magnetron sputtering. Typically, only 10 to 15% of the cathode material can be used before the grooves start to etch through the back of the cathode. 19 At high pressures, the distribution of sputtered atoms is smeared out due to gas scattering and deposition homogeneity increases, but the cost is a real reduction in the sputtered atom’s kinetic energy and a potential change in the film properties. There are two obvious solutions to the nonuniformity. The first is to move the sample in some way to average the deposition over the sample surface. For circular planar magnetrons, this requires a fairly complicated planetary motion. The alternative, using conven- tional rotating-sample motion, is to use deposition shields located between the cathode and the sample, which effectively collect the sputtered flux locally. This process, however, reduces the net deposition rate over the entire sample to the lowest level of the original distribution. For rectangular or other elongated magnetrons, the solution for increased uniformity is to translate the samples past the magnetron perpendicular to the “long” direction of the cathode. An example is shown in Figure 31.4, which shows a rectangular magnetron system viewed end-on, in which the samples move from one end of the system to the other. The dimensions of these systems on a manufacturing scale can be rather large. A common size uses cathodes 2 m in length in a sputtering system with an overall length that exceeds 20 m. 20 For some industrial applications, in particular those where contamination is a critical concern, it may not be desirable to move the samples during deposition. In this case, magnetrons have been developed that have a moving etch track. 21 Over time, the eroded area is fairly uniform, and a high degree of uniformity can be obtained when depositing films on large, stationary substrates. The moving etch track is set up by rotating the magnet assembly in the cooling water behind the cathode face. An industrial cathode of this design might have a diameter of 25 cm and be rated at a power of 25 kW. The second important advantage of these magnetrons is that the utilization of the cathode is very efficient: up to 80% of the cathode material can be used for sputtering, compared to 15% for a nonrotating magnetron. This results in much better efficiency and longer time periods between cathode changes. Because of this FIGURE 31.4 An automated in-line system based on rectangular planar magnetrons. Samples To High Vacuum Pump To Load-lock Pump To Load-lock Pump Load Un-load Valve Valve Magnetrons DK4036_C031.fm Page 8 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC Vapor Deposition Coating Technologies 31 -9 intrinsic efficiency, this type of magnetron is becoming more common and is being used in such varied applications as hard coatings and roll or web coating. 31.2.3.3 Unbalanced Magnetron Deposition The balanced magnetron sputtering has one peculiarity. It has a strong decrease of the substrate ion current with increasing distance of substrates from the magnetron target. It limits the possibilities to activate the substrate during deposition. In principle, there are two possible ways to increase the ion current density on substrates in magnetron sputtering, i.e., by (1) additional gas ionization, for instance, by a hot cathode electron beam or a hollow cathode as a source or (2) a magnetic confinement of plasma, for instance by an unbalanced magnetron. 22,23 In an unbalanced magnetron, a conventional magnetron is intentionally configured with an array of magnetic pieces or coils that add an additional vertical component to the magnetic field at the cathode. Three common configurations are shown in Figure 31.5. The first two configurations (Figure 31.5a and Figure 31.5b) are based on additional permanent magnets in the pole-piece configuration behind the magnetron cathode. In the first case, the central pole piece has been made much stronger than the FIGURE 31.5 Unbalanced magnetrons: (a) with a strong axial pole, (b) with a strong perimeter pole, and (c) with an additional electromagnet. (a) (b) (c) DK4036_C031.fm Page 9 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC 31 -10 Coatings Technology Handbook, Third Edition perimeter pole piece, resulting in an additional axial field. In the second case, the perimeter pole has The unbalanced magnetrons are characterized by the addition of magnetic field lines that are no longer constrained between the central and perimeter pole pieces of the magnetron. Additional field lines leave unconstrained by the E × B trapping effect near the cathode and is actually enhanced due to the drift of electrons from high-strength magnetic field regions to lower strength regions. As a result, electrons can leak away from the near cathode region. This sets up a very weak potential that tends to draw ions from the cathode region out to the near-sample region. It is these ions that can then be used to form the basis of a sample bias necessary for the enhancement of the TiN reaction. Titanium nitride has extensive applications in the commercial world for hard and decorative coatings. The unbalanced magnetron approach has been used successfully on a manufacturing scale for the production of TiN and related compounds. To cover large numbers of parts, or else to cover large parts with unusual shapes, systems are often configured with multiple magnetrons within a single chamber. 24 A simple example of this is shown in Figure 31.6, where two unbalanced magnetrons have been config- ured across from each other, with the sample placed in the middle. The magnetrons can be configured to be coupled or repelling, which results in a significant difference in the observed bias current densities at the sample. In sputtering systems equipped with unbalanced magnetrons, high ion current densities can be trans- ported to substrates, which are even greater than the magnetron current. If the magnetic field of unbal- anced magnetron reaching substrates is sufficiently strong (several mT), the discharge strongly differs FIGURE 31.6 The mirrored and closed-field magnet configurations: (a) mirrored, where like poles face each other; (b) closed field, where opposite poles face each other. SN NS NS SN NS SN SN NS Cathode 1 Cathode 2 Substrate Field Lines (a) SN NS NS SN SN NS NS SN Cathode 1 Cathode 2 Substrate Field Lines (b) DK4036_C031.fm Page 10 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC been made stronger, resulting in an additional cylindrical component to the field. In the third case (Figure the region of the magnetron and intersect the sample region. Electron motion along these field lines is 31.5c), an electromagnet has been added externally to the magnetron to provide a simple axial field. 31 -12 Coatings Technology Handbook, Third Edition it is costly in terms of the expense of added pump capacity and increased gas consumption. The added gas flow has the advantage of reducing contamination from vessel outgassing and leaks through dilution. Through partial-pressure control of the reactive gas, it is possible to produce all material compositions in spite of the hysteresis effect. If the reactive gas partial pressure is held constant at the same time that the power to the sputtering target is held constant, a balance between consumption and availability of the reactive gas is maintained. The partial pressure sets the flux of gas atoms at every surface. If the partial pressure is controlled, the availability of that gas will be controlled. If there is a process disturbance, such as an arc on the target, a partial-pressure controller will momentarily reduce flow to maintain constant partial pressure. Once the plasma is reestablished (after the arc is quenched) and the metal is being sputtered at the full rate, the flow will once again be increased to maintain the desired partial pressure. In partial-pressure control, there is inherent stability. The removal of material from the target is nearly constant except for perturbations such as arcs, and at the substrate, the metal and gas atoms arrive in the proper ratio to produce the stoichiometric compound. Partial-pressure control requires a species selective means of monitoring the gases in the process chamber in real time. The most frequently used piece of equipment is the quadrupole mass analyzer, which has the ability to separate gases by their mass ratios and which generally provides a unique signal for each gas present. Good partial-pressure control is achieved when an adequate signal-to-noise ratio is obtained by the analyzer in a time frame that is short enough that the flow can be adjusted before the inherent process instabilities take the partial pressure too far from equilibrium. To form the stoichiometric compound, the arrival rate of metal atoms must be matched by an appro- priate arrival rate of the desired reactive gas atoms at the substrate. If these arrival rates are not balanced, the resulting film will not be of the desired composition. By controlling the partial pressure of the reactive gas in the region of the substrate, it is possible to maintain the required arrival rate of gas atoms so that, when they are combined with the arriving metal atoms, the proper material phase is produced. FIGURE 31.8 Hysteresis curves for the deposition rate (a) and the chamber pressure (b) for the case of reactive sputtering. Deposition Rate (arb units) Chamber Pressure (mT) 024 Critical Flow Flow of Reactive Gas (SCCM units) (a) (b) DK4036_C031.fm Page 12 Thursday, May 12, 2005 9:40 AM © 2006 by Taylor & Francis Group, LLC [...]... DK4036_C0 31. fm Page 21 Thursday, May 12 , 2005 9: 40 AM 31- 21 Vapor Deposition Coating Technologies TABLE 31. 4 The Vickers Hardness of Various Compoundsa Compound HV 00.5 Compound HV 00.5 Compound HV 00.5 TiC VC Cr3 C2 TiN VN CrN Cr2 N TiB2 VB2 CrB CrB2 TiSi2 TaSi2 3000 290 0 13 50 210 0 15 80 11 00 15 80 3400 210 0 214 0 210 0 95 0 12 50 ZrC NbC β-Mo2 C 2700 2000 15 00 HfC TaC WC 2600 18 00 12 00–2500 ZrN NbN 16 00 14 00... Group, LLC DK4036_C0 31. fm Page 24 Thursday, May 12 , 2005 9: 40 AM 31- 24 Coatings Technology Handbook, Third Edition TABLE 31. 6 Optimal Properties of Ion Plated Filmsa Film Material Nb2O5 Ta2O5 ZrO2 HfO2 Si3N4 Y 2O 3 Al2O3 SiO2 SiOxNy Refractive Index (550 nm) 2.40 ± 1 2.23 ± 1 2.20 ± 1 2 .17 ± 1 2.06 ± 1 1 .95 ± 1 1.66 ± 1 1.485 1. 5–2.0 a See also J Narayan, N Biunno et al., in Laser and Particle Beam Modification... 14 00 HfN TaN 17 00 11 50 ZrB2 NbB2 MoB MoB2 ZrSi2 MoSi2 2250 2600 2500 2350 10 25 12 90 HfB2 TaB2 WB W2 B5 HfSi2 WSi2 290 0 2500 3750 2600 97 5 12 00 a See also W Buechner, R Schliebs, G Winter, and K H Buechel, Industrielle Angewandte Chemie: Weinheim: Verlag Chemie, 19 84 found wider application because of their higher vapor pressure Thus, Cu (acac)2 needs a temperature of 14 0°C, Cu (thd)2 11 0°C, and Cu... deposition system is shown in Figure 31. 9 The properties of the deposited films depend on the energy and fluxes of all the impinging particles (metallic and gas-phase atoms and ions), the substrate material, and the substrate deposition temperature © 2006 by Taylor & Francis Group, LLC DK4036_C0 31. fm Page 18 Thursday, May 12 , 2005 9: 40 AM 31- 18 Coatings Technology Handbook, Third Edition nature of the...DK4036_C0 31. fm Page 14 Thursday, May 12 , 2005 9: 40 AM 31- 14 Coatings Technology Handbook, Third Edition The spatial distributions of particles, which is of great importance because it determines the homogeneity of the coating on large area substrates, are very different Macroparticles are emitted mainly in the cathode plane, ions are emitted... (silicon, boron, and germanium) As hard coatings, Al2O3 and ZrO2 might be of interest, their hardnesses being 9. 5 and 7 to 9, respectively, on Mohs scale Al2O3 films can be prepared from several precursors The alkyl compounds AlR3 are very © 2006 by Taylor & Francis Group, LLC DK4036_C0 31. fm Page 23 Thursday, May 12 , 2005 9: 40 AM 31- 23 Vapor Deposition Coating Technologies 1. 0 Au a Reflectivity 0.8 0.6 b 0.4... used at temperatures as low as those used by the CVD technique and if it produces highly adhesive films © 2006 by Taylor & Francis Group, LLC DK4036_C0 31. fm Page 20 Thursday, May 12 , 2005 9: 40 AM 31- 20 Coatings Technology Handbook, Third Edition TABLE 31. 3 Acetylacetonate and Its Modificationsa acac fta hfa thd tpm ppm fod CH3 - CO - CH2 - CO - CH3 CH3 - CO - CH2 - CO - CF3 CF3 - CO - CH2 - CO - CF3 (CH3)3... energy of the ions is in the range of 1 to 10 0 eV However, the energy decreases with increasing gas pressure due to collisions with gas particles The flux of evaporated material also contains multiple-charged ions Macroparticle generation is an integral part of cathode spot operation There are several processes that can result in formation and acceleration of macroparticles: Joule heating accompanied... spectra of ZrN- and TiN-based coatings, obtained by reactive magnetron sputtering, are presented in Figure 31. 13.58 Closely stoichiometric ZrN coatings have gold-yellow color The TiNbased coatings with the increased amounts of oxygen and nitrogen have been studied Two effects have been observed: the surplus of nitrogen reduces the reflectivity on the long-wavelength side; the coatings become darker yellow... - CO - CF3 (CH3)3 C - CO - CH2 - CO - C2 F5 (CH3)3 C - CO - CH2 - CO - C3 F7 a See also J Narayan, N Biunno et al., in Laser and Particle Beam Modification of Chemical Processes on Surfaces A W Johnson, G L Loper, and T W Sigmond, Eds., Mater Res Symp Proc., 12 9, 425 ( 19 89) Steady evaporation is easier to realize with liquid precursors Bulky and asymmetrical substituents lower the melting points Sometimes . C WC 2600 18 00 12 00–2500 TiN VN CrN Cr 2 N 210 0 15 80 11 00 15 80 ZrN NbN 16 00 14 00 HfN Ta N 17 00 11 50 TiB 2 VB 2 CrB CrB 2 3400 210 0 214 0 210 0 ZrB 2 NbB 2 MoB MoB 2 2250 2600 2500 2350 HfB 2 Ta B 2 WB W 2 B 5 290 0 2500 3750 2600 TiSi 2 Ta. Deposition 31- 3 31. 3 Chemical Vapor Deposition 31- 16 31. 4 Decorative and Barrier Coatings 31- 22 31. 5 Conclusions 31- 28 References 31- 28 31. 1 Introduction . DK4036_book.fm Page 10 Monday, April 25, 2005 12 :18 PM © 2006 by Taylor & Francis Group, LLC 31 -1 31 Vapor Deposition Coating Technologies 31. 1 Introduction 31- 1 31. 2 Physical