Abstract

Highly reflective front-surface silver mirrors are needed for many optical applications. While various protective dielectric coating schemes have been developed, the long-term durability of Ag mirrors is still of great concern in the optics community for a variety of applications under harsh environments. The corrosion protection behavior of a SiNx-coated silver-mirror coating scheme was tested with electrochemical impedance spectroscopy (EIS) and accelerated environmental testing, including humidity and salt fog tests. The EIS data obtained were fitted with different equivalent circuit models. The results suggested that the 100Å thick SiNx coating produced by rf magnetron sputtering was porous and acted as a leaky capacitor on the Ag film, whereas the addition of a NiCrNx interlayer as thin as 3Å between SiNx and Ag films resulted in a much denser SiNx coating with a low-frequency impedance value of 2 orders of magnitude higher than that without the interlayer. Humidity and salt fog testing of different silver coatings showed similar results. The 100ÅSiNx/3ÅNiCrNx/Ag coating exhibited excellent corrosion resistance against the corrosive environments used in this study.

© 2006 Optical Society of America

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References

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  1. D. Y. Song, R. W. Sprague, H. A. Macleod, and M. R. Jacobson, 'Progress in the development of a durable silver-based high-reflectance coating for astronomical telescopes,' Appl. Opt. 24, 1164-1170 (1985).
    [CrossRef] [PubMed]
  2. M. E. MacDonald, 'Investigation of alternates to SiOx for protective scan mirror coatings in remote sensing instruments,' in Earth Observing Systems IV, Proc. SPIE 3750, 309-318. (1999).
  3. Optical Coating Laboratory, Inc., 'HR94 front surface mirrors for projection display,' Product Brochure HR94FSM (Optical Coating Laboratory, Inc., 2001).
  4. G. Hass, 'Reflectance and preparation of front-surface mirrors for use at various angles of incidence from the ultraviolet to the far infrared,' J. Opt. Soc. Am. 72, 27-39 (1982).
    [CrossRef]
  5. N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).
  6. T. E. Graedel, 'Corrosion mechanisms for silver exposed to the atmosphere,' J. Electrochem. Soc. 139, 1963-1969 (1992).
    [CrossRef]
  7. D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
    [CrossRef]
  8. J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.
  9. J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).
  10. M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).
  11. P. D. Fuqua and J. D. Barrie, 'Optical properties and corrosion resistance of durable silver coatings,' in Properties and Processing of Vapor-Deposited Coatings, R.Johnson, W.Lee, M.Pickering, and B.Sheldon, eds., Mater. Res. Soc. Symp. Proc. 555, 85-90 (1998).
  12. C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
    [CrossRef]
  13. G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
    [CrossRef]
  14. D. C. Silverman, 'Primer on the ac impedance technique,' in Electrochemical Techniques for Corrosion Engineering, R.Baboian, ed. (National Association of Corrosion Engineers, 1985).
  15. E. Katz, 'The history of electrochemistry, electricity, and electronics,' accessed 8 September 2005 http://chem.ch.huji.ac.il/∼eugeniik/history/randles.html.
  16. V. D. Jovic and B. M. Jovic, 'EIS and differential capacitance measurements onto single crystal faces in different solutions, PartI: Ag(111) in 0.01 M NaCl,' J. Electroanal. Chem. 541, 1-11 (2003).
  17. N. Kaiser, 'Review of fundamentals of thin film growth,' Appl. Opt. 41, 3053-3060 (2002).
    [CrossRef] [PubMed]

2003 (2)

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

2002 (1)

1992 (1)

T. E. Graedel, 'Corrosion mechanisms for silver exposed to the atmosphere,' J. Electrochem. Soc. 139, 1963-1969 (1992).
[CrossRef]

1985 (1)

1982 (1)

1981 (1)

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Ahhee, C.

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

Ahre, D.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Araya, C.

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

Barrie, J. D.

P. D. Fuqua and J. D. Barrie, 'Optical properties and corrosion resistance of durable silver coatings,' in Properties and Processing of Vapor-Deposited Coatings, R.Johnson, W.Lee, M.Pickering, and B.Sheldon, eds., Mater. Res. Soc. Symp. Proc. 555, 85-90 (1998).

Bi, Q.

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

Bierwagen, G.

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Boccas, M.

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

Bryan, S.

J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).

Cappell, R. J.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Carniglia, C. K.

J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.

Erlandson, A.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Farmer, J.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Fix, D.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Fuqua, P. D.

P. D. Fuqua and J. D. Barrie, 'Optical properties and corrosion resistance of durable silver coatings,' in Properties and Processing of Vapor-Deposited Coatings, R.Johnson, W.Lee, M.Pickering, and B.Sheldon, eds., Mater. Res. Soc. Symp. Proc. 555, 85-90 (1998).

Graedel, T. E.

T. E. Graedel, 'Corrosion mechanisms for silver exposed to the atmosphere,' J. Electrochem. Soc. 139, 1963-1969 (1992).
[CrossRef]

Gregg, H.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Hass, G.

He, L.

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Jacobson, M. R.

Jeffcoate, C.

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Jovic, B. M.

V. D. Jovic and B. M. Jovic, 'EIS and differential capacitance measurements onto single crystal faces in different solutions, PartI: Ag(111) in 0.01 M NaCl,' J. Electroanal. Chem. 541, 1-11 (2003).

Jovic, V. D.

V. D. Jovic and B. M. Jovic, 'EIS and differential capacitance measurements onto single crystal faces in different solutions, PartI: Ag(111) in 0.01 M NaCl,' J. Electroanal. Chem. 541, 1-11 (2003).

Kaiser, N.

Katz, E.

E. Katz, 'The history of electrochemistry, electricity, and electronics,' accessed 8 September 2005 http://chem.ch.huji.ac.il/∼eugeniik/history/randles.html.

Laird, R. E.

J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.

Lehan, J. P.

J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.

Leyland, A.

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

Li, J.

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Liu, C.

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

MacDonald, M. E.

M. E. MacDonald, 'Investigation of alternates to SiOx for protective scan mirror coatings in remote sensing instruments,' in Earth Observing Systems IV, Proc. SPIE 3750, 309-318. (1999).

Macleod, H. A.

Marshall, C.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Matthews, A.

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

Peterson, P.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Phipps, P. B.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Rice, D. W.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Rigby, E. B.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Sanders, D.

J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).

Siekhaus, W.

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Silverman, D. C.

D. C. Silverman, 'Primer on the ac impedance technique,' in Electrochemical Techniques for Corrosion Engineering, R.Baboian, ed. (National Association of Corrosion Engineers, 1985).

Song, D. Y.

Sprague, R. W.

Tallman, D.

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Thomas, N.

J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Tremaureux, R.

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

Vera, E.

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

Vucina, T.

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

Wolfe, J.

J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

Wolfe, J. D.

J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.

Appl. Opt. (2)

Corros. Sci. (1)

C. Liu, Q. Bi, A. Leyland, and A. Matthews, 'An electrochemical impedance spectroscopy study of the corrosion behavior of PVD coated steels in 0.5 N NaCl aqueous solution: Part I. Establishment of equivalent circuits for EIS data modeling,' Corros. Sci. 45, 1243-1256 (2003).
[CrossRef]

J. Electrochem. Soc. (2)

T. E. Graedel, 'Corrosion mechanisms for silver exposed to the atmosphere,' J. Electrochem. Soc. 139, 1963-1969 (1992).
[CrossRef]

D. W. Rice, P. Peterson, E. B. Rigby, P. B. Phipps, R. J. Cappell, and R. Tremaureux, 'Atmospheric corrosion of copper and silver,' J. Electrochem. Soc. 128, 275-284 (1981).
[CrossRef]

J. Opt. Soc. Am. (1)

Prog. Org. Coat. (1)

G. Bierwagen, D. Tallman, J. Li, L. He, and C. Jeffcoate, 'EIS studies of coated metals in accelerated exposure,' Prog. Org. Coat. 46, 148-157 (2003).
[CrossRef]

Other (10)

D. C. Silverman, 'Primer on the ac impedance technique,' in Electrochemical Techniques for Corrosion Engineering, R.Baboian, ed. (National Association of Corrosion Engineers, 1985).

E. Katz, 'The history of electrochemistry, electricity, and electronics,' accessed 8 September 2005 http://chem.ch.huji.ac.il/∼eugeniik/history/randles.html.

V. D. Jovic and B. M. Jovic, 'EIS and differential capacitance measurements onto single crystal faces in different solutions, PartI: Ag(111) in 0.01 M NaCl,' J. Electroanal. Chem. 541, 1-11 (2003).

M. E. MacDonald, 'Investigation of alternates to SiOx for protective scan mirror coatings in remote sensing instruments,' in Earth Observing Systems IV, Proc. SPIE 3750, 309-318. (1999).

Optical Coating Laboratory, Inc., 'HR94 front surface mirrors for projection display,' Product Brochure HR94FSM (Optical Coating Laboratory, Inc., 2001).

J. D. Wolfe, R. E. Laird, C. K. Carniglia, and J. P. Lehan, 'Durable silver-based antireflection coatings and enhanced mirrors,' in Technical Digest, Topical Meeting on Optical Interference Coatings (Optical Society of America, 1995), pp. 115-117.

J. Wolfe, D. Sanders, S. Bryan, and N. Thomas, 'Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, dc-pulsed magnetron sputtering,' in Specialized Optical Development in Astronomy, Proc. SPIE 4842, 343-351 (2003).

M. Boccas, T. Vucina, C. Araya, E. Vera, and C. Ahhee, 'Coating the 8-m Gemini telescopes with protected silver,' in Optical Fabrication, Metrology, and Material Advancements for Telescopes, Proc. SPIE 5494, 239-253 (2004).

P. D. Fuqua and J. D. Barrie, 'Optical properties and corrosion resistance of durable silver coatings,' in Properties and Processing of Vapor-Deposited Coatings, R.Johnson, W.Lee, M.Pickering, and B.Sheldon, eds., Mater. Res. Soc. Symp. Proc. 555, 85-90 (1998).

N. Thomas, A. Erlandson, J. Farmer, H. Gregg, C. Marshall, W. Siekhaus, J. Wolfe, D. Fix, and D. Ahre, 'Protected silver coatings for flashlamp-pumped Nd:glass amplifiers,' in Laser-Induced Damage in Optical Materials, Proc. SPIE 3578, 730-736 (1998).

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Figures (13)

Fig. 1
Fig. 1

Schematic drawing of the durable silver-mirror design.

Fig. 2
Fig. 2

Examples of electrochemical impedance spectra: (a) Nyquist plot and (b) Bode plot.

Fig. 3
Fig. 3

Simple corrosion process: (a) schematic model and (b) equivalent circuit model with the circuit description code.

Fig. 4
Fig. 4

Schematic model, equivalent circuit, and circuit description code used to describe the corrosion process of a coated metal in contact with an aqueous electrolyte: (a) dense coating and (b) coating with both permeable and impermeable defects.

Fig. 5
Fig. 5

Experimental setup for electrochemical impedance measurements.

Fig. 6
Fig. 6

Specular reflection spectra of different silver coatings.

Fig. 7
Fig. 7

Electrochemical impedance spectra: (a) bare Ag, (b) SiN x on Ag, (c) SiN x on 1Å NiCrN x on Ag, (d) SiN x on 3Å NiCrN x on Ag. The solid curves are calculated from equivalent circuit models shown in each plot with a CDC. CPEs (Q) were used in the models for better fitting.

Fig. 8
Fig. 8

Variation of the low-frequency limit of the impedance magnitude of SiN x ∕NiCrN x ∕Ag mirrors with NiCrN x interlayer thickness.

Fig. 9
Fig. 9

Specular reflectance spectra of various silver coatings before and after 96 and 240 h humidity exposure: (a) bare Ag, (b) 100Å SiN x over Ag, (c) 100Å SiN x over 2Å NiCrN x over Ag, (d) 100Å SiN x over 4Å NiCrN x over Ag.

Fig. 10
Fig. 10

SEM micrographs of the surface of different mirror samples after 240 h humidity testing: (a) bare Ag, (b) 100Å SiN x over Ag, (c) 100Å SiN x over 2Å NiCrN x over Ag, (d) 100Å SiN x over 4Å NiCrN x over Ag.

Fig. 11
Fig. 11

Specular reflectance spectra of various silver coatings before and after 24 and 72 h salt fog exposure: (a) bare Ag, (b) 100Å SiN x over Ag, (c) 100Å SiN x over 1Å NiCrN x over Ag, (d) 100Å SiN x over 3Å NiCrN x over Ag.

Fig. 12
Fig. 12

SEM micrographs of various silver coatings after 72 h salt fog exposure: (a) bare Ag, (b) 100Å SiN x over Ag, (c) 100Å SiN x over 1Å NiCrN x over Ag, (d) 100Å SiN x over 3Å NiCrN x over Ag.

Fig. 13
Fig. 13

Variation of reflectance change of SiN x ∕NiCrN x ∕Ag mirrors with NiCrN x interlayer thickness after (a) humidity testing and (b) salt fog testing.

Tables (2)

Tables Icon

Table 1 Deposition Conditions for the Multilayer Silver-Mirror Coating

Tables Icon

Table 2 EDS Elemental Analysis of Bare-Ag Mirrors before and after the 72 h Salt Fog Test

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

Z = E / I .
Z ( ω ) = R s + R c t 1 + ω 2 R c t       2 C d l       2 + j ω R c t       2 C d l 1 + ω 2 R c t       2 C d l         2 ,
ω max Z i = 2 π f max Z i = 1 / C d l R c t ,
1 / Z CPE = Z 0 ( j ω ) n ,

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