Plasma ion assisted deposition of hafnium dioxide using argon and xenon as process gases

Hafnium dioxide films have been produced by plasma ion assisted electron beam evaporation, utilizing argon or xenon as working gases. The optical constants of the layers have been investigated by spectrophotometry, while X-ray reflection measurements (XRR), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) have been performed with selected samples. The correlation between structural and optical properties is discussed. With respect to optical quality, the application of xenon as working gas results in coatings with higher refractive index and smaller surface roughness than the application of argon. This effect is attributed to a more efficient momentum transfer from high energetic working gas ions or atoms to hafnium atoms during deposition. ©2011 Optical Society of America OCIS codes: (160.4670) Optical materials; (310.3840) Materials and process characterization; (310.6860) Thin films, optical properties; (310.6870) Thin films, other properties; (310.1860) Deposition and fabrication. References and links 1. W. T. Tang, Z. F. Ying, Z. G. Hu, W. W. Li, J. Sun, N. Xu, and J. D. Wu, ―Synthesis and characterization of HfO2 and ZrO2 thin films deposited by plasma assisted reactive pulsed laser deposition at low temperature,‖ Thin Solid Films 518(19), 5442–5446 (2010). 2. J. M. Khoshman, A. Khan, and M. E. Kordesch, ―Amorphous hafnium oxide thin films for antireflection optical coatings,‖ Surf. Coat. Tech. 202(11), 2500–2502 (2008). 3. R. Thielsch, A. Gatto, J. Heber, and N. Kaiser, ―A comparative study of the UV optical and structural properties of SiO2, Al2O3, and HfO2 single layers deposited by reactive evaporation, ion-assisted deposition and plasma ionassisted deposition,‖ Thin Solid Films 410(1-2), 86–93 (2002). 4. J. M. Khoshman and M. E. Kordesch, ―Optical properties of a-HfO2 thin films,‖ Surf. Coat. Tech. 201(6), 3530– 3535 (2006). 5. T. Nishide, S. Honda, M. Matsuura, and M. Ide, ―Surface, structural and optical properties of sol-gel derived HfO2 films,‖ Thin Solid Films 371(1-2), 61–65 (2000). 6. N. Selvakumar, H. C. Barshilia, K. S. Rajam, and A. Biswas, ―Structure, optical properties and thermal stability of pulsed sputter deposited high temperature HfOx/Mo/HfO2 solar selective absorbers,‖ Sol. Energy Mater. Sol. Cells 94(8), 1412–1420 (2010). 7. J. Capoulade, L. Gallais, J.-Y. Natoli, and M. Commandré, ―Multiscale analysis of the laser-induced damage threshold in optical coatings,‖ Appl. Opt. 47(29), 5272–5280 (2008). 8. O. Stenzel, S. Wilbrandt, N. Kaiser, M. Vinnichenko, F. Munnik, A. Kolitsch, A. Chuvilin, U. Kaiser, J. Ebert, S. Jakobs, A. Kaless, S. Wüthrich, O. Treichel, B. Wunderlich, M. Bitzer, and M. Grössl, ―The correlation between mechanical stress, thermal shift and refractive index in HfO2, Nb2O5, Ta2O5 and SiO2 layers and its relation to the layer porosity,‖ Thin Solid Films 517(21), 6058–6068 (2009). 9. O. Stenzel, S. Wilbrandt, M. Schürmann, N. Kaiser, H. Ehlers, M. Mende, D. Ristau, S. Bruns, M. Vergöhl, M. Stolze, M. Held, H. Niederwald, T. Koch, W. Riggers, P. Burdack, G. Mark, R. Schäfer, S. Mewes, M. Bischoff, M. Arntzen, F. Eisenkrämer, M. Lappschies, S. Jakobs, S. Koch, B. Baumgarten, and A. Tünnermann, ―Mixed oxide coatings for optics,‖ Appl. Opt. 50(9), C69–C74 (2011). 10. B. Andre, L. Poupinet, and G. Ravel, ―Evaporation and ion assisted deposition of HfO2 coatings: Some key points for high power laser applications,‖ J. Vac. Sci. Technol. 18(5), 2372–2377 (2000). 11. D. Zhang, S. Fan, Y. Zhao, W. Gao, J. Shao, R. Fan, Y. Wang, and Z. Fan, ―High laser-induced damage threshold HfO2 films prepared by ion-assisted electron beam evaporation,‖ Appl. Surf. Sci. 243(1-4), 232–237 (2005). #144260 $15.00 USDReceived 16 Mar 2011; revised 12 May 2011; accepted 18 May 2011; published 26 May 2011 (C) 2011 OSA 1 June 2011 / Vol. 1, No. 2 / OPTICAL MATERIALS EXPRESS 278 12. M. Jerman, Z. Qiao, and D. Mergel, ―Refractive index of thin films of SiO2, ZrO2, and HfO2 as a function of the films’ mass density,‖ Appl. Opt. 44(15), 3006–3012 (2005). 13. A. Kunz, A. Hallbauer, D. Huber, and H. K. Pulker, ―Optische und mechanische Eigenschaften von RLVIP HfO2-Schichten,‖ Vak. Forsch. Praxis 18(5), 12–16 (2006). 14. E. E. Hoppe, R. S. Sorbello, and C. R. Aita, ―Near-edge optical absorption behavior of sputter deposited hafnium dioxide,‖ J. Appl. Phys. 101(12), 123534 (2007). 15. J. Aarik, H. Mändar, M. Kirm, and L. Pung, ―Optical characterization of HfO2 thin films grown by atomic layer deposition,‖ Thin Solid Films 466(1-2), 41–47 (2004). 16. M. Alvisi, F. De Tomasi, M. R. Perrone, M. L. Protopapa, A. Rizzo, F. Sarto, and S. Scaglione, ―Laser damage dependence on structural and optical properties of ion-assisted HfO2 thin films,‖ Thin Solid Films 396(1-2), 44– 52 (2001). 17. A. Gatto, R. Thielsch, J. Heber, N. Kaiser, D. Ristau, S. Günster, J. Kohlhaas, M. Marsi, M. Trovò, R. Walker, D. Garzella, M. E. Couprie, P. Torchio, M. Alvisi, and C. Amra, ―High-performance deep-ultraviolet optics for freeelectron lasers,‖ Appl. Opt. 41(16), 3236–3241 (2002). 18. J. Bellum, D. Kletecka, P. Rambo, I. Smith, J. Schwarz, and B. Atherton, ―Comparisons between laser damage and optical electric field behaviors for hafnia/silica antireflection coatings,‖ Appl. Opt. 50(9), C340–C348 (2011). 19. X. Cheng, Z. Shen, H. Jiao, J. Zhang, B. Ma, T. Ding, J. Lu, X. Wang, and Z. Wang, ―Laser damage study of nodules in electron-beam-evaporated HfO2/SiO2 high reflectors,‖ Appl. Opt. 50(9), C357–C363 (2011). 20. Z. Jinlong, C. Xinbin, W. Zhanshan, J. Hongfei, and D. Tao, ―HfO2/SiO2 chirped mirrors manufactured by electron beam evaporation,‖ Appl. Opt. 50(9), C388–C391 (2011). 21. S. Scaglione, F. Sarto, M. Alvisi, A. Rizzo, M. R. Perrone, and M. L. Protopapa, ―Correlation between the structural and optical properties of ion-assisted hafnia thin films,‖ Proc. SPIE 3902, 194–203 (2000). 22. A. V. Tikhonravov, M. K. Trubetskov, T. V. Amotchkina, G. DeBell, V. Pervak, A. K. Sytchkova, M. L. Grilli, and D. Ristau, ―Optical parameters of oxide films typically used in optical coating production,‖ Appl. Opt. 50(9), C75–C85 (2011). 23. G. Abromavicius, R. Buzelis, R. Drazdys, D. Perednis, and A. Skrebutenas, ―Optimization of HfO2, Al2O3 and SiO2 deposition leading to advanced UV optical coatings with low extinction,‖ Proc. SPIE 6596, 65961N (2007). 24. P. Torchio, A. Gatto, M. Alvisi, G. Albrand, N. Kaiser, and C. Amra, ―High-reflectivity HfO2/SiO2 ultraviolet mirrors,‖ Appl. Opt. 41(16), 3256–3261 (2002). 25. M. Gilo and N. Croitoru, ―Study of HfO2 films prepared by ion-assisted deposition using a gridless end-hall ion source,‖ Thin Solid Films 350(1-2), 203–208 (1999). 26. J. D. Targove and H. A. Macleod, ―Verification of momentum transfer as the dominant densifying mechanism in ion-assisted deposition,‖ Appl. Opt. 27(18), 3779–3781 (1988). 27. O. Stenzel, S. Wilbrandt, K. Friedrich, and N. Kaiser, ―Realistische Modellierung der NIR/VIS/UV-optischen Konstanten dünner optischer Schichten im Rahmen des Oszillatormodells,‖ Vak. Forsch. Praxis 21(5), 15–23 (2009). 28. M. Born and E. Wolf, Principle of Optics (Pergamon Press, 1968) 29. S. Wilbrandt, O. Stenzel, and N. Kaiser, ―All-optical in-situ analysis of PIAD deposition processes,‖ Proc. SPIE 7101, 71010D (2008). 30. E. C. Freeman and W. Paul, ―Optical constants of rf sputtered hydrogenated amorphous Si,‖ Phys. Rev. B 20(2), 716–728 (1979). 31. H. Finkenrath, ―The Moss rule and the influence of doping on the optical dielectric constant of semiconductors— I,‖ Infrared Phys. 28(5), 327–332 (1988). 32. O. Stenzel, ―A model for calculating the effect of nanosized pores on refractive index, thermal shift and mechanical stress in optical coatings,‖ J. Phys. D 42(5), 055312 (2009).