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Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications

Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications
Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications
Thin films of aluminium oxide (Al2O3), tantalum pentoxide (Ta2O5), titanium oxide (TiO2), yttrium oxide (Y2O3) and zirconium oxide (ZrO2) were deposited by plasma assisted reactive dual magnetron sputtering to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The effect of deposition parameters such as cathode, plasma power and oxygen gas flows were studied and operational working points determined. Both power and lambda control were used to optimize the optical quality of each material. By using lambda control feedback system, the magnetron power fluctuates to sustain a fixed oxygen flow in the target area reducing the compound layer growth on the material and maintaining a healthy deposition rate. The optical properties, structure and crystalline phase of each film was found to be dependent on the process parameters. X-ray diffraction (XRD) analysis revealed that the thin films varied from amorphous to highly crystalline depending on deposition conditions. X-ray photoelectron spectroscopy (XPS) was utilized for surface compositional analysis revealing that films had varying stoichiometric ratios which are controlled for each material by the deposition parameters chosen. The waveguide loss for the thin film layers was investigated and Ta2O5 was shown to have a slab waveguide loss of ~1dB/cm at both visible and infra-red wavelengths making it ideal for planar waveguide and laser applications. TiO2, Y2O3 and ZrO2 were found to deposit in a highly crystalline phase. Waveguiding in the TiO2 layers was not possible at 633nm or in the infrared region. The Y2O3 samples gave low loss (2 – 4dB/cm) at 1.3 and 1.5µm wavelengths but no waveguiding at 633nm or 833nm was possible. Atomic force microscopy showed rough surface topography for TiO2, Y2O3 and ZrO2 akin to their crystalline growth with the SEM images confirming the regular crystalline columnar structure for the case of Y2O3 and ZrO2.
dielectrics, crystalline, amorphous, reactive sputtering, feedback control, thin film deposition
0257-8972
4930-4939
Pearce, Stuart
1d0ee7c5-8f72-4783-a034-9b2f67de3531
Charlton, M.D.B.
fcf86ab0-8f34-411a-b576-4f684e51e274
Hiltunen, J.
cf4de971-1190-45ee-8809-c31cb8b4b8f4
Puustinen, J.
c575620e-daac-4c47-a6e2-f7ad00dcc1f5
Lappalainen, J.
01e5d8f7-4705-478b-b141-43fbf4975c51
Wilkinson, J.S.
73483cf3-d9f2-4688-9b09-1c84257884ca
Pearce, Stuart
1d0ee7c5-8f72-4783-a034-9b2f67de3531
Charlton, M.D.B.
fcf86ab0-8f34-411a-b576-4f684e51e274
Hiltunen, J.
cf4de971-1190-45ee-8809-c31cb8b4b8f4
Puustinen, J.
c575620e-daac-4c47-a6e2-f7ad00dcc1f5
Lappalainen, J.
01e5d8f7-4705-478b-b141-43fbf4975c51
Wilkinson, J.S.
73483cf3-d9f2-4688-9b09-1c84257884ca

Pearce, Stuart, Charlton, M.D.B., Hiltunen, J., Puustinen, J., Lappalainen, J. and Wilkinson, J.S. (2012) Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications. Surface and Coatings Technology, 206 (23), 4930-4939. (doi:10.1016/j.surfcoat.2012.05.110).

Record type: Article

Abstract

Thin films of aluminium oxide (Al2O3), tantalum pentoxide (Ta2O5), titanium oxide (TiO2), yttrium oxide (Y2O3) and zirconium oxide (ZrO2) were deposited by plasma assisted reactive dual magnetron sputtering to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The effect of deposition parameters such as cathode, plasma power and oxygen gas flows were studied and operational working points determined. Both power and lambda control were used to optimize the optical quality of each material. By using lambda control feedback system, the magnetron power fluctuates to sustain a fixed oxygen flow in the target area reducing the compound layer growth on the material and maintaining a healthy deposition rate. The optical properties, structure and crystalline phase of each film was found to be dependent on the process parameters. X-ray diffraction (XRD) analysis revealed that the thin films varied from amorphous to highly crystalline depending on deposition conditions. X-ray photoelectron spectroscopy (XPS) was utilized for surface compositional analysis revealing that films had varying stoichiometric ratios which are controlled for each material by the deposition parameters chosen. The waveguide loss for the thin film layers was investigated and Ta2O5 was shown to have a slab waveguide loss of ~1dB/cm at both visible and infra-red wavelengths making it ideal for planar waveguide and laser applications. TiO2, Y2O3 and ZrO2 were found to deposit in a highly crystalline phase. Waveguiding in the TiO2 layers was not possible at 633nm or in the infrared region. The Y2O3 samples gave low loss (2 – 4dB/cm) at 1.3 and 1.5µm wavelengths but no waveguiding at 633nm or 833nm was possible. Atomic force microscopy showed rough surface topography for TiO2, Y2O3 and ZrO2 akin to their crystalline growth with the SEM images confirming the regular crystalline columnar structure for the case of Y2O3 and ZrO2.

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More information

Published date: 15 July 2012
Keywords: dielectrics, crystalline, amorphous, reactive sputtering, feedback control, thin film deposition
Organisations: Optoelectronics Research Centre, Nanoelectronics and Nanotechnology

Identifiers

Local EPrints ID: 350300
URI: https://eprints.soton.ac.uk/id/eprint/350300
ISSN: 0257-8972
PURE UUID: 416570be-bdec-44eb-a25e-24252ced1954
ORCID for J.S. Wilkinson: ORCID iD orcid.org/0000-0003-4712-1697

Catalogue record

Date deposited: 25 Mar 2013 11:39
Last modified: 20 Jul 2019 01:29

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