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Polarisation dependent Raman study of single-crystal nickel oxide

100%

Mironova-Ulmane N., Kuzmin A., Sildos I., Pärs M.

Open Physics

2011

vol. 9

issue 4

1096-1099

The magnetic domain structure and Raman scattering have been studied in NiO single-crystals with three different (100), (110) and (111) orientations. Twin-domain structure was observed in NiO(100) and NiO(110) single-crystals using cross-polarized optical microscopy. We found that the ratio of the two-magnon (at 1500 cm−1) to the two-phonon (2LO, at 1100 cm−1) Raman bands intensity is sensitive in a particular way to the type of the twin-domain pattern.

Structural study of TiO2 thin films by micro-Raman spectroscopy

64%

Niilisk A., Moppel M., Pärs M., Sildos I., Jantson T., Avarmaa T., Jaaniso R., Aarik J.

Open Physics

2006

vol. 4

issue 1

105-116

The Raman spectroscopy method was used for structural characterization of TiO2 thin films prepared by atomic layer deposition (ALD) and pulsed laser deposition (PLD) on fused silica and single-crystal silicon and sapphire substrates. Using ALD, anatase thin films were grown on silica and silicon substrates at temperatures 125–425 °C. At higher deposition temperatures, mixed anatase and rutile phases grew on these substrates. Post-growth annealing resulted in anatase-to-rutile phase transitions at 750 °C in the case of pure anatase films. The films that contained chlorine residues and were amorphous in their as-grown stage transformed into anatase phase at 400 °C and retained this phase even after annealing at 900 °C. On single crystal sapphire substrates, phase-pure rutile films were obtained by ALD at 425 °C and higher temperatures without additional annealing. Thin films that predominantly contained brookite phase were grown by PLD on silica substrates using rutile as a starting material.

Atomic layer deposition of HfO2 on graphene from HfCl4 and H2O

52%

Alles H., Aarik J., Aidla A., Fay A., Kozlova J., Niilisk A., Pärs M., Rähn M., Wiesner M., Hakonen P., Sammelselg V.

Open Physics

2011

vol. 9

issue 2

319-324

Atomic layer deposition of HfO2 on unmodified graphene from HfCl4 and H2O was investigated. Surface RMS roughness down to 0.5 nm was obtained for amorphous, 30 nm thick hafnia film grown at 180°C. HfO2 was also deposited in a two-step temperature process where the initial growth of about 1 nm at 170°C was continued up to 10–30 nm at 300°C. This process yielded uniform, monoclinic HfO2 films with RMS roughness of 1.7 nm for 10–12 nm thick films and 2.5 nm for 30 nm thick films. Raman spectroscopy studies revealed that the deposition process caused compressive biaxial strain in graphene, whereas no extra defects were generated. An 11 nm thick HfO2 film deposited onto bilayer graphene reduced the electron mobility by less than 10% at the Dirac point and by 30–40% far away from it.

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3 Open Physics

2 2011

1 2006

3 Pärs M.

2 Aarik J.

2 Niilisk A.

2 Sildos I.

1 Aidla A.

1 Alles H.

1 Avarmaa T.

1 Fay A.

1 Hakonen P.

1 Jaaniso R.

1 Jantson T.

1 Kozlova J.

1 Kuzmin A.

1 Mironova-Ulmane N.

1 Moppel M.

1 Rähn M.

1 Sammelselg V.

1 Wiesner M.

Search results

Polarisation dependent Raman study of single-crystal nickel oxide

Structural study of TiO2 thin films by micro-Raman spectroscopy

Atomic layer deposition of HfO2 on graphene from HfCl4 and H2O