TY - JOUR
T1 - Control of slanting angle, porosity, and anisotropic optical constants of slanted columnar thin films via in situ nucleation layer tailoring
AU - Rice, Charles
AU - Mock, Alyssa
AU - Sekora, Derek
AU - Schmidt, Daniel
AU - Hofmann, Tino
AU - Schubert, Eva
AU - Schubert, Mathias
N1 - Funding Information:
The authors would like to acknowledge financial support from the National Science Foundation ( MRSEC DMR-0820521 , MRI DMR-0922937 , DMR-0907475 , ECCS-0846329 , EPS-1004094 ), the Nebraska Research Initiative , and the J.A. Woollam Foundation . The research was performed in part in the Nebraska Nanoscale Facility: National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Materials and Nanoscience, which are supported by the National Science Foundation under Award ECCS: 1542182, and the Nebraska Research Initiative.
Funding Information:
The authors would like to acknowledge financial support from the National Science Foundation (MRSEC DMR-0820521, MRI DMR-0922937, DMR-0907475, ECCS-0846329, EPS-1004094), the Nebraska Research Initiative, and the J.A. Woollam Foundation. The research was performed in part in the Nebraska Nanoscale Facility: National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Materials and Nanoscience, which are supported by the National Science Foundation under Award ECCS: 1542182, and the Nebraska Research Initiative.
Publisher Copyright:
© 2017
PY - 2017/11/1
Y1 - 2017/11/1
N2 - Electron-beam evaporation at a glancing angle of 85° is utilized to fabricate highly ordered, spatially coherent titanium slanted columnar thin films. Prior to deposition of the slanted columnar thin films, a titanium nucleation layer is deposited using electron-beam deposition at normal incidence with various intended nucleation layer thicknesses of 0 nm, 5 nm, 7.5 nm, 10 nm, 20 nm, and 50 nm. Structural and optical properties of the anisotropic porous thin films are studied by scanning electron microscopy, atomic force microscopy, and Mueller matrix generalized spectroscopic ellipsometry in the near infrared to ultra-violet spectral regions. An anisotropic effective medium approximation is employed for analysis of the ellipsometry data in order to determine slanting angle and porosity model parameters. We find that the slanting angle and titanium volume fraction are strongly influenced by the nucleation layer thickness. Structural parameters of SCTFs deposited on 50 nm nucleation layers are similar to those from SCTFs with no nucleation layer. For small nucleation layer thicknesses, the corresponding SCTF slanting angle and titanium volume fraction decrease reaching a minimum of ≈33° and ≈12%, respectively, at 10 nm nucleation layer thickness. In accordance with the strong decrease in volume fraction we observe substantial reduction of the effective anisotropic thin film optical constants. We find the slanting angle and porosity variation reproducible and suggest use of a nucleation layer for control of slanting angle and porosity of slanted columnar thin films.
AB - Electron-beam evaporation at a glancing angle of 85° is utilized to fabricate highly ordered, spatially coherent titanium slanted columnar thin films. Prior to deposition of the slanted columnar thin films, a titanium nucleation layer is deposited using electron-beam deposition at normal incidence with various intended nucleation layer thicknesses of 0 nm, 5 nm, 7.5 nm, 10 nm, 20 nm, and 50 nm. Structural and optical properties of the anisotropic porous thin films are studied by scanning electron microscopy, atomic force microscopy, and Mueller matrix generalized spectroscopic ellipsometry in the near infrared to ultra-violet spectral regions. An anisotropic effective medium approximation is employed for analysis of the ellipsometry data in order to determine slanting angle and porosity model parameters. We find that the slanting angle and titanium volume fraction are strongly influenced by the nucleation layer thickness. Structural parameters of SCTFs deposited on 50 nm nucleation layers are similar to those from SCTFs with no nucleation layer. For small nucleation layer thicknesses, the corresponding SCTF slanting angle and titanium volume fraction decrease reaching a minimum of ≈33° and ≈12%, respectively, at 10 nm nucleation layer thickness. In accordance with the strong decrease in volume fraction we observe substantial reduction of the effective anisotropic thin film optical constants. We find the slanting angle and porosity variation reproducible and suggest use of a nucleation layer for control of slanting angle and porosity of slanted columnar thin films.
KW - Glancing angle deposition
KW - Mueller matrix generalized spectroscopic ellipsometry
KW - Prepatterning
KW - Slanted columnar thin films
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U2 - 10.1016/j.apsusc.2017.03.134
DO - 10.1016/j.apsusc.2017.03.134
M3 - Article
AN - SCOPUS:85016447113
VL - 421
SP - 766
EP - 771
JO - Applied Surface Science
JF - Applied Surface Science
SN - 0169-4332
ER -