Spectroscopic characterization of highly doped ZnO films grown by atomic-layer deposition for three-dimensional infrared metamaterials [Invited]

Abstract

We systematically study the optical spectra of ZnO grown by atomic-layer deposition as a function of Al (and Ti) doping concentration. The spectra measured on films are well described by fits using a Drude freeelectron model. The derived plasma frequencies are consistent with the expected amount of doping and can be continuously and controllably tuned from small values to about 400 THz. The losses (damping) are also quantified. In addition, we achieve smooth conformal coatings of threedimensional polymer templates made by direct laser writing. Altogether, Al:ZnO appears as an attractive "tunable metal" for three-dimensional infrared metamaterials or transformation-optics architectures.

Experimental Evidence for Sign Reversal of the Hall Coefficient in Three-Dimensional Metamaterials

“…The film thickness has been determined by ellipsometry. We choose n-ZnO solely because we have experience with its deposition from different experiments [22] and because very smooth films can be achieved. Many other semiconductor materials should be possible, too.…”

Spectral tuning of a three-dimensional photonic-bandgap waveguide signature by silica atomic-layer deposition

“…In this case, i.e., if only very thin layers of silica or other dielectric materials amenable to ALD are infiltrated into the woodpile structure, the size of the PBG is only marginally decreased. Apart from varing the spaial distribution of the real part of the dielectric function by infiltration one could also imagine varying its imaginary part by ALD of a lossy material, e.g., doped ZnO [21], which could be employed for selective mode damping.…”

Ultra-thin films for plasmonics: a technology overview

“…[12,13] or II-VI semiconductors oxides (InTiO, Al:ZnO, Ga:ZnO, etc.) [14,15]. Others seem to be appropriate substitution of metals in mid-and far-IR or even in the terahertz range, where metallic properties of noble metal become too strong, and their behavior resembles more perfect conductors ousting truly plasmonic features.…”