Engineering Optical Properties of Nanorods Fabricated By Physical Vapor Deposition

Nanorod arrays fabricated by physical vapor deposition (PVD) have many technological applications due to its flexibility in changing morphology and structure of the materials. Tailoring the nanorod structures, optical properties of the materials can be manipulated.

There is a dependency of nanorod length as well as surface area in light absorbance of silver nanorod arrays. The long and high surface area nanorod arrays provide more space for light to couple with surface plasma and more propagation space to scatter and attenuate light intensity resulting lower reflectance. Changing the size and the length of the nanorods, surface plasma resonance wavelength (SPRW) can be tuned as shown in figure 1 for aluminum nanorods. With the increase of the nanorod length, absorbance increases and SPRW shifts from 248nm to 255nm. These nanorods are fabricated at a deposition angle of 86.5˚ and operating pressure of 1×10^-5Torr. Controlling the operating pressure and the substrate temperature, smaller nanorods can be fabricated and tuned to SPRW. Moreover, engineering the nanostructures, optical properties can be further manipulated. Figure 2 shows zigzag nanowalls of Silicon on diffraction gratings. These nanowalls can be used to confine light at a certain wavelength with well-defined spacing between nanowalls and number of zigzags.

Acknowledgements

The authors gratefully acknowledge financial support from the National Science Foundation (CBET-0748063).