Effect of Pore Thickness and the State of Polarization on the Optical Properties of Hexagonal Nanoarray of Au/Nanoporous Anodic Alumina Membrane

Mohamed Shaban

doi:10.1155/2015/347486

Abstract

Hexagonal nanoarrays of Au particles were deposited on nanoporous anodic alumina membrane (NAAM) utilizing r.f. magnetron sputtering. The thickness of the NAAMs is adjusted by changing the second anodization time from 5 min to 20 min. The surface morphology, composition, and optical properties are characterized by using SEM, EDX, and spectrophotometer, respectively. The effects of the NAAM thickness and state of polarization on the morphological changes and on the optical properties of the fabricated nanoarrays were addressed. According to the measured optical spectra, the rate of decrease of NAAMs refractive index was found to be 3.825 × 10−4 nm−1. Using the modified Kubelka-Munk radiative transfer model, the energy gap of NAAMs was calculated from diffused reflectance and was decreased from 1.682 to 1.376 as the anodization time increased from 5 to 20 min. Also, the saturation of interference fringes is substantially enhanced, and field enhancement can be achieved due to the excitation and constructive interference of surface plasmon waves by coating NAAMs with the hexagonal nanoarrays of Au. Based on the advantages of the fabrication approach and the enhanced and controlled properties, this new generation of samples can be used as promising building blocks for nanophotonic and nanoelectronics devices.

Highlights

In recent years, porous materials have attracted much interest because of their potential use in a variety of applications [1,2,3]
Homogenous deposition of metal nanostructures inside the pores of nanoporous anodic alumina membrane (NAAM) has gained much attention in recent years. This attention is ascribed to their extensive use as substrates for sensors based on surface-enhanced Raman scattering (SERS), laser induced fluorescence (LIF), and electrochemical measurements [3, 9,10,11]
Hexagonal aligned nanopores were formed in NAAM

Summary

Introduction

Porous materials have attracted much interest because of their potential use in a variety of applications [1,2,3]. Homogenous deposition of metal nanostructures inside the pores of NAAMs has gained much attention in recent years This attention is ascribed to their extensive use as substrates for sensors based on surface-enhanced Raman scattering (SERS), laser induced fluorescence (LIF), and electrochemical measurements [3, 9,10,11]. Experimental studies of Au particles size, pore diameter, and angle of the incident were addressed These studies showed the surface plasmon enhancement of NAAMs interference and illuminated the relationships between resonance position and structures (pore diameter and thickness) of porous gold layer and angle of incident. We studied the optical properties of NAAMs of different thicknesses before and after decoration with hexagonal nanoarrays of Au particles under illumination with s- and p-polarized light

Sample Fabrication and Characterization

Results and Discussion

Conclusion