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

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.

Controlling the Color and Effective Refractive Index of Metal-Anodic Aluminum Oxide (AAO)–Al Nanostructures: Morphology of AAO

“…Such mechanisms also play an important role in the generation of brilliant colors for metal-AAO–Al nanostructures, and this is being extensively studied. These nanostructures can be used in different applications, such as surface plasmon resonance, − optical interference, wavelength absorbers, RGB display devices, and chemical and optical sensors …”

Morphological and Optical Characterization of High Density Au/PAA Nanoarrays

“…In recent years, porous materials have attracted much interest due to their wide range of applications [1][2][3]. Among them, nanoporous anodic alumina (PAA) has been widely used as membrane in the fabrication of various nanostructures [3,4]. Two-step anodization was extensively used to fabricate PAA membranes because of the cheap equipment, simple technology, and high controllability of the process [5].…”

“…Two-step anodization was extensively used to fabricate PAA membranes because of the cheap equipment, simple technology, and high controllability of the process [5]. The applications of the PAA membranes can be extended by depositing metal nanostructures inside their nanopores or on their top surfaces [4,6]. So the conducting, mechanical, and optical properties of PAA membranes could be improved [1,6].…”

“…In our previous studies, different metallic nanostructures have been loaded on the outer surface of PAA membranes such as Au, Cr, Pt, and Sn [12,19,25,26]. Also, the effects of different parameters such as Au-particles size, pore diameter, PAA thickness, the state of polarization, and angle of the incident on the optical properties were addressed [4,19]. These studies showed surface plasmon enhancement of PAA interference.…”

“…Recently, Shaban studied the effect of PAA pore thickness and state of polarization of the incident light on the surface plasmon modes of hexagonal arrays of Au nanoparticles grown around the active dots on the top surface of PAA membrane by r.f. magnetron sputtering [4]. In addition, different methods have been used to deposit Au nanorod arrays inside the pores of PAA.…”