Abstract
In this study, we have prepared aluminum oxide (Al2O3 nanoparticles) NPs with size ranging from 50 to 90 nm by laser ablation of aluminum target in ethanol. The effect of laser fluence on the structural, morphological and optical properties of Al2O3 was demonstrated and discussed. X-ray diffraction XRD results confirm that the synthesized Al2O3 NPs are crystalline in nature. The sample prepared at 3.5 J/cm2/pulse exhibits single phase of γ-Al2O3, while the XRD patterns of the nanoparticles synthesized at 5.3 and 7.5 J/cm2/pulse show the co-existence of the α-Al2O3 and γ-Al2O3 phases. Nanostructured Al2O3 films have been used as anti-reflecting coating and surface passivation layer to improve the photoresponse characteristics of silicon photodiode. The experimental data showed that the optical energy gap decreases from 5.3 to 5 eV as the laser fluence increases from 3.5 to 7.3 J/cm2. The lowest optical reflectivity was found for silicon photodiode deposited with a single layer of Al2O3 prepared at 3.5 J/cm2/pulse. The effect of laser fluence on the refractive index and extinction coefficient of the nanostructured Al2O3 film was studied. The photosensitivity of the silicon photodiode increased from 0.4 to 1.4 AW−1 at 800 nm after depositing Al2O3 prepared at 3.5 J/cm2/pulse, followed by rapid thermal annealing at 400 °C for 60 s.
Highlights
Metal oxide nanoparticles have drawn attention due to their stable optical, electrical and structural properties (Hart 1990, Noda and Muramoto 2003)
Plane which indexed to face centered cubic c-Al2O3 metastable phase according to JCPD# 29-0063, no peaks related to pure Al element or other metastable phases were found in XRD pattern indicating the complete transformation of Al into c-Al2O3 after laser ablation
The XRD pattern confirms the co-existence of the c-Al2O3 and a-Al2O3 phases for nanoparticles prepared at 5.2 J/cm2
Summary
Metal oxide nanoparticles have drawn attention due to their stable optical, electrical and structural properties (Hart 1990, Noda and Muramoto 2003). Synthesis of nanoparticles by pulsed laser ablation in liquid (PLAL) has many advantages compared to other conventional techniques: the produced nanoparticles are pure and have no impurities; the process does not need any complex agents; a large variety of materials may be synthesized; material stoichiometry is preserved; there is fair control on the size of the produced nanoparticles; the process is cost-effective and fast (Petersen and Barcikowski 2009; Yang et al 2007). The reported data showed that the optical, structural and mechanical properties of Al2O3 nanoparticles prepared by PLAL depended on many parameters such as laser energy, laser wavelength, ablation time, laser pulse duration and liquid type (Piriyawong et al 2012; Emmanue et al 2009). Lee et al (Benjamin et al 2012)
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