Optical properties of germanium nanoparticles synthesized by pulsed laser ablation in acetone

Saikiran Vadavalli,Bharati Neelamraju,Narayana Rao Desai,Alessandro Chiasera,Mudasir H Dar,Maurizio Ferrari,Sreeramulu Valligatla

doi:10.3389/fphy.2014.00057

Saikiran Vadavalli, Bharati Neelamraju + Show 5 more

Open Access

https://doi.org/10.3389/fphy.2014.00057

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Abstract

Germanium (Ge) nanoparticles (NPs) are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

Highlights

Semiconductor nanoparticles (NPs) or quantum dots are very attractive and interesting area of current research
In this paper we focus on the synthesis of germanium NPs by pulsed laser ablation (PLA) in acetone and the optical and structural characterization of synthesized NPs using different methods such as Raman spectroscopy, transmission electron microscopy (TEM), optical absorption, X-Ray diffraction (XRD), photoluminescence (PL) etc
Micro-Raman spectroscopy measurements have been performed on all the different types of samples synthesized in acetone at different energies and on the ablated Ge wafers separately

Summary

INTRODUCTION

Semiconductor nanoparticles (NPs) or quantum dots are very attractive and interesting area of current research. Inexpensive and green synthesis method for synthesizing nanoparticles of desired sizes at room temperatures is pulsed laser ablation in liquids (PLAL) from bulk targets [23,24,25]. Laser ablation in liquids has the advantage that it can be done at room temperatures and control on the properties of the nanoparticles can be achieved by varying the liquid properties and laser ablation parameters This technique is considered effective for the synthesis of colloidal solutions of nanoparticles. In this paper we focus on the synthesis of germanium NPs by pulsed laser ablation (PLA) in acetone and the optical and structural characterization of synthesized NPs using different methods such as Raman spectroscopy, transmission electron microscopy (TEM), optical absorption, X-Ray diffraction (XRD), photoluminescence (PL) etc. Structural characterization and elemental composition of the Ge NPs were observed by selective area electron diffraction (SAED) and energy dispersive X-ray spectroscopy analysis (EDS) both of which are associated with TEM

RAMAN RESULTS

TEM RESULTS

CONCLUSIONS