Abstract—Alkylated silicon nanocrystals (C 11 -SiNCs) were prepared successfully by galvanostatic etching of p-Si(100) wafers followed by a thermal hydrosilation reaction of 1-undecene in refluxing toluene in order to extract C 11 -SiNCs from porous silicon. Erbium trichloride was added to alkylated SiNCs using a simple mixing chemical route. To the best of our knowledge, this is the first investigation on mixing SiNCs with erbium ions (III) by this chemical method. The chemical characterization of C 11 -SiNCs and their mixtures with Er 3+ (Er/C 11 -SiNCs) were carried out using X-ray photoemission spectroscopy (XPS). The optical properties of C 11 - SiNCs and their mixtures with Er 3+ were investigated using Raman spectroscopy and photoluminescence (PL). The erbium mixed alkylated SiNCs shows an orange PL emission peak at around 595 nm that originates from radiative recombination of Si. Er/C 11 -SiNCs mixture also exhibits a weak PL emission peak at 1536 nm that originates from the intra-4f transition in erbium ions (Er 3+ ). The PL peak of Si in Er/C 11 -SiNCs mixture is increased in the intensity up to three times as compared to pure C 11 -SiNCs. The collected data suggest that this chemical mixing route leads instead to a transfer of energy from erbium ions to alkylated SiNCs. Keywords—Photoluminescence, Silicon Nanocrystals, Erbium, Raman Spectroscopy. I. INTRODUCTION HE major component in microelectronic and optical communication system is silicon. There are three limitations that are associated with silicon related to their use in optical communication system i.e. Si is an indirect band gap, strong non radiative recombination pathways resulting in a very short non radiative lifetime and there is a mismatch between the band edge luminescence at 1.1 μm (1.1 eV) and the wavelength of 1.55 μm (0.8 eV) that is a requirement for compatibility with optical communication system [1]. This number of factors makes this element a poor light emitter. The limitation of the spectral mismatch is overcome by incorporating silicon with rare earth ions such as Er, Yb, Nd and Tm. Rare earth ions emission has been widely investigated in silicon last two decade [1]-[3]. Erbium ions especially have played a crucial role in the improvement of optical communication system, due to its luminescence band being at 1.54 μm, which is the requirement in this technology. Erbium is 11 th element in the series of rare earth elements K. M. Abualnaja is with the School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle Upon Tyne, UK (corresponding author: +44 (0) 191 208 5619; e-mail: k.abualnaja@ncl.ac.uk). L. Šiller is with the School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle Upon Tyne, UK (e-mail: lidija.siller@ncl.ac.uk). B. R. Horrocksis with the School of Chemistry, Newcastle University, Newcastle Upon Tyne, UK (e-mail: ben.horrocks@ncl.ac.uk). which located in the sixth row of the periodic table and the electronic configuration of Er is [Xe]4f 12 6s 2 . It is known that Er presents intense narrow luminescence bands in both visible and near infrared regions [4]. The erbium has two oxidation states i.e. Er 2+ and Er 3+ , out of which the former one is very commonly seen in semiconductors; due to its radiative transition at around 1.54 μm which corresponds to the most interesting wavelength in photonics community. Losing one electron of 4f orbital and both of 6s orbital produces the trivalent erbium (Er 3+ ); thus in this ion the incomplete 4f orbital is shielded by 5s and 5p orbitals resulting in luminescence dependent host. The radiative transition of Er 3+ in solid hosts looks like the free ion but with some changes due to Stark splitting [5]. The labels of the energy levels in rare earth ions e.g. 4 I 13/2 or 4 S 3/2 correspond to their angular momentum and spin quantum numbers [5]. The letters here are attributed to the total orbital angular momentum of the ion. The total orbital angular momentum is resulted by adding the orbital angular momenta of the individual electrons in the ion following the Clebsch- Gordan series [6]. Thus, the letter S indicates the orbital angular momentum (L) of 0, P of 1, D of 2, F of 3 and etc. Therefore, the letter I presents an L of 6. The superscript number 4 denotes the possible orientation of the total spin angular momentum of the ion, which is given as 2S+1, where S is attributed to quantum numbers of spin. While the subscript presents the total angular momentum of the ion. Consequently, in rare earth ions, it should be considered that each discrete energy level is attributed to 2S+1 L J [5]. The emission from trivalent erbium at 1554 nm (due to 4 I 13/2 → 4 I 15/2 transition in erbium) is a standard wavelength in the optical telecommunication system; thus it is important to achieve maximum enhancement in Er emission intensity i.e. long luminescent lifetime and high active concentration of erbium [7]. Recently, the investigation on enhancing the optical activity of erbium ions has been extensively reported [1], [8], [9]. The erbium emission can be increased by i) adding clusters which act as sensitizers for erbium excitation, ii) increasing the fraction of trivalent erbium by changing the local atomic environment and iii) optimizing the rate of erbium excitation by applying local field enhancement in presence of metallic particles [8]. The sensitization effect has recently become attractive subject because of the successful enhancement in erbium emission via range of sensitizers (host materials) including SiNCs, SiO 2 and Yb ions [7], [9]-[11]. Among the host materials, Si has received particular interest since the discovery of 1.54 μm light emission in erbium doped silicon at 20 K in 1983 by Ennen and co-workers [12] and Photoluminescence Study of Erbium-Mixed Alkylated Silicon Nanocrystals Khamael M. Abualnaja, Lidija Šiller, Benjamin R. Horrocks T World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:9, No:2, 2015 234 International Scholarly and Scientific Research & Innovation 9(2) 2015 ISNI:0000000091950263 Open Science Index, Chemical and Molecular Engineering Vol:9, No:2, 2015 publications.waset.org/10000323/pdf