Materials Chemistry and Physics 114 (2009) 194–198 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Influence of Fe doping on nanostructures and photoluminescence of sol–gel derived ZnO A.K. Srivastava a,∗ , M. Deepa a , N. Bahadur a , M.S. Goyat b a National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India b Guru Jambheshwar University of Science and Technology, Hisar 125001, India article info Article history: Received 26 May 2008 Received in revised form 19 August 2008 Accepted 10 September 2008 Keywords: Oxides Sol–gel growth Electron microscopy Luminescence abstract The doping of Fe (0.5, 2, and 50 mol%) in ZnO was performed using sol–gel process, which led to noteworthy alterations in the microstructure, phase formations and optical properties. Nanoparticles (20–50 nm) with euhedral shape morphology and aggregated nanowires (20–30 nm diameter) are observed at 2 mol% Fe doping, whereas well developed and facetted nanoparticles (50–100nm), nanowires (∼60 nm diameter) and ultrafine particles (2–5 nm) are seen at 50 mol% Fe doping. The hexagonal-ZnO was present as the dominant phase with the traces of cubic-ZnFe 2 O 4 up to 2 mol% Fe, while at highest 50 mol% Fe doping, ZnFe 2 O 4 was the observed prominent phase, which is also responsible for the observed violet (412nm, 3.0 eV) and blue emission bands (468 nm, 2.65 eV and 440 nm, 2.82 eV) together with quenched orange (632 nm, 1.96 eV) and green (523 nm, 2.37 eV) luminescence. © 2008 Elsevier B.V. All rights reserved. 1. Introduction ZnO-based nanostructures [1–8] have gained substantial research interest owing to its abundance, wide band gap (3.37eV), excellent chemical and thermal stability, large exciton binding energy (60 meV), large electron mass ∼0.3 m e (m e : bare electron mass) which is expected to exhibit a strong magnetic interaction between mobile carriers and localized magnetic ions and the ther- mal energy at room temperature (26 meV), which can ensure an efficient exciton emission at room temperature under low excita- tion energy. Besides, ZnO is an important low cost, environmentally friendly basic semiconductor material, which is used consider- ably for its catalytic, optoelectronic and photo-electrochemical properties. Recent advances in the field are demonstrated by dop- ing of different transition metal ions such as Mn 2+ [9,10], Co 2+ [11,12], Ni 2+ [13],V 3+ [14,15] and Fe 3+ [16–20] into the ZnO lat- tice to tailor the material for various optical and electro-magnetic properties. The major focus of these studies has been on the investigation of the carrier induced magnetism in the ZnO-based semiconductors. But it is equally important to have as well a fundamental study of evolution of different nano-scaled features, phase formations and their consequences on optical properties in order to understand intrinsic mechanism of magnetic ions (as Fe 3+ in ZnO) and itinerant carriers. These studies are defensi- ∗ Corresponding author. Tel.: +91 11 45609308. E-mail address: aks@nplindia.ernet.in (A.K. Srivastava). ble before conception of reliable application. Among the foresaid ions, the incorporation of Fe 3+ into the ZnO lattice promises to lead very interesting and novel magnetic, electrical and optical properties. In the present work, it has been demonstrated that depending on doping concentration of Fe (0.5, 2, and 50 mol%) in ZnO, different nanostructures, phases and emission bands can be achieved. The mechanism responsible for these emissions have been explained and these are special in a way that all possible emission bands in the visible region are observed in a single study, which with the best of our knowledge, not reported so far. 2. Experimental Sols were synthesized from zinc acetate (Himedia) precursor dissolved in double-distilled water. One of the sets was left undoped, while in the remaining sets, requisite amounts of iron (III) chloride were added to zinc acetate to obtain sols with 0.5%, 2%, and 50% Fe–Zn molar ratio, respectively. The sols were continuously stirred at room temperature till clear sols devoid of any precipitates or particulates were obtained. The sol samples were then heated on hot plate with continuous stirring until the solution becomes gel like, and later annealed at 800 ◦ C for 2 h. The crystallographic interpretations were performed by X-ray diffractome- ter (XRD, Mini Flex II Desk Top X-ray Diffractometer) using Cu K wavelength ( = 1.54059 Å) and scanning in 2 range from 20 ◦ to 80 ◦ . The topological features and the composition of Zn, O and Fe were determined by a scanning electron micro- scope (SEM model LEO 440) equipped with an energy dispersive X-ray spectrometer (EDS model OXFORD LINK ISIS 300). Microstructural features at high magnifications and selected area electron diffraction patterns were recorded using a transmission electron microscope (TEM, model JEOL JEM 200CX), operated at the electron acceler- ating voltage of 200 keV. The photoluminescence (PL) investigations were performed using a Perkin-Elmer LS-55 luminescence spectrophotometer having a standard Xe source with an excitation wavelength of 350nm. 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.09.005