Journal of Alloys and Compounds 476 (2009) 28–32 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Annealing effect on the structural, optical and electrical properties of Yb–Mn oxide thin films A.A. Dakhel ∗ Department of Physics, College of Science, University of Bahrain, P.O. Box 32038, Bahrain article info Article history: Received 10 September 2008 Accepted 17 September 2008 Available online 1 November 2008 PACS: 78.20.Ci 77.55.+f 72.20.-I 78.70.En Keywords: Optical properties Ytterbium–manganese oxide Crystal structure Oxides abstract Ytterbium–manganese oxide thin films were grown on quartz and p-type Si(1 0 0) substrates. The films were thermally annealed at different temperatures ranging from 400 to 1000 ◦ C to agitate interdiffusion and thus initiate a solid-state reaction. The structural characterisation of the films was carried out by X-ray diffraction (XRD) and energy dispersion X-ray fluorescence (EDXRF). The XRD investigation on films at 400 ◦ C reveals the beginning of Yb 2 O 3 crystallisation and a film of nano YbMnO 3 grains was formed at annealing at about 1000 ◦ C. Mn oxide molecules were totally diffused for interaction with Yb and did not crystallise or granulate alone. The optical properties of the films were studied in wavelength range 200–2500 nm. The ac-conductance and capacitance as a function frequency were studied on samples made in form of metal/oxide film/Si MOS devices. It was found that the power-law dependence controls the frequency dependence of the ac-conductivity, while Kramers–Kronig (KK) relations explain the frequency dependence of the relative permittivity. The calculation shows that the ac-conduction in YbMnO 3 film is realised by bipolaron hopping mechanism. Temperature dependence of dc-conduction was also studied. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Magnate rare-earth oxides have promises in magneto-optical and magneto-electronic applications. They have high quality of dielectric properties, magnetic ordering, colossal magneto- resistance, electric ordering, and stable chemical and thermal properties [1–4]. System such as Yb–Mn–O is one of magnetic semi- conducting materials, for which various electrical, magnetic, and structural studies have been carried out, especially on YbMnO 3 [5]. It was concluded that the stable hexagonal P6 3 cm structure of the compound YbMnO 3 (ferroelectric of Tc 1270K [4]) is a result of small ionic radius of Yb (relative to rare-earth ions), which restrain the formation of orthorhombic-perovskite phase [5,6]. However, only under high pressure with high annealing temperature (5 GPa and 1100 ◦ C), the orthorhombic-perovskite YbMnO 3 structure was obtained from hexagonal phase [7]. Optical and structural properties of some RMnO 3 compounds were studied in some previous works, where R was (Sc, Y, Er) [8], Y [6], (Y and Yb) [5], Yb [3], Lu [9]. However, a little optical and electrical work was done on a Yb–Mn–O system especially on the compound YbMnO 3 . The aim of the present investigation is to study ∗ Fax: +973 17449148. E-mail address: adakhil@sci.uob.bh. the structural, electrical, and optical variations during post anneal- ing process of Yb–Mn–O multi-layered films grown on silicon and quartz substrates. In addition, this research concerns the prepara- tion of a nanocrystalline YbMnO 3 film and investigates its optical and electrical properties. 2. Experimental The starting materials were Yb (Puriss-Fluka Chemica) and a MnO2 (from BDH chemical Ltd.). The Yb–Mn double oxide films were prepared by alternating layer- by-layer (12 layers) thermal evaporation method of starting constituent materials on silicon and clean quartz (SPI Supplies, W. Chester, USA) substrates held at about 100 ◦ C in a vacuum chamber of residual pure oxygen atmosphere of pressure about 1.3 × 10 -2 Pa. The used Si substrate was cleaned by a standard technique using potas- sium hydroxide solution, acetone, and deionised water. All the as-grown amorphous films were oxidised by means of annealing at 400 ◦ C in pure dry oxygen atmo- sphere for 30 min. Some of these samples were investigated under name S400. The other samples were further annealed at different temperatures in order to agitate solid-state reaction between Mn oxide and Yb oxide and study the crystallisation conditions. Therefore, samples were named according to their annealing tempera- ture: samples annealed at 600 ◦ C for 30 min in air atmosphere were named S600, at 800 ◦ C–S800, and at 1000 ◦ C–S1000. Thickness of each layer was monitored and controlled during preparation with a thickness monitor and then ellipsometrically measured with Gaertner L117 to be around 300nm. The relative weight compo- sition of Mn/Yb in the prepared Yb–Mn oxide film was evaluated with energy dispersion XRF method by using a setup with a Ni-filtered X-ray beam from Cu anode and Amptek XR-100CR detector. The crystal structures were investigated by Philips PW 1710 X-ray diffractometer with Cu K line. The spectral transmittance T() and reflectance R() were measured with a Shimadzu UV-3600 double beam 0925-8388/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2008.09.095