Transport Studies of Transition Metal Ion Doped ZnO: Bulk and Thin Films
- PDF / 275,641 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 106 Downloads / 204 Views
0957-K10-43
Transport Studies of Transition Metal Ion Doped ZnO: Bulk and Thin Films Shubra Singh, N. Rama, and M.S. Ramachandra Rao Department of Physics, Indian Institute of Technology, Madras, Chennai, 600 036, India ABSTRACT The effect of doping of transition metal ions (Fe and Co) on transport properties of ZnO has been studied in both bulk and thin films. The solubility limit of these ions have been found to be higher in thin films compared to bulk. Optical measurements reveal the presence of Fe in both 2+ and 3+ state. Co is believed to be in 2+ states. Electrical resistivity measurements show that while for bulk Fe doped ZnO samples there is a decrease in ρ (T) compared to undoped ZnO, it increases for bulk Co doped ZnO samples. However, thin film samples of both types of doped compounds show a decrease in ρ (T) compared to undoped ZnO. This difference in bulk and thin film behaviour has been explained on the basis of experimental results. INTRODUCTION In contrast to magnetic semiconductors, dilute magnetic semiconductors (DMS) offer the possibility of studying magnetic phenomena in crystals with a simple band structure and excellent magneto-optical and transport properties. The most challenging task for broad applications is to find magnetic or diluted magnetic semiconductors which would operate at room temperature. In this regard, GaN and ZnO appear to be the most promising materials to have Curie temperature at and above room temperature. Due to the low solubility of transition metal impurities in GaN, incorporation of transition metal ions of higher concentration is difficult. Zinc oxide (ZnO), on the other hand, is a promising DMS material. It is a wide bandgap (~3.3 eV) semiconductor, which has received increasing attention due to its broad applications and ZnO possess many interesting applications. The existence of DMS based on Mn doped p-type ZnO [1] and V, Ti, Fe, Co or Ni doped n-type ZnO has been predicted in theory [2]. N-type ZnO behaviour in ZnO doped with Fe and Co has been confirmed experimentally [36] with Fe and Co doping leading to ferromagnetism at room temperature. Thus the study of transport properties of Zn1-xMxO (M=Transition metal, x=dopant concentration) is important from the viewpoint of transparent conducting ferromagnets. Recently we reported on the electrical resistivity of bulk Ni doped ZnO [7]. In the present work we report on the electrical, optical and structural properties of bulk and thin film form of Zn1-xMxO (x=0.0, 0.01, 0.02, M=Co, Fe). EXPERIMENT Zn1-xMxO(x=0.0, 0.01, 0.02; M=Co, Fe) targets were prepared using solid state reaction route. Thin films were deposited on quartz substrates by pulsed laser deposition (PLD) technique. All films were deposited at 500°C in O2 ambient pressure of 2x10-5 mbar with a laser energy density of 2 J/cm2. Phase analyses of the films were done by X-ray diffraction using a Cu Kα source. Electrical resistivity was measured by linear four probe technique. The nature of carriers was determined via Hall measurements. The diffuse reflectance
Data Loading...
