IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 42 (2009) 185009 (5pp) doi:10.1088/0022-3727/42/18/185009 Magnetoresistance fluctuations in a weak disorder indium nitride nanowire Y W Su 1,7,8 , K Aravind 2,7,8 , C S Wu 3 , Watson Kuo 4 , K H Chen 5 , L C Chen 6 and K S Chang-Liao 2 , W F Su 1 and C DChen 7,9 1 Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan 2 Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan 3 Department of Physics, National Chang-Hua University of Education, ChangHua 500, Taiwan 4 Department of Physics, National Chung Hsing University, Taichung 402, Taiwan 5 Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan 6 Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan 7 Institute of Physics, Academia Sinica, Nankang 115, Taipei, Taiwan E-mail: chiidong@phys.sinica.edu.tw Received 7 April 2009, in final form 6 August 2009 Published 4 September 2009 Online at stacks.iop.org/JPhysD/42/185009 Abstract We report measurements of magnetoresistance (MR) fluctuations in a weak disorder indium nitride nanowire. The MR fluctuations are reproducible, aperiodic and symmetric in magnetic field but are asymmetric upon reversal of bias direction. The fluctuations are analysed for both perpendicular and parallel external magnetic field configurations in the light of tunnel magnetoresistance at low field and impurity scattering at higher field. The asymmetry in bias reversal is caused by breakdown of time reversal symmetry. (Some figures in this article are in colour only in the electronic version) Nanowires are a promising class of powerful materials, which, together with controlled growth and organization, can open avenues for next generation nano-scale electronic devices [1]. Indium nitride (InN) is an interesting candidate for these applications because of its revised direct band gap of 0.7–0.8 eV in the visible range [2–4]. Magnetoresistance (MR) is the relative change in electrical resistance upon application of a magnetic field and this has already found much scope for application. It is our attempt to integrate these versatile nanowire materials with advanced fabrication technology. The state-of-the-art patterning techniques allow us to make electrodes with very small separation so that the device falls into the mesoscopic regime. In this paper we present the interesting interplay between MR fingerprints and diffusive electron transport in single crystal wurtzite InN nanowires in both parallel and perpendicular magnetic field configurations. In particular, the low field (within ±1 kGs) data show typical signatures of tunnel magnetoresistance (TMR) while the high field (up to ±50 kGs) data exhibit aperiodic, non-attenuating fluctuations, which are a characteristic manifestation of the 8 These authors contributed equally for this work. 9 Author to whom any correspondence should be addressed. hypothesis [5] predicting a complete change in impurity configuration in a sweeping magnetic field. Single crystalline nanowires used in this device were grown by guided stream thermal chemical vapour deposition with trimethyl indium as indium source, ammonia as nitrogen source and gold as catalyst [6]. The diameters of the wires were in the range 35–120 nm with a typical length 15–20 µm. The nanowires were first dispersed in isopropanol solution. A few droplets of this solution were then placed on Si substrates with micrometre-sized Pt/Ti measurement pads pre-fabricated on a 300 nm thick SiO 2 oxide surface. Subsequently, nano- scaled electrodes were fabricated by standard electron beam lithographic technology, which served as inter-connectors between nanowires and Pt/Ti pads. Electron beam writing and identification of the positions of the dispersed nanowires for e-beam exposure purpose were performed using a field emission scanning electron microscope (FESEM). The nanometre electrodes were made of Ni (50 nm) covered with Au (50 nm) protection layer and were found to provide good Ohmic contacts to the InN nanowires. The top-left inset of figure 1 shows an FESEM image of the measured device. For this device the wire diameter is about 80 nm and the separation between the source and drain electrodes is approximately 0022-3727/09/185009+05$30.00 1 © 2009 IOP Publishing Ltd Printed in the UK