Technical Digest, 2015 28th International Vacuum Nanoelectronics Conferernce, 13-17 July, Guangzhou, China 978-1-4673-9357-7/15/$31.00 ©2015 IEEE Synthesis of GdB 6 Nanostructures Using Nanosecond (Nd: YAG) Laser: Field Emission Investigation S. R. Suryawanshi, Dattaatry J. Late, M. A. More* Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007, India. *Corresponding author: mam@physics.unipune.ac.in Anil K. Singh, S. Sinha*, Laser and Plasma Technology Divison, Bhaba Atomic Research Center, Trombey, Mumbai, 40085, India. *Corrospondin author:ssinha@barc.gov.in . Abstract - We herein report field emission characteristics of GdB 6 nanostructures grown directly on a pellet via laser processing (laser fluence ~ 6 J/cm 2 ). The laser processed GdB 6 pellet was characterized by X-ray diffraction, which revealed no change in phase upon laser processing. The values of the turn-on field required to draw emission current density of 1 μA/cm 2 is found to be ~ 2.95 V/μm, for the laser processed GdB 6 emitter. Furthermore, the Fowler–Nordheim (F-N) plot exhibits non- linear behavior over the entire range of applied field and the field enhancement factor (β) calculated from slope of the F-N plot (low field region) was found to be ~ 543. The emission current stability over a period of 3h was observed to be fairly good. The observed results demonstrate that laser processing can be efficiently used to make GdB 6 nanostructure emitter having potential for practical applications. Keywords: - GdB 6, Field Emission, Nanostructures, Laser Processing. I. INTRODUCTION Gadolinium hexaboride (GdB 6 ) has received renewed research interest in recent years because of exotic physico-chemical properties and potential for applications in various devices. Its cubic crystal structure composed of rare earth metal atom embedded inside a stable boron octahedron case offers a unique combination of the desired set of properties for an excellent cathode material, such as low work function, low volatility, low electrical resistivity, low sputtering coefficient, high mechanical strength, and chemical resistance, etc. [1] In the context of field emitters, the nanostructures due to their high aspect ratio offer unprecedented advantages over the micro-crystalline bulk structures in terms of noticeable lowering of the operating voltages and relaxation of base pressure by an order or two.[2] From application point of view, for fabrication of cold cathodes based on nanostructures, two parameters viz, the aspect ratio and work function are very important. It is desirable that the nanostructures should have high aspect ratio and low work function.[3] In the present studies, we report laser induced surface modification of GdB 6 pellet and its FE investigations. II. EXPERIMENTAL Laser induced surface structuring of the GdB 6 pellet was carried out using the Q-switched Nd: YAG laser operated at λ = 532 nm, pulse duration ~ 10 ns and 10 Hz repetition rate. The GdB 6 pellet (diameter ~10 mm, thickness ~ 5 mm) was prepared from commercial GdB 6 powder (purity 99.99%, Sigma Aldrich Chemicals) with poly vinyl alcohol as a binder by applying a pressure of ~8 kN/cm 2 followed by sintering under Argon ambient at ~700 °C for ~4 hours. For laser processing GdB 6 pellet was mounted onto the holder, the vacuum chamber was evacuated to a base pressure of ~8 × 10 - 6 mbar. The laser beam was at 45 o incidence to the surface of GdB 6 pellet. In order to generate the nano/micro structures on the GdB 6 pellet surface, the pellet was irradiated with laser fluence of ~ 6 J/cm 2 for 20 minute duration. The structural property of the GdB 6 emitters was revealed using X-ray diffraction (D8 Advance Bruker AXS). Surface morphology of the GdB 6 pellet was examined under a scanning electron microscope (SEM, JEOL 6360A). The field emission (FE) current density (J) versus applied electric field (E) and emission current (I) versus time (t) characteristics were measured in a planar ‘diode’ configuration at base pressure of ~1.0×10 −8 mbar. A typical ‘diode’ configuration consist of a phosphor coated semitransparent screen (a circular disc having diameter ~40 mm) as an anode. The FE measurements were carried out at fixed cathode-anode separation of ~1 mm. The emission current was measured on Keithely Electrometer (6514) by sweeping dc voltage applied to cathode with a step of 40 V (0- 40 kV, Spellman, U.S.). The UHV chamber is equipped with rotary backed turbo molecular pump, sputter ion pump and titanium sublimation pump. For achieving base pressure of ~1x10 -8 mbar, the chamber is baked at 200 0 C for 24 hrs. Special care was taken to avoid any leakage current using shielded cables and ensuring proper grounding. Before recording the FE measurements, pre-conditioning of the cathode was carried out by keeping it at ~2500 volts so as to remove loosely bound particles and/or contaminants by residual gas ion bombardment. In order to confirm the reproducibility and repeatability of the results, the FE