Characterization of Laser-Assisted Pulsed Laser Deposited BaFe 12 O 19
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CHARACTERIZATION OF LASER-ASSISTED PULSEI) LASER DEIPOSITED) BaFe 1 2 O 1 9 J.S. HORWITZ, D.B. CHRISEY, K.S. GRABOWSKI, C.A. CAROSELLA, P. LUBITZ AND C. EDMONDSON* Naval Research Laboratory, Washington, DC 20375-5345 *U.S. Naval Academy, Annapolis MD, 21402-5026 ABSTRACT High quality, epitaxial barium hexaferrite (BaFe12019) thin films have been deposited by pulsed laser deposition (PLD) onto basal plane sapphire at substrate temperatures of 900 *C in 400 mTorr of oxygen. Thin films (< 500 nm) were smooth while thick films (> 1000 nm) had rough, polycrystalline surfaces and "soot-like" appearances. The integration of ferrite films with semiconductors will require thick films (< 70 gim) and low substrate processing temperatures (< 600 "C). Films deposited at 600 °C were mostly amorphous with the presence of some crystalline, non-hexaferrite material. In an effort to improve the quality of barium hexaferrite fihns, we have investigated the effects of excimer-laser-assisted PLD (LAPLD) on the growth of BaFel2O19. During the deposition, the substrate was illuminated with the output 2 of a second pulsed excimer laser (KrF) weakly focused to an energy of 10 to 130 mJ/cm . 'llTe output of the second laser was synchronized such that the delay between the vaporization laser and the annealing laser was 0 to I ms. The X-ray diffraction analysis of LAPLD films 2 deposited at 600 'C with an annealing fluence of 50 mJ/cm indicated that the films were a crystalline mixture of hexaferrite and non-hexaferrite phases. Both phases exhibited a preferred orientation characterized by narrow x-ray rocking curve widths (FWHM - I°). Magnetic properties (magnetic moment, saturation magnetization and coercive field) detennined from a vibrating sample magnetometer (VSM) also confirmed the presence of oriented hexaferrite material in the laser annealed samples. These results show clear advantages of LAPLD for improved structural and magnetic properties of BaFel2OI9 deposited at substrate temperatures compatible with semiconducting materials. INTRODUCTION Ferrites are magnetic oxides which exhibit hysteretic behavior in an applied magnetic field. They have a number of useful properties which include strong magnetic coupling, high resistivity and low dielectric loss. Unlike magnetic metals, ferrites are transparent at rf anld microwave frequencies and as such these materials are use in many high frequency applications. These applications include tunable filters, circulators, monolithic microwave integrated circuitry (MMIC) and magnetic recording. Many of these applications will require thick ferrite films (20 - 70 lgm) in order to have a sufficient volume of the electromagnetic energy in the tunable (ferrite) element. In addition, many of these applications will require The integration of ferrites with integrated circuit technology will oriented single crystals. 0 require low (< 600 C) processing temperatures. Recently, several papers have reported the deposition of ferrite thin films using pulsed laser deposition (PLD) 11-51. High quality BaFel
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