Structural and magnetic properties of pure and cobalt doped Gallium Nitride nanocrystals
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1257-O03-37
Structural and magnetic properties of pure and cobalt doped Gallium Nitride nanocrystals V. Ganesh, S.Suresh and K. Baskar* Crystal Growth Centre, Anna University Chennai, Chennai-60 0025, India. ABSTRACT In the present study pure and doped gallium nitride (GaN) nanocrystals were synthesized using gallium trichloride (GaCl3), ethylene diamine tetra acetic acid (EDTA) and cobalt chloride as raw materials at a temperature of 900 ºC in ammonia (NH3) atmosphere. The XRD spectrum for pure and cobalt doped GaN nanocrystals shows the formation of single phase wurtzite structure. No impurity phases were observed in the X-ray diffraction pattern for 5% Co doped sample whereas secondary phases were observed when the doping concentration exceeds 5 %. Shift in X-ray diffraction peaks were observed in Co doped samples towards lower angle side compared to pure GaN, it confirms that the Co atoms introduces in to the GaN lattice. Transmission electron microscopy images were taken for pure and Co doped GaN. Hexagonal morphology was observed in pure GaN samples. The average size of the particle was found to be ~20 nm for pure and Co doped GaN. The magnetic measurements were carried out for the Co (5% & 10%) doped samples both at 10K and 300K. Clear hysteresis loop in the magnetization curve suggest the presence of ferromagnetic behavior in cobalt doped GaN. Temperature dependent magnetization (M-T) measurements were also carried out for doped samples using Super Conducting Quantum Interface Device (SQUID) from 10K to 300K The results have been discussed and correlated to structural and magnetic properties of the materials. . INTRODUCTION (III, Mn)N appears to be the natural choice of a material for spintronics due to higher solubility limit of Mn in nitrides and high-Tc values [1-5]. Ferromagnetic Curie temperature (Tc ) of some III– V Dilute Magnetic Semiconductor (DMSs) materials, notably (In, Mn)As and (Ga, Mn)As [6-7] are too low for practical applications. Theoretical reports on GaN-based DMSs show Curie temperature higher than the room temperature [8, 9]. Previous reports on Co doped GaN have shown ferromagnetic behavior below room temperature [10-12]. In the present study, we report the synthesis of pure and cobalt (Co) doped GaN nanocrystals by nitridation of GaEDTA and Co doped Ga-EDTA complexes. The structure, morphology and magnetic behavior of the pure and Co doped GaN nanocrystals were studied and discussed. EXPERIMENT Ga-EDTA.NH4 complex was prepared from the mixture of gallium trichloride (GaCl3), ethylene diamine tetra acetic acid (EDTA) and ammonia in aqueous solution at a pH of 9. The solution was stirred for 6 hours and dried in an oven at 343 K to yield Ga-EDTA.NH4 complex. Then the complex was put in an alumina boat and placed inside the quartz reactor. Subsequently N2 was passed through the reactor till the synthesis temperature (1173 K). After reaching the synthesis temperature NH3 was introduced in to the quartz reactor. The synthesis was carried out
for a reaction period of 8 h at 1173 K to obt
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