Síntese por reação de combustão de ZnO dopado com Mn+2, Co+2 e Ni+2 para obtenção de semicondutores magnéticos diluídos (SMD).

Abstract

With the advancement of technology in the production of microprocessors, there is the need to increase the number of transistors in order to generate a greater processing speed and greater capacity for storing information, which is essential in the development of integrated circuits. With this electronic technology semiconductor silicon based, it is limited due to increased heat dissipation in the miniaturization of integrated circuits. This limitation can be overcome with the advent of spintronics. In this context, this research work aims to synthesize combustion reaction diluted magnetic semiconductors (DMS) based on ZnO doped with transition metals Mn+2, Co+2 and Ni+2, aiming at application in spintronics. Three systems with different concentrations of dopants were defined: i) Zn1-xMnxO, x = 0.1, 0.15, 0.2, 0.25, 0.3 and 0.4 mol of Mn+2, ii) Zn 1-xCoxO where x = 0.02, 0.03, 0.05, 0.06, 0.07, 0.1 and 0.2 mol of Co+2 and iii) Zn1-xNixO, where x = 0.07, 0.1 and 0.2 mol of Ni+. The systems were synthesized by combustion reaction using the concepts and theory of propellants and explosives. All reactions were performed on a vitreous silica crucible as a container, a ceramic base with electrical resistance as a source of external heating, and urea as fuel. During the reaction was carried out measuring the temperature and time of the combustion reaction. The product of the reaction was characterized by X-ray diffraction, X-ray fluorescence energy dispersive, nitrogen adsorption (BET), scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. The results reported show that: for all systems studied the maximum temperature reached in the reaction was between 353 and 512ºC. The type of dopant and its concentration influenced both the structural and morphological characteristics. The XRD spectra show that at all doping with Mn+2 and Co+2 doping of 0.02, 0.03, 0.07 and 0,1 mol resulted in a single phase product, ie, we observed the presence of phase ZnO crystallite size smaller than 50 nm. In the systems doped with Co+2 at concentrations of 5%, 6% and 20% had formation of a phase of waste decomposition of nitrate and urea in the 2θ range between 7.83 to 28.52º. All systems Ni-doped ZnO phase was observed with the majority presence of the secondary phase of NiO and waste phase similar to phase observed for the system doped with Co+2. The systems studied had good responses to magnetic Curie temperatures above room temperature ranging from 305 to 364K. The system doped with Mn+2 was the one that had the best response with values of saturation magnetization between 12 to 29 emu/g while the systems doped with Co+2 and Ni+2 values of saturation magnetization between 1 and 3.2 emu/g and 4.6 to 7.6 emu/g respectively. It is concluded that the synthesis of combustion reaction seems to be promising for the preparation of nanomaterials in the production of SMD suitable for application in spintronics.