Dewetting of Co thin films obtained by atomic layer deposition due to the thermal reduction process
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Research Letter
Dewetting of Co thin films obtained by atomic layer deposition due to the thermal reduction process Daniela Alburquenque, Departamento de Física, Universidad de Santiago de Chile, 9170124 Santiago, Chile Victoria Bracamonte, Facultad de Matemática, Astronomía, Física y Computación (FaMAF), Universidad Nacional de Córdoba, IFEG, CONICET, Córdoba, Argentina Marcela Del Canto, and Alejandro Pereira, Center for the Development of Nanoscience and Nanotechnology, 9170124 Santiago, Chile Juan Escrig, Departamento de Física, Universidad de Santiago de Chile, 9170124 Santiago, Chile; Center for the Development of Nanoscience and Nanotechnology, 9170124 Santiago, Chile Address all correspondence to Juan Escrig at [email protected] (Received 30 May 2017; accepted 30 August 2017)
Abstract Cobalt oxide thin films with different thicknesses were synthesized by atomic layer deposition. After a thermal reduction process, under a controlled atmosphere of hydrogen, it was possible to convert cobalt oxide to metallic cobalt. The different thicknesses were obtained considering from 500 to 2000 cycles of CoCp2/O3. The thin films were characterized by x-ray diffraction, scanning electron microscopy, energydispersive x-ray microanalysis, and by magneto-optical Kerr effect measurements. The indirect synthesis process allows us to obtain cobalt oxide and cobalt thin films with controlled thicknesses and extraordinary magnetic properties, with coercivities above 500 Oe.
Introduction Ferromagnetic materials are of great interest not only as bulk materials but also in the format of thin films. As a function of their coercivity and remanence they can be used in magnetic recording systems of high density and in magnetic sensors.[1–5] Among the different ferromagnetic materials available, cobalt has been intensively investigated due to its interesting magnetic properties,[6,7] being proposed to be used as a contact material,[8] in spintronic applications,[9] in giant magnetoresistance sensors,[10] and in random access magnetic memories.[11] Cobalt thin films must be very uniform so they can be used in potential applications. However, it is well known that the synthesis method used influences its structural, electrical and magnetic properties. To date, cobalt thin films have been synthesized by sputtering,[12] laser pulse deposition,[13] CVD (chemical vapor deposition)[14] and atomic layer deposition (ALD).[15] It is well known that the latter technique allows precise control of the thickness of films with excellent conformal coverage.[16] In addition, the synthesis of cobalt thin films has been reported directly (without an additional thermal reduction process) using plasma-enhanced ALD from different cobalt precursors in the presence of hydrogen, NH3, and H2/N2, among others.[17–19] One of the major drawbacks of plasma depositions is that it can damage substrates giving a non-uniform coverage in high aspect ratio structures due to the recombination of hydrogen atoms on the substrate surface.[20] In addition, most of these methods obt
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