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author:("magan, César")
1.  Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition 
Iron nanostructures grown by focused electron beam induced deposition (FEBID) are promising for applications in magnetic sensing, storage and logic. Such applications require a precise design and determination of the coercive field (H C), which depends on the shape of the nanostructure. In the present work, we have used the Fe2(CO)9 precursor to grow iron nanowires by FEBID in the thickness range from 10 to 45 nm and width range from 50 to 500 nm. These nanowires exhibit an Fe content between 80 and 85%, thus giving a high ferromagnetic signal. Magneto-optical Kerr characterization indicates that H C decreases for increasing thickness and width, providing a route to control the magnetization reversal field through the modification of the nanowire dimensions. Transmission electron microscopy experiments indicate that these wires have a bell-type shape with a surface oxide layer of about 5 nm. Such features are decisive in the actual value of H C as micromagnetic simulations demonstrate. These results will help to make appropriate designs of magnetic nanowires grown by FEBID.
PMCID: PMC4505150  PMID: 26199835
coercive field; focused electron beam induced deposition; iron nanowires; magnetization reversal; magneto-optical Kerr effect; transmission electron microscopy
2.  Nanoscale chemical and structural study of Co-based FEBID structures by STEM-EELS and HRTEM 
Nanoscale Research Letters  2011;6(1):592.
Nanolithography techniques in a scanning electron microscope/focused ion beam are very attractive tools for a number of synthetic processes, including the fabrication of ferromagnetic nano-objects, with potential applications in magnetic storage or magnetic sensing. One of the most versatile techniques is the focused electron beam induced deposition, an efficient method for the production of magnetic structures highly resolved at the nanometric scale. In this work, this method has been applied to the controlled growth of magnetic nanostructures using Co2(CO)8. The chemical and structural properties of these deposits have been studied by electron energy loss spectroscopy and high-resolution transmission electron microscopy at the nanometric scale. The obtained results allow us to correlate the chemical and structural properties with the functionality of these magnetic nanostructures.
PMCID: PMC3237113  PMID: 22085532
Co deposits; FEBID; EELS; HRTEM
3.  Heterovalent cation substitutional doping for quantum dot homojunction solar cells 
Nature Communications  2013;4:2981.
Colloidal quantum dots have emerged as a material platform for low-cost high-performance optoelectronics. At the heart of optoelectronic devices lies the formation of a junction, which requires the intimate contact of n-type and p-type semiconductors. Doping in bulk semiconductors has been largely deployed for many decades, yet electronically active doping in quantum dots has remained a challenge and the demonstration of robust functional optoelectronic devices had thus far been elusive. Here we report an optoelectronic device, a quantum dot homojunction solar cell, based on heterovalent cation substitution. We used PbS quantum dots as a reference material, which is a p-type semiconductor, and we employed Bi-doping to transform it into an n-type semiconductor. We then combined the two layers into a homojunction device operating as a solar cell robustly under ambient air conditions with power conversion efficiency of 2.7%.
To use colloidal quantum dots in applications such as p-n junction solar cells, doping of the quantum dots is needed. Here, Stavrinadis et al. achieve lead sulphide quantum dot p-n homojunctions by heterovalent cation substitution of lead using bismuth.
PMCID: PMC3905696  PMID: 24346430

Results 1-3 (3)