Synthesis and Characterization of Dilute Magnetic Semiconductor Manganese-Doped Indium Arsenide Nanocrystals

• Published in: Nano letters 2003-10, Vol.3 (10), p.1441-1447
• Main Authors: Stowell, Cynthia A, Wiacek, Robert J, Saunders, Aaron E, Korgel, Brian A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Nanocrystals and nanoparticles; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl034419+

Organic monolayer-passivated Group III−V dilute magnetic semiconductor (DMS) Mn x In1 - x As nanocrystals, ranging from 2.2 to 10 nm in diameter, were synthesized by high-temperature colloidal arrested precipitation using the dehalosilylation of InCl3 and MnBr2 with tristrimethylsilylarsine in the coordinating solvent, trioctylphosphine. Doping levels up to x = 0.05 (∼1020 cm-3) were obtainedthree to 4 orders of magnitude higher than the thermodynamic Mn solubility in the InAs host lattice. Relatively size-monodisperse nanocrystals, with standard deviations ranging from ±11% to 17% as measured by TEM and small-angle X-ray scattering (SAXS) were achieved by size selective precipitation. The Mn x In1 - x As nanocrystals exhibit near-infrared photoluminescence (PL), with PL (i.e., exciton) energies red-shifted relative to InAs nanocrystals of equivalent size. Elemental analysis, magnetization, and electron spin resonance (ESR) measurements before and after a chemical surface exchange confirmed that the majority of dopant was located in the nanocrystal core. The doped magnetic nanocrystals behave as paramagnets down to the lowest measured temperature of 5 K, with total magnetic moments ranging from 2.0 to 3.7 μB/Mn atom that interact through antiferromagnetic superexchange, with exhange integrals (J nn /k B) ranging from −2 to −4 K.