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

Abstract

Organic monolayer-passivated Group III−V dilute magnetic semiconductor (DMS) Mn x In 1 - x As nanocrystals, ranging from 2.2 to 10 nm in diameter, were synthesized by high-temperature colloidal arrested precipitation using the dehalosilylation of InCl 3 and MnBr 2 with tristrimethylsilylarsine in the coordinating solvent, trioctylphosphine. Doping levels up to x = 0.05 (∼10 20 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 In 1 - 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 μ B /Mn atom that interact through antiferromagnetic superexchange, with exhange integrals ( J nn / k B ) ranging from −2 to −4 K.