General Control of Transition-Metal-Doped GaN Nanowire Growth: Toward Understanding the Mechanism of Dopant Incorporation

Abstract

We report the first synthesis and characterization of cobalt- and chromium-doped GaN nanowires (NWs), and compare them to manganese-doped GaN NWs. Samples were synthesized by chemical vapor deposition method, using cobalt(II) chloride and chromium(III) chloride as dopant precursors. For all three impurity dopants hexagonal, triangular, and rectangular NWs were observed. The fraction of NWs having a particular morphology depends on the initial concentration of the dopant precursors. While all three dopant ions have the identical effect on GaN NW growth and faceting, Co and Cr are incorporated at much lower concentrations than Mn. These findings suggest that the doping mechanism involves binding of the transition-metal intermediates to specific NW facets, inhibiting their growth and causing a change in the NW morphology. We discuss the doping concentrations of Mn, Co, and Cr in terms of differences in their crystal-field stabilization energies (DeltaCFSE) in their gas-phase intermediates and in substitutionally doped GaN NWs. Using iron(III) chloride and cobalt(II) acetate as dopant precursors we show that the doping concentration dependence on DeltaCFSE allows for the prediction of achievable doping concentrations for different dopant ions in GaN NWs, and for a rational choice of a suitable dopant-ion precursor. This work further demonstrates a general and rational control of GaN NW growth using transition-metal impurities.

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“…Various one dimensional GaN nanostructures including, nanowires [2,3], nanorods [4,5] and nanotubes [6,7], have been researched. Apart from the various GaN nanostructures, there is a kind of nanostructure, tip or needle-structure which has attracted a great deal of interest and it can be applied in field emission [8], high resolution atomic force microscopy (AFM) tip [9] and scanning near field optical microscopy [10].…”

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“…Thus, in recent years, atomic and molecular doping techniques have been intensively studied for semiconductor nanodots/nanowires and carbon-based nanomaterials, which often led to drastic changes in their physical and chemical properties. [1][2][3][4][5] In particular, doping metallic nanowires is very interesting also in fundamental points of view, since dopants can strongly interact with exotic quantum states of one-dimensional ͑1D͒ metals such as the non-Fermi-liquid state 6,7 and brokensymmetry states ͑density waves or superconducting states͒. [7][8][9] The microscopic understanding of intriguing interactions of dopants with those quantum states is an important issue not only in nanowires but also in bulk low-dimensional materials.…”