High-resolution electron microscopy and microanalysis of ordered arrays of size-controlled amorphous gallium nitride nanoparticles synthesized in situ in a block copolymer matrix

The objective of this work was to produce an ordered array of size-controlled gallium nitride (GaN) nanoparticles. The synthesis was performed by the in situ formulation and subsequent decomposition of cyclotrigallazane in a polystyrene (PS)-b-poly(4-vinylpyridine) (b-P4VP) block copolymer matrix. The matrix served as a templating medium to constrain the particle size and to allow the control of particle morphology, spacing and packing arrangement. The size and spacing of nanoparticles were controlled by the molecular weight of the entire polymer chain (81 000g mol⁻¹), and the particle morphology and packing arrangement were controlled by the ratio of the sequestering block to the matrix block (21 wt% P4VP to 79 wt% PS by elemental analysis). High-resolution and analytical transmission electron microscopy revealed the amorphous nanoparticles to be composed mainly of gallium and nitrogen (with oxygen detected in some particles) about 10nm in diameter with an average interparticle distance of 60 nm and organized in a regular hexagonal packing arrangement. The impact of this synthesis technique is to afford the means to investigate systematically the effect of quantum confinement and quantum coupling on the optical properties of small GaN particles.