Formation, structure and properties of highly ordered sub-30-nm phase change materials (GST) nanoparticle arrays

Chalcogenide phase change material Ge1Sb2Te4 (GST) nanoparticle arrays with long-range-order were fabricated by using a monolayer of self-assembled polystyrene (PS) spheres as mask. The morphology of nanoparticle arrays can be controlled via changing RIE processing conditions. Images of atomic force microscopy (AFM) and scanning electron microscopy (SEM) show that highly uniform GST nanoparticle arrays with particle density around 109 cm(-2) were formed. The sizes of nanoparticles can be reduced to a tiny diameter in the range of 30-40 nm (top diameter). The GST nanoparticle arrays exhibit a prominent peak near 580 nm in reflectance spectra, which indicates that they possess a photonic band gap. These results confirm that GST nanoparticle arrays have a 2D periodicity and long-range order. The method of nanosphere lithograph may apply to manufacturing of high density memory devices based on phase change-based memory materials.