Selective Growth of Highly Packed Array of ZnCdS Quantum Dots with a Mask Prepared by Atomic Force Microscope Nanolithography

Abstract

Preparation of a highly ordered and packed array of ZnCdS quantum dots (QDs) by selective-area growth (SAG) is reported. For this purpose, we have developed a method to prepare nanoscale mask openings with an atomic force microscope (AFM) for SAG employing electron-beam-induced carbonaceous films. AFM anodization in a modulated-amplitude pulsed bias mode is applied, making it possible to obtain dotlike patterns with a resolution of ∼26 nm and an interdot distance of ∼100 nm in the masks ready for SAG. Nanoscale SAG of ZnCdS and ZnMgCdS alloys by metalorganic molecular-beam epitaxy is studied on (001) GaAs surfaces masked with the carbonaceous film. The array of ZnCdS/ZnMgCdS quantum dots each with a size of ∼26 nm as defined by the mask openings, and with a density of 1×1010 cm-2, is successfully grown with this method. The photoluminescence from the dot array, recorded at 30 K, is strong and shows a 6 meV blueshift as compared with that observed from the uniformly grown region.