We have successfully fabricated high-density two-dimensional indium (In) nano-dot arrays on a GaAs substrate with periods of 50 nm. These nano-dot structures were formed using an atomic force microscope (AFM) probe with a specially designed cantilever (the Nano-Jet Probe) having a hollow pyramidal tip with a sub-micron size aperture on the apex and an In-reservoir tank within the stylus. These ordered In nano-dot arrays can be directly converted to InAs quantum dot (QD) arrays by subsequent irradiation of arsenic flux in the molecular beam epitaxy chamber, which is connected to the AFM chamber through an ultra-high-vacuum (UHV) tunnel. (C) 2004 Elsevier B.V. All rights reserved.