Spins of electrons bound to donor electrons are attractive candidates for exploration of quantum information processing in silicon. We present results from our development of donor electron spin qubit structures. Donors are placed into isotopically enriched 28 Si by ion implantation. The coherence properties of donor implants in pre-device structures are probed by pulsed electron spin resonance (ESR). The spin de-coherence time, T 2 , for 121 Sb donors implanted into a peak depth of 50 nm from a thermal oxide interface is 0.3 ms at 5 K, increasing to 0.75 ms when the silicon surface is passivated with hydrogen. A technique for formation of donor arrays by ion implan-tation with scanning force microscope alignment is presented, and we discuss coherence limiting factors with respect to the implemen-tation of a single spin readout scheme. Published by Elsevier B.V.