Self-assembled InAs quantum dots were grown on (0 01) orientated Si substrates by molecular beam epitaxy. Growth condition dependence of dot formation was studied. The evolution of size and shape of quantum dots with InAs coverage was examined using plan-view and cross-section transmission electron microscopy. Dot formation started at below 1 monolayer (ML) of InAs coverage, indicating Volmer-Weber growth mode. Dot size and density grew with increasing InAs coverage up to 0.7 ML. Dot density was observed to be strongly dependent on arsenic (As) beam equivalent pressure (BEP). A decrease of As BEP from 9.2 x 10(-6) to 1.2 x 10(-7) torr resulted in an increase in dot density from 4.3 x 10(9) to 1.8 x 10(11) cm(-2) at a constant InAs coverage of 0.7 ML. Further increase in InAs coverage led to a clear broadening of dot size distribution and a slight decrease in dot density, presumably due to coarsening. (C) 2004 Elsevier B.V. All rights reserved.