Two groups of porous silicon (PS) samples are treated by rapid thermal oxidation (RTO) and electrochemical oxidation (ECO), respectively. Scanning electron microscopy images show that PS samples are segmented into two layers. Oxidized film layer is formed on the top surface of PS samples treated by RTO while at the bottom of PS samples treated by ECO. Both ECO and RTO treatment can make emission current density, diode current density, and emission efficiency of PS increase with the bias voltage increasing. The emission current density and the field emission enhancement factor beta of PS sample treated by RTO are larger than that treated by ECO. The Fowler-Nordheim curves of RTO and ECO samples are linear which indicates that high electric field exists on the oxidized layer and field emission occurs whether PS is treated by RTO or ECO. (C) 2011 Elsevier B. V. All rights reserved.