In this work, we investigated the possibility of carrier doping of various types of DNA molecules including poly(dG)-poly(dC). DNA poly(dA)-poly(dT) and lambda DNA molecules at low temperatures (i.e., room temperature, 90, 100, and 130 degrees C) using a rapid thermal annealing processor. N(2) and O(2) were used as doping gasses. Annealing at low temperatures in a vacuum (i.e., without gas doping) was also performed to clarify the roles of both gas sources and heat treatment. The results of this study show that both O(2) doping and heat treatment have certain roles in changing the conduction properties of DNA molecules. Specifically, the conductivity of poly(dG)-poly(dC) molecules increases as the annealing temperature rises, regardless of the gas type. However, the highest value of conductivity at a given annealing temperature was always obtained with the samples annealed at O(2) ambient, suggesting that O(2) doping is more effective at making p-type semiconductor-like poly(dG)-poly(dC) molecules. In contrast, O(2) doping of poly(dA)-poly(dT) and lambda DNA molecules resulted in reduced conductivity. This phenomenon suggests that poly(dA)-poly(dT) and lambda DNA molecules behave like n-type semiconductors due to O(2) doping. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.