Highly reproducible, active and stable SERS substrates were prepared by a nanocluster deposition system. SERS studies were carried out on these substrates with R6G as a test molecule using near Raman resonant and off resonant laser excitation wavelengths. Our results show that Ag nanoclusters of average particle size of ( 157 +/- 119) nm act as very good SERS substrates for the ultra trace detection of R6G with an AEF of 2 x 10(12) corresponding to a detection limit of 10(-16) M. The present substrates could improve the detection limit of R6G by two orders of magnitude as compared to the previous reports. (C) 2011 Elsevier B.V. All rights reserved.