Ellipsometric and interferometric characterization of DNA probes immobilized on a combinatorial array

We have used ellipsometry to study oligonucleotides bound on an array by observing changes in the optical thickness of the organic material attached to the surface. Interferometry has been used as a complementary technique to confirm our ellipsometry measurements. We have used these optical methods to characterize the chemical steps involved in synthesizing oligonucleotides on a solid support. Large area arrays have been mapped by ellipsometry with a spatial resolution of similar to 1 mm(2) and a sub-nanometer optical thickness resolution. We have demonstrated that this method can differentiate between areas containing oligonucleotides of different lengths.