The present invention provides an electron beam apparatus for evaluating a sample surface, which has a primary electro-optical system for irradiating a sample with a primary electron beam, a detecting system, and a secondary electro-optical system for directing secondary electron beams emitted from the sample surface by the irradiation of the primary electron beam to the detecting system. The drift path has drift zones of a first conduction type and charge compensation zones of a complementary conduction type with respect to the first conduction type. The compound binds to a target mRNA with a Tm of between 50\xb0 to 60\xb0 C. The applied suspension is exposed to energy to remove the capping groups and fuse the particles into cohesion.