Patent ID: 7396684

Claim:
A method for quantitatively and/or qualitatively detecting layer thicknesses of biological or chemical molecules which due to interactions are deposited from a gaseous or liquid medium on at least one metal layer that is provided with an immobilization layer, by determining ellipsometric parameters Ψ and Δ by ellipsometric measurements, for which the following holds: rp/rs =( Erp/Eep )/( Ers/Ees )=tan Ψ·exp( i Δ)=tan Ψ(cos Δ+ i sin Δ) rp, rs: complex reflectivities E: complex electric field amplitude indices: p: parallel to plane of incidence s: perpendicular to plane of incidence e: radiated r: reflected the method consisting of the steps: applying electromagnetic radiation on a side of the at least one metal layer facing away from the immobilization layer; adjusting an angle of incidence and determining a wavelength for an excitation of surface plasmon resonance; measuring tan Ψ and cos Δ curves for several different metal layer thicknesses and as a function of wavelength; adjusting the at least one metal layer thickness so that a steep slope in the cos Δ function is achieved; after the angle of incidence, a frequency of the electromagnetic radiation and the thickness of the at least one metal layer have been adjusted, taking at least one ellipsometric measurement during or after deposition of the molecules without varying wavelength and the angle of incidence and evaluating at least the associated cos Δ to determine the thickness of the molecular layer to be detected.