Ellipsometry Using a Retardation Plate as Compensator*

The equations of ellipsometry are derived relating the specimen properties, ρ=tanψeiΔ, to the instrument settings P, A, and Q. The treatment differs from previous works in that both of the important parameters of the retardation plate are considered, namely, the retardation δ and the transmission ratio T, of the slow to the fast axis. Equations are developed which determine δ and T from the instrument readings. Conventional averaging procedures to obtain ψ from readings of A are shown to be valid; however, it is demonstrated that the usual procedures for obtaining Δ from readings of P are invalid and a correction is derived. Furthermore, an unsuspected source of error, namely, orientation of the retardation plate oblique to the light beam, is shown to produce large errors in some measurements.