A VARIATIONAL-GREENS FUNCTION-APPROACH TO THEORETICAL TREATMENT AND APPLICATIONS OF THE CAPACITANCE OF 3-DIMENSIONAL GEOMETRIES

A combined variational-Green's function approach to the determination of the capacitance of various useful three-dimensioinal geometries is developed. This formalism leads to general, exact expressions for the capacitance, which can be used with all geometries provided the spatial distribution of the charge can be determined. In particular, the theory takes into account the finite thickness and unequal areas of the capacitor plates. Specific applications of the theory include circular capacitors with disk and ring-shaped charge plate geometries. Such geometries are commonly encountered in experimental set-ups for capacitive measurements of thin film thicknesses in the field of microelectronics. Numerical results indicate that the values of thin film thicknesses calculated via simplified one-dimensional formulae for the capacitance may be incorrect by more than 10%.