Capacitance method for determination of basic parameters of porous silicon

Abstract

PACS 61.43. Gt, 77.22.Ch Microstructure and physical characteristics of porous silicon (PS), such as thickness, bulk porosity, dielectric permittivity, and refractive index depend directly on the production conditions, e.g., on the electrolyte composition, anodizing current density, duration of etching etc. Many various possibilities of applications of PS generate high interest towards elaboration of new or modified operative nondestructive methods for testing the microstructure characteristics of PS layer for the adjustment of its processing regimes. According to the mechanism of formation of porous silicon and experimental data on the morphology of PS layers, a porous layer represented as a structure with cylindrical pores of equal lengths piercing the silicon frame. This approximation allows considering the structure using the parallel plate model with in parallel connected capacitances of the silicon frame and the air or liquid dielectric filled pores. A method for obtaining information on the volume porosity, thickness, and dielectric permittivity of a PS layer by means of two measurements of the structure capacitance -in dry air and when the pores are filled by a condensed medium having a dielectric permittivity strongly differing from that of air (e.g., methanol) is described. Sufficiently good agreement has been revealed between the data calculated from the capacitance measurements and obtained by other methods.

Geometry-dependent band shift and dielectric modification of nanoporous Si nanowires

“…4c , we can see that the effective dielectric constant of np-Si nanowires decreases linearly with increasing porosity. The variation trends are consistent with the experimental observations 6 , 7 , 23 . For example, Sarafis et al .…”

“… 22 developed a parallel and serial model for the porosity dependence of dielectrics for np-Si. Experimentally, Adamyan and co-workers 23 elaborated a method for determination of dielectric constant by means of analysing capacitance measurements of np-Si. Sarafis et al .…”

“…Moreover, the self-equilibrium strain induced by CN imperfection will take place spontaneously. According to size-dependent surface energy 23 , 28 , the lattice strain ( ) in the self-equilibrium state can be obtained by optimizing the total energy of np-Si nanowires. Thus, we have where the subscripts and , respectively, denote the inner and outer surfaces of np-Si nanowires, and are the diameters of the pore and that of the entire nanowires, and represent the corresponding elastic strain and surface energy density.…”

Impedance measurement for microstructure characterization and internal surface estimation of macroporous silicon

“…In that case an additional capacitance measurement on thermally oxidized macroporous silicon using a liquid of known dielectric constant is to be taken similar to the method reported in Ref. 14.…”