A model for the electromagnetic properties of a dielectric half-space covered by a regular array of planar bianisotropic particles is described. The model allows us to homogenize the structure, presenting it as a half-space covered by a nite-thickness layer of bianisotropic medium. The array particles' mutual coupling is studied within the frame of the assumption of "electric and magnetic dipole," which implies the rather sparse arrays of particles, though the presented approach can be generalized to the case of dense arrays taking into account the higher multipoles. The model is numerically tested for the case of a bianisotropic array in free space.
normalGaAs
epitaxial films have been deposited on heavily Si‐doped (100)
normalGaAs
substrates by closely spaced vapor transport from a semi‐insulating (undoped)
normalGaAs
source. Charge density (N) profiles of the epitaxies have been determined electrochemically by a succession of photocorrosion steps and capacitance measurements. When the films are thick enough, typicalN profiles show four regions. Starting from the surface of the film and going toward the
normalGaAs
substrate, there is a first region (I) of constant N, extending over a length varying with the deposition time. It is followed by a second region (II) extending over
12±2 μnormalm
, where N slowly rises. In region III , there is an abrupt increase of N followed by region IV which is the substrate region. Consistently, close spaced vapor transport technique layers were n‐type with N values in region I varying from
4×1015 normalto 2×1016 cm−3
. Region III of the N profile displays a fine structure which has been explained in terms of Si which is released from the Si‐doped
normalGaAs
substrate into the vapor phase and redeposited within the growing film. Region III is also due to Si diffusion from the substrate into the growing film. A diffusion coefficient of Si into
normalGaAs
of
6.5±2.5×10−14 cm2 s−1
at
760°±3°C
has been calculated from the N profile curves. The slow variation of N in region II results neither from a fast diffusive shallow donor impurity from the
normalGaAs
substrate, nor from Si released from region III into the vapor phase and redeposited into the growing film. It is suggested that region II probably reflects a variation of the off‐stoichiometry in the epitaxial film. Epitaxial layers of
normalGaAs
grown on semi‐insulating (SI) (100)
normalGaAs
substrates show region I and II of the N profile curve. Hall effect measurements performed on these layers agree with the electrochemical results.
Results of rotating ring‐disk experiments, impedance measurements, surface analysis, and chemical analysis of the electrolyte (to study the long‐term stability) demonstrate that a protection of n‐GaAs against photocorrosion and chemical attack can be achieved in acidic concentrated iodide electrolytes under a few mW/cm2 illumination and in the dark.
Although n-GaAs is known to be unstable in presence of iodine, it is shown that this semiconductor can be efficiently stabilized by using highly concentrated acidified iodide aqueous solutions. The effects of proton activity and iodine and iodide concentrations on the electrode stability are investigated by means of rotating ring-disk experiments, RHEED observations, and chemical analysis of the electrolyte. Impedance measurements show a positive shift of the bandedges of GaAs with iodine concentration and illumination level. At a nominal pH of 0, the stabilization ratio S is measured close to 100% (80%) for n-GaAs in contact with a 7M (2M) NaI solution, respectively. Under illumination, the I-/I3-redox level is found to be favorably located near midgap. Kinetic analysis of the competing hole reactions yields a satisfactory simulation of S vs. I concentration. The hole capture by reduced species is found to be proportional to the concentration of iodide ions, not to their activity, in contrast to expectation. Furthermore, it is shown that chemisorbed Ru 3+ cations act as a catalyst for hole transfer and thus improve the stability of n-GaAs in 7M NaI solution.) unless CC License in place (see abstract).ABSTRACT A general mathematical model for studying the kinetics of electrochemical reactions at a rotating disk electrode under steady-state potentiostatic conditions is presented. The model, apart from predicting the net and partial current densities at given values of the applied potential, the ohmic potential drop, and the concentration and potential profiles in the solution, also accounts for homogeneous reactions of any order in the solution and noncharge transfer reactions at the electrode surface. The versatility of the model is demonstrated by the application of the model to a variety of complex reaction schemes.
This article concerns a structure of high-impedance wires (HIW) based on ferrite substrate coplanar waveguide (CPW). Slotted planar stubs are etched on one or two ground planes of the CPW line. Several prototype measurements have been performed showing excellent performance to implement narrow-band microwave isolators. These HIW components can work at low bias-field giving an easier implementation in microwave devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.