摘要：

Inhomogeneous samples of n-type CdS xSe 1x(0.2 x <1) were prepared by vapor-phase diffusion of SE into a single-crystal n-CdS substrate. Characterization of the samples by Auger electron spectroscopy (AES)/Ar ion sputter etching indicates that Se substitutes for S in the lattice to produce a graded region where x monotonically increases with depth from 0.2 at the surface to unity over a distance of ~ 1 μm. Photoluminescence (PL) and electroluminescence (EL) of these CdS/Se samples are dominated by edge emission characteristic of the near-surface CdS xSe 1 x compositions ( ~ 650–700 nm). The narrowness of the spectra compared to spectra reported for CdSe/S graded solids prepared by diffusion of S into n-CdSe is rationalized in terms of the electronic structures of the two compounds. A previously established linear correlation between emission maxima and composition in homogeneous CdS xSe 1 x samples provides a spatial probe of electron—hole pair recombination in the inhomogeneous material: Regions from which PL and EL originate can be inferred from their spectral distribution in combination with the AES/depth profile data. The CdS/Se samples can be used as photoanodes of photoelectrochemical cells (PEC's) employing aqueous (poly)sulfide electrolyte. PL quenching accompanying the passage of photocurrent indicates that the effective electric field (EEF) in the solid at ~ 0.3 V vs. SCE extends ~ 0.1–0.2 μm into the solid. By etching away the graded layer from one face of the CdS/Se crystal, PL can be excited and viewed through the exposed CdS face and yields a similar value for the EEF thickness; photoaction spectra support the PL data in identifying the near-surface portion of the graded zone as principally responsible for photocurrent. Both CdS/Se and CdSe/S electrodes lend themselves to the construction of display devices by spatially-controlled etching: by appropriate masking and etching techniques, patterned, multi-colored emitting electrodes can be fabricated. For the CdS/Se samples, PEC etching can be exploited to control etching depth with excitation wavelength

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