Abstract
This work reports the coating of porous silicon (PS) with LaF3 and its influence on the photoluminescence (PL) property of PS. PS samples, prepared by electrochemical etching in a solution of HF and ethanol, were coated with e-beam evaporated-LaF3 of different thicknesses. It was observed that the thin LaF3 layer on PS led to a good enhancement of PL yield of PS. But with the increasing thickness of LaF3 layer PL intensity of PS was decreasing along with a small blue-shift. It was also observed that all the coated samples showed degradation in PL intensity with time, but annealing could recover and stabilize the degraded PL.
Highlights
Porous silicon (PS) can be considered as a silicon (Si) crystal having a network of voids in it [1]
The fabricated porous silicon (PS) samples with LaF3 layers were investigated with a scanning electron microscope (SEM)
Thicker layer of LaF3 lowered the PL intensity that may be due to the degradation of refractive index of the LaF3 layer induced by the mechanical stress which depends on the film thickness
Summary
Porous silicon (PS) can be considered as a silicon (Si) crystal having a network of voids in it [1]. Due to the aging effect, the structural and optical properties of PS show continuous change with storage time [2]. One possible way to reduce the aging effect could be “passivation” of PS [3] This surface coating can be achieved from various chemical adsorbates by several techniques [4,5,6]. LaF3 is a large band-gap (about 10.3 eV) [7] material having a hexagonal crystal structure with a refractive index of 1.61 [8]. Due to its high band-gap and refractive index, higher than those of the other VUV transparent films, LaF3 is a useful material for VUV optics. The experimental results show that coating the PS with optimum LaF3 thickness could provide stabilization of PL of PS, which is very important for PS to be a potential material in photonic devices
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