镶嵌于多孔硅微腔中8-羟基喹啉铝的窄峰发射

利用浸渍法将8羟基喹啉铝(Alq₃)镶嵌到多孔硅微腔中,制备了多孔硅微腔—Alq₃镶嵌膜,研究了多孔硅微腔对镶嵌其中的Alq₃自发发射的微腔效应,观察到了光谱窄化、发光强度增强等现象。镶嵌于多孔硅微腔中的Alq₃荧光光谱的半峰全宽只有15nm,而非微腔样品,即镶嵌于普通的单层多孔硅中Alq₃荧光谱半峰全宽在85nm以上。并且有微腔时Alq₃发光强度比没有微腔时Alq₃发光强度增强一个数量级。随机改变微腔中Bragg反射镜高折射率层的几何厚度可使高反射区展宽,从而更加有效地抑制了多孔硅本身的发光模,使发光色度更纯,但由于峰值透射率减小,导致共振峰强度有所减小。多孔硅微腔有机镶嵌膜有可能成为进一步发展Alq₃在电致发光器件方面应用的一条新途径。

Narrow-line Light Emission from 8-Hydroxyquinoline Alumina Assembled in Porous Silicon Microcavities

The spontaneous emission of a material can be controlled by placing it in a micron sized optical cavity. In this paper we assembled 8 hydroxyquinoline aluminum (Alq₃) into porous silicon microcavities(PSMs) fabricated by pulsed electrochemical etching. The pulsed current etching is superior to DC etching in obtaining flat interfaces within the distributed Bragg reflectors because of its minor lateral etching. The measured peak reflectivity of the microcavities before the impregnation is 99.5%,and its full width at half maximum(FWHM)is Δλ=6 nm,and after impregnation Δλ=15nm. The spontaneous emission spectrum of the optically excited 8 hydroxyquinoline aluminum is drastically modified by micro cavity effects. Compared with the luminescence of a filled single P Si layer with the same thickness as the microcavity, and with an average of the porosity of the layers constituting the microcavity, the full width at half maximum of PL spectrum in a filled microcavity is drastically reduced from 85 nm to 15 nm, the peak emission intensity increased by one order.However,beside the resonant peak of PSMS, the weak side peaks origina ting from PS can be observed, because the reflectivity of the microcavities is decreased in this region. Random porous silicon dielectric multilayers are proposed as interesting materials for application as optical components. The use of random instead of periodic multilayers has the advantage of obtaining a wider stop band in Bragg reflectors with the same difference in the refractive indexes of the layers and in a higher finesse in Fabry Perot filters. In the case of Alq₃ being impregnated into random FP interference filter, the off resonant optical modes are highly depressed. The experimental results suggested that the porous silicon microcavities is a good encapsulated media for Alq₃, and Alq₃ emission properties was improved by the microcavities. This may make a new way for Alq₃ in application in electroluminescence.