مطالعه و بررسي جفت شدگي پلاسمون اكسيتون در سامانه‌هاي آميخته‌ي نانوساختارهاي فلزي ايجاد شده به روش لايه نشاني با زاويه‌ي گرايش و نقاط كوانتومي سلنيدكادميوم

Study an‎d Investigation of Plasmon-Exciton Coupling in Hybrid Systems of Metal Nanostructures Fabricated by Glancing Angle Deposition an‎d Cadmium Selenide Quantum Dots

فيزيك

In this dissertation, exciton–plasmon interactions in a hybrid system composed of CdSe/ZnS core–shell quantum dots an‎d silver nanostructures fabricated via glancing angle deposition (GLAD) were investigated. In the GLAD technique, the deposited film thickness, substrate rotation speed, an‎d deposition angle are key parameters that determine the optical an‎d geometrical properties of the resulting silver nanostructures. In the hybrid system consisting of silver nanostructures an‎d quantum dots, a polymer spacer layer (PMMA) was employed to precisely control the separation distance between the metallic nanostructures an‎d the quantum dots. To study the optical behavior of the fabricated hybrid systems, photoluminescence (PL) an‎d optical density (absorption) spectra were measured. Variations in PL intensity, full width at half maximum (FWHM), an‎d spectral peak shifts were systematically analyzed. Among the silver nanostructures fabricated by GLAD with deposition thicknesses of 15, 25, 35, an‎d 45 nm, the sample with a 15 nm thickness exhibited the strongest enhancement of the photoluminescence of the CdSe/ZnS core–shell quantum dots. Specifically, the GLAD-fabricated silver nanostructure with a 15 nm deposition thickness, an 87° deposition angle, an‎d a rotation speed of 12 rpm led to a 90% increase in the PL intensity of the quantum dots. In addition, another configuration with the same 15 nm thickness but an 85° deposition angle an‎d a rotation speed of 12 rpm resulted in an 88% enhancement in PL intensity. In contrast, silver nanostructures with 25 nm an‎d 35 nm deposition thicknesses induced a strong quenching effect an‎d only a limited enhancement, respectively, in the PL response of the quantum dots. In the hybrid system, a red shift was observed in the photoluminescence peak of the CdSe/ZnS quantum dots. The enhancement of PL intensity, together with the redshift of the emission peak toward longer wavelengths, indicates that the hybrid system operates in the weak-coupling regime.

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