Fabrication And Research On Characteristics Of ?-? Self-rolled-up Microtubes Combined With Nano-functional Materials

Semiconductor microtubes fabricated by micro-/nano self-rolling technologies have natural hollow channel,epitaxially-smooth tube wall,controllable sizes as well as good optical,electrical and mechanical properties.Meanwhile,site-position and forming arrays can be easily realized.These characteristics make the applications of self-rolled-up microtubes have promising prospects in the fields of integrated optics,MEMS,microfluidics,biomedics and etc.In recent few years,research on combining self-rolled-up microtubes with nano-functional materials such as quantum well(QW),quantum dots(QDs),metal nanoparticles,fluorescent dyes is becoming a hot topic,several phenomena including whispering gallery modes(WGM),optically/electronically pumped lasing and surface enhanced raman scattering(SERS)have been observed,which attracts attention of many researchers to pursue much deeper theoretical and experimental research.In this thesis,we focus on the research on the fabrication,morphological and optical characterizations of III-V InGaAs/GaAs semiconductor self-rolled-up microtubes which have been combined with nano-functional materials(e.g.,QW,QD,metal nanoparticles and fluorescent dyes).The main research and corresponding results are presented below:1.GaAs-and Si-based self-supporting InGaAs/GaAs microtubes and corresponding arrays have been fabricated respectively.Scanning electron microscope(SEM)measurements show that wall surface of both types of microtubes are smooth and their arrays are uniform.In addition,the diameter of Si-based microtubes is a little bit bigger than that of GaAs-based microtubes.Micro-photoluminescence(?-PL)measurements at room temperature(300K)for both types of microtubes show the spectral redshift of PL peaks compared with those from as-grown areas.Simultaneously,micro-Raman(?-Raman)spectra at 300K show that both GaAs longitudinal optical(LO)and transverse optical(TO)phonon modes are redshifted to lower wavenumbers after the strained bilayers roll up into microtubes.Above spectral redshifts in ?,-PL and ?-Raman have been induced by the strain release during rolling process.2.GaAs-based InGaAs/GaAs self-supporting microtubes with GaAs/AlGaAs single quantum well(SQW)and InAs quantum dots(QDs)gain medium embedded into the tube wall have been fabricated.Only PL peak from GaAs quantum well appears in the ?.-PL spectrum of SQW microtubes,its blueshift induced by quantum confinement effect(QCE)can be clearly observed.The ?-Raman spectrum for SQW microtubes shows GaAs-like and AlAs-like LO phonon modes of AlGaAs barrier layer,demonstrating two modes behavior.For QD microtubes,resonant modes have been preliminarily observed in ?-PL spectrum at 80K.3.Au nanoparticles have been coated on the surface of InGaAs/GaAs strained bilayer through thermal annealing of Au film and then non-self-supporting rolled-up microtubes are fabricated.SEM measurements show that the Au nanoparticles coated on the inner wall of microtube have provided assistance to the rolling of microtubes,which makes the diameters of(15nm)InGaAs/(35nm)GaAs and(10nm)InGaAs/(20nm)GaAs bilayer microtubes decrease about 14.5%and 11%,respectively.4.Confocal-Micro-Raman spectroscopy measurements show that self-rolled-up microtubes with Au nanoparticles coated on the inner wall make the Raman intensity of filled photoluminescence dye Rhodamine 6G three times stronger than those in the microtubes without Au nanoparticles incorporated,which lays the foundation for the research on the fabrication of SERS substrates.