Structure and optical properties of SiO2-ZrO2 doped Er3+ ions thin films and nanofibers / Nurul Fasihah Mohd Suhaimi

The thin film samples in the composition of (100-x)SiO2-(x)ZrO2 doped 0.58 mol% Er3+ with x varies from 30 mol% to 70 mol% were prepared via sol-gel dip coating technique, meanwhile the nanofibres were prepared using electrospinning technique. All the thin film samples were characterized for morphological, optical and structural properties while the nanofibres samples were characterized based on the morphological and optical properties. The AFM results of the thin film samples showed that the surface morphology were crack-free with compact and uniform structure. The thickness, surface roughness and refractive index of the thin film samples increases as the x mol% increase, meanwhile the transparency of the films reduced. The XRD results of thin film samples showed that tetragonal phase of ZrC>2 and amorphous phase of SiC>2 were observed. The narrowing of the diffraction peak width indicates the better crystallinity of the films at higher content of zirconia. The luminescence spectra of thin films showed that there was an increase in the emission intensity which results in the enhancement of the green and red emission from the samples. The observed emission spectra exhibit three strong emission bands centered at 578 nm, 655 nm and 678 nm which correspond to the 4S3/2 —»• 4Ii5/2 and 4F9/2 —»• 4Ii5/2 transition respectively. The addition of ZrC>2 into the silica glass matrix facilitates the Er3+ ions to disperse homogeneously within the matrix and thus promotes intense luminescence intensity. For nanofibres samples, PVA solution was added into the (100-x)SiO2-(x)ZrO2 doped 0.58 mol% Er + solution in order to achieve desired viscosity for electrospinning process. Based on FESEM images, the images of (100x)Si02-(x)Zr02 doped 0.58 mol% Er3+/PVA nanofibres samples showed the electrospun nanofibres consisted of smooth and uniform surfaces with random orientation. The nanofibres images after the calcinations process at 600°C showed the surface morphology of nanofibres is well preserved and exhibits shrinkages with average diameters reduced by about 25%. Finally, the luminescences properties of nanofibres as compared to thin film have showed that nanofibres sample demonstrate higher intensity of emission and shifting the erbium emission to the lower wavelength.