Improved luminescence properties of pulsed laser deposited Y3(Al,Ga)5O12:Tb thin films by post deposition annealing

Abstract

Y3(Al,Ga)5O12:Tb thin films were successfully deposited on Si (100) substrates in an oxygen working atmosphere by the pulsed laser deposition (PLD) technique. The as-deposited films were amorphous but crystallized when annealed in air at 400°C and 800°C for 1h as confirmed by X-ray diffraction. Three dimensional atomic force microscopy (AFM) images of the as-deposited film show well defined spherically grains that were uniformly distributed over the surface with a root mean square (RMS) roughness value of 9nm. After annealing at 800°C the surface became smooth and the RMS value was reduced to 6nm. The smooth layer was confirmed to be a surface oxide layer enriched with Ga from the images captured using a nano-scanning Auger electron microprobe (NanoSAM). The PL intensities were observed to increase as a function of annealing temperatures and this was attributed to improvement of the crystallinity of the films and a possible variation of Ga concentration in the thin films. In addition, cathodoluminescence (CL) properties of the films were recorded when the films were irradiated with a beam of electrons in the vacuum chamber of the Auger electron spectrometer. The CL intensity of the deposited film was recorded as a function of electron dose as well as the accelerating voltage.