Nd : YVO4 thin films grown by pulsed laser deposition: Effects of temperature and pressure on the grain morphology and microstructure

Nd:YVO4 thin films were grown by pulsed laser deposition (PLD) on single-cr ystal r-cut sapphire(1 (1) over bar 02) substrates, and the grain morpholog y and microstructure of the films were investigated as a function of substr ate temperature and oxygen pressure employed during growth. Highly crystall ine (200)-oriented films were grown using the following optimized growth pa rameters: 700-900 degreesC and 250-350 mTorr of O-2. Below these values, a- axis-textured polycrystalline films were formed exhibiting no epitaxial rel ationship with the sapphire substrate. Scanning electron microscopy studies revealed that the films contain grains that undertake a morphological tran sformation from spherical to rectangular in the temperature range of 650-67 0 degreesC, with the latter being well faceted and having dimensions as lar ge as 1 x 5 mum Transmission electron microscopy (TEM) and X-ray diffractio n (XRD) revealed that the films are epitaxial and exhibit a high degree of crystalline perfection because of their 2 theta- and omega -FHWM values of 0.06 degrees and 0.12 degrees. respectively. The importance of certain grow th parameters, specifically substrate temperature and oxygen pressure, on t he microstructure and grain morphology of the films is discussed in detail.