Nd:YVO₄Thin Films Grown by Pulsed Laser Deposition: Effects of Temperature and Pressure on the Grain Morphology and Microstructure

Abstract

Nd:YVO4 thin films were grown by pulsed laser deposition (PLD) on single-crystal r-cut sapphire(11̄02) substrates, and the grain morphology and microstructure of the films were investigated as a function of substrate temperature and oxygen pressure employed during growth. Highly crystalline (200)-oriented films were grown using the following optimized growth parameters: 700−900 °C and 250−350 mTorr of O2. Below these values, a-axis-textured polycrystalline films were formed exhibiting no epitaxial relationship with the sapphire substrate. Scanning electron microscopy studies revealed that the films contain grains that undertake a morphological transformation from spherical to rectangular in the temperature range of 650−670 °C, with the latter being well faceted and having dimensions as large as 1 × 5 μm. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) revealed that the films are epitaxial and exhibit a high degree of crystalline perfection because of their 2θ- and ω-FHWM values of 0.06° and 0.12°, respectively. The importance of certain growth parameters, specifically substrate temperature and oxygen pressure, on the microstructure and grain morphology of the films is discussed in detail.