Influence of substrate temperature on the growth rate and the composition of calcium phosphate films prepared by using pulsed laser deposition

Abstract

Calcium phosphate films were prepared by using a pulsed laser deposition (PLD) technique with a KrF excimer laser (248 nm, 2 J/cm2), and the influence of the substrate temperature on the growth rate and the composition of those films was studied at substrate temperatures ranging from room temperature to 700 C. Sintered hydroxyapatite (HA) was used as the target, and the films were deposited under 0.25 Torr of H2O. The temperature dependency of the erosion of the film by the energetic deposition flux is also discussed. The substrate temperature critically affected the growth rate and the composition of the deposited films. The mass of the PLD calcium phosphate film decreased 8 % with increasing substrate temperature from room temperature to 700 C, and this was explained by enhanced sublimation of the film by the bombardment of the deposition flux at higher substrate temperatures. The Ca/P ratio also gradually increased from 1.7 to 1.9 with increasing temperature because the amount of phosphorus sublimated from the growing film increased more rapidly as compared with the amount of calcium that sublimated. A high density and a strong (300) preferred orientation were also observed at high substrate temperatures.