Pulsed Laser Deposition of Biocompatible Thin Films: Calcium Hydroxylapatrte and Other Calcium Phosphates

Abstract

ABSTRACTCalcium phosphate-based ceramics were deposited on Ti, Ti-6Al-4V and Si substrates by pulsed laser deposition. The calcium phosphate phase (amorphous, α- or β-tricalciumn phosphate, tetracalcium phosphate, or hydroxylapatite), Ca/P ratio and surface morphology of the films were related to deposition conditions. At substrate temperatures <400°C, films were amorphous. Above 400°C, the gaseous environment during deposition determined the crystalline phase of the films. In O2, deposition of α-tricalcium phosphate was favored between 400 and 700°C and β-tricalcium phosphate was favored above 700°C. Films deposited in low pressures of O2 (<0.05 Torr) were P-deficient. The correct stoichiometry was approached as the pressure of O2 in the chamber during deposition increased. In water vapor-enriched inert gas environments, deposition of hydroxylapatite was observed at temperatures between 400 and 700°C and tetracalcium phosphate was observed at temperatures above 700°C. The surface morphology of hydroxylapatite films depended on the temperature of deposition. Surfaces deposited at higher substrate temperatures showed more recrystallization than those deposited at lower substrate temperatures.