Hydroxyapatite coatings grown by pulsed laser deposition with a beam of 355 nm wavelength

Abstract

Calcium phosphate coatings, obtained at different deposition rates by pulsed laser deposition with a Nd:YAG laser beam of 355 nm wavelength, were studied. The deposition rate was changed from 0.043 to 1.16 Å/shot by modification of only the ablated area, maintaining the local fluence constant to perform the ablation process in similar local conditions. Characterization of the coatings was performed by scanning electron microscopy, x-ray diffractometry, and infrared, micro-Raman, and x-ray photoelectron spectroscopy. The coatings showed a compact surface morphology formed by glassy grains with some droplets on them. Only hydroxyapatite (HA) and alpha-tricalcium phosphate (␣-TCP) peaks were found in the x-ray diffractograms. The relative content of ␣-TCP diminished with decreasing deposition rates, and only HA peaks were found for the lowest rate. The origin of ␣-TCP is discussed.

Calcium orthophosphate coatings, films and layers

“…To sputter calcium orthophosphates, several types of the physical vapor deposition techniques are used, such as ion beam (Stevenson et al 1989; Barthell et al 1989; Ong et al 1991, 1992, 1994; Yoshinari et al 1994; Cui et al 1997; Kim et al 1998; Luo et al 1999; Choi et al 2000; Wang et al 2001; Hamdi and Ide-Ektessabi 2003; Lee et al 2003; Fujihara et al 2004; Lee et al 2005b; Rabiei et al 2006; Lee et al 2007a; Blalock et al 2007), radio-frequency (RF) magnetron (Cooley et al 1992; Yamashita et al 1994; Jansen et al 1993; Wolke et al 1994; van Dijk et al 1995, 1996; Wolke et al 1998, 2003; Nelea et al 2003, 2004; Feddes et al 2003a, 2003b; Ding 2003; Yamaguchi et al 2006; Wan et al 2007; Ozeki et al 2007; Ueda et al 2007; Snyders et al 2008; Ievlev et al 2008; Toque et al 2009), pulsed laser (Nelea et al 2000, 2002, 2004; Cotell et al 1992, Cotell 1993; Torrisi and Setola 1993; Cotell 1993; Singh et al 1994; Wang et al 1997; Hontsu et al 1997; Fernández-Pradas et al 1998, 1999, 2001; Mayor et al 1998; Arias et al 1998; Craciun et al 1999; Fernandez-Pradas et al 1999; Zeng et al 2000; Cleries et al 2000a; Nelea et al 2000; Zeng and Lacefield 2000; Fernandez-Pradas et al 2001; Nelea et al 2002; Socol et al 2004; Kim et al 2005a; Bigi et al 2005b; Koch et al 2007; Kim et al 2007a; Paital and Dahotre 2008; Paital et al 2009; Dinda et al 2009; Tri and Chua 2009; Sygnatowicz and Tiwari …”

“…A PLD process is used for forming thin (0.05 to 5 μm) calcium orthophosphate coatings, layers or films on various substrates (Nelea et al 2000, 2002, 2004; Cotell et al 1992, 1993; Torrisi and Setola 1993; Singh et al 1994; Wang et al 1997; Hontsu et al 1997; Fernández-Pradas et al 1998, 1999, 2001; Mayor et al 1998; Arias et al 1998; Craciun et al 1999; Fernandez-Pradas et al 1999; Zeng et al 2000; Cleries et al 2000a; Zeng and Lacefield 2000; Socol et al 2004; Kim et al 2005a, 2007a; Bigi et al 2005b; Koch et al 2007; Paital and Dahotre 2008; Paital et al 2009; Dinda et al 2009; Tri and Chua 2009; Sygnatowicz and Tiwari 2009). The process involves ablation of a calcium orthophosphate (usually, HA) target using a pulsed (usually, pulses of 30 ns and 120 mJ at a repetition of 10 Hz) KrF excimer laser beam ( λ  = 248 nm) in 0.3 Torr/H 2 O atmosphere and deposition of the ejected HA material on a heated (400°C to 800°C) substrate.…”

Formation of hydroxyapatite coating on titanium at 200°C through pulsed laser deposition followed by hydrothermal treatment

“…The first one is the ejection of target material in the form of micrometer-sized particulates and making them adhere to the substrate surface. The second one is the conversion of target material to atoms, molecules and small clusters and allowing them to migrate over the substrate surface to nucleate and grow as crystallites (Fernandez-Pradas et al 1999). The optical emission studies indicate that the latter mechanism dominates in the present deposition experiment, as the atomic and ionic emissions of calcium, phosphorous and oxygen are present in the spectrum.…”

Recent developments in processing and surface modification of hydroxyapatite

“…A very high repetition rate of several MHz can provide sufficient energy (at least several hundred nanojoules) to achieve highly efficient ablation producing a continuous stream of material to a target substrate that requires a deposited thin film or coating of close to epitaxial quality. 162,163 Pulsed laser ablation typically involves an excimer laser and has been applied to various types of HA bioceramic material creating a plume of mixed evaporated and particulate material. The plume material condenses quickly onto the substrate material such as a metal implant for dental or orthopaedic application where the benefit of the HA film or coating can enhance the biocompatibility of the implant combining the excellent mechanical properties of metals with the outstanding bioactivity of HA.…”