Novel Materials Applications of Pulsed Laser Deposition

Abstract

The successful use of pulsed laser deposition (PLD) to fabricate thin film superconductors has generated interest in using the technique to deposit thin films of other materials. The compositional fidelity between laser target and deposited film and the ability to deposit films in reactive gas environments make the PLD process particularly well suited to the deposition of complex multicomponent materials. Cheung and Sankur recently provided an excellent review of the PLD field, including a table of over 100 elements, inorganic and organic compounds, andsuperlattices that have been laser evaporated. Over 75 of these materials were deposited as thin films.The goal of this article is to provide an introduction to some of the newer applications of PLD for thin film fabrication. Four classes of materials are highlighted: ferroelectrics, bioceramics, ferrites, and tribological materials. Ferroelectric materials are structurally related to the high-temperature superconducting oxides and therefore are a direct extension of the recent superconducting oxide work. Bioceramics are dissimilar in structure and application to both ferroelectrics and superconducting oxides, but they are complex multicomponent oxides and, therefore, benefit from the use of PLD. Ferrites, also complex, multicomponent oxides, represent another exciting, but only lightly explored opportunity for PLD. In contrast, tribological materials are typically neither complex nor multicomponent. Nevertheless, interesting structures and properties have been produced by PLD. A few of the more important ones will be discussed. These different types of materials demonstrate the diversity of capabilities offered by PLD.

The study of surface transformation of pulsed laser deposited hydroxyapatite coatings

“…Despite PLD's effectiveness in obtaining CaP coatings with high crystallinity with respect to HA structure, [25][26][27][28][29][30][31] its inability to create pure HA coating should not be ignored. [29][30][31] However, the presence of non-HA phases may be desirable.…”

“…The primary stability of these coatings was probably due to the high percentage of HA structure in the coatings achieved by PLD with the help of elevated substrate temperature and H 2 O enriched ambient gas during deposition. [25][26][27][28][29][30][31] The ability of these coatings to exhibit sufficient stability in a simulated physiological solution while undergoing a certain degree of dissolution/reprecipitation that resulted in the formation of HA material suggested that these coatings are chemically suitable for implant applications. However, generally a porous structure is susceptible to mechanical failure more than a dense structure 38 in addition to the tendency for higher dissolution; although it was shown that the particles (especially those close to the substrate surface) within the coating were well bonded to the coating matrix by the condensed vapor phases formed during deposition.…”

“…[21][22][23][24] However there is concern about the coating stability, since it is generally agreed that the implant surface need to be mechanically stable at the early stage of implantation to provide primary mechanical strength. It seems that to deal with the excessive dissolution of CaP coatings for long-term stability and yet retain a certain degree of bioactivity for enhanced tissue attachment, a coating with controllable dissolution/reprecipitation and sufficient stability is [25][26][27][28] has the ability to produce both dense and porous and both crystalline and amorphous coatings. [29][30][31] However, little has been reported about the dissolution and reprecipitation properties of PLD HA coatings.…”

Fundamental absorption edge and near‐absorption edge properties of PLZT thin films

“…This strong shift in E g could not be caused by strains alone. Another possible contribution to the E g shift is related to the presence of charged defects, like grain boundaries that may cause the appearance of electrostatic potentials and band banding 29–33. Just below E g in insulators and semiconductors α is expected to vary exponentially with the incident photon energy E , which is known as the Urbach tail 30 where α 0 and E 0 are characteristic parameters of the material, and E U is the width of the exponential tail or localized states in the bandgap.…”

“…This fact, most probably, reflects a specific technique used for the film preparation. The high volatility of lead and its low reactivity with diatomic oxygen leads to poor control of lead stoichiometry in the sputtering methods like PLD 33. So, as a rule, the sputtered lead‐based ferroelectric films (like PZT, PLZT, etc.)…”