Thin Film Substrate
How PLD and RF sputtering are different over each other ? Or why one should choose PLD over sputtering except depositing complicated oxides (e.g: super conductors or perovskites). It is well known that PLD can transfer the exact phase from the target to substrate, but thats what RF sputtering can also do for insulating target.
Basically PLD has been successful for growing epitaxial films. This naturally demands well matched epitaxial substrates. The substrate temperature must be carefully optimized, and the rate of deposition ( determined by the energy per pulse), and the repetition rate setting. PLD provides a stoichiometric transfer of material from the target to the substrate, and thereby ensures better stoichiometric control, and has been very effective with oxide targets.
Reserchers are often using PLD for making coatings on other substrates (like silicon, SiO2/Si) etc., which may not be epitaxially matched. Such a\depositions always result in polycrystalline coatings, and necesscitate post deposition annealing. A complex oxide compound PZT is a classical example. For this compound it is noted that in the literature excellent PZT films on epitaxial substrates, and epitaxially mathched electrodes (oxides) have been developed with excellent properties, whereas polycrystalline films on unmatched substrates do not result in good properties.
Sputtering is a slower process relatively. For oxide target it becomes more complicated. You cannot apply higher powers, the targets loos oxygen stoichiometric, makeing large area targets is a costly affair, and demand good bonding with metallic plates for cooling. Although sputtering has also been useful for making epitaxial films, but somehow the target surface changes after a few sputtering runs, and this affects the stoichiometric control.
Sputtering can handle deposition over a large area of substrates upto 4inches to 6 inches in diameter. Because it is easily to develop oxide films usisng reactive sputtering, which involves sputtering oxygen or Ar+O2 gas mixtures, and one can easily use large area metallic targets and sputter them easily in oxygen.
Large area deposition is possible only through sputtering, whereas PLD is limited to tiny substrates (5mm x 5mm), larger single crystal substrates also can be used, but then the substrate becomes costly.
PLD is a fast turn around process to check the growth of epitaxial films, and establish the properties in epitaxial films. PLD is really not effective for making films on unmatched epitaxial substrates and growing of polycrystalline films. Use it more for epitaxial growth studies.
Sputtering is a technique, and when properly optimised, it can be upscaled to larger area substrates. Simple oxide compounds like (SnO2, ZnO et) are rel;atively easy to optimize, whereas multi-component oxides the optimization takes a little longer. With this technique you can easily up scale for industrial applications.
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