Continuous compositional-spread technique based on pulsed-laser depositionand applied to the growth of epitaxial films

A novel continuous-compositional-spread (CCS) technique based on the nonuni formity of the deposition rate typically observed in pulsed-laser depositio n (PLD) is introduced. Using rapid (submonolayer) sequential deposition of the phase spread's constituents, intermixing of the constituents occurs on the atomic scale during the growth process. Therefore, a pseudobinary or ps eudoternary phase diagram is deposited without the requirement of a postann eal. The approach uses the spatial variations in the deposition rate natura lly occurring in PLD; therefore, there is no need for the masks typically u sed in combinatorial techniques. Consequently, combinatorial materials synt hesis can be carried out under optimized film growth conditions (for exampl e, complex oxides can be grown at high temperature). Additionally, lifting the need for postannealing renders this method applicable to heat-sensitive materials and substrates (e.g., films of transparent oxides on polymer sub strates). PLD CCS thus offers an interesting alternative to traditional "co mbi" for situations where the number of constituents is limited, but the pr ocess variables are of critical importance. Additionally, the approach bene fits from all the advantages of PLD, particularly the flexibility and the p ossibility to work with targets of relatively small size. Composition deter mination across the sample and mapping of physical properties onto the tern ary phase diagram is achieved via a simple algorithm using the parameters t hat describe the deposition-rate profiles. Experimental verification using energy-dispersive x-ray spectroscopy and Rutherford backscattering spectros copy measurements demonstrates the excellent agreement between the predicte d and the calculated composition values. Results are shown for the high-tem perature growth of crystalline perovskites [including (Ba,Sr)TiO3 and the f ormation of a metastable alloy between SrRuO3 and SrSnO3] and the room-temp erature growth of transparent conducting oxides. (C) 2001 American Institut e of Physics.