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

A novel continuous-compositional-spread (CCS) technique based on the nonuniformity of the deposition rate typically observed in pulsed-laser deposition (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 pseudoternary phase diagram is deposited without the requirement of a postanneal. The approach uses the spatial variations in the deposition rate naturally occurring in PLD; therefore, there is no need for the masks typically used in combinatorial techniques. Consequently, combinatorial materials synthesis can be carried out under optimized film growth conditions (for example, 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 substrates). PLD CCS thus offers an interesting alternative to traditional "combi" for situations where the number of constituents is limited, but the process variables are of critical importance. Additionally, the approach benefits from all the advantages of PLD, particularly the flexibility and the possibility to work with targets of relatively small size. Composition determination across the sample and mapping of physical properties onto the ternary phase diagram is achieved via a simple algorithm using the parameters that describe the deposition-rate profiles. Experimental verification using energy-dispersive x-ray spectroscopy and Rutherford backscattering spectroscopy measurements demonstrates the excellent agreement between the predicted and the calculated composition values. Results are shown for the high-temperature growth of crystalline perovskites [including (Ba,Sr)TiO3 and the formation of a metastable alloy between SrRuO3 and SrSnO3] and the room-temperature growth of transparent conducting oxides. (C) 2001 American Institute of Physics.