The piezoelectric properties of compositional spread (1 À x)BiFeO 3 -xGaFeO 3 epitaxial thin films are investigated where Ga 3þ substitution for Bi 3þ is attempted in Bi 1Àx Ga x FeO 3 compounds. Ga content x was varied from 0 to 12% (atomic). Ferroelectric characterizations are reported at various length scales. Around 6.5% of Ga content, an enhancement of the effective piezoelectric coefficient d eff 33 is observed together with a change of symmetry of the film. Measured d eff 33 values in 135 nm thick films increased from 25 pm/V for undoped BiFeO 3 to 55 pm/V for 6.5% Ga with no extrinsic contribution from ferroelastic domain rearrangement. V

In this chapter we will describe a new development of combinatorial pulsed laser deposition (CPLD) which targets the exploration of interface libraries. The idea is to modulate continuously the composition of interfaces on a few atomic layers in order to alter their functional properties. This unique combinatorial synthesis of interfaces is possible due to very specific PLD characteristics. The first one is its well-known ability for complex oxide stoichiometry transfer from the target to the film. The second one is the layer by layer control of thin film growth at the atomic level using in-situ RHEED characterization. The third one relates to the directionality of the ablated plume which allows for selective area deposition on the substrate using a mobile shadow-mask. However PLD also has some limitations and important PLD aspects to be considered for reliable CPLD are reviewed. Multiple examples regarding the control of interface magnetism in magnetic tunnel junctions and energy band and Schottky barrier height tuning in ferroelectric tunable capacitors are presented.

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