By careful positioning of where the laser pulse ablates the target relative to the substrate and not rotating the substrate, it is possible to deposit a thickness gradient across the substrate. Both the PLD/MBE 2300 and nanoPLD1000 have multi-target carousels that allow the sequential deposition from different target materials without breaking vacuum. For most films, each nanometer of film requires 40 laser-pulses. If a combinatorial film of materials A, B and C is required: First, 40 pulses of material A would be deposited without substrate rotation; Second, the substrate would be rotated 120° and 40 pulses of material B would be deposited, again, without substrate rotation; Third, the substrate would be rotated an additional 120° in the same direction and 40 pulses of material C would be deposited, again, without substrate rotation. The system would then be returned to the original substrate rotation. The process of depositing materials A, B and C would be continued until a film of the desired thickness was obtained. Because each layer is so thin, there is complete mixing of materials A, B and C without the need for diffusion. The software is equipped with a “recipe” option that allows the entire film to be programmed and deposited without operator intervention during the deposition. See more here