In PLD, the laser is external to the deposition chamber. The laser pulse enters the deposition chamber through a UV-grade laser window and is coupled to the target. During deposition, the chamber-side of the laser window that is in direct line-of-sight to the plasma plume receives a small percentage of the ablated material that forms a thin layer on the window. Depending on the optical properties of this deposited layer and the amount of the material deposited, the laser energy entering into the deposition chamber will get attenuated correspondingly. For reproducible film properties, it is critical to maintain the fluence (J/cm2 ) on the target within a narrow and optimum range. The laser window therefore needs to be cleaned or replaced periodically in order to maintain this optimum fluence range on the target. This requires venting the chamber to atmosphere which is undesirable in certain cases such as UHV systems.
Neocera laser window-change accessories provide a solution to the laser window coating problem and provides clean optical beam path for extended periods of operation. A UV-grade silica liner is placed inside the main laser window and only a small part of the liner is exposed to the deposit. As the exposed portion of the silica liner is coated, an uncoated portion can be moved into it’s place, maintaining a clean optical beam path.
Automated and manual options are available for Neocera laser window-change accessories. In the automated case, a cassette of 6 silica slides are provided which can be changed automatically using System software. A software controlled actuator carries out the window change operation, as per the deposition protocol chosen by the operator. In manual cases, the silica liner is rotated to an uncoated portion. One automated option and two manual options are available based on the vacuum requirements.