I want to grow Cobalt ferrite thin films of 6nm to 50 nm by PLD on STO substrate. How can I control the thickness of film in this range?
When using PLD to grow films, the thickness of the material will depend upon quite a few variables, all of which will effect the amount of material deposited per pulse. For example, the energy of the incident laser is important to ablate the target surface as well as it creating the plasma plume. The gas pressure within the the chamber at deposition is also important, since the higher the pressure, the greater the resistance for the ablated material to cross the gap to the substrate. As one could then draw from this, the distance between the target and the substrate is also important.
All these should be optimised (along with substrate temperature) to ensure not only a reasonable deposition rate, but one that produces good film stociometry, crystallography and epitaxy and desired physical characteristics, as well as low surface roughness. For example, the energy of the laser is too large, or the target-substrate distance too low, you could end up with "boulders" within the film. While this would be ok for much thicker films, when you are working with 6-50 nm, this can have detrimental problems with any desired results.
All this would need to be experimentally optimised, but once you work out the best method to grow good quality thin films, Then you can experimentally determine the film thickness (for example by using cross sectional TEM) and work out how much material is deposited per pulse, you can then simply calculate the approximate film thickness by knowing the pulse rate, and the length of time you deposit. Therefore, if you wanta film of a desired thickness you can simply just calculate the length of time you need to deposit and at which pulse rate.
You can also get some expensive RHEED equipment that allows you to monitor film thickness as you grow it, but as mentioned it can be expensive and adds complexity to the system, but does permit extremely good control over desired film thickness.
For further information on PLD optimisation see the books
D. B. Christey and G. K. Hubler, Pulsed Laser Deposition of Thin Films,
John Wiley & Sons, 1994.
and Pulsed laser deposition of thin films : applications-led growth of functional materials / edited by Robert Eason John Wiley & Sons, 2007
U can start with 7000C substrate temperature, Oxygen pressure during deposition ~ 100 mTorr and cooling at 400 Torr.. Frequency ~ 7 Hz.. Please see our paper on CFO (on my Research gate profile).. may be of your interest and reading !
When using PLD to grow films, the thickness of the material will depend upon quite a few variables, all of which will effect the amount of material deposited per pulse. For example, the energy of the incident laser is important to ablate the target surface as well as it creating the plasma plume. The gas pressure within the the chamber at deposition is also important, since the higher the pressure, the greater the resistance for the ablated material to cross the gap to the substrate. As one could then draw from this, the distance between the target and the substrate is also important.
All these should be optimised (along with substrate temperature) to ensure not only a reasonable deposition rate, but one that produces good film stociometry, crystallography and epitaxy and desired physical characteristics, as well as low surface roughness. For example, the energy of the laser is too large, or the target-substrate distance too low, you could end up with "boulders" within the film. While this would be ok for much thicker films, when you are working with 6-50 nm, this can have detrimental problems with any desired results.
All this would need to be experimentally optimised, but once you work out the best method to grow good quality thin films, Then you can experimentally determine the film thickness (for example by using cross sectional TEM) and work out how much material is deposited per pulse, you can then simply calculate the approximate film thickness by knowing the pulse rate, and the length of time you deposit. Therefore, if you wanta film of a desired thickness you can simply just calculate the length of time you need to deposit and at which pulse rate.
You can also get some expensive RHEED equipment that allows you to monitor film thickness as you grow it, but as mentioned it can be expensive and adds complexity to the system, but does permit extremely good control over desired film thickness.
For further information on PLD optimisation see the books
D. B. Christey and G. K. Hubler, Pulsed Laser Deposition of Thin Films,
John Wiley & Sons, 1994.
and Pulsed laser deposition of thin films : applications-led growth of functional materials / edited by Robert Eason John Wiley & Sons, 2007
To Sandip,
Jonny McAneney is explained in a better way about how to control the thickness of film, growing by PLD. Substrate-target distance, gas pressure inside the chamber, substrate temperature and mainly laser energy can play important role.... All these parameters can also vary from one deposition chamber to other chamber... You have to optimise the synthesis parameters to confirm the epitaxy and thickness....
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