I am currently trying to emulate a process known as Glancing Angle Deposition (GLAD) by manufacturing sculptured thin films of different compositions of alloy. I am just wondering has anyone else tried to do this to form an array of nanostructures on either a seeded or unseeded substrate.
I am using DC Sputtering (PVD) and would like to know what base pressures the chamber should be at. then what differential pressure the chamber should be at during the Argon flow (i.e the Argon pressure) and what throw distance should be used between the target material and substrate.
Any suggestions are very welcome; as I can quickly change the set-up of my equipment to investigate any augmentations to my current set-up.
Regards,
Christopher Quinn
Dear Christofer,
I can provide you some clues or ideas, but first of all i have to understand what exactly are you planning to do. More details of what you want to do or what you are thinking are welcome.
The key in sputtering techniques is, most of the time, the kinetic energy of the species you want to deposit, because the whole sputtering process is driven by mechanical phenomena.
You can also check refs. to see if you need to prepare substrates depositing a certain catalytic layer or a certain treatment.
I hope these general keys will help you. For any other help, you can ask me!
Thanks Gregory.
Thanks for your input.
I have successfully made lots of FeGa thin films with no problems, I have my sputtering pressure set to around 2.5 mbar - which gives me a kinetic mean free path of around 100mm. The problem I am having is when I have my substrate set at an oblique angle (say 80 degrees) to the horizontal - I can only grow what can be described as small bumps; then the more matter I deposit, the film starts to build up and the growths just dissapear into the film.
I have seen these growths done with other materials, but not with FeGa; a colleague of mine works on growing nanowires using gold quantum dots as seed points - successfully growing vertical arrays of wires, but when he used Gallium as the seed for the wires, they just grow horizontally along the substrate - I am just wondering if the Gallium instills this preferred growth direction.
Here is a paper on GLAD just so you can understand what I am trying to do.....
http://www.physics.queensu.ca/~robbie/papers/RobbieJVSTB_1998_AdvancedGLADDeposition.pdf
First of all, the way that a film grows on a substrate depends on the material (i mean growth type, like layer-by-layer, island formation or stranski-crastanov). maybe you can drive the deposition to the result you want by calculating the effective area of the sputtered material...let's say that the deposition at the edges of the plasma plume (let me call it this way) is way too different to the centre. Different kinetic energy and a lot different deposition rate (leading to different relaxation time and diffusion).
As it has to do with gold and gallium, they are two different materials with different catalytic properties. I think that's why using Ga leads to unsuccessful growth.
The material I am using is a cast alloy target FeGa (80% Fe and 20% Ga). The composition of the thin films have been confirmed as Fe 81% Ga 19% by EDX - this is probably due to the slightly two different vapour pressures of the 2 materials.
To try to grow the structures, I have even tried seeding my substrates with 50nm and 500nm nanospheres; but with little success. I think there must be a way to do this - maybe by either using e-beam or RF sputtering.
The reason we are using FeGa is that the material is a magnetostrictive and has many potential uses in remote sensing applications - especially at the nano level - this is why we are trying to grow sculptured films as we have several applications in mind for there use.
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