Dear all :
I need help with the following question :
It is possible to grow n-type Bi2Te3 thin films, deposited on glass substrates using the e-beam technique ? If so, What would I require ? or What considerations do a have to take ?
I have acces to an e-beam deposition chamber and I have Intermetallic crucibles (BN-TiB2) and Graphite crucibles.
Then, I have a commercial bulk-Bi2Te3 n-type. So, my plan is to cut a piece of the ingot, and then breake pieces into little pellets, to place them directly into the crucible ,
Will this work ?
Thank you for the help ! :)
Regards !
Dear Franklin Uriel Parás Hernández,
I understand you want to make a beam target for for e-beam technique. I think this is not a good idea. Since the composition of your target can change dramatically during the melting process, it can also become saturated with impurities, which will ultimately affect the results of film deposition. You need clean films.
I think you should to buy clean beam target of n-type Bi2Te3 or mechanically grind at the turner from what is.
Dear Andrei Pligovka , but I'm talking about an e-beam physical vapor deposition system, it doesn't use a target of material, but a crucible with pieces of the material on it.
Regards ,
Franklin Uriel Parás Hernández, for e-beam physical vapor deposition system In the e-beam target serving as an anode, the electron flux is directed with an energy of several keV emitted by the cathode, resulting in the evaporation of atoms neprervynomu. Or you talk about thermal evaporation? No e-beam?
Dear Andrei :
Yes I'm talking of e-beam deposition. And it doesn't use a target, we (I and my labmates) have deposited Al, Cr and Ti a few times, we have an e-beam evaporator system of TORR INT. and what you use on its configuration is a crucible, where you have to introduce little pellets of the material.
Maybe we are speaking about different things,
I don't know what do you refer as the "target". Because what I think of a target is e.g. the target of material you have to use in the Sputtering technique.
So, my question is: if I can make pellets from a commercial ingot (or another commercial target, but a material not thought for been used for an e-beam system) like the n-Bi2Te3 ingot I have? and if place tiny pieces of it into my intermetallic crucible, Will the Bi2Te3 be evaporated well ? homogeneously ? without problems ? so the deposited n-Bi2Te3 in the films would end uniformly deposited ?
Regards, !
Dear Franklin,
you can try to use co-deposition by tuning deposition rates of Bi and Te to get proper composition on the substrate. It becomes more tricky because of two e-beam evaporators are required. Furthermore, they have to be properly aligned and deposition rates have to be stable.
In the case of a single evaporator, deposition rate of different alloy components can be different. It leads to the different stoichiometry of deposited film.
I think that magnetron sputtering or PLD is more suitable technic for this application.
Best regards
All:
Thank you for your advices and comments :)
Dear Yevhen Zabila :
Unfortunately, I don't have the required equipment to do what you recommend, I think this is also one of the things we have to learn how to deal with in science, to work with what we have. Anyways ...
So, I'm thinking in trying with the single-evaporation source, single-chamber e-beam we have.
However, If yourself or others colleagues, can comment something about the large difference in Vapor Pressures between that of Bi and that of Te, this will be helpful :
The Vapor Pressure of Te can be two or three orders of magnitude higher than that of Bi, at low temperatures ...
Do you think this will be a factor to certainly assure that the Rate of physical evaporation Bi/Te will be far from the one required to deposit n-Bi2Te3 films with a roughly uniform thickness, and a Bi2Te3, stoichiometrically enough to end with a n-type semiconductor (opposite to a p-type material).
What do you think about this fact of the Bi-Te relation ?
Regards ! :)
Dear Franklin,
I'm not sure about the result. So why just not to try? In this case, it's better to have an RBS to check the final composition or some other analytical technics if it's available in your lab.
The Vapor Pressure of Bi2Te3 will be different than of pure Bi or Te. Furthermore, in the case of thermal decomposition of molten alloy, it can vary in time. I'm afraid this parameter does not help you to find an answer.
You can crosscheck the data in Kurt J. Lesker Material Deposition Chart
https://www.lesker.com/newweb/deposition_materials/materialdepositionchart.cfm#b
The most valuable part there is the comment in the last column. Usually, it looks like hints but there is a lot of experience behind it.
Unfortunately, there is no information about E-Beam performance in a table. There only some helpful suggestions about boat/crucible materials for thermal evaporation. One of the possible reason it's a low melting point. The power of the simple resistive heater should be sufficient to evaporate the material and there is no needs to use e-beam.
I took a look at publications and it wasn't difficult to find some which deal with thermal deposition. If it's work for PVD it should also work for e-beam heater. According to Kurt J. Lesker, graphite crucible you mentioned fits fine. The J-M. Lin at al. reported what Bi2Te3-powder with 1 to 10mm particles were used by them.
[Lin13] https://scholar.google.pl/scholar?q=Thermoelectric+properties+of+Bi2Te3+thin+films+prepared+by+thermal+evaporation+method&hl=en&as_sdt=0&as_vis=1&oi=scholart
If you have two evaporators you can also use layer-by-layer deposition to reach proper composition. But additional post-annealing step will be required to convert the layered structure into the alloy.
[Aro17] Article Properties of Nanostructure Bismuth Telluride Thin Films Usi...
Take care about purity, especially if you are working with dopped semiconductor or semimetals. It happens that it's difficult to reproduce/compare results sometimes. It's better to use the material coming from the same supplier, even if it's 99.999% purity or some fixed alloy composition.
Best regards
Yevhen
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