Chemical reaction of electrochemical etching

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krik krik krik
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Greetings all,

I have some questions regarding to chemical reaction between Silicon,Si (wafer) and chemical dissolution. FYI, I'm doing electrochemical ething to fabricate porous Si. Could anyone help me to solve this chemical reactions?

1) Si (silicon wafer) + HF (hydroflouric acid)+ C2H5OH(ethanol) = ?

2) Si + HF + C2H5OH + H202 (hydrogen peroxide)= ?

3) Si + HF + (CH3)2NC(O)H (dimethylformamide)= ?

Thanks :smile:
 
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Hopefully somebody can correct me if I'm wrong. This is what I've found :

1) Si (silicon wafer) + HF (hydroflouric acid)+ C2H5OH(ethanol) = H2SiF6+ C2H6 + H2O + H2

2) Si + HF + C2H5OH + H202 (hydrogen peroxide)= H2SiF6+ C2H5F + H2O+ H2O2+H2

3) Si + HF + (CH3)2NC(O)H (dimethylformamide)= H2SiF6 + (CH3)2NCF + H2O+H2

To be honest chemistry is not my field. Any suggestion/comment? The equations is not balance at all.

Thanks.
 
My bet is that neither ethanol nor DMF take part in the reaction, they are just spectators/solvents.
 
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Borek said:
My bet is that neither ethanol nor DMF take part in the reaction, they are just spectators/solvents.

Thanks for the suggestion. But from my point of view, these organic solvent plays an important role for uniformity and well-define shapes of my porous structure. Either ethanol or DMF gives us different morphology of porous Si. Sort of 'tricky' reaction involved in this etching process that i investigate with.

What say you?:smile:
 
No contradiction here. Different solvents can stabilize different forms of products and intermediates, so the final morphology of the product can be different. It doesn't mean basic reaction equation is different.
 
Borek said:
No contradiction here. Different solvents can stabilize different forms of products and intermediates, so the final morphology of the product can be different. It doesn't mean basic reaction equation is different.

Oh yeah? So, that's mean ethanol and DMF just stabilized the products to gives different type of morphology! Thanks for the explanation. Very pleased indeed.
 
krik krik krik said:
Oh yeah? So, that's mean ethanol and DMF just stabilized the products to gives different type of morphology!

Note: all I am saying is that what you observe doesn't call for completely different reactions.

The only sure way is to research the reaction products and mechanism, but that can be quite demanding.