Sciencemadness Discussion Board

Homebrew NMOS Transistor

kencbk - 3-7-2010 at 06:47

Hi guys kencbk here,

Hey just want to share something i found in youtube. Home brew transistors:

this video, how she made it:
awesome video and detailed explanations.
want to try it out.
maybe some of you guys are also interested of trying it too. :)

kencbk - 3-7-2010 at 23:42

can i use sodium hydroxide in substitute for hydrofluoric acid in etching glass instead?

Mr. Wizard - 4-7-2010 at 09:23

If anybody is interested in this subject, they should also look at this guy's web sites:
He does some amazing things with simple materials. Just one example is his homemade Negative resistance oscillator with a home made tunnel diode.

Xenoid - 4-7-2010 at 15:42

Quote: Originally posted by kencbk  
can i use sodium hydroxide in substitute for hydrofluoric acid in etching glass instead?

Hmmm... Using a solution of NaOH it would take many weeks or months, I don't recommend using molten NaOH, it would probably be more dangerous than HF for this application!

There are many glass etching pastes available for craft work, they contain low concentrations of HF and are readily available and fairly cheap, here are some;

Alternatively, you could try the method that was a popular home experiment back in the "good old days". Warm a little fluorspar (CaF2) or some other fluoride with concentrated H2SO4 and expose the glass to the evolved fumes (HF). Take care :o

12AX7 - 6-7-2010 at 21:04

NaOH is a bad idea. Even the slightest sodium contamination causes the gate threshold voltage to drift considerably in operation, because sodium ions get trapped in the gate oxide and move around in the electric field.

Though FETs (MOS and junction) were recognized early on, they were impossible to make until the 60s and 70s, when silicon and other chemicals were finally pure enough to reduce or eliminate sodium contamination and surface states.

As I recall, Jeri has acknowledged that, despite best efforts, her gates are comtaminated, so the threshold voltage changes measurably.

As I recall, NaOH is used for some etching processes, where it is anisotropic, preferentially etching along crystal axes. So instead of pitting corrosion, you get "pyramidding". I think this only works on silicon, not the oxide (whereas HF eats oxide and not metal!).


peach - 10-7-2010 at 22:56

Jeri Ellsworth, the actual Kari Byron of science

She is true nerd porn, but I do think she gets somewhat unfair amounts of praise with regards to her electronics

[Edited on 11-7-2010 by peach]

peach - 18-8-2010 at 04:56

Ms Ellsworth has made her own transistors and is constantly fiddling around with silicon.

There are lots and lots of videos by her on the interwebs showing how she's doing it. In one of them, she's built a little box with a slit in lid and three cups inside, so she can dip the silicon in HF, then rinse and then do a final rinse, without having the risk of the acid spilling.

Have a search and you may find she's already made a video showing you how to do it.