Making My First Successful Film

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ian_krase
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Re: Making My First Successful Film

Post by ian_krase »

Casting a silver sputtering target. A silver bullion coin was bent in half, melted in a crucible, and poured into an open mold (made out of some kind of "alumina plaster" called Resbond 919). The mold was then heated and a little brazing flux added to re-melt and clean up the silver. Finished "button" should be about the size of a nickel, and will then be cold forged to proper thickness and clamped to the magnetron with aluminum or brass clips.

IMG_20170308_235230.jpg
ian_krase
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Re: Making My First Successful Film

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Today in "Ian messes around with sputtering while waiting to get guidance and setup for cleaning glass substrates", I tried sputtering silver onto a piece of paper (from a clothes price tag). It worked, to my surprise (since my other organic substrates failed miserably with goop).

I had to run it in short pulses to deal with the massive outgassing whenever the plasma hit the paper. After a while, I was able to quickly pump down to 20 microns (low enough to extinguish plasma if not careful!) but when the plasma was on, the pressure would gradually rise, reaching 60 microns pretty quickly. Keeping the pressure low but the plasma ready to restart (which requires around 26 microns) was tricky, not much like sputtering on glass or ceramic where once the initial outgassing is dealt with you can just set the leak valve and the isolation valve and run with it.

Electrical resistance is about 7 ohms over a distance of 7mm.
IMG_20170403_211402.jpg

Bonus picture of my overall setup.
IMG_20170403_224358.jpg
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Dennis P Brown
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Re: Making My First Successful Film

Post by Dennis P Brown »

Not exactly a fusor post but congratulations on smelting (why?) and sputtering; yes, plastics and many organics can be coated via sputtering (it is a very low temp method. More like a super fast "diffusion" process than a vapor deposition method (which it obviously is not.)) So, any of this work going to be used for a fusor, later?
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Rich Feldman
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Re: Making My First Successful Film

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Ian:
Are you familiar with the four-point probe method to measure sheet resistance of thin layers? It eliminates the contact resistance and current-spreading-from-contact issue. One popular, practical configuration has the four probes equally spaced in a straight line, with the film extending well beyond the probes in two dimensions.

The math is conceptually simpler if your film is a strip at least 3 times longer than wide. With force-current connections (e.g. alligator clips) at the ends, and measure-voltage contacts 1 width apart near the middle, the V/I ratio directly gives you the film's sheet resistance in ohms per square.

When metals are deposited by evaporation in vacuo, one kind of real-time thickness monitor is based on the changing frequency of a bare quartz crystal oscillator. I bet you knew that already. Don't know if it's applicable to sputtering. A four-point film resistance measurement could certainly run in real time, and be subject to temperature sensitivity.

Thanks for sharing the metalwork story. Nice little kiln you got there, and pictures apparently free of color pollution from near-IR brightness.
downsized_1227062335.jpg
What's your button thickness as cast, compared to that of the coin you started with?

Dennis:
Did Ian say he smelted anything? Smelting is a high-temperature process that chemically reduces ore to metal.
All models are wrong; some models are useful. -- George Box
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Re: Making My First Successful Film

Post by Pablo Llaguno »

Very nice setup Ian, your vacuum looks awesome! Question: the mini convectron gauge you bought, what fitting does it have, KF? Also, are you using a NST? Your vacuum chamber in the pic above looks black, that happened to mine and it was very difficult to remove.
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Re: Making My First Successful Film

Post by ian_krase »

I am aware of the four-point method, but I don't think I have the equipment to *do* it, and certainly not without messing around with a bunch of instrumentation. I mostly just wanted to get a comparison to my silver-on-glass and to the dead short of bulk metal plate.

I haven't *smelted* anything lately, but I'm going to be recovering some silver eventually, that might count. I did melt some silver to cast it into a sputtering target. Was in the form of silver bullion coin, and I needed a much smaller and thinner round sputtering target since my magnetron is itself pretty small. If I had my machine shop here, I would have just hammered it out and then cut a circle, but it was easier to melt it and cast it. The coin was nearly 1/8 inch thick, IIRC, and the sputtering target made from it via cuttlebone casting is more like 3/64, and slightly dished to fit the magnetron. I used a nickel as a model and then hammered it down slightly after casting.

That muffle furnace was probably not one of my smarter purchases. I'm considering selling it.

IDK if I will make anything fusorish with the sputtered films, but in a few days I will have the hardware needed to reverse the polarity on my OBIT-based power supply and then a demo fusor will probably quickly follow. Stay tuned, I guess.

I know about quartz crystal monitors, and have seen modules for them on the tiny SPI coaters (rotary-vane-backed, meant for preparing samples for electron microscope) but I don't have the feedthroughs or honestly the instrumentation expertise. Maybe later. Would be very cool to have if I could keep it from getting trashed by HV.

The convectron has a KF16. They commonly have that, KF25, or NPT. Swagelok VCR fittings are also common but I never even considered buying one. The plain old Mini-Convectron is much more common and less likely to leak than the Convectron ATM that I have.

I'm using an Oil Burner Ignition Transformer, which is very similar to a 12kV NST, but frequently cheaper and with a bit less current (25 mA rather than 30, IIRC)

The chamber looks black because the silver sputtering goes *everywhere*, not just on the substrate. This can be controlled using chimneys and baffles, potentially, but I don't have any. A closer look would show that the "black" is actually silver where it's thicker. Eventually it will get thick enough to short out a feedthrough over the insulator (this can be limited with baffles on the feedthrough). To remove it, I use potassium nitrate mixed with vinegar (poor man's nitric acid) and a swab to scrub the silver off of the glass and ceramic portions. This is a *mostly* mechanical process, with the acid only dissolving a little bit of silver sufficient to loosen the rest. Then I wash the chamber first in soapy water, then with acetone, then with alcohol. Your coating won't be silver if you didn't have any in the chamber but this method will likely be effective against a variety of metallic and metal-oxide contaminants. (Many will be removed by muriatic, aka hydrochloric acid which is in hardware stores). If it's sooty or organic, you might be in for a harder time and/or scarier oxidizing treatments. IDK.
ian_krase
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Re: Making My First Successful Film

Post by ian_krase »

IMG_20170411_211946.jpg
Well, my labors have borne fruit. Today, I RCA cleaned the substrate and, without touching it with either gloved or bare hands, transferred it to the sputtering chamber clamp.

The result was a film that was not pulled off with scotch tape, and which accumulated pinholes when brushed maybe 2-3 times slower than previously.

It wasn't perfect, as you can see a large swath *did* come away with the tape. However, I tried twice right down the middle and the bulk of the film persevered.
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Re: Making My First Successful Film

Post by ian_krase »

I managed to use sharpie marker as a resist for a lift-off process, though I think i contaminated my film... somehow. Actual pictures coming tomorrow... because I am tired.
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Re: Making My First Successful Film

Post by John Futter »

Ian
True sputtering requires the atoms to have energy to overcome whatever bonds are prevalent on the surface de jour
so you need to acellerate the ions so thay have 100 eV or above so when they arrive at your substrate they can dislodge contaminants
(such as water vapour, grease or whatever) and combine with the ligands protruding from the surface to make a true chemical bond
any less than what i am saying makes films equivalent to evapouration ie they do not pass the 3M test (sellotape at right angles).
you will need to bias your substrate negative to the tune of 400 to 1000 volts to get this to happen with the scheme you are using.
so why 400 to 1000 volts when all you need is 100
mean free path, surface contaminents, physical reality, and a measure of good luck.

all for now have fun!!!!!
ian_krase
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Re: Making My First Successful Film

Post by ian_krase »

I've already passed the 3M Test several times. Sample preparation is an RCA SC-1 clean.

I'm not sure how I would bias my substrates with a well-defined voltage when they are made of insulating glass. And what would they be biased relative to, the target? Or would the bias be applied to a plate mounted behind a thin substrate? John Strong doesn't say anything about this.

In any case, I don't have the feedthroughs needed for that, and my substrate clamp (as you can see in the pictures) is by mechanical practicality connected to the cathode. Meanwhile the anode is actually above the substrate.

The last test (described, not pictured) was as follows:

- Take fresh microscope slide, cut in half

- RCA SC-1 clean (NH3 + H2O2 + H2O)

- Rinse and dry (DI water)

- Draw pattern (cross) with Sharpie marker

- Mount, close chamber, pump down to 35 micron air

- Commence sputter, regulate pressure (air) between 20 and 50 microns

- Stop sputter when the entire sample is sufficiently opaque that a lamp cannot be seen through it (harder than it sounds)

- Stick Scotch tape to the sample, and peel off at 90 degree angle (removes silver from over the sharpie marker, but not the clean area).

- Wash with ethyl alchohol

Result: A silver mirror on glass with a cross-shaped clear unsilvered area
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Dennis P Brown
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Re: Making My First Successful Film

Post by Dennis P Brown »

The plate is biased; at those voltages and pressures the gas conducts and the ionized atoms "knock" off metal atoms that then move to and adhere to the glass. Your picture shows a rather badly "burned" film. It might just be the photo but if not, the issue of contamination looks to be a problem in your system. I don't bias my substrates but do use a DC voltage in the high hundreds (400 - 850 volts.) I've used higher voltage systems with magnetrons.

Also, your pressure is a bit on the low end. By the way, do you use air or argon? Air with oxygen can causes issues with your films.

Using an RCA cleaning process is over-kill for most sputtering systems (that is generally used only for semi-conductor systems and require ultra clean glassware ...); in any sputtering system the ionized gas will clean the substrate as long as you have first used alcohol to clean it of any minor contamination. For grossly contaminated glass surfaces using detergent and water, and then following this up by alcohol is ok.

I sputter films all the time and routinely make ultra-high quality films and I don't even bother to clean the substrates since standard slides are more than clean enough (you are using gloves to handle them?)
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Re: Making My First Successful Film

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I'm using air, as I don't have access to argon yet. DC voltage you mean is just the magnetron sputtering voltage? Mine is probably something similar, I don't have any instrumentation. The power supply is a rectified OBIT.

I know the pressure is a bit low. One frustrating problem is that either higher pressures or the low pressures I mentioned work due to Paschen's Law, but intermediate pressures cause the plasma to leave the magnetron. But its my impression that sputtering works at a wide range of pressures and lowering the pressure makes it more radiant.

It is 110% the light in that last picture. My workspace is poorly lit and the surroundings are not of uniform color. Most of my films are pretty much white silver.

The last film i did, with the cross, is burned/contaminated and actually is the way that picture looks.
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Dennis P Brown
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Re: Making My First Successful Film

Post by Dennis P Brown »

Yes, all my sputtering is done with DC.

Any good sputtered film will be a highly specular - that is, perfect mirror reflector on a piece of glass.

I sputter onto very thin plastic films (as thin as 20 microns) all the time with no trouble since sputtering and the plasma offer no significant heat load; that is not always the case for the grounding plate, however; and that can cause issues. So for thin plastic films I mount them above the ground plate using a plastic support.

Argon is popular for home based Tig welding and inexpensive (comparatively) gas systems are available in many locations. Argon is vastly superior for sputtering and allows for very high quality films to be deposited.

Scientific American has an excellent article on Sputtering in its Amateur Scientist back in the Oct 1967 issue.
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Rich Feldman
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Re: Making My First Successful Film

Post by Rich Feldman »

Dennis sure is fast!
I was about to ask who else remembered that old Amateur Scientist column, from the era that I grew up with. Really cool projects, including plenty that could kill you if followed carelessly. And things that today would scare people for miles. Amateur glassblowers could work their way up to DIY mercury-vapor diffusion pumps. Bookstores were allowed to sell the magazine to just anybody!

Ian, do you live in the San Francisco Bay area?
My day job is across the street from a company called Meivac, where they manufacture industrial sputtering systems & similar vacuum gear. I got a tour & some free stuff once, years ago, when I was mentoring some science fair kids and first joined this forum. Could find my old contact info if you're interested.
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ian_krase
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Re: Making My First Successful Film

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Oh, cool!

I live in the south bay area bordering on Silicon Valley, and work at a company that makes MEMS devices (though I am not at all involved in microfabrication processes). I'd love to have that info.

I've been scheming to set up argon, but it costs money and I've not yet decided to spend it especially as the results on silver are so good without it.

My sputtered films are quite specular, though the exact specularity isn't totally uniform -- there's a very faint haze in the center. Of course, it's easy to sputter long enough that spalling starts and then it's not so nice.
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I Finally Justify My Presence On The Fusor Forums

Post by ian_krase »

I finally built a... very sloppy... demo fusor, thereby justifying my presence on the Fusor Forums, which are not really the Sputtering Forums. (I also dismounted my sputtering magnetron from my chamber)

It successfully forms a globule of plasma inside the grid, and also forms an impinging beam that must not be allowed to heat and crack/spall my glass.

Unfortunately I also managed to heat my grid (of the extremely easy and very sloppy spiral type) to incandescence and may have evaporated a small amount of copper oxide over the inside of the jar. Or maybe it's just the light.

Pictures are a series taken over the course of pumpdown. Power, as before, is provided by an oil burner ignition transformer with microwave oven diode rectifiers. This supply is capable of providing positive and negative outputs simultaneously but is capped at about 5kv, current-limited.

(unfortunately, I still don't really have the trick to properly photographing glow discharges.)
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Richard Hull
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Re: Making My First Successful Film

Post by Richard Hull »

Regarding heating the grid to incandescence........Don't do that.

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Re: Making My First Successful Film

Post by ian_krase »

Because of melting/evaporation, or for some other reason?
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Dennis P Brown
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Re: Making My First Successful Film

Post by Dennis P Brown »

As you are noticing, metal is evaporating from your filament! That occurs when one over heats their cathode. This also tends to allow current to run along the walls reducing power to the cathode when metal is covering all the insulating surfaces in the system. A more serious issue (especially for home made systems) is that the support rod/conductor will heat up and this can weaken the feed thru sealant resulting sudden vacuum failure.

Your pictures are fine.

Glad you made your first demo fusor and got a plasma with it.
ian_krase
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Re: Making My First Successful Film

Post by ian_krase »

Yeah. I kinda want to try one of the tiny simple mass specs that people have posted here.

Feedthrough is probably a good point. My feedthroughs are sealed with epoxy and viton. So they don't want to get hot. Though I think they heatsink fairly well.

I'll need to clean the thing. Fortunately I have done this before (and it's nowhere near the level of total silver coatings I got when sputtering).
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Dennis P Brown
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Re: Making My First Successful Film

Post by Dennis P Brown »

Acetone works very well with removing metal coatings from glass and even off of some metals like steel; do wear proper gloves and do it outside. While acetone isn't very toxic, it is best to minimize exposure. Do wear proper eye protective googles.
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Re: Making My First Successful Film

Post by ian_krase »

Interesting and not intuitive. How does it do that?
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Re: Making My First Successful Film

Post by John Futter »

A proper sputtered film will not rub off with acetone or pull off with the scotch tape test
evaporated films may come off with either methods as mentioned above.
I clean our sputter system viewports @ work with aqua regia and if its being a bit slow i'll add some hydrogen peroxide to jazz it up
SEM techs use KOH solution to clean the apertures from tungsten deposits
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Re: Making My First Successful Film

Post by ian_krase »

And the KOH does not destroy the glass? Or etches it very slowly, while stripping tungsten quickly? What were you stripping with aqua regia?
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Re: Making My First Successful Film

Post by John Futter »

aqua regia strip for Ag, Au, Mg, Ca, Bi alloys various, ZnO As, Cu, Ti, Al,W, WO, Sb and Sb alloys, Fe, Ni, Te, Zr, Gd, Sc, Pb, S, C, B, BN, ITO,Co, Dy, Si, SiO, TiN,Na,K,, and a few more I cannot remember at the mo.
usually there are several differing layers on the pyrex viewports
KOH will not attack glass in the short term.
For layers that are highly resistant to the aqua regia I drop a couple of mls of 70% HF on top but you have to be carful as this does etch the viewport and you must neutralize the acid before removing from the solution otherwise the viewport will go opaque (Frost)
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