Applied Science - 2022-05-31
An orange plasma display will retain an image caused by incident near-UV light. This is an interesting visual combination of photoelectric, hot carrier injection, plasma, and charge trapping effects. Correction: The orange display is running at 700Hz, 130V in the video. Also, the laser emits no 365nm light. I measured some as low as 380, but the tail isn't as long as I implied! Thanks Matthew King for pointing this out in the comments. I realize that I may have conflated the issues of one-resistor-per-pixel and the display's ability to maintain an image throughout row scanning. They are separate problems that are both addressed by designing the panel to work on AC. Each pixel can maintain its state (on or off) by being supplied constantly with a lower "sustaining" voltage, and can be set or cleared by giving it a momentary higher or lower amplitude. The sustaining voltage allows the pixel to be emitting light or not, and its state remains because of its own impedance until updated on the next scan. In color plasma displays, separate electrodes are used for sustaining and addressing pixels, and the discharge may be sustained between coplanar electrodes instead of plane-to-plane, as in this display. It's also a possibility that the dielectric and MgO layer only exists on one electrode (the metal), and the ITO is bare. I don't know. On this display, if all rows are electrically connected together, and all columns are connected together, and AC is applied to rows and columns, this effect does not work -- no light is emitted at all! At least some of the electrodes (ie every other column) must be left floating to emit any light, and to show this memory effect. So, driving AC plasma panels requires more waveform tricks that I do not fully understand. Photo of the TFT LCD with funny attribution: https://en.wikipedia.org/wiki/File:Dell_axim_LCD_under_microscope.jpg Applied Science video with rotating, flashing neon light: https://www.youtube.com/watch?v=h8VJft5Xq5g Prior art patents: https://patents.google.com/patent/US7283301B2/en https://patents.google.com/patent/US20060132716A1/en Physics coffee mug in opening shot: https://www.atomstoastronauts.com/collections/mugs Refs: https://sci-hub.se/https://doi.org/10.1016/j.tsf.2015.08.001 https://sci-hub.se/https://doi.org/10.1021/acsphotonics.7b01132 https://sci-hub.se/10.1109/TPS.2003.810178 https://sci-hub.se/10.1109/TED.2003.813452 https://www.nature.com/articles/ncomms7785 https://sci-hub.se/10.1016/S0026-2714(97)00179-0 https://patents.google.com/patent/KR19980085547A/en https://www.slideserve.com/urian/i-structure-of-ac-plasma-display-panel-schematic-of-pdp-drive-system https://patents.google.com/patent/US7589697B1/en Support Applied Science on Patreon: https://www.patreon.com/AppliedScience
During my first night flight while training for the my pilot's licensee, in the school's beater C172 from the 70's, the radio's orange display quit working when we needed to be changing and monitoring Air traffic frequencies. The radio still worked, we just couldn't see what channel we were on or what channel we'd be changing to. Having an unknown electrical issue in the air at night was pretty nerve racking, hoping it is not the beginning of a bigger systematic failure. Even the CFL was unable to troubleshoot the issue.
After a couple rounds of troubleshoooting and restarting the avionics to no avail, I shined my LED head lamp near by and the display lit up! I don't remember if the screen was refreshing properly, but I remember for the remainder of the flight, I'd have to "reignite" the display with the LED light every now and then.
I always wondered what the phenomena was, I always assumed the display was just barley being driven below some some energy state threshold and the LED photons gave it just enough kick to change states. I thought the display was an orange cold cathode, but maybe it was a plasma display as show in this vid.
Very cool video as always!
Wow.
Great story!
Okay that's a situation where piss would pour down my ankles
If the display was neon, then as it ages, sputtering can lower the gas pressure so that it needs more voltage to ionize (ignite) a spot to get light emission. Shining a light on it adds energy to the neon atoms with the same effect as increasing the supply voltage.
Barely and barley are 2 different things.
When I worked for a large chip manufacturer who makes processors for computers... You know the guys. We just used SiO2 for the ILD, inter-layer dielectric, material which separated the layers of metal lines. So essentially just glass. I don't think it was any special recipe of any kind. I think that it is pretty standard semiconductor tech. We just used silane gas and oxygen at specific temperatures and mixtures to grow SiO2 if my memory serves correctly. Now, the chemistry to keep copper from diffusing into it and the techniques to get nice square bottomed etched lines was extremely sensitive and I don't believe that I can discuss that. Glass is a really easy to manufacture dielectric material with suitable properties. It also etches really easily and predictably with HF. It would seem that manufacturing panels like this would be very similar in process techniques.
All I know is I wanna get to know you and bring my styro, explosions n ire, and Neil friends.
@Derrek Van Ee We all need to have dreams.
BIG HINT 🤣🤣
It might work similar to the old Tektronix storage tubes. They use flood guns to flood the whole screen with electrons, but the phosphor does not glow because it's not enough energy to excite the electrons until you get a more intense beam of electrons to "activate" the phosphors by giving them an extra charge so that the energy of the flood gun is enough to get the electrons over that charge state and produce light in that spot.
I was going to say that. I'm not that clear on exactly how those worked, but it immediately occurred to me that this might be related physics.
@Hfuy I'm not sure either, but I think it has to do with energy states of the phosphors. It's as if they have some sort of hysteresis.
Yes! Came here to say that. Glad someone was able to say it before it got lost in comments.
I don't think you need to worry about your video output schedule, we, your crowd, appreciate your "quality over quantity" approach...
Funny you mentioned neon bulbs. I noticed the output of a neon bulb can be affected by the amount of ambient light.
I have a power on indicator neon on our boiler that's usually in a dark room, and it has a slight AC flicker to it. When I shine a light on it the flicker stops and its light constantly.
Indeed, I also noticed this on a simple mains power block with neon indicator. The bulb would flicker in the dark and be steady when sunlight hit it. Unfortunately that bulb died a long time ago…
I recall reading that neons for logic applications had a touch of some alpha emitting radioisotope in them for that reason.
Maybe it's just more difficult to perceive the flickering when not in the dark. In the dark you would get the maximum amount of 'dynamic range' and thus easier to notice.
After reading further it seems what OP is referring to is an actual thing.
I've got an old power strip with a neon indicator... sure enough, it flickers with lights off and steady with lights on.
Back in the 80s I worked with people like your colleague (and you). They invented a microwave chamber that heated a cup of coffee (not patented) a discrete-logic version of the Pong game (not patented) a laser-based digital data storage/retrieval device using a photographic plate and LASER (patented), which later became the basis of the CD-ROM. These were fun people, often a bit eccentric, but usually quite humble. The best job I ever had primarily because of the people!
You actually can sort of get away with neon bulbs in parallel. Yes, initially, one will hog all the current, but over time (weeks to months, in my experience) it will degrade until they even out. But then, they won't light up all at once, no, instead, on each half-cycle, a random one will light up (and then a different one and then a different one). If you connect about a dozen of them in parallel, after the initial burn-in, they create a really nice dancing light effect.
Interesting effect. Are you sure you are not just simply ionizing one of the UV lines of the argon or neon? One way to find out is to try it in a regular neon bulb. If you can strike it by shining the laser in-between the electrodes, it’s ionization, if it works inly by shining it on the metal, it’s photoemission. But if it were really photoemission, it would make more sense to me that it comes from the MgO, not from the ITO or metal layer buried under a dielectric. Just don’t see how you can have an electron current nearly high enough to strike a neon plasma coming through a dielectric. Just talking out of my rear-end since I have not researched the subject properly…
I think the purple photons are too feeble aren't they? 405nm is equal to 3eV per photon but argon's first ionization energy is like 15-16eV.
You're on the right track, the real explanation is that F (oxygen ion vacancy) and F+ (oxygen ion vacancy + one electron) defect centers in MgO crystals are located at 3.0 and 2.96 eV above the valence band maximum (VBM), respectively. This means that the 3.1eV 405nm laser light is exciting MgO valence electrons into the F level or maybe even exciting an electron in a F+ level into the conduction band as well and that is main reason for increasing the free carrier density in the device. The reason there is an asymmetry in the dot brightness is because the excitation of carriers in those defect levels are populated and depopulated on one side of the device for each polarization of the AC electric field. So you can imagine you have a box of balls and you raise one side and lower the other. The balls will go back and forth. This is the displacement AC current and you're not having a charge pass through the dielectric. So then the laser power is attenuated when it reaches the bottom layer of MgO because it had to travel through the first layer of MgO. Normally the high voltage AC is enough to excite these defect levels or rip them out of their position, but he is operating it in lower voltage where only the laser gives it enough energy to excite the states. The gas in the middle that becomes plasma is used as the luminescent source with a threshold limit minimum it seems. Like there needs to be enough voltage between the MgO layers to start the plasma going. The dielectric is still too insulative to pass enough charge through it. Most metals have a work function higher than 4eV and wouldn't even get excited at 365nm. The amount of 365nm light is miniscule as well. You should be able to do the same effect with regular AC EL displays with MgO too. It's all about the defect states in MgO, that is where the excited carriers start.
@Ross is this the F for farbzentrum / color centers?
@Muonium F (oxygen ion vacancy) and F+ (oxygen ion vacancy + one electron)
@Ross That is a very convincing and knowledgeable explanation!
Other things of note : The ITO and metal conductors will be at opposite ends of the triboelectric series.
Also: Are you sure the dotted effect is due to the AC cycle and not PWM output from the laser? (I've noticed this when waving laser pointers around especially ones with single cell power supplies which rely on a DC-DC converter to power the diode)
I was wondering if it was possible PWM causing it too.
Pretty sure it's because the F and F+ defect centers in MgO crystals are located at 3.0 and 2.96 eV above the valence band maximum (VBM), respectively. This means that the 3.1eV 405nm laser light is exciting MgO valence electrons into these defect levels and that is what is increasing the amount of electron density in these defect states. The reason there is an asymmetry in the dot brightness is because the excitation of carriers in those defect levels are populated and depopulated on one side of the device for each polarization of the electric field. So imagine you have a box of balls and you raise one side and lower the other. The balls will go back and forth. This is the displacement AC current. So then the laser is attenuated when it reaches the bottom layer of MgO because it had to travel through the first layer of MgO. Normally the high voltage AC is enough to excite these defect levels, but he is operating it in lower voltage. The dielectric is still to insulative to to pass enough charge through it. Most metals have a work function usually higher than 4eV and wouldn't even get excited at 365nm. The amount of 365nm light is miniscule as well. It's all displacement current still. You can do the same process with regular AC EL displays with MgO too. It's all about the defect states in MgO, that is where the excited carriers start.
I'm guessing most of Ben's audience would've had that thought.. I'm sure he tried sweeping the laser over some laser-sensitive phosphor like a CRO screen to discount that..
this is one of the most creative channels ever. well done man. this is so cool. you’ve made and demonstrated some crazy stuff, but this is so rad. i love how humble you are and how you share all this cool stuff constantly.
thanks for always including the journey of how you got to the final result. it's really enlightening to learn how you look at things, amazing content as always.
For the large dot small dot trail, perhaps you could set up a high speed camera and also try to visualize the AC waveform in the same shot (perhaps something as simple as a red/green led to show positive/negative) to see if if the positive cycle consistently produces the larger/smaller dot.
Super interesting video as always! I remember thinking that it would be cool to have an "analog" notepad to draw on (stylus on a glass LCD) and this is essentially what I imagined; really cool to see it. With the excellent EEPROM comparison, I'd be curious if the plasma display could be read off of and save/reload the temporary images/drawings on the display. Keep up the great work!
The thing you're thinking of remind me of the LCD notepad/clipboard. It's pressure activated and erases the writing area using an electrical pulse. Costs a couple dollars. I wonder how it works. For sure there are no individual pixels there though.
SONY e-book readers with a Vizplex ePaper display also have a resistive touchscreen option, those that have it come with a sketchpad application. Unfortunately the quality of implementation was garbage software wise.
I love seeing your investigation process, the questions you ask going through the tests etc, so interesting! 🙌
If you do make your own driver, try increasing the drive voltage and frequency such that power is kept constant. I'm interested to see if the higher electromotive force on the high side of the AC waveform would lower the photon energy required to liberate electrons from the metal layer (possibly permitting this effect at longer wavelengths, maybe visible?). Thanks for the vids!
I was also gonna add, could the AC be made non-symmetrical to compensate for the differing brightness of which end is positive and negative? Instead of 50/50 positive and negative in reference to 0, could you do 60/40 or 40/60 and give it the additional power on that side of the waveform so it comes out even?
So many rabbit holes, so little time!
Another reason for making the back electrode from metal (except price) is that metals are generally reflective and send additional light in the direction of the viewer. Anyway, superb video again Ben!
This is part of the optogalvonic effect, in which the discharge changes it’s resistance due to incoming light. If you sweep a continuous spectrum of laser light (like from a dye laser), you can measure the resistance change of that gas filling the discharge. I used this as a calibration standard (neon lamp - also argon or other gasses that have emission spectra peaks at important calibration wavelengths), and as you tune / sweep the dye laser (in my case a grazing incidence R6G pulsed dye laser) thru the spectrum, when the due laser matches a peak emission of the gas, the resistance dips… and so you know the dye laser is at that exact frequency / spectrum. I would partially power the discharge lamp, and when the laser wavelength matched a strong emission peak, the lamp would light. There are a few other related phenomena to this, one used for deep space photography, by CCD deep-discharging using deep UV from the sun.
This was incredibly fascinating, and your ability to explain it clearly is admirable! You've given me a lot to think about!
Anyone with any kind of medical degree watching this instantly recognized the burn-in pattern on that plasma display
All the time I've spent looking at these I don't think I ever realized (some of them) were plasma technology 🤷♂️
No medical degrees needed to recognize it either! Lol
It was only once I saw the burnt-in image that I finally had any idea what a "plasma display" was! (I have no medical qualifications, but I've seen those displays enough to recognise them.)
I don't think I've ever heard that term before, and I wasn't aware that those displays were a different technology to the display types I'm more familiar with. I'd never really thought about what kind of display they were, but I probably would have just assumed them to be some kind of backlit LCD tbh.
@Andrew Gillard Most displays that looks like that are just backlit LCDs. It actually has been that way for quite a while. During the transition period of actual plasma displays and backlit LCDs, there were quite a few displays that do a very good job of looking like plasma displays. To the point you would have to take apart the device to see that it wasn't plasma.
Not quite sure why they put so much effort into hiding the fact that it wasn't plasma.
i remember when plasma screen tv's were a big deal and cost 3000$ and people would freak out about turning them off if you paused something or left the room to get something. idk. those things were impossible to see from more than one narrow angle and basically self exploded after owning them for a year or two. sounds like the perfect type of tv to make lots of money with. guess our new tech must be a lot cheaper idk
I love how you always come up with every possible angle to anything. After about 2/3 of the video I thought: Mhhh, I have an old plasma TV in my basement I haven't used in some years. Wonder what this will do to it. And sure enough, you went there :) Thanks for yet another super fascinating video!
This reminds me of those CRTs with high-retention phosphorus that were used as display "memory" in some early terminals. I only saw one in the 1990s and back then we didn't have UV lasers at the ready, but I imagine the phosphorus could be excited the same way and retained by the bias voltage (I think that's how they worked).
I find the laser effect is always dotted when swiped across a surface. Try it on your wall back and forth. It’ll leave a pattern, not a clean line. At least on my cheap laser it seems to be pulsed despite being a battery operated diode, possibly they’ve developed a micro inverter for cheap lasers
Yes Prescott, I had considered that the laser might be pulse driven. The large and small dots could result if the waveform of its driving circuitry is asymmetric.
Man. You continue to impress me with every video you upload.
He definitely provides a unique treasure of priceless informative video content, unparalleled not just on this platform but on the entire internet. He's long since impressed me to the point where I can't even measure it anymore.
hes like the golden goose of weird science ideas. dude never misses
You always seem to come up with the most obscure yet most amazing effects.
What I would like to know is how you actually came up with this, were you just playing around with a 405nm laser one day and aimed on a plasma display by pure luck?
Looking forward to see where this journey may take you, your potential ideas at the end sound very intersting.
This was very cool. You mentioned the idea of using it for I/O, but I didn't see anything about reading the laser-scanned image out of the display. Is it too basic to cover?
Probably terrible res
If it's possible to read, it would be revolutionary. You could turn any old plasma tv into an incredible artistic device
One way would be to stick a CCD behind the display
The resistance of the pixel changes, so that should definitely be detectable through current measurement
@Albertweber16 like to know more details about, how to do that. I have plasma TV with me. Wanna convert it as drawing panel.
absolutely fascinating ! Ben, thank you for the amazing content and your explanation about the physical/working principles.
Yep, there were a few “ah ha” moments! I wasn’t familiar with the term, “ITO” and now feel compelled to dig in and learn more. Also intrigued by the complexity of color plasma displays that you briefly touched on.
Finally, you left me wondering if it was possible to play with the AC waveform in such a way to tease out the different properties of the metal layer vs the ITO layer and perhaps shed some “light” on which of your two theories might be correct. 🤔
I'm not sure but I think he has videos where he applies his own Ito.
take a look at the Apollo electroluminescent display projects.
there’s just nothing like the glow of these old plasma displays. miss them. they looked just so cool!
I remember the first time I saw an IBM portable with that orange plasma display. Love at first sight!
Something similar to the neon bulb incident happened to me, but with a christmas tree light. I was no more than 7 or 8 at the time and figured that if 50 lights could go on the outlet, surely one could go as well. I had yet to learn about series and parallel.
I did the same thing but with an led, they were very new at the time and I didn't know you needed a resistor... connected directly to a power supply and it just exploded... bits of the plastic body all over the desk!
Learnt so much from this, what a rabbit hole indeed. Thanks for taking the time and effort to upload these videos Ben!
I'm very interested in the idea of reading the marks scribed by the laser. If u drive the pixels in sequential fashion, then u can monitor the current changes synchronously to figure out the lightened pixels. Very interesting, please keep investing! I'm looking forward to the follow-ups.
INA219 or INA260 come to my mind. You can hook one up on each and every pixel and read/save the values on a per-refresh basis, "theoretically". Or, maybe there's a way to use rows and columns as resistor ladders. As you said, this rabbit hole is awesome.
Brilliant demo, still amazed the UV from these lasers and the glass barriers don't diminish the effect. Been using this to trigger a plasma in a bottle lately. If you could read back the written data from the array maybe it could make a cheaper X-ray imaging panel. :-)
Thank you for the quality content.
Awesome work. I am myself working on that nerd-sniping issue. I want to both video log and write articles regarding my rabbit holes but I keep digging in them. Anyway, very inspiring video, thank you for making it!
I love the idea of using this for animation, sort of like a pinscreen animation technique.
I can imagine there are possibly many uses for art installations as well.
Are there any tutorials or instructions that I can follow (as an artist with no technical know-how) to get a screen like this?
Cheers!
+1 - I'm also a technical nincompoop and would love to get my hands on the hardware. Is there a common (cheap, <$200) plasma display I can find online to purchase and mess around with?
Glad I listened till the end, your intuitions are genius. The patent surprise is a fun twist. Thanks for another great discovery!
It is a sad twist that just serves to highlight the issue with the patent system.
Protecting investment in research yes, stumbling on something no. And not being able to utilize an idea because someone patented it "just because", and not actually protecting a product they would be producing is just sad. The person who stubs his toe on something first should not be allowed to collect royalties on the dispersal of rocks.
Not only are the dots big/small/big/small, the distance between them changes. It looks like the small is closer to the big that came before it than the one after it.
Yeah that's true, I feel the simplest explanation would be that his function generator isn't producing a perfectly symmetrical drive current, or that the panel behaves nonlinearly.
However I wonder if it's bc 'freeing a hole' isn't strictly possible, i.e. it's always the electrons that actually move. So possibly you can eject electrons from the metal surface, but can't effectively eject electrons from the gas, therefore the e field has to be weak for the electrons to be ejected from the metal in the reverse polarity (but close enough to the peak to actually cause ignition) therefore shifting the reverse polarity dots to the raising edge of the reverse polarity curve.
as interesting and amazing as always, Ben, thanks for another great lesson
This is fascinating, oddly enough my first thought on how that worked was the one you mentioned last.
It's cool that a coworker had a patent for this.
I've never been disappointed by one of your videos, stay curious for the rest of us who can't delve as deeply!
Ben it's amazing how consistently you make videos that are just absolutely fascinating. Hilarious that a coworker just happened to have patented the observation. Brilliant stuff, I hope I'll make it to the ranks of your fascinating, brilliant people.
What great timing - I recently used a UV flashlight on glow-in-the-dark material and found that I could doodle pretty well on it. I've since been thinking about painting a ceiling or feature wall with glow paint and using a computer-controlled UV laser pattern scanner to make a big phosphorescent/fluorescent vector display...
I’m interested in this and am wondering if it could be used with a laser designator to capture the profile of small objects?
The exact same thing happened to me when I was a kid, I got the bright (ha ha) idea of removing the resistor from a neon bulb night light and got the result you'd expect. Pretty scary and it startled me so much that I accidentally touched the exposed AC wires and got a serious shock. Definitely a learning moment, thankfully not a terminal experience.
Thank you. I absolutely find your videos entertaining while informational. I appreciate all of the detailed thought you put into your topic.
Very awesome! I'm all for the nerd sniping to continue.I'd much rather have nice in depth videos or even a series of in depth videos and updates once every few months then a higher upload cadence but more superficial videos.
Absolutely fascinating video as always Ben!
If you use a camera flash on magnesium carbonate, you get a short duration blue glow. Something I found through experimentation and though you might find interesting. So maybe the MgO layer is excited by the laser to release electrons into the plasma.
Muonium - 2022-06-01
Several things amaze/surprise me about this video. First, that you are able to come up with topics so consistently novel, fascinating, and non-intuitive that I never would've thought to investigate such things on my own if given about a thousand years to do so. Second, that people are still finding use for images that I uploaded to wikipedia 15 years ago, like that reflection microscope image of a Dell Axim PDA's TFT at 8:40 - this is greatly pleasing to me. Thirdly, that there is 365nm radiation coming out of 405nm laser diodes as you mentioned at 5:20. Can that be right? I've measured the spectrum of these cheap laser diodes before and while they're obviously not as clean and monochromatic as a gas laser, they're still way narrower than an LED and have a FWHM of only a couple nm - I'd like to hear more about this because I know you have a spectrometer too so I guess you've seen it firsthand. And fourthly, that nobody ever even knew about this throughout the entire heyday of the neon plasma display during the 80s and early 90s and no one ever made a product exploiting it! Anyway, you are my fav science youtube channel for many years now and I hope the new videos never end!
Applied Science - 2022-06-01
Thanks so much for your photo! I might have gotten the attribution wrong, but it was taken verbatim from Wikipedia, and I added a link in the description. People were asking about the "forklift driver" ;) Also, I was indeed playing too fast and loose regarding the 365nm from a 405nm laser. I just measured it, and found some 380nm, but definitely no 365. I updated the description.
Jeremois DE - 2022-06-01
So @Muonium you are Not the Gabelstaplerfahrer? Oder doch?
Novgorod - 2022-06-01
Powerful solid-state UV emitters (or even lasers) weren't really a thing until quite recently, so there was no practical way to make it into a consumer product back then unless you want kids at the arcade to fool around with high-voltage mercury lamps and get eye cancer from the hard UV.
zyeborm - 2022-06-01
@Novgorod .... do you not?
eyescreamcake - 2022-06-02
One time a coworker was trying to explain something about a particular part, and she brought up an image from Wikipedia to show me, and it was a photo I had submitted to Wikipedia lol