<Degi>
The problem with scanning over the whole surface is that it is very slow, otherwise you could just use an electron beam (afaik that's used in research applications, but not suitable for mass production)
<diginet>
drift is a huge huge problem with any kind of raster lithography
<fltrz>
Degi, diginet I assume you are responding to my idea?
<Degi>
Yes
<fltrz>
yes those are the expected issues with scanning the cheapo single pixel version
<fltrz>
I was thinking about a slightly alternative version: instead of a single pixel, a quadrature sensor, so that the collisions can be detected by an increase in total signal of 4 diodes, and for such peaks the position of the collision can be derived from the 4 individual components on the quadrature sensor
<fltrz>
Degi, did I miss more conversation (my laptop battery ran out while I slept, and forgot to connect to power)
<Degi>
No
<fltrz>
Degi, regarding electron beam, I am trying to come up with a democratizable / cheap method, so preferably atmospheric, preferably optical, preferably visible light based
<fltrz>
I believe that the biggest hurdle to DIY microfabrication is the inability to see what we do in real time or short time, once we can see what we are doing on the nano scale at real time, we will be able to use feedback or discard ideas as we can visually identify what goes wrong
<Degi>
Hm yes kinda pricy to make a chip and find out that one step had a small fault and the whole thing is trash
<fltrz>
ah, I know what I need essentially, the device I am envisioning already exists for another purpouse
<fltrz>
to inspect quality of mirrors by interferometry
<fltrz>
I think the setup would also detect collisions against the first lense / optic of the setup, unless care is take no beam or reflection of the beam from the target surface hits the mirror
<Degi>
Hm I think a machine for making low resolution ICs at home would be a good start. Like a 4k beamer (with a narrow bandwidth lamp) focused onto a small wafer area the size of one IC.
<fltrz>
yeah thats very ambitious, like Sam Zeloof
<fltrz>
I'd be happy if I can just view the small scale and try my hand at making miniature factory for micromanipulators
<Degi>
Hm a DIY electron beam microscope could be possible to make
<fltrz>
my (probably faulty) thinking is if small scale tools and actuators are available, and mountable by some type of microscope, then people could experiment more, and if the first things we make are small factories, then we can trade products to each other by sening 100 in a small box in the mail, perhaps in an envelope
<fltrz>
Degi, I don't like the vacuum, nor the x rays
<Degi>
Hm why though
<Degi>
Put some lead foil or water around it
<Degi>
Or put it into another room and use a remote computer to connect to it
<fltrz>
plus its not exactly trivial to focus electron optics, you can get the earliest versions up and running easy enough, but higher resolution seems nontrivial to me
<fltrz>
if you read the papers of the evolution of electron microscopes, its obvious its pretty hard to make
<Degi>
I mean as long as its better than an optical microscope... How small do you want to make the miniature eements?
<fltrz>
Degi, as small as possible, thats why I am looking for a way to circumvent the diffraction limit, not beat it by going to higher energies
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<Degi>
Hm I think I don't really understand your idea with the gas particles, but isn't the only way to circumvent that to use the near field?
<Degi>
(A picture would be nice)
<fltrz>
Degi, ok, I will try make a picture
<fltrz>
Degi, it will take some time
<Degi>
And how does the molecule scatter the light? (I'm not sure but I think you'd need a relatively big molecule for that, since single atoms usually don't really scatter light or scatter it into every direction equally by absorbing and re-emitting it)
<fltrz>
my idea is based on the Rayleigh scattering without absorption/emission, yes the molecule will scatter in many angles, like blue light scatters more in the atmosphere
<fltrz>
Degi, I'm too lazy to type it out and create plots, so I just freestyled on physical paper, scanned it... is there a recommendable accountless platform to upload my scans?
<Degi>
Hm I usually use imgur though I wouldn't rly recommend it
<fltrz>
yeah I don't like to login for such trivial tasks
<fltrz>
I tar.gz ipped it, so now I wonder what the best file paste site is
<fltrz>
huh I uploaded it and supposedly its at https://nofile.org/v/e7d0de but I am unable to download it from there?
<fltrz>
Degi, I could also send file through IRC Send File mechanism...
<Degi>
First link works for me
<Degi>
Hmm a problem is that the reflection changes the velocity of the molecule
<fltrz>
great, theres lots of language errors, Im usually not dyslectic, just wrote it down very fast
<fltrz>
Degi, yes, I was thinking that too, and also parabolic trajectory perhaps due to gravity
<Degi>
Hm reads fine to me
<fltrz>
"molecul" "constand" ...
<fltrz>
at least the concept / idea is clear
<Degi>
So this is going to be a microscope, right? But circumventing the diffraction limit?
<fltrz>
Degi, right, so I started of with understanding the fluorescence based super resolution microscopy
<fltrz>
i.e. only few dots in the field of view
<Degi>
Hmm wont it still need a partial vacuum to have a big enough mean free path?
<fltrz>
so then I thought, what if we could visualize just the colliding gas molecules, so we dont need a fluorescent molecule
<fltrz>
so a single reflecting molecule would still give a PSF blob on an image sensor
<fltrz>
so the time responsee of the photodiode must be high enough, but I think theres too many problems with my idea
<Degi>
Hm do you want to send one molecule onto the surface?
<fltrz>
mostly just the high density of gas molecules, so theres too many collisions unless we make Delta t small enough
<fltrz>
but then intensity lowers too
<fltrz>
Degi, no it's ambient air at some pressure (preferably atmospheric pressure, but for prototypes proof of concept lower pressures are ok too, so that there are fewer "simultaneous" collisions in the time window Delta t
<Degi>
Hm if you can get one collision per few nanoseconds, 1 ps resolution or lower could be feasible with some work...
<fltrz>
so its like the fluorescent super resolution but instead of fluorescence a random collision signal
<fltrz>
Degi, is it worth pursuing the idea?
<fltrz>
I mean worth pursuing more detailed calculations to find gotchas etc
<fltrz>
because I feel there will be profound gotcha that prevents this from being usable
<Degi>
Hmm I don't really know, I'm a 3rd semester physics student tbh, I think potential problems are getting a strong enough signal and good enough time resolution. I don't really know much about that scattering mode though...
<fltrz>
yeah, if we can get ~ 1 collision per photodiode response time, then a quad photodiode should be able to report the 2d position
<Degi>
I think a problem is in determining where the collision happens
<Degi>
Hm quad photodiode and then measure relative timing?
<Degi>
A problem is that light travels at c and to get good spatial resolution you need a really good time measurer, because even a picosecond is a few hundred µm...
<fltrz>
Degi, with a quad photodiode, and a lense the scattering point particle will result in a gaussian smudge on the quad photodiode, so if we detect a peak in the sum signal of 4 photodiodes, then we know we saw a smudge, and the position corresponds to the relative A,B,C,D quadrant signal levels
<fltrz>
so position is not with timing, but amplitude of the relative A,B,C,D signals
<Degi>
Ahh
<fltrz>
I guess I could look at oscilloscope trigger circuits, and sample and hold the 4 signal values, then digitize them with ADC, then release S&H for next flash... so dead time between flashes... form the image with software
<Degi>
Hm maybe you should try to calculate the amplitude of the flashes
<Degi>
I mean one scattered molecule probably doesn't reflect very much light? idk
<fltrz>
I also think it should be possible to detect Delta v of the molecule with 3 different wavelengths
<fltrz>
Degi, right, it will be below noise floor I think, perhaps with oversampling hmmm
<fltrz>
I better simulate the noise issue and see if its possible to reconstruct it numerically before trying physically
<fltrz>
Degi, if you have alternative ideas just hit me up :) would be really cool to make nano images at home
<Degi>
You could use PMT tubes
<Degi>
They're sorta okayishly priced and can detect single photons
<Degi>
And some even have pretty good timing resolution
<Degi>
But you'd need to gain match them...
<fltrz>
Yeah, I should buy a CAMAC crate, or the newer kind PXI?
<Degi>
What's a camac crate?
<Degi>
Ahh a bunch of modules in a rack like thing
<fltrz>
it was this standard type crate, into which you could load modules like amplifiers, constant fraction discriminators etc, and wire them up with LEMO cables ... really useful gear that I sorely miss
<fltrz>
right
<fltrz>
very useful for quick prototyping, and once it works you can think of shrinking it, and implementing with cheaper electronic parts
<Degi>
Hm neat
<fltrz>
I thought airline industry used it a lot too, at least in the past... perhaps if some go bankoronarupt it'll be more cheaply available...
<Degi>
Oh I think I have a LEMO cable in my cables box lol
<fltrz>
I make my own BNC cables with cheap cable and connectors
<fltrz>
when I need to hook up to scope
<fltrz>
yeah I was watching exact same one 2 days ago
<fltrz>
but more than half the price is shipping for me
<Degi>
Yes that's usual for that heavy stuff
<fltrz>
yup
<fltrz>
but in europe, all this gear is just grabbed by employees etc at institutions when they are written off I think
<fltrz>
because theres almost no cheap used test equipment in europe
<Degi>
Hm that's where I got a bunch of stuff from
<fltrz>
Degi, where you live?
<Degi>
Berlin
<fltrz>
Degi, what platform you buy from?
<Degi>
Usually ebay, but not lab equipment. Never bought that, I barely have any good stuff
<Degi>
University trash sometimes has interesting things. But ideally you'd want to know when a lab closes or throws out equipment...
<fltrz>
yeah, I also have peruse and wait for a really good cheap deal, usually with risk
<Degi>
peruse?
<fltrz>
Degi, yeah, I never found out what happens with discarded lab equipment at local universities
<fltrz>
even though I explicitly asked around and tried to locate where when
<Degi>
Hm sometimes it gets relocated to other labs
<fltrz>
also having had a professor introducing you to the CAMAC crate equipment etc,... points at 3 or 4 large cardboard boxes, full of LEMO, modules, ... says its worth a BMW, perhaps 2... then I had a friend who also studied physics tell me he went to CERN with the professor, who grabbed some empty cardboard boxes and instructed him to put a lot of gear in the boxes
<fltrz>
so when a big experiment is over, all the researchers tear down and pocket the equipment... well for the university in home country... but still
<fltrz>
peruse = search around and compare
<Degi>
And in the trash you find sometimes reaaaally old shit
<Degi>
We found something with incandescent light bulbs in a rackmount thing, some kinda ballast
<fltrz>
perhaps it was a sceance ghost extractor
<fltrz>
:P
<Degi>
Ohh I once saw a 3 kV battery
<fltrz>
in their trash?
<Degi>
Yes
<Degi>
With some tape over the contacts lol
<fltrz>
yeah Id leave that be
<Degi>
It was made from 10 300 V batteries
<fltrz>
they must have wanted a very clean HV supply...
<Degi>
Yes probably
<fltrz>
wonder what the opamp looked like
<Degi>
opamp?
<fltrz>
operational amplifier...
<fltrz>
was a joke, as if the opamp handled 3kV
<Degi>
I found some 450 V op amps lol
<Degi>
With BeO insulators
<fltrz>
perhaps 10 opamps in series
<Degi>
Hm they probably only needed a noise free voltage, not a regulated voltage.
<fltrz>
right, probably
<fltrz>
Degi, or the experimenter was uncomfortable putting multiple AC outlets in series
<fltrz>
Degi, I am starting to think that instead of a fast quad, just having an image sensor, and since the collisions on different places are uncorrelated, it should be possible to get the high resolution image by subtracting even frames from odd frames...
<fltrz>
Hmm, where did I put that textbook on statistical processes for imaging..
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<fltrz>
so, one could increase intensity of the laser, but then we risk damaging the sample, perhaps fast air cooling, but then we damage the sample with particulate matter
<fltrz>
otherwise decrease pressure to lower collision rate and allow longer exposures per frame
<fltrz>
the idea is probably bullshit in the end
<Degi>
Hm how about pulsed lasers
<Degi>
Yes lowering pressure would be good
<fltrz>
Degi, I was thinking the same about pulsed lasers, but the start and end of the pulse will leave a signal through the system because of the delay arm
<fltrz>
perhaps use some kind of shutter (mechanical or electro-optic)
<fltrz>
ah no the shutter doesnt change anything
<Degi>
Hm yes
<fltrz>
I can't modify camera sensor array to enable disable the photodiodes with a global shutter at the speeds of the pulsed laser
<fltrz>
but perhaps it could be used for the quad photodiode
<fltrz>
that should actually be possible I guess
<fltrz>
do optical tweezers work in water?
<Degi>
Hm probably somewhat, usually they probably work in vacuum I think? I guess flow forces would be stronger than the optical tweezers probably
<fltrz>
I think they use them in atmospheric air
<fltrz>
I was thinking perhaps we could scan some kind of probing molecule / particle, with tweezers at high speeds over the surface, like scanning probes, but faster...
<fltrz>
but I guess the tweezers are to weak
<fltrz>
I'm convinced theres some cheap technique readily possible at amateur budget, but nobody has thought it up yet...
<Degi>
Hm there are those tunneling microscopes with a piezo controlled tip, that's possible on a hobbyist budget
<Degi>
But kinda bad depth of field
<fltrz>
yeah, also want something with eventually decent frame rates, well theres always the pizza roller of STM tips idea... lol
<fltrz>
~ 400 tips slightly deflected so they each scan a line of the image
<Degi>
Hm cant you just make the STM go faster
<Degi>
And how are you gonna bring 400 tips that close?
<fltrz>
also, not very fond of the STM limitation that the sample should be conductive...
<fltrz>
will be nightmare to prevent vibrations though
<fltrz>
magnetic levitation?
<fltrz>
and how complete the circuit?
<fltrz>
huh, I guess the levitated blade could be monitored by 3 pairs of STM tips at 120 degree intervals, and the current passes the monitor STM tips through the blade to the 400 tips, to the sample...
<Degi>
You'd need to levitate sample and tips, just put them onto 1 platform
<fltrz>
Degi, so without a rotating blade of tips?
<fltrz>
Degi, I'm worried about the vibrations of any rotary bearing for the blade which must rotate with respect to the sample to scan it
<Degi>
I'm not sure why you'd want to rotate it
<Degi>
Like how big is the sample area in question?
<fltrz>
its a dumb idea again, because if 1 tip crashes how do you replace it, the whole blade goes to the bin?
<Degi>
And how do you figure out where the tip is in the first place
<fltrz>
Degi, I'd want to rotate it so that it scans the surface by uniform rotary motion, so now sweeping the tip, then stopping and sweeping back etc.. this vibrates the whole setup
<fltrz>
Degi, some marker on the rotating blade, perhaps a polarization film
<Degi>
Hm not sure if you can get that rotary motion to advance by 1 atom or so per rotation
<fltrz>
A full rotation of the blade would scan all 400 lines, rotating just 1/400th of a turn scans 1 tip over its line on the sample
<fltrz>
like how CRT monitor works
<Degi>
Yes so a rotation then equals like 20 atoms?
<fltrz>
the axis and the sample are in rest with each other
<Degi>
And the rotation vibrates the whole thing...
<fltrz>
but yeah if you want 20 lines per atom sounds about right
<Degi>
Also it'd only scan on a very small area and you'd need a piezo on every tip...
<fltrz>
Constant depth scanning, so just measure the change in current
<fltrz>
put a piezo on the sample to bring closer or further
<fltrz>
but its probably a brainfart this idea
<fltrz>
I'd prefer an optical method
<Degi>
Hm the problem is that towards the sides of the scanning field, the blade curves upwards. Also the sample probably has higher inertia than the tip unless its a tiny sample...
<fltrz>
Degi, right, so its not truly constant depth but cylindrical depth, just calibrate on a known flat surface
<Degi>
Pretty sure that a hobbyist electron microscope with like 100 nm resolution can be made for < 3000 €
<fltrz>
the sample is at rest
<fltrz>
hmm, that would be cool
<fltrz>
why can't we have some atmospheric optical method work :S its a conspiracy to keep people dependent on universities and megacorp :P
<Degi>
Yeh turbomolecular pumps cost a few hundred each and you could probably use an STM tip as an electron emitter lol. The insulation could be a bit hard to get right.
<Degi>
You can get 10^-6 vacuum on a hobbyist budget though...
<fltrz>
Hmm I should be calculating collision rate per surface area, and mid air collision rate per volume
<fltrz>
I guess if I take the hammer looking for a nail path, it could at least be used as a vacuum pressure gage by sensing volumetric collision density...
<fltrz>
then sell those then buy SEM :P
<SpeedEvil>
Todays fun fact.
<SpeedEvil>
Thermoses don't really work if the mean free path is under the gap between the walls.
<Degi>
Hm so you could put the walls realllly close to eachother and make it work at atmospheric pressure? :P