A saddle‐shaped cyclooctatetrathiophene derivate was used to construct a fully π‐conjugated 3D covalent organic framework (BUCT‐COF‐1). Extended conjugated structures are facilitated for electron delocalization and transport, furnishing BUCT‐COF‐1 with semiconducting properties. Pellet samples of BUCT‐COF‐1 exhibited ultrahigh Hall electron mobility up to ≈3.0 cm2 V−1 s−1, and demonstrated band‐like charge transport character.
Abstract
Although π‐conjugated two dimensional (2D) covalent organic frameworks (COFs) have been extensively reported, developing fully π‐conjugated 3D COFs is still an extremely difficult problem due to the lack of fully π‐conjugated 3D linkers. We synthesize a fully conjugated 3D COF (BUCT‐COF‐1) by designing a saddle‐shaped building block of aldehyde‐substituted cyclooctatetrathiophene (COThP)‐CHO. As a consequence of the fully conjugated 3D network, BUCT‐COF‐1 demonstrates ultrahigh Hall electron mobility up to ≈3.0 cm2 V−1 s−1 at room temperature, which is one order of magnitude higher than the current π‐conjugated 2D COFs. Temperature‐dependent conductivity measurements reveal that the charge carriers in BUCT‐ COF‐1 exhibit the band‐like transport mechanism, which is entirely different from the hopping transport phenomena observed in common organic materials. The findings indicate that fully conjugated 3D COFs can achieve electron delocalization and charge‐transport pathways within the whole 3D skeleton, which may open up a new frontier in the design of organic semiconducting materials.
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Hello fellow engineers! I'm a college student studying semiconductors , specifically the topic of electron mobility, lattice scattering and impurity scattering. But something came up that buffled me and i could use your guidance.
I understand that the electron mobility caused by lattice scattering is higher in high temperatures. However, in lightly doped semiconductors, where lattice scattering is more eminent, the electron mobility falls in high temperatures.
This seems completely counter intuitive to me. Am i getting something wrong? I could really use your help. If for some reason this reddit isn't the appropriate place to ask this kind of question, please redirect me somewhere else. Thank you in advance!
Hello guys,
I've got a sort of second hobby/job designing instruments for teaching physics.
I want to share with you this one I made for the university of Tartu in Estonia (N/E EU).
As you can see it has toroid with permanent magnets of variable gap. There's a thermocouple measuring the temperature, which is also managed so you can go from -150°C to +150°C. The whole temperature sweep allows to measure the electron mobility in the Germanium sample (P-doped).
It has a cute little current generator of 0-20mA (very stable), an extra gaussmeter probe, and some extra circuitry for safety, heater control etc etc
Usually doing this experiment is not really possible in a didactical enviroment because there are too many factors to consider. This one goes from earth's magnetic field to the 0.5T field of the magnets in one sweep of a know!
I'm very proud of it.
Small curiosity: the wire are wound in a braid because in the strong magnetic field they would act as microphones and pic up any vibration.
https://preview.redd.it/n0jf04s3yfa41.jpg?width=2865&format=pjpg&auto=webp&s=1494f5c6a0ee9112c3b5f039b70df44ce394ab44
https://preview.redd.it/ervf0kj4yfa41.jpg?width=2774&format=pjpg&auto=webp&s=5389e931def51e82a05d0faf8ec7c6820669538e
https://preview.redd.it/ztvf7hs6yfa41.jpg?width=3440&format=pjpg&auto=webp&s=af69913660f0de09ec3413643b959e6af5335a94
Trying to figure out how 3900 and 1900 was obtained in this question. Pretty much nothing was explained.
Here is the solution to in the question: https://imgur.com/a/rwa3IQj
Holes are just the absence of a balancing electron, so how do electrons move (on average) at a different rate than their absence and vice versa?
Yes, I have searched on Google, but I am too dumb to understand, so I thought if someone here could help me.
This question was kind of glossed over in my undergrad course (explained as just different effective masses depending on the material), but I still don't understand what that really means. I looked it up in another textbook and it just resulted in more confusion as it wasn't explained any further. It said something like this:
>Silicon is an indirect bandgap semiconductor, so electron transport occurs in 6 equivalent conduction band minima located along the <100> crystallographic directions while hole transport occurs at two degenerate subbands located at zero in k-space. The different electron and hole mobilities arises from differences in the shape of the minima.
O_o
Can someone explain this to me in simpler terms? Also, can someone orient me towards some resources that contain the material relevant to understanding the above?
Thanks!
Also, side question, on high-side injection in bipolars, I understood the mechanism being recombination of electron-hole pairs in the base so those carriers don't contribute to the collector current and reflected on the gummel plot. This book says that what really happen is "a decrease in mobility due to the higher probability for mutual Coulombic interaction of mobile carriers about a common center of mass." Is this basically just electron-hole recombination in the base?
v=uE where u is mobility, v is drift velocity, and E is electric field. I'm not sure why a higher electric field would lower mobility? I think a stronger pull on electrons/holes would increase mobility.
I couldn't find an answer which I can wrap my head around. The holes are defined as absence of electrones. So my understanding is when an electron moves a hole is created, therefore a hole's mobility depends on the electron mobility. Shouldn't be the mobilities same for these two in this case? I'm surely missing something here.
Obviously I can't get a better conductor than gold (Platinum would do the trick, but in this economy?) so the resistance of the wiring is what it is. The first thing I tried was profusing the gold with Teflon, but that didn't actually work very well, as Teflon is non conductive. Duh. Should have guess that one first, right?
Then I thought: Well, if I can't lubricate the wiring, why not lubricate the electrons? I've had some success with olive oil, one tea spoon of olive oil per pound of electrons actually got me 2% closer to c than I had anticipated! Unfortunately I still have a ways to go if I want to frenulate my amulite.
Anyway, I've got, like, WD-40 (Classic), I've got some old fashioned 3-in-1; I've got heavier stuff, too, butter, lard, white lithium, stuff like that, but I don't have quite enough electrons to fuck around and find out. Do you think a dry lube might work? I think I've got some corn starch around here somewhere. (Lol, sorry, that was redundant. I've got lots of lubes, is what I'm saying.)
I dunno, just looking for some ideas, I guess. All I need is a minimum of 22% over c and I'm good to go. Thoughts?
During the last month, we conducted a usability survey for the Electron Cash mobile wallets. We received 22 complete responses to the survey.
You can review the raw results here:
- redacted form replies + my raw summary notes + all videos: https://www.dropbox.com/sh/gts72pa7v9d322g/AAAfS73LsfvYYFjqvIC_wKYxa?dl=0
- YouTube playlist of 10 narrated over-the-shoulder videos done in Caracas Venezuela (also included in the dropbox dump): https://www.youtube.com/playlist?list=PLfCBnMrjKRCnhuJWr7aZIzqewtkGO0qYw
- Earlier feedback in Spanish gathered from the Panmoni team that includes other wallets: https://forum.bitcoincash.site/t/we-need-to-choose-a-new-primary-bch-wallet-necesitamos-elegir-una-nueva-billetera-bch-primaria/225
82.1% tested Android and 17.9% tested iOS.
Financial Disposition
Approximately $1050 USD in BCH was paid out for this initial round of usability testing.
$500 in BCH came out of the Panmoni/BitcoinCash.site budget to pay for testing in Caracas Venezuela, specifically the production of the over-the-shoulder videos.
11 additional payments were made from Panmoni/BitcoinCash.site for remote testing, totaling 0.93675216 BCH, approximately $550 USD.
0.65913062 BCH was donated via r/btc chaintips. Thank you u/dadoj, u/fshinetop, u/sanch_o_panza, u/ErdoganTalk, u/darkbluebrilliance, u/moleccc and u/rshap1.
This leaves a shortfall of -0.27762154 BCH which Panmoni/BitcoinCash.site will cover. Chaintips are welcome and appreciated to help us defray this expense.
My Analysis
This is only my analysis. Your analysis is very much welcome, needed and appreciated in the comments. Use the wallet and let us know. Review the raw data and share your thoughts please. It all helps.
- The wallet is fast and basic.
- The onboarding flow asks you to do too much without giving you enough motivation to do it. Asking people after the new wallet screen if they want a new wallet or to restore stumps them a bit. It sends you into a black hole without context. The UI of this is also a bit unconventional, as it essentially pops up a window, t
Hi all, working with Jonald at the Electron Cash team and Cameren, a super helpful BCH UI/UX guy, we are doing some usability research on the Electron Cash mobile wallets for Android and iOS.
The goal is to improve the polish of the EC mobile wallets so they can be more widely adopted, as they are the leading FOSS mobile wallets for BCH.
We need your help. We’re looking for 10 people to help us with this research. Perform the activity described below to completion and perfection and you will be eligible to receive a BCH tip. The first 10 unique individuals to do this will receive $50 in BCH. Additional submissions beyond 10 may also get tipped but the tip and amount will be at my discretion.
If I have any doubts that your submission is not unique, it will simply not get tipped.
Help us defray the cost of this research with a chaintip. If we get more than $500 in chaintips, we will do more research. Thanks!
Activity Description
Please download a mobile (not desktop) Electron Cash wallet, screen-record yourself performing the tasks and then fill out the survey.
Deadline: Thu 30 Sep 2021
A. Tasks:
Be sure to screen record your performance of these tasks. Bonus points if you also record your voice (English only) and narrate your experiences and reactions as you perform these tasks. Feel free to be critical.
- download the wallet (mobile only) https://electroncash.org/
- create a new wallet
- receive a payment (from any wallet)
- send a payment (to any wallet)
- find the recovery phrase
B. Survey:
To complete the survey, please upload your screen recording of your tasks to YouTube, Streamable.com, Dropbox, iCloud or some other video host that gives you a public URL to your video.
Fill out the survey here: https://forms.gle/XfNSqHFubaFfwPQd8
Payment
If your submission meets the criteria to be paid for your help with this research, we will pay it to the BCH address listed in the survey at our earliest convenience. This could take 1-3 weeks to fully process. Thanks in advance for your patience.
Support
If you have questions, please ask in the r/btc thread. We are happy to assist you.
And let's keep building Bitcoin Cash!
20211103 Update: The results are in: https://www.reddit.com/r/btc/comments/qlx8fn/electron_cash_mobile_wallets_uiux_survey_results/
Although π‐conjugated two dimensional (2D) covalent organic frameworks (COFs) have been extensively reported, developing fully π‐conjugated 3D COF is still an extremely difficult problem due to the lack of fully π‐conjugated 3D linkers. Here we synthesize a fully conjugated 3D COF (named as BUCT‐COF‐1) by designing a saddle‐shaped building blocks of COThP‐CHO. Attributing to the fully conjugated 3D network, the BUCT‐COF‐1 shows ultra‐high Hall electron mobility up to ~3.0 cm 2 V ‐1 s ‐1 at room temperature, one order of magnitude higher than the current π‐conjugated 2D COFs. The temperature‐dependent conductivity reveals that the charge carriers in BUCT‐COF‐1 exhibit the band‐like transport mechanism, which is entirely different from the hopping transport phenomena observed in common organic materials. This work confirms that the fully conjugated 3D COFs could indeed achieve the electron delocalization and charge transport pathway within the whole 3D skeletons, which would open a new frontier for the organic semiconducting materials.
https://ift.tt/3oJLGuO
