Generally, on a board like this, such an observation is taken to be a lead-in to an explanation of the topic mentioned. In this case, Flash memory.
-FrL-
Well that is entirely possible (other than the brief explanations I have seen). I was really thinking more in terms of the iPod/battery system in general, it’s all just movement of electrons, I don’t see where there would be a gain or a loss.
Even just the battery, it’s my understanding that re-charging is not actually depositing electrons, it’s just moving what is there, transferring energy into potential energy within the battery.
Is my understanding incorrect? Or does flash memory rely on the net loss and gain of electrons from the environment external to the system (electrical circuit)?
Yes, Flash just moves electrons, but my supposition is if one moves electrons far enough away, then you create a region that can accept new electrons. Probably not many, but non-zero.
But then you would need to get those electrons from somewhere.
This may indeed happen in the case of static charge build up.
But it has absolutely no relation to the electronic processes that the flash memory operates by.
In other words you have introduced something of a red herring to the discussion by superimposing an electrostatic situation on top of the charge separation that is used by the memory device. In general, static build up is considered undesirable in electronic devices and is to be avoided. In no way does the operation of an ipod depend on its ability to gain or lose electrons from an external source. Within the device the electrons are repositioned but are not lost or gained.
Oh, there are plenty of free electrons available.
Ever get a static shock when you walk across a carpet? Just moving in a chair can generate billions of free electrons, much more than enough to replace the few that the iPod needs. If you follow the thread all the way back, i specifically said that the weight wouldn’t change until it was charged (although I believe that just touching the iPod would be enough).
Carpet static – once again a transfer of electrons from an external source.
But the thread (at least the serious portions) was about whether the actual act of storing information on a memory device involves and transfer of mass. Ipod memory works just fine (better) without carpet static. Therefore the answer has to be no. Not even the minute amount of mass transfer invoved in the repositioning of elecrons within the device causes any gain or loss of overall mass.
Mass may be altered by
- physical processes – wear and tear and dirt buildup and maybe the occasional chemical reaction at the surface
- relativistic processes – get it hot, gain some mass
- electrostatics – as you have mentioned: get some free electrons from somewhere
All of these are extrinsic to the process of memory storage and are moot points. (Of course the question was trivial enough to begin and discussion proceeded with multiple whooshes, so don’t think I am getting to you.)
You are forgetting that the act of adding music requires the iPod to be connected to your computer, so it can easily pick up the free electrons it needs from there. Obviously, the weight difference between an “empty” and a “full” iPod is going to be too small to measure…
beowulff
What is keeping the free electrons in the bulk and in the power and ground plane from moving away from the region of negative charge when the Ipod is connected to the computer via very low resistance conductors?
Distance.
THe thickness for the gate dielectric.
Explain this more in depth. How is the electric field from the trapped electrons in the gate going away? Sure it goes down as a function of distance but it does not go to zero. So there will be an electric field and it will cause electrons to move in the conductors until the field goes to zero.
I’ve been looking into this since yesterday. My intention was to prove [b[beowulff** wrong, but from what I can tell, he is right. Of course we have plenty of flash drives that work on battery alone, so obviously in that case I’m guessing that the electrons are supplied by the anode which is interesting becauswe it implies that the half reaction at the cathode is not completed. On the otherhand, we’re talking about tiny amounts of charge so it is not that big a deal.
My understanding is that semiconductive oxide layer in the floating gate transistor holds the charge in. It may even be an insulating oxide layer since apparently tunneling is involved.
Keep in mind, solid state chemistry is not my thing. I don’t have ton of spare time to learn an entirely new feild, but I’m curious about this so I’ll read up when I can.
Again we are not talking about the electrons in the floating gate. Yes those are trapped. Yes trapping them is the non volitle part of flash.
The point is if we say that the Ipod has gained weight because of the electrons trapped in the floating gates the Ipod is now negatively charged. Where did those electrons come from? What is keeping the electrons in the wires and the bulk of the flash chip from moving from this negatively charged region to what is now more positively charged since it gave up its electrons to put them in the floating gates.
Think of it this way:
I have a rod made of insulating material. The rod is 1 mile long, with metallized ends.
If I pump some free electrons from one end to the other, you will agree that one end has a positive charge and one has a negative charge, right? Now, the side that has the positive charge can accept some new electrons from it’s surroundings, correct? After all, the electrons we moved are very far away, and aren’t exerting much of a repulsive force.
Now, the rod weighs slightly more than it did to begin with.
Now, shrink the rod. At what point does this analogy no longer hold true?
Agian we have a negatively charged Ipod connected with wires to the computer. What is keeping the huge amounts of free electrons in the Ipod from moving from this area of negative charge to area that are less negatively charged. Are you saying that the net negative charge of the ipod is not setting up an electric field?
Taking your long rod example and making it more like the flash chip. If I them take this long rod with charges end and move it to system much bigger than the rod and put a large conducting plate near the positive end are you saying the whole system of the rod and the enormously bigger conducting plate will be negatively charged? Especially since the whole system was neutral at the beginning?
By your thinking, it should be impossible to ever have a negative or positive charge on any object. Clearly not the case.
Yes, it sets up an electric field. This electric field decreases or increases the threshold voltage for the controling gate thus switching it from a 0 to a 1 or a 1 to a 0. This is a tiny charge though, and if you are running off a battery then there is not net charge on the device because the electrons had to come from the battery.
And the end that has a negative charge can emit some electrons into the environment, correct? So the mass of the whole rod remains unchanged.
As I understand it, you have a standard current going from positive to negative. Of course the electrons are going from negative to positive. The current creates an electric field which provides enough energy for the higher energy electrons to tunnel from the current carrying wire into the floating transistor where they stay because they don’t have enough energy to leave. As a result, some of the electrons that started out at the cathode (I get those confused and I think I reversed it in a previous post. Of course I may have reversed it this time.) don’t make it to the anode.
If you are running on battery power, then that means there is a net positive charge on the battery. On the otherhand, if you are plugged in, then there is a net positive charge at the power source. This part does make me uneasy, because as a chemist, i am always concerned with balancing equations and I have a difficult time figuring out how all this balances when you are connected to city power. With the battery, I don’t have any problem with a net positive charge given the minute quantity of electrons I’m thinking are involved.
Like I said, I’m not an expert here and I would appreciate any clarifications to be made on my understanding.
If the side (of the flash memory bit) that lost the electrons gained them back, then the value for that bit would get flipped because the difference in voltage between the sides has been reduced below the threshold, right? Doesn’t that imply this doesn’t happen? Or does it happen to such a small degree that it doesn’t change the bit value?
I’m not entirely sure what your asking, but I think I might resolve the issue you have. Understand I only have a vague understanding so anyone with better knowledge please help. The portion of the floating gate transistor that holds a charge is surrounded by a semiconducting oxide layer. A current passes through a nearby path. As you understand the current is made up of electrons which creat an electric field. Within this current is a Boltzmann distribution of elecrons som some electrons have a lot of energy.
Strangely, none of the electrons technically have “enough” energy to cross the oxide barrier. But where QM is concerned, standard rules don’t apply. Instead, a few of the higher energy electrons tunnel right across that barrier. But since by all rights they didn’t have enough energy to cross the barrier in the first place, they are stuck until a high enough voltage is applied to cross the band gap of the semiconducting oxide layer.