FWIW, gallium manganese nitride is supposed to have a Curie temperature of several hundred degrees too. Both ZnO and GaN are hard to make into devices, though.
The margins in the chip business are SO tight now I am not sure Intel will be willing to invest heavily in developing new techniques. IBM's dumping fabs, prices are low, etc.... Tough times right now. They haven't really made their money from.13um yet, so till they do, they probably won't be looking to adopt squat.
This (recrystallized Si) is actually standard practice. Yes, the Si in the laser-affected area becomes polycrystalline, but this Si (known as "polysilicon") becomes an electrode, used for its conductivity, not the doped Si which actually takes part in the transistor action.
Which Japanese companies? Every time I hear about a nanotube breakthrough, it comes out of an American university or IBM. I know IBM basically just handed its storage hardware business to Hitachi, but that hardly qualifies.
As a side note, IBM seems hell-bent on getting out of the hardware business, so if they manufacture carbon transistors themselves or license the technology to another firm remains to be seen.
It seems like that (a) every month someone has a new nanotube device, (b) it's always coming out of IBM, (c) no indication how they are going to economically integrate it with existing components. This is the wave of the future, I guess, but it will probably be after Si CMOS has run its course (5-15 years, depending on who you talk to). There's a lot that can be done with alloying Ge into Si, but I think right now most of that's aimed at the microwave communications market. If it is shown to be capable of making quantum computers, though, it probably will get more research money because it is very similar to existing technology.
This article is dated December 2000, but I don't think that the information is obsolete yet. A quote from the article:
"In their latest report, in the Nov. 24 issue of Science, the group describes machining 200-nanometer-high mounting posts on a nickel substrate. By using a series of coatings and chemical treatments, the ATPase molecules can be made to stick to the tops of the posts, and tiny nickel propellers, about 750 nm in length and 150 nm in diameter, are made to bond to the tops of the shafts. Immerse them in a bath of ATP and other chemicals and the tiny props begin to spin."
So you see even a very advanced genetically engineered machine such as this requires a ultralow-throughput step (in this case, e-beam lithography; often atomic force microscopes are used as well). Also it's important to note their yield rate ("5 out of the first 400").
But this article shows that there's hope for nanomachines that work in vivo, although military technologies like enhanced reflexes or strength are probably far off, since the former requires playing with the brain (ultracomplicated) and the latter muscles (would require hordes of nanomachines). For ex vivo machines in the wild -- crawling in the ground, etc. -- there is a need for a power source. Solar is a possibility but then all the well-known limitations of that come into play.
With all these limits, I think it's way too early to worry that the MIBs are going to come to your university and drag you away or whatever Reynolds was getting at.
Considering where we are with current nanotech research, I'm a little surprised everyone's so worried about it. What's the forefront of nanotech right now? You have molecular machines, but so far no known way to really make them independently powered or make them self-replicate in anything more than the simplest manner -- "goo" (harmful self-replicating swarms of nanomachines) is a long long long way off, if in fact it's ever possible. While several researchers have used nanotubes to demonstrate some interesting electronic devices, such as single-atom transistors, but the performance offered by such devices is still not "leaps and bounds" ahead of silicon CMOS. More conventional solid-state work is going on in pursuit of quantum computation that the US DoD is sponsoring, not suppressing.
I thought the analogy with 1950s comptuers was interesting, but I think a more appropriate analogy would be 1930s computing -- we're still a long way off.
And did anyone else note that Reynolds of the article didn't cite any sources for these "rumors" of a "nanotechnology clampdown"? Bad journalism + ignorance = hysteria.
In Heat, Robert de Niro's character impresses Ashley Judd's by being a metallurgical salesman and reading a book on Ti alloys. *sigh* If it were only that easy;)
Your pregnancy analogy is flawed and points to exactly what I'm getting at. You can definitely test to determine if, indisputably, a woman is pregnant. That's easy. Climate change is not testable along those lines. You can take data and speculate and whatever, but there are way too many natural variables to pin down causes of change with the same certainty you can determine if a woman is pregnant. And if she is pregnant, you can be pretty sure how she got that way.
There is a moral component to my argument that I omitted -- that no one would seriously consider his/her wasteful, destructive materialistic lifestyle more important than protecting the habitat of other living things. It's not a self-contained argument but I would everyone would grasp the underlying concept.
I disagree wholeheartedly with the insinuation that the Scientific American critique of this book was an "attack." Readers, please do not be swayed by this horribly biased statement. Several environmental scientists dissected Skeptical Environmentalist's methodology, statistics, and conclusions, and the reviewers found many, many weak points not only in the author's facts but also his logic. The tone varied from reviewer to reviewer, but all the reviewers seemed to take the book pretty seriously.
The truth of the matter is, climatology, geology, etc. do not have the luxury that physics, molecular biology, and other "benchtop" sciences have in that, in the latter fields, it is mostly possible to construct the systems in question in the lab and probe them. However, testing most major hypotheses in climatology is simply not possible as they would require altering the climate in a deliberate manner which is neither possible nor desireable.
Personally, I am of the opinion that we need to enforce much stricter emission, land development, and recycling standards not because I believe that these activities are damaging the environment, but because they indisputably might be damaging the environment.
I do a lot of work with magnetic materials, and consider myself more an engineer than a scientist, and whenever I send samples out for measurement the results I get back are always in cgs (kOe, emu/cm^3, the works). This is a company whose customer base is primarily manufacturing firms. Also, cgs still seems to be the standard in magnetics and electronics literature (e.g. mobilities are still cm^2/V*s). Therefore, I would say it's not as clearly delineated as you would indicate.
It's almost always the case in physics (and EE) that you see people using cgs (cm, grams, seconds). This includes eV, etc. That's all fine and good till you get to the supposedly "dimensionless" quanities like "emu," "esu," and so on. I'm not really sure what these units are a holdover from. eV are really convenient, but the rest are just really annoying, and I wish there was some push to move the physics community to a mks/SI system.
There will be a spintronics symposium at the upcoming Fall 2001 meeting of the Materials Research Society meeting. It appears that about half of the talks will be about MTJs (the type of structures used in TMR MRAM) and another really big block about these dilute magnetic semiconductors. These are not new per se, but have been strongly revived by spintronics research. Especially important is the development of III-V and Group IV magnetic semis, primarily the result of dilute manganese doping. Really exciting stuff nowadays.
Actually, I think the original poster hit it on the head. Some of the states (e.g. Tennessee, my point of origin) didn't just badly want the tobacco settlement money; they badly needed it. Things like boosting local software industries probably played a role, but I don't believe AGs or governors think that abstractly. Since many of them (e.g., again, TN) flaunted the terms of the settlement and spent the money on whatever they saw fit, who can honestly say they didn't want to leap on that chance again?
The fact that at the top of the valence band there exists degeneracy (i.e. equal energy) between different hole types; i.e. the energy to change types at zero momentum becomes zero so there is all kinds of intermingling when holes accelerate to nonzero velocity again.
Sometimes weird things happen like in lead sulfide (PbS) where the hole mobility is greater than the electron mobility, but this is because the electron mobility is really low, not vice versa.
That's not an ignorant question; actually, it's a really good question...My best attempt to explain this without using the word "degeneracy": The limiting factor on electron velocity is the scattering between the conduction electrons (the ones that are basically free). A free electron is a free electron, so when they collide and scatter, that's that. However, holes are what's left behind whenever electrons are freed; the electron that jumps in the direction counter to that of the hole isn't really free in the same sense as a conduction electron, and it has to go to different levels closer to the nucleus. So in addition to "hole-hole" collision scattering, analagous to the aforementioned electron-electron collision scattering, there's this confusion as to where the hole is supposed to come from, and energy is lost in making these "inter-level" transitions. Hope this makes sense; it's not a great explanation.
GaAs is actually a very, very poor choice for "rad hard" chips. IDK who gave you your information, but they're pretty much dead wrong. Rad-hard materials are like SiC, GaN, ZnO, diamond...things with bandgaps > 3 eV.
That's true, but the holes in GaAs are actually slower: mobility of holes in Si is about 450 cm^2/V*s and about 400 in GaAs (both numbers for intrinsic material).
"Lynx compatible." They were the sign of a compassionate page author who really cared if anyone, anywhere, with nothing much better than a 2400-baud modem (whatever happened to "baud"? Perfectly good unit of measure) could see their page. This was back before Flash, Java, etc. ruined the WWW. While they're pretty neat, they really hurt the accessibility of people in developing areas, and they also created a race to see who could abuse them the most. Nowadays you can't even get the ESPN homepage without a Java-enabled browser because they've added those stupid little scrolling things with the headlines on them.
Frontpages using Flash are the online version of an SUV. Someone somewhere might really need it to get their message across but for most people it's just a titanic waste, IMVHO.
just wait a few years...
on
Dorm Storm?
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At the rate the Tennessee General Assembly is going, the University of Tennessee won't have any money and therefore no students at Knoxville, so the problem will take care of itself.:-P
UTK was my first exposure to broadband and while setting things up was really rough in the early years (giving random students off the streets static IPs and an armload of floppies for the software and drivers required a lot of help for lots of people) the speed was phenomenal. Kind of like DSL in microcosm, now that I think of it. I've not had anything like it in a long time.
Thanks for all the work you did. It made my DOOM, Worms, Bolo, and Quake experiences much more enjoyable.:-)
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FWIW, gallium manganese nitride is supposed to have a Curie temperature of several hundred degrees too. Both ZnO and GaN are hard to make into devices, though.
Electrons are fermions, photons are bosons ... Arrgh!
The margins in the chip business are SO tight now I am not sure Intel will be willing to invest heavily in developing new techniques. IBM's dumping fabs, prices are low, etc. ... Tough times right now. They haven't really made their money from .13um yet, so till they do, they probably won't be looking to adopt squat.
Anyway, any clean electron-beam process requires VACUUM, which increases cost and decreases throughput by at least one order of magnitude, often more.
This (recrystallized Si) is actually standard practice. Yes, the Si in the laser-affected area becomes polycrystalline, but this Si (known as "polysilicon") becomes an electrode, used for its conductivity, not the doped Si which actually takes part in the transistor action.
As a side note, IBM seems hell-bent on getting out of the hardware business, so if they manufacture carbon transistors themselves or license the technology to another firm remains to be seen.
It seems like that (a) every month someone has a new nanotube device, (b) it's always coming out of IBM, (c) no indication how they are going to economically integrate it with existing components. This is the wave of the future, I guess, but it will probably be after Si CMOS has run its course (5-15 years, depending on who you talk to). There's a lot that can be done with alloying Ge into Si, but I think right now most of that's aimed at the microwave communications market. If it is shown to be capable of making quantum computers, though, it probably will get more research money because it is very similar to existing technology.
I thought they mostly killed off the older characters so they wouldn't be promoting out-of-production toys with the movie ...
"In their latest report, in the Nov. 24 issue of Science, the group describes machining 200-nanometer-high mounting posts on a nickel substrate. By using a series of coatings and chemical treatments, the ATPase molecules can be made to stick to the tops of the posts, and tiny nickel propellers, about 750 nm in length and 150 nm in diameter, are made to bond to the tops of the shafts. Immerse them in a bath of ATP and other chemicals and the tiny props begin to spin."
So you see even a very advanced genetically engineered machine such as this requires a ultralow-throughput step (in this case, e-beam lithography; often atomic force microscopes are used as well). Also it's important to note their yield rate ("5 out of the first 400").
But this article shows that there's hope for nanomachines that work in vivo, although military technologies like enhanced reflexes or strength are probably far off, since the former requires playing with the brain (ultracomplicated) and the latter muscles (would require hordes of nanomachines). For ex vivo machines in the wild -- crawling in the ground, etc. -- there is a need for a power source. Solar is a possibility but then all the well-known limitations of that come into play.
With all these limits, I think it's way too early to worry that the MIBs are going to come to your university and drag you away or whatever Reynolds was getting at.
I thought the analogy with 1950s comptuers was interesting, but I think a more appropriate analogy would be 1930s computing -- we're still a long way off.
And did anyone else note that Reynolds of the article didn't cite any sources for these "rumors" of a "nanotechnology clampdown"? Bad journalism + ignorance = hysteria.
In Heat, Robert de Niro's character impresses Ashley Judd's by being a metallurgical salesman and reading a book on Ti alloys. *sigh* If it were only that easy ;)
There is a moral component to my argument that I omitted -- that no one would seriously consider his/her wasteful, destructive materialistic lifestyle more important than protecting the habitat of other living things. It's not a self-contained argument but I would everyone would grasp the underlying concept.
The truth of the matter is, climatology, geology, etc. do not have the luxury that physics, molecular biology, and other "benchtop" sciences have in that, in the latter fields, it is mostly possible to construct the systems in question in the lab and probe them. However, testing most major hypotheses in climatology is simply not possible as they would require altering the climate in a deliberate manner which is neither possible nor desireable.
Personally, I am of the opinion that we need to enforce much stricter emission, land development, and recycling standards not because I believe that these activities are damaging the environment, but because they indisputably might be damaging the environment.
I do a lot of work with magnetic materials, and consider myself more an engineer than a scientist, and whenever I send samples out for measurement the results I get back are always in cgs (kOe, emu/cm^3, the works). This is a company whose customer base is primarily manufacturing firms. Also, cgs still seems to be the standard in magnetics and electronics literature (e.g. mobilities are still cm^2/V*s). Therefore, I would say it's not as clearly delineated as you would indicate.
It's almost always the case in physics (and EE) that you see people using cgs (cm, grams, seconds). This includes eV, etc. That's all fine and good till you get to the supposedly "dimensionless" quanities like "emu," "esu," and so on. I'm not really sure what these units are a holdover from. eV are really convenient, but the rest are just really annoying, and I wish there was some push to move the physics community to a mks/SI system.
...did these people isolate a signal on the order of 10^-12 eV? My lock-in amplifier will only manage 10^-11.
There will be a spintronics symposium at the upcoming Fall 2001 meeting of the Materials Research Society meeting. It appears that about half of the talks will be about MTJs (the type of structures used in TMR MRAM) and another really big block about these dilute magnetic semiconductors. These are not new per se, but have been strongly revived by spintronics research. Especially important is the development of III-V and Group IV magnetic semis, primarily the result of dilute manganese doping. Really exciting stuff nowadays.
Actually, I think the original poster hit it on the head. Some of the states (e.g. Tennessee, my point of origin) didn't just badly want the tobacco settlement money; they badly needed it. Things like boosting local software industries probably played a role, but I don't believe AGs or governors think that abstractly. Since many of them (e.g., again, TN) flaunted the terms of the settlement and spent the money on whatever they saw fit, who can honestly say they didn't want to leap on that chance again?
Sometimes weird things happen like in lead sulfide (PbS) where the hole mobility is greater than the electron mobility, but this is because the electron mobility is really low, not vice versa.
That's not an ignorant question; actually, it's a really good question...My best attempt to explain this without using the word "degeneracy": The limiting factor on electron velocity is the scattering between the conduction electrons (the ones that are basically free). A free electron is a free electron, so when they collide and scatter, that's that. However, holes are what's left behind whenever electrons are freed; the electron that jumps in the direction counter to that of the hole isn't really free in the same sense as a conduction electron, and it has to go to different levels closer to the nucleus. So in addition to "hole-hole" collision scattering, analagous to the aforementioned electron-electron collision scattering, there's this confusion as to where the hole is supposed to come from, and energy is lost in making these "inter-level" transitions. Hope this makes sense; it's not a great explanation.
GaAs is actually a very, very poor choice for "rad hard" chips. IDK who gave you your information, but they're pretty much dead wrong. Rad-hard materials are like SiC, GaN, ZnO, diamond...things with bandgaps > 3 eV.
Sorry. (In,Ga)(As,P) LEDs can emit in the visible range, but not GaAs.
That's true, but the holes in GaAs are actually slower: mobility of holes in Si is about 450 cm^2/V*s and about 400 in GaAs (both numbers for intrinsic material).
Frontpages using Flash are the online version of an SUV. Someone somewhere might really need it to get their message across but for most people it's just a titanic waste, IMVHO.
UTK was my first exposure to broadband and while setting things up was really rough in the early years (giving random students off the streets static IPs and an armload of floppies for the software and drivers required a lot of help for lots of people) the speed was phenomenal. Kind of like DSL in microcosm, now that I think of it. I've not had anything like it in a long time.
Thanks for all the work you did. It made my DOOM, Worms, Bolo, and Quake experiences much more enjoyable. :-)
(UTK Class of 1999)