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#11
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Asad wrote:
HI, How can I perform doping of silicon manually? You can't. -- American democracy has sunk to a level where elections are considered no different from sports and the consequences go no further than the record books. -- The Iron Webmaster, 3433 nizkor http://www.giwersworld.org/nizkook/nizkook.phtml flying saucers http://www.giwersworld.org/flyingsa.html a2 |
#12
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On Sat, 04 Jun 2005 09:47:36 GMT, Matt Giwer
wroth: Asad wrote: HI, How can I perform doping of silicon manually? You can't. I remember that back in the late 50's that Bell Labs was distributing science project kits to schools to promote education. Remember that this was back when the US was playing catch-up to the Russians. One of the lits was put together to allow school kids to make silicon solar cells right in the classroom with ordinary stuff found there. The kit included silicon wafer slices, some chemicals, a 115 volt heating element similar to the ones used in small radiant room heaters, some asbestos sheets for insulation, some fine carbide sandpaper, and a list of instructions. You built an oven from the heater and the asbestos sheets. The heater was a ceramic cylinder with nichrome wire coiled around the outside and an Edison screw base. The inside of the cylinder was open and you broke the silicon wafer into pieces small enough to fit inside. The wafer pieces were dipped into a water slurry of the chemical, I forget exactly which chemical (probably something with phosphorous in it), and placed in the heater/oven to get red hot. The original wafer pieces were probably grown with an N or P dopant and the subsequent difusion created a complemental doping. The wafers were allowed to cool and then the carbide was used to remove the surface on one side of the wafer to get back down the original silicon. I forget exactly how the wires were added to each side, probably a loose flat spiral of bare copper held in contact mechanically. When finished the kids had a working solar cell. My brother was given the kit by his science teacher to put together on his own for "extra credit". I suspect the teacher just wasn't up to the task of using the kit the way it was intended. I got the kit and played around with it. So, in short, you CAN manually dope silicon without Billions of dollars of equipment. I know because I've done it. Jim |
#13
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On Sat, 04 Jun 2005 18:47:44 GMT, James Meyer
wrote: On Sat, 04 Jun 2005 09:47:36 GMT, Matt Giwer wroth: Asad wrote: HI, How can I perform doping of silicon manually? You can't. I remember that back in the late 50's that Bell Labs was distributing science project kits to schools to promote education. Remember that this was back when the US was playing catch-up to the Russians. One of the lits was put together to allow school kids to make silicon solar cells right in the classroom with ordinary stuff found there. The kit included silicon wafer slices, some chemicals, a 115 volt heating element similar to the ones used in small radiant room heaters, some asbestos sheets for insulation, some fine carbide sandpaper, and a list of instructions. You built an oven from the heater and the asbestos sheets. The heater was a ceramic cylinder with nichrome wire coiled around the outside and an Edison screw base. The inside of the cylinder was open and you broke the silicon wafer into pieces small enough to fit inside. The wafer pieces were dipped into a water slurry of the chemical, I forget exactly which chemical (probably something with phosphorous in it), and placed in the heater/oven to get red hot. The original wafer pieces were probably grown with an N or P dopant and the subsequent difusion created a complemental doping. The wafers were allowed to cool and then the carbide was used to remove the surface on one side of the wafer to get back down the original silicon. I forget exactly how the wires were added to each side, probably a loose flat spiral of bare copper held in contact mechanically. When finished the kids had a working solar cell. My brother was given the kit by his science teacher to put together on his own for "extra credit". I suspect the teacher just wasn't up to the task of using the kit the way it was intended. I got the kit and played around with it. So, in short, you CAN manually dope silicon without Billions of dollars of equipment. I know because I've done it. Jim Thanks, Jim, for that post. I had started to respond similarly here, with my own twists and then read what you wrote -- with more detail than I remembered, actually. I think the kit that Bell Labs put out was back in the early-to-mid 1960's. I recently spoke with the people who currently own the rights to this kit (recently being a few years ago) and they are/were still selling it. Unfortunately, it would be very difficult for me to find the phone number, today -- it was in 2001 when I last had this information at hand. But they were on the east coast. to the OP: Modern, pure silicon wafers are rather cheap, thanks to the number of them being processed. I haven't directly purchased any, but someone at HP's Deer Creek facility told me they were only a "few dollars each" (my memory says the figure was near $4) when I pointed to the boxes and boxes of them they had laying around. This is sliced, polished, and cleaned so that no particles larger than a micron remained, if memory serves. Perhaps you could contact a fab or someone who might know someone at one who might help you get fragments of broken ones. I use such broken pieces (which I treat rather poorly) as convenient and well studied reflectors/filters, sometimes. However you proceed, if it is based on choices you are making and not on someone else's well-thought-out design, you should research it well. If you are considering doing this "manually," then you should study how these things were done when there were no fabs and they were just experiments in laboratories. And run anything you come up with by a knowledgeable chemist before you try it. You will want an informed opinion about the risks and mitigations and advise about what to consider trying. Hot materials can easily produce noxious gases. As a side bar, I've built ovens from spare parts that could easily raise a wafer to passivating temperatures, such as near 1500 C for rapid oxide growth, that sat in my garage. Just for testing some optical ideas, not for making wafers, though. Got plenty of free wafers from fabs, no problem. Used 'plenty' of dry nitrogen gas to fill the chamber (1500 C and open air with 20% oxy isn't so good an idea) and keep it at slightly higher pressure than ambient so oxygen doesn't get inside. Cripes, do things become a mess if you forget to run the nitrogen! You can construct quite a nice little "oven" of your own with a water cooled quartz jacket and some tungsten lamps from your local hardware or home construction store, a power controller, and a nickel plated chamber (much, much cheaper than gold and works "pretty good".) Just a tap water flow is usually enough. You don't want the quartz to get too hot, as it grows more opaque where it counts when it does and absorbs even more energy and melts in the resulting positive feedback. With a few kW of lamp energy and not enough cooling, bad things happen. In any case, don't plan on building much other than a solar cell to start. And keep things really simple and as safe as you can, as you learn. Jon |
#14
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On Sat, 04 Jun 2005 21:25:38 GMT, Jonathan Kirwan
wroth: In any case, don't plan on building much other than a solar cell to start. And keep things really simple and as safe as you can, as you learn. Jon Of course, there's always the possibility of building point contact transistors out of silicon in the comfort of your garage or kitchen. With a flouride etchant to thin down a silicon wafer in the right spots and some indium solder you could probably make a passable junction transistor. Jim |
#15
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James Meyer wrote:
Of course, there's always the possibility of building point contact transistors out of silicon in the comfort of your garage or kitchen. With a flouride etchant to thin down a silicon wafer in the right spots and some indium solder you could probably make a passable junction transistor. Or you could buy one for $0.10 -- \___/ / O O \ \_____/ FTB. For email, remove my socks. In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. - Carl Sagan, 1987 CSICOP keynote address |
#16
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James Meyer wrote:
On Sat, 04 Jun 2005 09:47:36 GMT, Matt Giwer wroth: Asad wrote: HI, How can I perform doping of silicon manually? You can't. I remember that back in the late 50's that Bell Labs was distributing science project kits to schools to promote education. Remember that this was back when the US was playing catch-up to the Russians. One of the lits was put together to allow school kids to make silicon solar cells right in the classroom with ordinary stuff found there. The kit included silicon wafer slices, some chemicals, a 115 volt heating element similar to the ones used in small radiant room heaters, some asbestos sheets for insulation, some fine carbide sandpaper, and a list of instructions. You built an oven from the heater and the asbestos sheets. The heater was a ceramic cylinder with nichrome wire coiled around the outside and an Edison screw base. The inside of the cylinder was open and you broke the silicon wafer into pieces small enough to fit inside. The wafer pieces were dipped into a water slurry of the chemical, I forget exactly which chemical (probably something with phosphorous in it), and placed in the heater/oven to get red hot. The original wafer pieces were probably grown with an N or P dopant and the subsequent difusion created a complemental doping. Then you have the hard part of the job in the delivered kit. The wafers were allowed to cool and then the carbide was used to remove the surface on one side of the wafer to get back down the original silicon. I forget exactly how the wires were added to each side, probably a loose flat spiral of bare copper held in contact mechanically. When finished the kids had a working solar cell. My brother was given the kit by his science teacher to put together on his own for "extra credit". I suspect the teacher just wasn't up to the task of using the kit the way it was intended. I got the kit and played around with it. So, in short, you CAN manually dope silicon without Billions of dollars of equipment. I know because I've done it. The problem is with the word _manually_. Obviously anything that can be done by a machine can be done by hand. Obviously with enough hardware for doing it and testing it and enough experimentation one can learn to get the results desired. However anyone who has looked into the process would know the right answer and not ask the question. The question appears in line with the kit you mention. Is there a simple way to do it? is more like the question sounds and the answer is no. And with the kit efficiency was likely so low that a high impedance voltmeter was needed and no way to measure the current short of lab equipment the efficiency would be so low compared to even the cheapest commercial production. So the answer is also no if the intention is a "try and see" bright idea. The idea might be sound but the success so low as to be unmeasurable. So again the answer is no. And again anyone who knew the difficulties involved would not ask the question. -- America was made safer by turning the entire Muslim world against America. As any Republican. -- The Iron Webmaster, 3449 nizkor http://www.giwersworld.org/nizkook/nizkook.phtml http://www.giwersworld.org |
#17
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James Meyer wrote:
On Sat, 04 Jun 2005 21:25:38 GMT, Jonathan Kirwan wroth: In any case, don't plan on building much other than a solar cell to start. And keep things really simple and as safe as you can, as you learn. Of course, there's always the possibility of building point contact transistors out of silicon in the comfort of your garage or kitchen. With a flouride etchant to thin down a silicon wafer in the right spots and some indium solder you could probably make a passable junction transistor. But it is far more difficult than finding a sweet spot on a gallium crystal for a radio. You can go through a lot of wafers before making one with little enough leakage to measure the effect. It took Schokley and company a while to get an effect that could not be attributed to measurement error beyond getting the effect in the first place. -- Zionist refusal to admit Palestinians are people whose ancestors converted from Judaism to Islam does not help to bring peace. -- The Iron Webmaster, 3445 nizkor http://www.giwersworld.org/nizkook/nizkook.phtml commentary http://www.giwersworld.org/opinion/running.phtml a5 |
#18
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fungus wrote:
James Meyer wrote: Of course, there's always the possibility of building point contact transistors out of silicon in the comfort of your garage or kitchen. With a flouride etchant to thin down a silicon wafer in the right spots and some indium solder you could probably make a passable junction transistor. Or you could buy one for $0.10 plus $4 shipping and handling -- When there is knowledge there is no need for belief. -- The Iron Webmaster, 3431 nizkor http://www.giwersworld.org/nizkook/nizkook.phtml http://www.giwersworld.org |