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Technology Stocks : Frank Coluccio Technology Forum - ASAP -- Ignore unavailable to you. Want to Upgrade?

To: Raymond Duray who wrote (1466)	4/21/2000 1:34:00 AM
From: Raymond Duray	Read Replies (2) \| Respond to of 1782

This subject would be a monologue, except for my silent partner: Hi Y'all, Now that you've had your fill of 'the good earth', let's get back to something a bit more elemental: To wit, here's some more ramblings on the nanosphere, from the guy I just mailed: Nitride 101: a unique 2.6 hr GaN Primer video featuring development experts: Shuji Nakamura formerly of Nichia,and now a professor at UCSB, Bob Karlicek of EMCORE/GELcore, and Steve DenBaars of UCSB/Nitres compound-semiconductor.com Call or write if you want to be the next in line. Excellent primer. If you can write a five paragraph statement on the importance of bandgaps, you don't need this. Here's the Glassguy, refering to the C&EN article mentioned upstream: <snip> An associate (see Frank, I'm getting better! :)) posed the following interesting question in a private email and I trust he will not object to my replying in public: >Could this be a substitute for molecular beam epitaxy (MBE), the fabled but >horrendously expensive method now used to make some high performance >semiconductor devices? Certainly seeems relevant to the work HP is doing >trying to construct devices from self ordering chemistry a molecule at a time. I am far from expert at MBE, but I think I understand it well enough to explain this. The answer I think, is yes and no. MBE is a diffusive process where layers of materials are deposited onto a heated substrate in an ultra-high vacuum chamber. The deposited materials form very slowly (approximately one atomic layer every few seconds), and by using multiple beam sources and rapidly switching between them, incredibly thin layers of different inorganic and even organic materials can be precisely deposited as discrete or doped (mixed) layers. The specific organization of the layered materials is largely a function of the atomic uniformity of the crystalline substrate (as subsequent layers are affected by and will magnify underlying crystal defects) and temperature. The atomic uniformity of substrates is now reliably attainable. The technique described in the C&EN article is quite different from MBE as the material applied to the substrate bonds chemically (covalently), thus the organization of a coating is not a function of deposition conditions but of the intrinsic structure of the substrate - an excess of layering material may therefore be used and only that which is needed will adsorb. In other words, the coating may be 'spread' or 'washed' onto the substrate and the excess rinsed off. It's not rocket science ;) Not discussed in my previous post is the very peculiar chemistry that occurs on the substrate surface. The coating molecules are physically deformed when adsorbed, and chemical bonds are forged that would otherwise be impossible. For example, there are four different ways for benzene to bond to a silicon substrate, and the assortment of benzene bonds presented for subsequent reaction differs with each - this bond deformation is similar to what happens on the surface of catalysts. This in itself is extremely important, but combining this unusual chemistry with the atomic precision of the subsequent coating is very exciting. Finally, if a coating material is synthesized such that the adsorbed material binds covalently to the substrate and presents a reactive side-group facing outward from the new surface, then conventional chemistry techniques may be utilized to create and modify subsequent layers. Layers may be created that would be impossible to form directly on the substrate surface. This is very similar in concept to 'priming' a metal surface before painting it with glossy enamel, and IMHO the functional difference from MBE techniques. Clear as mud? Rats... Michael OK, I'm waiting.... does anyone care about this subject? If not I'm going back to the Eisenia foetida discussion. Can ideas be composted? Just wondering, FOTH