Endings for Si(111) Twins

Giga-scale integrated circuit silicon in the next century will be grown on wafers typically twelve inches in diameter, and larger. Such silicon experiences larger forces due to thermal gradients across its breadth. One consequence of this may be an increased incidence of slip planes and other extended defects in the silicon ingots, before they are sliced into wafers. We expect that twins and nano-twins along Silicon (111) planes may be found in association with these defects, and hence may give us some clues to the mechanisms (and possible control processes) involved with such defects.

Expect more on this subject soon. In the meantime, look for a chance to check out Danielle Kozemczak's StL Gateway Magnet School Senior Project and Science Fair Entry, currently located in our M114 Scanned Tip and Electron Image Lab. One image of a tiny (several atom) segment of a germanium (111) twin boundary viewed down an orientation we've been modeling can be found here.

Cerius 2 model with HREM images of Danielle's first-order prediction for atom locations at the end of the twin. The next step: relaxation of the atoms theoretically, to see if the image acquires an even better match with the experimental image.

Darkfield TEM image taken at UM-StL, by P. Fraundorf and D. Savitskij, of a nanotwin lath di-pair in GigaScale Integrated Circuit Silicon.

Here are some references to high resolution TEM images of defects in diamond FCC crystals, with + if we have it, o if we don't yet, and ? if it may be irrelevant. Also find some refs to twins in larger silicon crystals as well. The Ge image above is a tiiiiiny part of the image referenced with a * below.

References to silicon particles...
+ Sumio Iijima, Proc. 46th EMSA Meeting (San Francisco Press, 1988), 1010.
o S. Iijima, Jpn. J. Appl. Phys. (1987) 26, 357.
o S. Iijima & T. Ichihashi, Phys. Rev. Lett. (1986) 56, 616.
? A. Ourmazd et. al, Phys. Rev. Lett. (1987) 59, 213.
? S. Iijima & M. Ichikawa, J. Catalysis (1985) 94, 313.

References to germanium precipitates...
+ Cover*, EMSA Bulletin 16, 2 (Fall 1986)
o U. Dahmen and J. Turner, Proc. 44th EMSA Meeting (SF Press, 1986), 538.

References for large-crystal silicon twins so far...
+ W. R. Runyan, Silicon Semiconductor Technology (McGraw-Hill, 1965) 98-101.
+ Fumio Shimura, Semicond. Si Crystal Technology (Academic Press, 1989) 74-75.
? E. O. Hall, Twinning & Diffusionless Transf. in Metals (Butterworths, 1954).
o K. V. Ravi, Growth of EFG silicon ribbons, J. Cryst. Growth 39 (1977) 1-16.
o R. Gleichmann et al., "...solar cells", J. Appl. Phys. 58 (1985) 223-229.

Runyan also has references to related literature from the 1920's to 1950's, which may hold some surprises. It might be cool to try getting the ones of these we don't have through inter-library loan.

Overview