1. For example, see Mater. Res. Soc. Proc. 256 (1992); 283 (1993); 298 (1993).
Canham, L. T., Appl. Phys. Lett.
57, 1046 (1990)
Lehmann, V. and Gösele, U., Appl. Phys. Lett.
58, 856 (1991)
Schuppler, S., Friedman, S. L., Marcus, M. A., Adler, D. L., Xie, Y.-H., Ross, F. M., Harris, T. D., Brown, W. L., Chabal, Y. J., Brus, L. E., and Citrin, P. H., Phys. Rev. Lett. 72, 2648 (1994).
5. See, e. g., Delerue, C., Allan, G., and Lannoo, M., Phys. Rev. B
48, 11024 (1993), and references therein.
MacDowell, A. A., Hashizume, T., and Citrin, P. H., Rev. Sci. Instr.
60, 1901 (1989).
Lee, P.A., Citrin, P. H., Eisenberger, P., and Kincaid, B. M., Rev. Mod. Phys.
53, 769 (1981).
Erbil, A., Cargill, G. S., Frahm, R., and Boehme, R. F., Phys. Rev. B
37, 2450 (1988). Escape depths have been crudely estimated by multiplying by 5 to account for the 80% porosity.
9. Preparations of the por-Si samples studied here (referred to as A, B, C, and D) follow those in Refs. 2, 10, and 11, namely, C : p-type Si(lO0), >50 Ω-cm, 20%HF in alcohol, 20 mA/cm2 for 5 min; A : same as C, but etched 60 min; B : p-type Si(100), >50 (Ω-cm, 15%HF in alcohol, 25 mA/cm2 for 12 min; D : p-type Si(100), 0.5–0.8 Ω-cm, 40% HF in alcohol, 50 mA/cm2 for 80 sec, soaked 2 hr unetched in same solution.
Friedman, S. L., Marcus, M. A., Adler, D. L., Xie, Y.-H., Harris, T. D., and Citrin, P. H., Appl. Phys. Lett.
62, 1934 (1993).
Xie, Y. H., Hybertsen, M. S., Wilson, W. L., Ipri, S. A., Carver, G. E., Brown, W. L., Dons, E., Weir, B. E., R.Kortan, A., Watson, G. P., and Liddle, A. J., Phys. Rev. B
49, 5386 (1994); Y.-H. Xie (unpublished).
12. Oxidized Si nanocrystals were made by homogeneous nucleation in high-pressure He at 1000°C from thermal decomposition of disilane with subsequent oxidation in O2 at 1000°C for ∼30 msec. See K. A. Littau, Szajowski, P. J., Muller, A. J., Kortan, A. R., and Brus, L. E., J. Phys. Chem.
97, 122 (1993); W. L. Wilson, P. J. Szajowski, and L. E. Brus, Science 262, 1242 (1993); P. J. Szajowski and L. E. Brus (unpublished).
13. Like the nanocrystals, the por-Si sample also consists of small particles whose band structure is not fully developed, and therefore exhibits neither the larger white-line to edge-jump ratio nor the split white-line structure of c-Si. Our results are completely unaffected by this choice because only difference spectra are being compared.
14. Densities and molecular weights for bulk c-Si, SiO2, and SiO were used, i. e., 2.33, 2.4, and 2.1 gm cm−3, respectively.
15. It should be noted that while the outer diameters of the nanocrystals, determined by TEM in Ref. 12, have very conservative error limits of ≤20 %, the relative mass fractions, determined by NEXAFS, are much more precise. Thus, the relative error limits of the inner diameters and the oxide layer thicknesses are just the same as for the outer diameters.
Brus, L. E., Szajowski, P. F., Wilson, W. L., Harris, T. D., Schuppler, S., and Citrin, P. H., J. Amer. Chem. Soc. (to be published).
Street, R. A., Hydrogenated Amorphous Silicon (Cambridge University Press, Cambridge, 1991).
18. The volumes used for integrating the measured SiHx concentrations in the por-Si samples were obtained from TEM.
19. Surface sensitivity of <1 μm was obtained using a grazing internal incidence angle in a Ge plate positioned next to the por-Si samples.
20. For a Si cube of side L, Nsi = 8L
3; for a sphere of diameter L, Nsi= (π/ 6 )NSi