X-ray absorption spectroscopy from H-passivated porous Si and oxidized Si nanocrystals
- AT and T Bell Labs., Murray Hill, NJ (United States)
- Stanford Univ., Palo Alto, CA (United States). Dept. of Applied Physics; and others
Quantum confinement in nanoscale Si structures is widely believed to be responsible for the visible luminescence observed from anodically etched porous silicon (por-Si), but little is known about the actual size or shape of these structures. Extended x-ray absorption fine structure data from a wide variety of por-Si samples show significantly reduced average Si coordination numbers due to the sizable contribution of surface-coordinated H. (The IUSI ratios, as large as 1.2, were independently confirmed by ir-absorption and {alpha}-recoil measurements.) The Si coordinations imply very large surface/volume ratios, enabling the average Si structures to be identified as crystalline particles (not wires) whose dimensions are typically <15 {Angstrom}. Comparison of the size-dependent peak luminescence energies with those of oxidized Si nanocrystals, whose shapes are known, shows remarkable agreement. Furthermore, near-edge x-ray absorption fine structure measurements of the nanocrystals shows the outer oxide and interfacial suboxide layers to be constant over a wide range of nanocrystal sizes. The combination of these results effectively rules out surface species as being responsible for the observed visible luminescence in por-Si, and strongly supports quantum confinement as the dominant mechanism occurring in Si particles which are substantially smaller than previously reported or proposed.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Alexander von Humboldt-Stiftung, Bonn (Germany)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 79699
- Report Number(s):
- LBL-36911; CONF-941144-149; ON: DE95012352
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 28 Nov - 9 Dec 1994; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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