The nature of encapsulated silicon nanoclusters in zeolite Y

Luminescent silicon clusters have been synthesized by chemical vapor deposi tion of Si2H6 into the supercages of H32Na24Y zeolite. The encapsulated Si clusters are air stable and exhibit a room-temperature photoluminescence in the green-yellow region. The electronic band gap of the cluster is determi ned to be about 2.4 eV from photoelectron and photoabsorption spectroscopie s. A saturation loading of seven disilane molecules per supercage was deter mined directly from multiple quantum H-1 nuclear magnetic resonance spin co unting of the precursor material. Intrazeolitic Si-n clusters are formed af ter heating with loss of SiH4 and H-2. The new quantitative spin counting r esult is consistent with an average value of 12+/-2 Si/cluster obtained fro m previous indirect measurements using x-ray photoelectron spectroscopy and Si K-edge x-ray absorption near-edge spectroscopy [J. He, D. D. Klug, J. S . Tse, C. I. Ratcliffe, and K. F. Preston, Appl. Phys. Lett. 71, 3194(1997) ]. This observation reveals a mechanism for the conversion of gaseous Si2H6 into silicon nanoclusters. (C) 1999 American Institute of Physics. [S0003- 6951(99)02506-1].