LOW-TEMPERATURE SYNTHESIS OF GE NANOCRYSTALS IN ZEOLITE-Y

A method for obtaining Ge nanocrystals has been developed using the po rous structure of zeolite Y as a matrix. Samples were obtained by redu ction of GeO2 nanocrystals, previously grown in zeolite alpha cages, i n H-2 at 470 degrees C. This is apparently the lowest GeO2 reduction t emperature reported and is probably due to the influence of the host. Ge crystallites so formed present an absorption edge at 2.2 eV, which is shifted similar to 1.4 eV with respect to the bulk value, A softeni ng and an asymmetric broadening of the Raman peak were also observed. We can estimate an average diameter of 3 nm for the, Ge nanocrystals f rom both results. (C) 1996 American Institute of Physics.