Intense visible light emission from three-dimensional periodical arrays of Si clusters

We report a strong visible light photoluminescence (PL) from three-dimensional Si cluster arrays. Using a chemical self-assembly process of Si clusters in aqueous solutions, three types of array structures are prepared: (I) BCC arrays with a=6.1 angstroms, (II) FCC arrays with a=7.5 angstroms, and (III) BCC arrays with a=6.9 angstroms. The distance between the centers of adjacent Si clusters is 5.3 angstroms for both sample I and II, and 6.0 angstroms for the sample III. In the PL measurements, red, orange, and blue-green are the three different colors observed at peak wavelengths of 700, 610, and 530 nm, respectively. The red, orange, and blue-green light emissions are thought to originate from the samples I, II, and III, respectively. PL is strong enough to be seen by the naked eye in all the samples. Possible mechanisms for the strong visible light luminescence are discussed.