矿床地球化学国家重点实验室知识库

Even though economic advantages of silicon still keep it as the dominant material for the solar cell industry in the near future, crystal silicon in the diamond structure (d-Si) is an indirect bandgap semiconductor which prevents to consider it as a next-generation platform for optical material technologies. Here, we report the formation of a new allotrope of silicon on surface, Si₉, using a novel two-step synthesis methodology. First, a film of amorphous silicon was produced by using pulsed laser deposition method, and second, new Si₉ was synthesized under irradiation of coherent electron beam on the amorphous Si film. It is important that the structure of Si₉, forming six-membered sp3 silicon rings and involving 9 silicon atoms in one unit, possesses a direct bandgap near 1.59 eV, around which we have measured the emission peak in photoluminescence spectra on the pure Si₉. It is discovered that Si₉ can be easily doped as both p- and n-type on surface, where boron and nitrogen are demonstrated as the most promising elements for the p-type and n-type doping in Si₉, respectively, due to their low formation energies and reductions in the band gap. These properties suggest great potential in constructing a novel Si₉-based p-n junction which is highly desired for future industrial application of optoelectronic technologies and photovoltaic devices.