Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: The role of the surfaces in the photon absorption in Ge nanoclusters embedded in silica | Cosentino et al. Nanoscale Research Letters 2011 6 135 http content 6 1 135 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access The role of the surfaces in the photon absorption in Ge nanoclusters embedded in silica 1 1 1 2 1 Salvatore Cosentino Salvatore Mirabella Maria Miritello Giuseppe Nicotra Roberto Lo Savio Francesca Simone1 Corrado Spinella2 Antonio Terras 1 Abstract The usage of semiconductor nanostructures is highly promising for boosting the energy conversion efficiency in photovoltaics technology but still some of the underlying mechanisms are not well understood at the nanoscale length. Ge quantum dots QDs should have a larger absorption and a more efficient quantum confinement effect than Si ones thus they are good candidate for third-generation solar cells. In this work Ge QDs embedded in silica matrix have been synthesized through magnetron sputtering deposition and annealing up to 800 C. The thermal evolution of the QD size 2 to 10 nm has been followed by transmission electron microscopy and X-ray diffraction techniques evidencing an Ostwald ripening mechanism with a concomitant amorphous-crystalline transition. The optical absorption of Ge nanoclusters has been measured by spectrophotometry analyses evidencing an optical bandgap of eV unexpectedly independent of the QDs size or of the solid phase amorphous or crystalline . A simple modeling based on the Tauc law shows that the photon absorption has a much larger extent in smaller Ge QDs being related to the surface extent rather than to the volume. These data are presented and discussed also considering the outcomes for application of Ge nanostructures in photovoltaics. PACS Introduction Nanostructured materials represent a promising route of development for photovoltaics PV because of the unique optical and electronic properties caused by the quantum confinement of electrons and holes allowing to increase the .
