Photoluminescence excitation spectroscopy obtained for spark-processed Si

Photoluminescence excitation spectroscopy (PLE) studies have been performed for spark-processed Si (sp-Si), which exhibited intense PL in the UV/blue spectral range peaking at 400 nm (3.1 eV) and a green luminescence peak near 525 nm (2.36 eV), A broad absorption band was observed at 5 eV (248 nm), 4.2 eV (295 nm), and 3.6 eV (344 nm). Furthermore, a relatively low energy narrow absorption band was detected at 2.7 eV (459 nm) and 2 eV (620 nm), These absorption bands determined by PLE studies enabled us to clearly understand a PL peak position dependence on laser excitation energy for both blue and green luminescence sp-Si. Specifically, the blue and green photoluminescence peaks of sp-Si. which were detected by the excitation of 325 nm (3.81 eV) He-Cd laser, were interpreted to originate from energy levels at 3.6 eV (344 nm) into 3.22 eV (385 nm) and 2.36 eV (525 nm) via non-radiative transition. At that point electrons reverted to ground state by a radiative transition. In contrast, an Ar+ laser excitation pumped electrons into a closely spaced lower energy absorption band at 2.0 eV (620 nm), and thus resulted in only a 1.9 eV (650 nm) radiation. (C) 2002 Elsevier Science B.V. All rights reserved.