About the Luminescence Mechanisms of Composite a-Si:nc-Si System Obtained by Ion-Beam Amorphization in the Wide Dose Reg
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About the Luminescence Mechanisms of Composite a-Si:nc-Si System Obtained by IonBeam Amorphization in the Wide Dose Region David I. Tetelbaum, Alexander A. Ezhevskii1, Alexey N. Mikhaylov, Mikhail Yu. Lebedev1, Yuliya A. Mendeleva1, Roman G. Ershov1, Sergey V. Morozov2 Physico-Technical Research Institute of University of Nizhny Novgorod, 23/3 Gagarin prospect, Nizhny Novgorod, 603950, RUSSIA 1 University of Nizhny Novgorod, 23 Gagarin prospect, Nizhny Novgorod, 603950, RUSSIA 2 Institute for Physics of Microstructures of Russian Academy of Science, GSP-105, Nizhny Novgorod, 603950, RUSSIA ABSTRACT Red/near-infrared photoluminescence (PL) of silicon irradiated by ions for wide dose range is investigated. The results are presented obtained for doses near amorphization threshold, where PL is associated with the formation of composite structure composed of nanocrystals (quantum dots) embedded into amorphized matrix and for doses that are strongly larger than amorphization threshold. The PL in this case is caused by formation of nanocrystals due to recrystallization of amorphous layer and penetration of stresses behind the border of this layer. INTRODUCTION Recently [1,2], a new (very simple) method of the formation of silicon-based nanostructures which can luminescence at room temperature in visible/near IR spectral range have been developed. The method consists in ion irradiation of silicon at conditions corresponding to fractional amorphization of surface layer, when the residual nanocrystals (NC) yet retain in amorphized region. Two photoluminescence (PL) bands were obtained: the short-wave – at ∼ 700 nm and long-wave – at ∼ 900 nm. It was assumed that first band is associated with NCs and second one – with amorphous phase. Such interpretation is based on quantum confinement model for which the a-Si plays the role of wide-band material for NCs as quantum dots. Later, it was established that very similar PL takes place not only for pointed doses (that precedes to full amorphization) but for much higher doses [3], as well, when the existence of residual NCs is hardly possible. The similarity of PL spectra for both dose regions has required more detailed study of ion irradiated silicon properties in wide dose range and additional discussion of PL mechanisms. EXPERIMENTAL Samples of p-Si (111) were irradiated with Kr+, Ge+ (80 keV), Ar+ (150 keV) and Ne+ (40 or 150 keV with doses Ф = 5⋅1014 – 6⋅1017 cm-2, j ≤ 5 µA/cm2). For low doses, some samples were annealed at 300°C (0.5 h). The PL was measured at room temperature by Ar laser (λ = 488 nm) excitation. For noise reduction spectra were processed by using frequency filtration method. The ESR spectra measurements were carried out by RE-1306 spectrometer at 77 K. Etching of irradiated silicon layers was produced in 40% HF acid or in of HNO3:HF solution. The surface topography was investigated on scanning probe microscope (SPM) TopoMetrix TMX-2100
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Accurex in contact mode with use of silicon nitride probes. Electron diffraction method was employed to stu
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