Neodymium in hydrogenated amorphous silicon sub-nitrides (a-SiNx:H) / Neodimio em sub-nitretos de silicio amorfo hidrogenado (a-SiNx:H)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In this work, we report a study of the photoluminescence (PL) optimization of a-SiNx:Hthin films prepared by RF co-sputtering. The PL was investigated as a function of nitrogen and neodymium concentrations. We observed that the Nd ions are excited through the amorphous matrix. The excitation mechanism is more efficient in samples where the optical gap E04 is twice the 4 I 9/2 ® 3 F 3/2 transition of Nd ions, showing an excitation process mostly dominated by non-radiative recombinations of electrons from conduction band tails into dangling bonds. The most adequate model to describe the excitation of Nd 3+ ions is the DRAE model (Defect Related Auger Excitation), originally proposed for Er 3+ in a-Si:H. We study the PL of the samples with thermal annealing at temperatures up to 700°C. Micro Raman and HRTEM (High Resolution Transmission Electron Microscopy) measurements show that small structural changes (presence of Si and/or Si3 N4 nano crystals) appear when no more PL is detectable. This implies that the annealing enhances the PL mainly modifying the chemical neighborhood of the Nd3+ ions to be more favorable for the 4f transitions. In samples with planar waveguide geometry, we performed optical gain measurements, PL lifetime as a function of temperature and excitation power. The results showed optical gain only at low temperatures and under excitation intensities higher than 5 kW/cm 2. The behavior of the PL as a function of excitation intensity shows a change in its derivate also at an excitation power higher than 5 kW/cm 2 . These results allow us to consider this material as promising for applications in integrated optical amplifiers

ASSUNTO(S)

luminescence photonics fotonica neodymium compounds silicon nitride luminescencia compostos de neodimio terras raras nitreto de silicio rare earths

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