In this study, we characterize the structural properties of the nanoparticles (NPs) formed in different dielectric matrices namely: Si₃N₄ and SiO_xN_y by ion implantation followed by thermal annealing. Two different types of Si₃N₄ matrix, PECVD and LPCVD, were examined. Also, SiO_xN_y with different stoichiometries, close to pure SiO₂ and Si₃N₄,were examined. This study focuses on understanding the role of the host matrix on the structural properties and size evolution of embedded NPs. TEM, Raman and RBS measurements were performed to study the size, vibrational and compositional properties of NPs. Furthermore, the structure and local environment of NPs were investigated using x-ray absorption spectroscopy.

Semiconductor nanoparticles (NPs) embedded in a dielectric matrix are of technological interest because of their ability to emit light and store charge.  Ge NPs have been investigated for novel optoelectronic and non-volatile memory devices. Intensive research has focused on the structural and vibrational properties of Ge NPs embedded in SiO₂. These properties are typically size dependent and highly reliant on the host matrix. An alternative dielectric matrix commonly used in the fabrication of micro-electronic and optoelectronic devices is Si₃N₄. Chemical vapor deposition (CVD), in particular low pressure (LPCVD) and plasma enhanced (PECVD) techniques, are the main methods for depositing an amorphous Si₃N₄ film. Many studies have been performed on the properties of Si NPs embedded in LPCVD and PECVD Si₃N₄. However, few studies have focused on the structural properties of Ge NPs embedded in Si₃N₄ by ion implantation. Therefore, a better understanding of the matrix role on the properties of the NPs could lead to the fabrication of more efficient optoelectronic devices. Here, we discuss the various structural properties and phase transformation of both the embedded NPs and the host matrix.

Ge ions were implanted into amorphous PECVD and LPCVD Si₃N₄ and SiO_xN_y thin layers. The implantations were performed at 400 °C. Samples were subsequently annealed at different temperatures (700, 900, and 1100 °C) for 1 hour under a N₂ atmosphere.

Different types and sizes of NPs were obtained depending on the host matrix. The EXAFS study confirms the size-dependent properties of NPs, which vary significantly depending on the host matrices. The most striking difference between LPCVD and PECVD was the formation of both SiGe and Ge NPs. NP formation in SiO_xN_y matrices were significantly different from pure SiO₂ or Si₃N₄, an effect that is attributed to the role on N on Ge diffusivity.  Finally, we report an impurity induced phase transition (crystallization) for Si₃N₄ matrices (LPCVD and PECVD) during annealing at 1100^oC. We investigate and isolate different mechanisms involved with this low temperature crystallization process.

Our research has made inroads into understanding the role of the matrix and thermal annealing on properties of Ge NPs.