Stress Evolution of Ge Nanocrystals in Dielectric Matrices.

5 years ago

Stress Evolution of Ge Nanocrystals in Dielectric Matrices.

Rosario Raciti, Rahim Bahariqushchi, Emre Gür, Eren Kalay, Atilla Aydınlı, Ahmet Emre Kasapoğlu, Meltem Sezen, Salvatore Salvatore Mirabella

Germanium nanocrystals (Ge NCs) embedded in single and multilayer silicon oxide and silicon nitride matrices have been synthesized using plasma enhanced chemical vapor deposition (PECVD) followed by conventional furnace annealing (CFA) or rapid thermal processing (RTP) in N2 ambient. Compositions of the films were determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). Formation of nanocrystals under suitable process conditions were observed with high resolution transmission electron microscope (HRTEM) micrographs and Raman spectroscopy. Stress measurements have been done using Raman shifts of the Ge optical phonon line at 300.7 cm-1. Effect of the embedding matrix and annealing methods on Ge nanocrystal formation have been investigated. In addition to Ge NCs in single layer samples, stress on Ge NCs in multilayer samples was also analyzed. Multilayers of Ge NCs in silicon nitride matrix separated by dielectric buffer layers to control size and density of NCs were fabricated. Multilayers consist of SiNy: Ge ultrathin films sandwiched between either SiO2 or Si3N4 by proper choice of buffer materials. We demonstrated that it is possible to tune stress state of Ge NCs from compressive to tensile, a desirable property for optoelectronic applications. We also observed that there is a correlation between stress and crystallization threshold in which the compressive stress enhances the crystallization, while the tensile stress suppresses the process.

Publisher URL: http://doi.org/10.1088/1361-6528/aaaffa

DOI: 10.1088/1361-6528/aaaffa