Van Vuong Hoang

Recently the GexOy nanomaterials have been studying intensively due to their interesting electronic materials, which have many particular properties and applications in nanotechnology and nano-devices fabrication. Much work has been done on many different synthesis methods and their properties of Ge and GexOy nanomaterials. However, the effects of the different Ge substrate surface states and Au catalyst layer thicknesses on the formation of different forms/morphologies of nanomaterials (nanowires, nanorods, nanoparticles, and nanocrystals particularly) have not yet to be discussed more in detail. This paper outlines the synthesis methods to grow the different GexOy nanomaterials on the different Ge surface states at different Au catalyst layer thicknesses such as mechanically polished surface, deep Chemical etched surface, chemical polishing surface, and initial rough surface. The morphological, and structural properties of GexOy nanomaterials have been investigated using SEM, EDX, and TEM techniques. The formation of different morphological, and structural properties of different GexOy nanomaterials grown have been explained by the effects of the Au/Ge/O droplets/clusters formation situations and surface defects on the Ge substrate surface caused. The growth mechanisms have been explained by the model of the VLS growth method with the Oxide Assist Growth mechanism. The results showed that the effects of the different Ge substrate surface states and Au catalyst layers’ thickness strongly influence the formation of GexOy materials in terms of the sizes, structures, and percentages of elements. The results of the controllable different GexOy nanomaterials have many significant meanings for both theoretical and practical applications in nanomaterials and nano-device fabrication.

In this study, strain measurement can be analyzed in sub-10nm SiGe layer (~7 nm) grown on [100] Si substrate by chemical vapor deposition at the nanoscale level. The measurement technique is based on transmission electron microscopy (TEM), in which high-resolution transmission electron microscopy (HRTEM) image is combined with the image processing of geometric phase analysis (GPA) software. In this case, GPA analyzes the HRTEM images formed at the [011] zone axis to obtain information about strain maps along the [100] growth direction of the nanoscale SiGe region. The strain analyzed in the SiGe layer is within 1.6-2.9% with high precision and high spatial resolution.