First-order Raman spectra of hydrogenated nanocrystalline silicon (nc:Si:H) films show unexpected features in their optical vibrational modes for crystallites with sizes ranging from 2 to 6 nm. Two size-dependent spectral regions, one with the stronger intensity peaking at 505–509 cm−1 and another a shoulder-like band between 512 and 517 cm−1, are clearly identified using a detailed line-shape analysis and the strong phonon confinement model. The strong size dependence of the relative integrated intensities of the two bands suggests that the modification of the vibrational spectra can be attributed to an effect induced by the atomic vibrations from the near-surface region of the nanocrystals.
A new type of hydrogenated nanocrystalline Si film with high electronic conductivity is investigated by means of transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Nearly parallel columnar structures with growth orientation along the [110] zone axis of Si are found from cross-sectional TEM images of the film. HRTEM observation reveals that these columns are composed of nanocrystallites (3–6 nm size) and dendritelike growth morphology, while in the region between columns the texture consists of smaller sized (<3 nm) grains embedded in a hydrogenated amorphous Si. The volume fraction of the crystalline component is about 58% measured by Raman spectroscopy. The conductivity of the film is very high, about 10−1 (Ω cm)−1. It is considered that this is directly related to the characteristic structure of the film.
A HREM study on the defects in the high‐Tc superconductor YBaCuO discovered recently is reported. It is found that there are large amounts of local lattice distortions, point defects, and misarrangements of Y or Ba atoms within the specimens observed. HREM images of grain boundaries and interfaces between the crystalline state and so‐called intermediate‐ordered state are obtained. It is found that the tripled period lattices are distorted, especially near the interfaces.
The microstructure of as‐deposited granular CoAg thin films is investigated by high resolution electron microscopy. Our results suggest that the thin films consist of two separate phases. The crystallized Co particles, with nonuniform size and preferential lattice orientations 〈110〉, 〈111〉, 〈112〉, 〈100〉 in the direction of the film surface normal, are directly observed. There is a tendency that two connecting grains have two groups of parallel lattice planes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.