The columnar morphologies commonly found in all vapor‐deposited thin films prepared under low mobility conditions have been classified by several variations of what have been termed structure zone models. Such morphological structures are found to have a strong similarity in shape and form over six orders of magnitude in film thickness and three orders of magnitude in magnification for films of a given thickness. Thick (45‐mm) pyrolytic graphite films are shown to be a good demonstration of the continuous growth evolution of conical‐shaped units. Due to competition for growth each cone eventually goes through a death stage. A model based upon these general structural observations is presented and is shown to be a geometric construction similar to a Sierpinski gasket. The origin of this morphology seems to be the natural clustering which occurs due to the random process of ballistic aggregation.

Geometry of thin‐film morphology

Structural studies of plasma-deposited a-Si:H are presented that show that a major class of defect is an anisotropic density fluctuation. Studies of the hydrogen environment suggest that an inhomogeneous hydrogen distribution is associated with these fluctuations. From considerations of the deposition chemistry and nucleation theory a model is proposed to describe the film growth process and its relationship to defects.

Growth morphology and defects in plasma-deposited a-Si:H films

https://psec.uchicago.edu/Papers/Electron_and_light_emission_from_island_metal_films_and_generation_of_hot_electrons_in_nanopartic_0.pdf

Electron and light emission from island metal films and generation of hot electrons in nanoparticles

Classical magnetic dipolar interactions can make significant contributions to magnetic anisotropy in amorphous ferrimagnetic alloys with slight structural anisotropies on either atomic or microstructural scales. Simple expressions have been derived for this magnetic anisotropy in terms of structural anisotropy parameters, p, V, and Δx. For an alloy with atomic‐scale structural anisotropy (pair ordering), p is a measure of alignment of unlike nearest‐neighbor pairs. For an alloy with aligned elongated composition inhomogeneities, V is the volume fraction of inhomogeneities and Δx is the composition difference (atom fraction) between the inhomogeneities and their surroundings. Accounting for magnetic anisotropy observed experimentally in bias‐sputtered GdCo‐based alloy films solely in terms of pair ordering and classical dipolar interactions requires p∼0.015. Accounting for the anisotropy solely in terms of composition inhomogeneities requires Δx∼0.1 for V=0.5. Although such atomic‐scale structural anisotro...

Magnetic anisotropy from dipolar interactions in amorphous ferrimagnetic alloys

Structural studies were performed on Si films formed by chemical‐vapor deposition on SiO2 films using silane under pressures below 150 mTorr and temperatures below 640 °C. The mode of growth of these films was found pressure dependent. Films grown at pressures below 10 mTorr were found to have a columnar structure with a (001) preferred orientation ending at a curved surface. The radius of the crystallites increases and the radius of curvature of their free surface decreases as the pressure decreases, while the converse is true for the temperature dependence. Transition from this mode is associated with diminishing of the capillarity effects. For pressures above 10 mTorr the structure is striated with a 〈111〉 twin texture almost perpendicular to the substrate. At pressures above 100 mTorr the structure is similar to the previous one but with a tufty appearance. This structure is associated with compressive and dilatational strain. The size of initial crystallites was found also pressure dependent increasi...

Structural studies of low‐temperature low‐pressure chemical deposited polycrystalline silicon

Computer simulation of the post-nucleation growth of thin amorphous germanium films

The very early stage of formation of amorphous germanium films by vapour deposition is simulated. A simplified model is considered. In the post-nucleation stage particles are formed by an atom-by-atom building process. Re-evaporation of adatoms and migration along the edge of already formed particles are taken into account. An upper limit is obtained for the maximum edge migration distance for which irregularly shaped particles can still be formed within our model. From the results it is concluded that, during the formation of thin evaporated amorphous germanium films which show a supernetwork with irregularly shaped particles of high density, self-surface diffusion or diffusion along the edge of a particle cannot be significant.

Computer simulation of the post-nucleation growth of thin amorphous germanium films.

Structural anomalies disturbing measurement of the quantum size effect

An inhomogeneous structure such as the one known for evaporated amorphous Ge films has also been found in evaporated amorphous Si and sputtered CoGd films. This structure is characterized by a coherent supernetwork (SN) of low density material filling the channels between the rodlike high density regions. The properties and implications of the SN and the possible mechanisms for its development are discussed.

H. Sugawara

Papers

Computer simulation of the post-nucleation growth of thin amorphous germanium films

Computer simulation of the post-nucleation growth of thin amorphous germanium films.

Structural anomalies disturbing measurement of the quantum size effect

Some remarks on the structure and formation of thin amorphous films