Ye Gao-Xiang

Formation Mechanism and Orderly Structures of an Iron Film System Deposited on Silicone Oil Surfaces

A new iron film system, deposited on silicone oil surfaces by vapour phase deposition method, has been fabricated and its formation mechanism as well as orderly structures has been studied. It is found that the formation mechanism of the films obeys a two-stage growth model, which is similar to that of the other metallic films on liquid substrates. Large and orderly structures are observed in the continuous iron films. The experiments show that the orderly spatial structures result from the local material gathering in these nearly free sustained films.

Condensation Behavior of Ag Aggregates on Liquid Surfaces

We report a condensation behavior of silver aggregates on silicone oil surfaces. The deposited Ag atoms diffuse and aggregate on the oil surface, and then form granular clusters and ramified islands. The apparent Ag coverage of the total area increases linearly with the nominal film thickness h for h < 0.9 nm. However, the coverage exhibits a fluctuation behavior for 1.0 nm < h < 2.5 nm. it is found that the anomalous behavior of the coverage is resulted from a characteristic material condensation process in the aggregates.

Unperturbed dimensions of atactic poly(dibenzyl itaconate)s

The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.

Kinetic Roughening with Surface Diffusion: Crossover from Ramified Aggregates to Continuous Films on Liquid Surfaces

Ramified iron aggregates are fabricated on silicone oil surface by thermal evaporation method at room temperature and the crossover from ramified aggregates to continuous films is studied by atomic force microscopy. It is shown that the aggregates are composed of numerous granules with the average diameter around 34 nm. The dynamic scaling analysis shows that the growth exponent β= 0.23 ±0.02 and the roughness exponent α evolves from 0.65 to 0.42 with the nominal film thickness, indicating a roughening behavior transfer may exist during the growth process. The physical interpretation for the scaling behavior is presented.

Structural and Critical Behaviors of Ag Rough Films Deposited on Liquid Substrates

A new Ag rough film system, deposited on silicone oil surfaces by rf-magnetron sputtering method, has been fabricated. The chrysanthemum-like surface morphology at micron length scale is observed. It is proposed that the anomalous critical behavior mainly results from the relative shift between the Ag atom clusters and the substrate. The discussion of the deposition mechanism is also presented.

AFM Study on the Formation Mechanism and Microstructure of Ni Atomic Aggregates on Liquid Substrates

We study the formation mechanism and microstructure of nickel (Ni) atomic aggregates on the silicone oil surfaces by atomic force microscopy (AFM). Initially, the deposited atoms nucleate and form the compact clusters on the liquid surfaces. Then they perform Brownian motion and adhere upon impact. Finally the branched aggregates are formed. The Ni aggregates exhibit granular structure. The mean size of the granularities in the aggregates is of the order of 10 nm and it decreases with the nominal film thickness. The experiment shows that the Ni aggregates perform a directional diffusion towards the sample edge. The interpretation for this phenomenon is presented.

Formations of fractal islands aggregated with discs in Gaussian distribution on nonlattice substrates

The growth mechanism of fractal islands on a two-dimensional nonlattice substrate with periodic boundary conditions has been investigated by using Monte Carlo technique. Results show that the fractal dimension df of the final ramified islands is almost independent of the diffusion step length, mobility and rigid rotation of the islands. The characteristics of the size distribution of the discs in an island do not change the dimension df of the island. However, we find that df increases linearly with the surface coverage ρ of the system and its slope decreases with the increase of the mean diameter of the discs.

Critical size of iron nanoparticles on liquid substrates

We study the iron atomic aggregates deposited on silicone oil surfaces by using atomic force microscopy. The aggregates are composed of disk-shaped nanoparticles with the mean diameter Φc 31.7 nm and height Hc 4.5 nm, which are nearly independent of the nominal film thickness. The experiment shows that a material condensation process must occur in the nanoparticles during the growth period. The anomalous phenomenon is explained.

Morphology and microstructure of Ag islands of aggregated atoms on oil surfaces

The morphology evolution of silver islands on silicone oil surfaces is measured and the microstructure of the islands is studied. The deposited Ag atoms diffuse and aggregate on the oil surface and then Ag islands with the width of the order of 102-nm form. After the samples are removed from the vacuum chamber, the immediate measurement shows that the apparent Ag coverage of the total area decays with the magnitude up to (23.0±3.8)% in few minutes. In the following two hours, the samples are kept in the ambient atmosphere and several unexpected results are detected: 1) as the topological structure of the islands evolves, the total area of each island decreases gradually and the maximum decrement measured is around 20%; 2) if an island breaks and becomes two small pieces, the total area decreases obviously; 3) however, if two small islands meet and stick together, a sudden increment of the total area is observed. These phenomena, mirroring the evolution process of the island microstructure, are resulted from both the diffusion of the atoms and the combination of the defects inside the islands.

Microstructure and Magnetic Domains of Iron Films on Liquid Surfaces

Iron (Fe) films with a thickness ranging from 1.0 nm to 80.0 nm are deposited on silicone oil surfaces by a vapor phase deposition method. The films with a thickness of d < 2.0 nm do not exhibit planar morphology but ramified aggregates instead. Magnetic force microscopy studies for the Fe films (10.0 nm ≤ d ≤ 80.0 nm) show that the domain wall structure is widespread and irregularly shaped and the oscillation phase shift Δθ, which records as the magnetic force image, changes from 0.29° to 0.81°. Correspondingly, the magnetic force gradient varies from 1.4 × 10−3 to 4.0 × 10−3 N/m, respectively. In our measurement, the characteristic domain walls, such as Bloch walls, Neel walls and cross-tie walls, are not observed in the film system clearly.