Quan-Lin Ye

An internal stress pattern in free standing films

We report a sinusoid appearance of cracks existing in a continuous nickel (Ni) film system deposited on silicone oil surfaces. The sinusoid cracks start from the sample edges or from other cracks, then their oscillatory amplitudes decrease gradually as they extend and finally disappear. One crack may bifurcate into two or three cracks, or two cracks may coalesce harmoniously. The sinusoid appearance of the cracks represents a sinusoid stress pattern in the Ni films, which mainly results from the characteristic boundary condition and interactions among the atoms in these free sustained films.

Anomalous hysteresis properties of iron films deposited on liquid surfaces

A nearly free sustained iron film system, deposited on silicone oil surfaces by vapor-phase deposition method, has been fabricated and its crystal structure as well as magnetic properties has been studied. Both the temperature-dependent coercivity Hc(T) and exchange anisotropy field HE(T) of the iron films possess a maximum peak around the critical temperature Tcrit=10–15 and 4K, respectively. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase below freezing temperature Tf=30–50K.

Structural and electrical properties of an Au film system deposited on silicone oil surfaces

An Au thin film system, deposited on silicone oil surfaces by the thermal deposition method, has been fabricated and its structure as well as electrical properties has been studied. A web-shaped characteristic surface morphology of the films is observed. The dc sheet resistance R of the metal films on the liquid surfaces is measured during and after deposition in situ by the four-probe method. The time dependence of the sheet resistance can be explained in terms of the film growth mechanism on the oil surface. The anomalous I–V characteristics of the film system can be interpreted as a competition among the local Joule heating, hopping and tunnelling effects. It is found that the dc third-harmonic coefficient B0 and the zero-power resistance R0 satisfy the power-law relation B0 R02+w and the exponent w is close to zero. This result indicates that the hopping and tunnelling effects in the samples are much stronger than those of the other film systems. We also find Im R0−β with β = 0.79 ± 0.08 and Im B0−γ with γ = 0.49 ± 0.07, where Im is the critical current. The physical origins of the phenomena are discussed.

Growth mechanism of ordered stress-induced patterns in Al films deposited on silicone oil surfaces

An optical microscope study of large spatially ordered patterns in an aluminium (Al) film system deposited on silicone oil surfaces is presented in this letter. The ordered patterns, namely bands, are composed of a large number of rectangle-shaped domains, which are evolved from small triangle-shaped domains with size less than 1??m in vacuum conditions. The bands start from the film edge and then extend towards the central region of the sample. Both the length and width of the rectangle-shaped domains in each band decrease approximately linearly as the band extends. It is pointed out that the appearance of the bands represents the distribution of the internal stress in the Al films. The theoretical analysis shows that due to the characteristic boundary condition and interactions between the metallic films and the liquid substrates, the nearly free sustained Al films may contain a series of sinusoidal stress distributions with different amplitudes and frequencies, and their composition results in the formation of the ordered stress-induced patterns.