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To clarify vacuum effects on fatigue crack growth in freestanding metallic thin films, experiments were conducted on approximately 500‐nm‐thick copper films inside a field emission scanning electron microscope. Fatigue crack growth accompanied by intrusion/extrusion formation occurred in vacuum, and da/dN was smaller than in air in the middle‐ΔK region (ΔK ≈ 1.7‐3.1 MPam1/2). Conversely, in the low‐ΔK region (ΔK ≲ 1.7 MPam1/2), da/dN was larger in vacuum than in air. Further, fatigue crack growth in vacuum occurred below the fatigue threshold in air (ΔKth,air). A nonpropagating crack after reaching ΔKth,air continued to propagate in vacuum when the environment changed from air to vacuum. This indicates that fatigue crack growth resistance is smaller in vacuum than in air under the same effective driving force. The fatigue damage area near the crack paths in vacuum in the low‐ΔK region became wider, suggesting that the nucleation of fatigue damage was enhanced in vacuum.

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The structure of nonstoichiometric silicon oxide (SiO_ x ) has been studied by the methods of highresolution X-ray photoelectron spectroscopy and fundamental optical-absorption spectroscopy. The conductivity of SiO_ x ( x = 1.4 and 1.6) films has been measured in a wide range of electric fields and temperatures. Experimental data are described in terms of the proposed SiO_ x structure model based on the concept of fluctuating chemical composition leading to nanoscale fluctuations in the electric potential. The maximum amplitude of potential fluctuations amounts to 2.6 eV for electrons and 3.8 eV for holes. In the framework of this model, the observed conductivity of SiO_ x is described by the Shklovskii–Efros theory of percolation in inhomogeneous media. The characteristic spatial scale of potential fluctuations in SiO_ x films is about 3 nm. The electron-percolation energy in SiO_1.4 and SiO_1.6 films is estimated to be 0.5 and 0.8 eV, respectively.

Experimental technique of in situ FESEM fatigue/creep experiments has been developed to investigate the mechanisms of fatigue/creep crack propagation in freestanding metallic nano-films. We developed an in situ FESEM fatigue/creep dual-mode testing machine which was able to conduct the fatigue or creep experiments inside the FESEM chamber. The testing machine has the capability to apply high-frequency cyclic load or constant load under load-control conditions to the freestanding metallic nano-film specimens. In situ FESEM observations of the fatigue crack propagation in 523-nm-thick freestanding copper (Cu) films confirmed that intrusions/extrusions were formed ahead of the fatigue crack tip in the lower stress intensity factor range (K), and the size of the intrusions/extrusions increased as the number of stress cycles increased. The fatigue crack then propagated preferentially through these intrusions/extrusions. In the higher K, the fatigue crack propagated in tensile fracture mode. In addition, in situ FESEM observations of the creep crack propagation in 391-nm-thick freestanding gold (Au) films confirmed that voids were formed ahead of the creep crack tip, and the crack then propagated by coalescence of the voids and the crack. These results indicate that this experimental technique is effective to clarify the mechanisms and mechanics of fatigue/creep crack propagation in freestanding nano-films.