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GST (GeSbTe) thin films were deposited on glass substrates by electron beam evaporation; Ni was used as the top and bottom electrodes. The I–V (current–voltage) characteristic of the phase change memory (PCM) cell was measured; results showed an electrical threshold switching characteristic for the sample with a threshold voltage of 3.08 V. The threshold switching is attributed to the formation of conductive filaments in the amorphous matrix. Current-voltage spectra which were obtained by C-AFM show that the GST thin film switching from amorphous to the crystalline phase occurs at 1.51 V. C-AFM was used to fabricate crystalline nanoarrays on the sample surface and examine the electrical properties of arrays. In the I–V measurements by C-AFM, when the applied voltage is higher than threshold voltage, conducting nanofilaments with average sizes of 15–60 nm were formed and crystallized spots with current signals were observed. Different times of I–V spectroscopies were applied on thin films to investigate the electrical properties of films during the phase change process. C-AFM results show that as the times of I–V spectroscopies increased, the morphology of crystallized spots changed from bump to pit; the sizes of conductive nanofilaments and detected current signals increased. These results can be attributed to the energy induced by Joule heating dissipated to surrounding films increases with the increasing times of I–V spectroscopies.

Highly-pure iron powder was covered on porous silicon for fabricating semiconducting β-FeSi2 structures. X-ray diffraction and Raman scattering results confirm the formation of pure-phase β-FeSi2 after high-temperature annealing at 1100°C and then long-time persistence at 900°C. Scanning electron microscope observations reveal that large-size (>μm) β-FeSi2 grains mainly form in the pores of porous silicon and some nanocrystals grow on local surfaces. The temperature-dependent photoluminescence spectra disclose that the observed ∼1.54 μm emission arises from free exciton recombination, which is confirmed via the activation energy (0.25 eV) measurement. Our method provides a way to synthesize single-phase β-FeSi2 materials.