Abstract

X-ray irradiation- and annealing-induced structural changes in undoped hydrogenated amorphous silicon (a-Si:H) and pure amorphous silicon (a-Si) have been investigated in detail by X-ray photoemission spectroscopy (XPS). The irradiation-induced shifts of both the Si 2s and Si 2p peaks of a-Si:H are found to be unstable even at room temperature. They can be reversed by annealing, following a stretched exponential time dependence with a lower activation energy than that for the metastable changes in electronic properties (Staebler–Wronski effect). The absence of metastable XPS changes in a-Si suggests that hydrogen may be actively involved in the X-ray irradiation-induced structural changes. Our present results suggest that these structural changes may be an independent metastable phenomenon or a precursor process of metastable defect creation.

Abstract

We have investigated the changes in quasi-elastic (QE) relaxation behavior in a low-frequency range 10–80 cm⁻¹ near stiffness transition in Ge_xSe_1−x glasses using temperature-programmed Raman scattering technique. We confirm that the QE contribution originates from the fast (β) process of relaxation. Since the QE intensity depends on glass composition, the origin of the relaxational modes is traced to floppy modes. We attribute the relaxation modes mainly to the damping or jumping motions of the rotating Se_n segments, which could be regarded as the microscopic origin of floppy modes in the Se-contained network glasses.

Abstract

Recently, we reported on reversible non-volatile memory effects in nitrogen doped tetrahedral amorphous carbon (ta-C:N) thin films, and the properties of 1-bit memory cells fabricated to utilize such effects. In this paper, we investigate the electrical stability of ta-C:N devices with respect to the effects of many repetitive read, write, and erase cycles on their ON and OFF state resistances.

Graphical abstract

Diffraction pattern of a crystallite of La_1/3Zr₂(PO₄)₃ showing the transformation under the electron beam (a) at the beginning and (b) at the end.