A hypothesis based on the model that explains the resistance change effect of resistive random access memory by redox reaction is proposed. This hypothesis leads to the conclusion that the relationship between the polarity of the applied bias voltage and the resultant resistance change in p-type semiconductors is opposite to that for n-type semiconductors. The bias polarity dependence of the resultant resistance change in ZnO and Ga-doped ZnO (GZO), which are n-type semiconductors, and that in NiO, which is a p-type semiconductor, were investigated using conducting atomic force microscopy. Opposite bias polarity was confirmed to induce GZO and NiO into the same resistance state, which is consistent with the hypothesis.

An orange-emitting, long-persistent phosphor, Ca2Si5normalN8:Eu2+,Tm3+ , was developed. Afterglow of this phosphor decays more slowly than that of the conventional red-emitting, long-persistent phosphor, normalY2normalO2S:Eu3+,Ti,Mg . After 420 nm excitation, the afterglow luminance is initially lower, but, after 8 min, gets higher than luminance of normalY2normalO2S:Eu3+,Ti,Mg . Long afterglow results from electron traps formed by Tm3+ at the Ca2+ site. The origin of two main thermoluminescence glow peaks at 220 and 350 K is discussed based on their dependence on Eu or Tm concentration and Ca/Si atomic ratio. Increased thermoluminescence intensity is observed by excitation in Eu2+ 4f-5d transition at room temperature followed by the fundamental absorption of the host at low temperature.

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Rare-earth oxyapatites MLn 4 Si 3 O 13 (M=Ca, Sr, Ba Ln=La, Gd) have been proposed as a new plasma display panel (PDP) host material to overcome the problems of Zn 2 SiO 4 :Mn commercial green phosphor, such as luminance degradation and poor surface charge. Tb-doped MLn 4 Si 3 O 13 phosphor powders show a green luminescence with the CIE color coordinate (x, y) = (0.337, 0.562). The PL excitation band lies continuously in the wavelength region from 130 to 260 nm. The photoluminescence (PL) peak intensity of SrGd 4 Si 3 O 13 :Tb is comparable with that of Zn 2 SiO 4 :Mn. The phosphor is a candidate for a green PDP phosphor for Xe 2 excitation.