06 Å (100), which are similar (2.69 Å (200), 3.09 Å (111), and 1.89 Å (220)) to those reported in the literature [43]. This suggests that this as-deposited Gd2O3 film is polycrystalline. The energy diffraction X-ray spectroscopy (EDX) spectra confirm the presence of expected elements Ir, Gd, W, and O in respective layers, as shown in Figure 4b. The X-ray photoelectron spectroscopy (XPS) spectra of Gd 3d 5/2 and Gd2O3 3d 5/2 peaks are located at 1,186.73 and 1,189 eV, respectively (Figure 5), which proves a Gd-rich Gd2O3 film, i.e., GdO x . The height ratio of

Gd/Gd2O3 is 1:0.93, and area ratio of Gd/Gd2O3 is 1:0.89. Arhen et al. [44] reported the same chemical bonding states at 1,186 click here and 1,188 eV for the Gd 3d 5/2 and Gd2O3 3d 5/2 peaks, respectively. This suggests that the as-deposited Gd2O3 film is a Gd-rich GdO x film. It is known that the grain boundary has more defects or weak Gd-O bonds. This suggests that the Gd-O bonds will break easily under external bias, and more oxygen vacancies will be created. The conducting filament will be formed through the grain boundaries. However, the nanotips on the W BE will help the structure have repeatable resistive switching memory characteristics. Figure 4 TEM image and EDX spectra. (a) Cross-sectional selleck products TEM image of IrO x /GdO x /W structure. Selleck C646 Polycrystalline GdO x film is observed.

(b) EDX spectra show the Ir, Gd, W, and O elements. Figure 5 XPS characteristics of the Gd 2 O 3 films. XPS spectra of the Gd 3d and Gd2O3 3d core-level electrons. Figure 6a shows the typical current–voltage (I-V) characteristics of a IrO x /GdO x /W RRAM device in via-hole structure, as illustrated schematically in Figure 3. The pristine device shows very low leakage current (arrow 1). In order to activate 4-Aminobutyrate aminotransferase the resistive switching, an initial soft breakdown process (forming) was carried out by applying negative bias on the TE. The negative forming

voltage (V form) is -6.4 V to initiate the resistive switching with a current compliance (CC) of 100 μA. During the formation process, the Gd-O bonds break, which creates oxygen vacancy as well as oxygen vacancy filament, and set LRS. In consequence, the oxygen ions (O2–) will be migrated toward the W BE and react partially at the BE. Bipolar I-V characteristics are indicated by arrows 2 to 4. The SET (V SET) and RESET voltages (V RESET) are found to be -2.2 and +2 V, respectively. To elucidate the conduction mechanism of the IrO x /GdO x /W memory device, the I-V curves are plotted in log-log scale, as shown in Figure 6b. Both LRS and HRS show ohmic conduction behaviors with a slope approximately 1.1. The LRS is ohmic because of the conducting filament formation in the GdO x layer. The HRS is also ohmic because the electrons move through the defects of the GdO x grain boundary. The ohmic behavior of the HRS was also reported by Jung et al.