Electron transport experiments for molecular devices have been evaluated by using single-molecule bridging nano-and/or sub-nanoscale junctions between two metallic electrodes. Thus, although several techniques have been developed to make the junctions, many of the actual junction surfaces structure cannot be defined. Ideally, it is better to use a welldefined single-metal surface to simplify transport characterization in the simple structure modeling. If the clear crystal surface with well-defined crystal orientation can be used for the single-molecule characteristics, more rapid scientific progress can be expected. Then, a molecular-scale space "nanogap" deformed with two facetedge Au crystals is the ideal tool for a metal−molecule junction to realize molecular electronics devices. For fabricating such a molecular-scale space nanogap, we developed a feedback-controlled electromigration (FBEM) combined with alternate polarity voltage operation (inversed-FBEM: iFBEM). The nanogaps fabricated via iFBEM under low temperature and an H 2 atmosphere were confirmed as two single-domain Au crystals in direct observation via field-emission scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. It can be expected that distributions of molecular angles adsorbed on the electrode surface and the variability of molecular devices are both suppressed.

We investigated the thermal robustness of a nonvolatile memory using polycrystalline platinum (Pt) nanogap electrodes. The temperature dependences of resistance states were evaluated from room temperature to 773 K. At high temperatures, the resistance of the high-resistance state (HRS) was slightly altered as the temperature changed. This slight alteration could be neglected, and the thermal robustness was improved by etching a SiO2 layer just under the nanogap. This indicated that the thermal alteration was caused by current leakage through the SiO2 layer. The nonvolatile memory employing Pt nanogaps is expected to be potentially useful as a thermally robust memory up to 773 K.