Development of single-electron optical memory

本研究的一个主要目的是研制一种单电子光存储器。实现这一目的的关键要素是用于库仑岛的有机分子、用于器件配置的多层结构和作为量子现象的单电子隧穿。在传统的单电子存储器的情况下，电子的传输由外部电场控制。同时，在我们的装置中，电子可以通过光照射来传输。为此，采用光致变色分子作为绝缘体/分子/绝缘体多层膜中的库仑岛。通过光致异构化可以改变分子的HOMO-LUMO能级，并且可以通过不同波长的光照射来重构。在我们的研究中，我们分别采用卟啉衍生物作为分子，SiO2和CaF 2薄膜作为隧道势垒，高掺杂Si衬底和Au薄膜作为电极。发现I-V曲线存在周期性的阶梯，并在光照下发生位移。重要的是，I-V曲线的移动是可逆的，即移动后的I-V曲线返回到原来的。这些结果提供了证据，卟啉分子可以作为库仑岛的电子隧穿和我们的器件结构具有单电子光存储的潜力。

A main purpose of this study is to develop a single-electron optical memory. Key elements for this purpose are organic molecules for Coulomb islands multi-layer structure for device configuration and single-electron tunneling as a quantum phenomenon. In the case of conventional single-electron memories, transportation of electrons is controlled by external electric field. Meanwhile, electron can be transported by light irradiation in our device. For this purpose, photochromic molecules are employed for Coulomb islands in the insulator/molecule/insulator multilayers. HOMO-LUMO levels of the molecule can be changed through the photo-isomerization, which can be reconstituted by another light irradiation with different wavelength. In our study, we employed a porphyrin derivative for a molecule, SiO2 and CaF2 thin films for tunneling barriers, highly-doped Si substrate and Au thin film for electrodes, respectively. We found a periodic staircase in I-V curve and its shift caused by light irradiation. Importantly, the shift in I-V curves was reversible, i.e. the shifted I-V curve returned to the original one after the These results give evidences that the porphyrin molecule can act as Coulomb islands for electron tunneling and our device configuration have a potential of single-electron optical memory.