In the big data era, data storage is one of the cores in the whole information chain, which includes production, transfer, sharing, and finally processing. Over the years, the growth of data volume has been explosive. Today, various storage services need memories with higher density and capacity. Moreover, information storage in the big data applications should be green, safe, and long life. The storage density of memories was largely enhanced in recent years because of the rapid development of nanotechnology. The minimum feature size of optical, magnetic, and electrical memories is...