“...our research found an ultimate important characteristic—the smallest mark size. This result predicts many promising features for these memory devices.”

The topic is very current, as it is related to optical and electrical phase changes, which are now commercialized as DVDs (digital versatile disks) and PRAMs (phase-change random access memories). Also, our research found an ultimate important characteristic—the smallest mark size. This result predicts many promising features for these memory devices.

  Does it describe a new discovery, methodology, or synthesis of knowledge?

The ultimate future direction of our research has been discovered and is being interpreted using a physical model.

  Could you summarize the significance of your paper in layman's terms?

Our study is related to DVDs, which are now utilized as video and computer memories. The most recent system has a memory capacity of 50 GB/disk, which is governed by the size, 150 nm in diameter, of bit marks written in Ge-Sb-Te films. Naturally, for obtaining higher capacities, we must write smaller marks.

Then, what is the smallest mark which can be produced in film at room temperature? We have demonstrated, using an electrical phase-change technique, that the smallest is ~10 nm, or more modestly, 50 nm, which can increase the memory capacity by 9 times or more. We have also given a thermo-dynamical interpretation to the problem as to why the minimal mark is ~10 nm.

  How did you become involved in this research, and were there any obstacles along the way?

There is a long story. When I was a student, around 1970, I studied semiconductors such as Ge and InSb. When I got a job, my interest shifted to more elusive and exotic materials, and since 1975, I have worked on chalcogenide glass, which is a kind of amorphous semiconductor. DVD material such as Ge-Sb-Te is one of these.

In addition, around 1995, I wanted to add an atmosphere of "nano" to my studies for educational and other purposes. Then, I found an interesting topic to be DVD-related. The most apparent obstacles have included the limited amount of experimental facilities and a limited amount of researchers within this discipline.

  Are there any social or political implications for your research?

Yes. As mentioned above, there is an extensive amount of DVD-related research and development.