Alp Findikoglu

Doctor Silicon

February / March 06 By: John R. Grizz Deal Volume 4 Number 1

Print this Article

E-mail this Article

Superconductors are materials that have little or no resistance to electric current at certain temperatures. Lack of resistance means higher efficiency for transmitting electricity, theoretically 100 percent for dc currents.

Superconductors have other unique properties, such as expelling magnetic fields, leading to magnetic levitation, useful to eliminate friction for bullet trains.
Since their discovery in 1911 by Dutch physicist Heike Kamerlingh Onnes of Leiden University, superconductive materials have been both a solution looking for an application, and a rich source of discovery by the world's top scientists.

Alp Findikoglu is one such scientist at Los Alamos, who has adapted discoveries from superconductivity to create the next generation of solar cells and flexible displays. He works at the Superconductivity Technology Center (STC) and met with TechComm to discuss his work.

How did you come to study superconductive materials at Los Alamos?
I came as a postdoctoral fellow ten tears ago, initially to work on high-temperature superconductors. Over the years I became interested in technological applications of various other materials, using techniques we have learned as part of our superconductivity research. Recently I focused on using these techniques to make better semiconductors.

Give us an example of a real world use of superconducting material.
Today, for high-temperature superconductors, the biggest application is in power transmission. This means taking power from the generator to the main distribution point using superconducting cables, so that much less energy is lost in transit. The government is interested in sponsoring this activity and right now there are companies who are making cables for this purpose. This innovation alone could save billions per year in electrical losses.

So how would this apply to semiconductors?
The key to making high quality wires and cables from high-temperature superconductors turned out to be controlling the properties of very small grains of these materials, organized into thin films in many layers. It turns out that our techniques also allow us to create highly organized silicon films quite cheaply, and that these films have the attributes of expensive silicon crystals.

What are the benefits of this cheap but well organized silicon?
Our process, aligned crystalline silicon (AC-Si), creates a film structure that allows for the efficient flow of electricity through silicon. In addition, we can manufacture these AC-Si films in large sheets and rolls using fairly conventional manufacturing techniques.

I imagine the "AC" in "AC-Si" is the key?
Exactly. AC is short for aligned crystalline, which is the key to creating high-performing Si films. This alignment in the film is achieved by using a special buffer layer under the Si film. That special buffer layer is created by using ion beams.

Sounds very James Bond or Austin Powers—€¦didn't one of them almost get killed by an ion beam?
No. You're thinking of the laser Goldfinger used on James Bond. An ion beam is simply a stream of ions moving in the same direction. We use the ion beam to order a deposited film, the buffer layer, on a desired substrate as part of the manufacturing process. We use argon ions to bombard the film surface. The atomic species at such high energies impart their energy to the growing film. This effect leads to preferential etching of the material but also some preferential alignment of the crystals within the material.

So it's sort of like engraving it?
The technical term is "sputtering." Sputtering is well known but in most other uses of the ions for sputtering, one does not care much about the directional effect. In our case, we pay particular attention to the direction at which the ions come and hit the surface. This creates the texturing effect and the well-ordered, aligned crystal growth in the buffer layer. This aligned crystalline structure in the buffer layer is then transferred to the Si film in the manufacturing process.

You indicated this AC-Si process lead you to some very interesting product ideas.
Yes. The fact that we can manufacture this highly organized, highly efficient silicon-based material cheaply and in large sheets and rolls leads one to think about highly efficient, single-crystal semiconductors that could be used in such applications as gigantic solar cells, that would say cover the roof of the Kingdome and generate electricity, or flexible televisions the size of a building.

I see the advantages of manufacturing large and efficient semiconductors, but what about going the other direction?
You mean smaller? Sure, one of the most expensive components in a mobile computing or telephonic device is the display. Those displays are also very fragile. AC-Si solves both of these problems.

The ramifications of your invention are enormous.
Silicon is currently the most important material in the semiconductor industry. It has many applications and in most of these applications, the technologies are evolving toward higher performance and lower cost. These are divergent paths. To achieve the lowest cost, industry tends to use amorphous silicon. In amorphous silicon, the material itself has no crystalline order. These materials are relatively easy to make and they are relatively versatile because one can put amorphous silicon films on almost any substrate.
The other development branch requires really highly ordered silicon, where the highest possible performance is needed. The ideal case is single crystal silicon. What we have created with AC-Si has the benefits of single crystal silicon (for the highest performance) and the lower cost found in amorphous silicon.

So what's next? What do you do with this innovation?
We're already working with one of the world's largest display manufacturers, and looking for other collaboration opportunities with partners in the solar energy business. This is just the very beginning of our work with industry.

What about the interaction with industry? How can partners work with Los Alamos?
Since the day I came to Los Alamos, I have never felt the closed nature of the lab; for many people who work here it is a creative and open environment with the output being very practical applications for industry and government. The STC is outside the fence in the Los Alamos Research Park, making us very accessible to firms outside the Los Alamos family.

John R. Grizz Deal is Visiting Entrepreneur at Los Alamos National Laboratory.