A transparent metal

A figure showing the crystal structure of strontium vanadate (orange) and calcium vanadate (blue). The red dots are oxygen atoms arranged in 8 octohedra surrounding a single strontium or calcium atom. Vanadium atoms can be seen inside each octahedron. Credit: Lei Zhang/Penn State

Just two weeks ago I posted a news of an ingenious way to use nano pillars of transparent silicon to make light reaching the silicon semiconducting material in a photovoltaic cell through the metal electrode increasing the cell yield. That solution was a way to circumvent the fact that metals block light.

Actually not all metals are blocking light. Indium Tin Oxide (ITO) is an example. It is widely used for conductors in LCD display. The problem is that Indium is rare and its price has kept increasing, along with the increase demand of screens. So, as smartphone and tablet chips get cheaper their screens get more expensive and are now representing close to 40% of a tablet and smartphone price.

Now I see that material scientists and engineers at Penn University have discovered a new metal architecture that is also transparent. They have used a class of metals called "correlated" in which electrons flow like a liquid (in normal metals they flow like gas).

They have experimented with strontium vanadate and calcium vanadate, creating thin films, 10nm thick. They have turned out to have very good conductivity and be optically transparent.

In these materials the electrostatic interactions among electrons is very large, in comparison to their kinetic energy, and this interaction makes them behave like a liquid. In turns this lead to less reflection of light still showing a very good conductivity.

The breaking point is the cost: 5% of the cost of indium tin oxide.

The next step is to fine tune an industrial manufacturing process. Once this is done the researchers feel these new materials could replace ITO as conductor in displays as well as in photovoltaic cells.

Author - Roberto Saracco

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