Scientists have developed a way to engineer new forms of matter by stacking different types of layers, each only one atom thick, on top of one another. These composite materials are called metamaterials, and many exhibit surprising and useful properties that no material found in nature possesses.
In the lab, the stacking of layers is done by using Scotch tape to peel off single-atomic layers from solids and then putting them together under a microscope. Industrial-scale techniques are also under development. There are hundreds of different atomic layers to choose from, each with unique properties, so the possible combinations are countless.
The potential applications of these “atomic Lego” materials are just as wide-ranging. In the structure shown in Fig. 1, the top layer, tungsten disulfide, is a good light absorber. The bottom layer, graphene, is a good electrical conductor. This is a perfect combination for solar cells, which must absorb light energy and convert it to electricity. When we made and tested this structure, we found that, because the material is so thin, energy absorbed by the top layer is transferred to the bottom layer in one picosecond (that’s one-trillionth of a second!) with nearly 100% efficiency.