Home >Opinion >Hope from honeycombs

Graphene came first, then slicene, germanene, tienene and phospherene. As the physical limits of miniaturized silicon—and the demand for computers that would make today’s appear like snails—force a search for exotic, virtually invisible materials, science is back to its atomic basics.

Barely two years after silicene was first created in a laboratory—with some questioning if the material even existed—a team of scientists at the University of Texas at Austin last week announced the creation of a one-atom thick sheet of silicon atoms and used it as a rudimentary transistor.

Working with a team of Italian scientists, the Texans worked around silicene’s greatest problem: exposed to air, it falls apart within two minutes, revealing the fragility of its diaphanous sheets and the enormous difficulty of building it into a working transistor. The silicene built in Texas demonstrated something its more widely celebrated cousin, graphene—a material otherwise known to be a very efficient conductor of electricity—has not managed: the ability to craft electrodes on it, enabling electrons to hop, a critical function in relaying a current and, by extension, enabling the binary language (logic operations) of computing—on and off, 1 and 0.

Silicene also scores over graphene because it is made from silicon, the material that underlies the vast, global computer-manufacturing industry. Graphene is built from a gossamer sheet of carbon (an elemental building block of everything on earth, from human beings to oil), and is so strong that a square metre, one-atom thin graphene hammock weighing as much as a cat’s whisker could support a 4-kg cat.

It does not currently allow logic operations, but graphene is more stable than silicene and easier to make. Graphene can be peeled off a block of graphite using adhesive tape, while unstable silicene, the journal Nature reported earlier this week, must be created from a hot mist of silicon atoms deposited within a protective sandwich of silver and alumina in a powerful vacuum.

But silicine, if its formidable production hurdles could be overcome, would not require the world to use an entirely new material, as graphene would.

Across the Pacific Ocean at the Aix-Marseille University in France, another team of scientists hopes to imitate the ingenious process of creating silicene with another transient material, germanene.

Like the other two, germanene—created last year jointly by French, Spanish and German scientists—is not something that nature produces. In other words, they exist nowhere in the universe except in the laboratories that make them. Unlike graphene whose atoms naturally take a hexagonal, honeycomb shape, germanene and silicene must be forced into honeycombs in those hot, airless chambers.

First proposed in the form of a research paper in the journal Physical Review Letters in 2009, germanene—unlike its cousins—could not even be synthesized until 2014.

Making germanene required the same high-temperature, powerful-vacuum technique used with silicene—except the silver part of the sandwich failed. What worked as a foundation was gold (a Chinese team working on a parallel track used platinum), on which researchers deposited a one-atom layer of germanium, the base material.

Carbon, silicon and germanium follow one another on the periodic table. Scientists are already talking about using the next element on the table, tin, to make tienene, another theoretical option in building tomorrow’s computers.

Another candidate for powerful transistors and semiconductors that could be used in superthin, flexible electronics is phosphorene. Its base material is black phosphorus, which until last year could not be isolated in single layers; once it was, it could be peeled off into layers two or three atoms thick, using sticky tape, in much the same way as graphene from graphite. Currently, phospherene suffers from the same instability as silicene: it cannot tolerate the air we breathe. However, a paper in the journal Nano Letters, three months ago, described a process that encapsulates it in alumina—not unlike the methods used to create silicine and germanene—to keep it stable in air for up to two weeks.

The development of phosphorene is so new that papers are relatively scarce and the name does not show up in some scientific search engines. On the other hand, what is hard to keep up with is the oldest kid on the new-computing materials block, graphene.

In 2013, this column noted that thousands of papers had been written and hundreds of patent applications filed since two Russian emigres at the University of Manchester in the UK were awarded the 2010 Nobel for creating graphene.

New discoveries come thick and fast, some reporting workarounds to graphene’s chief problem—the inability to allow the electron-hopping so critical to computer language. Last week, a team of physicists at the University of California-Riverside said they had found a way to induce magnetism in graphene, potentially opening up its use for a new class of data-storage devices. The old cousin isn’t giving up just yet.

Samar Halarnkar is editor of, a data-driven, public-interest journalism non-profit. He also writes the column Our Daily Bread in Mint Lounge.

Comments are welcome at To read Samar Halarnkar’s previous columns, go to

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