American scientists have developed a way to create a new form of silicon with a unique hexagonal structure.
Elements can take various crystalline forms – allotropes, depending on the arrangement of their atoms. They can have completely different properties. For example, carbon can exist in the form of two-dimensional sheets in the form of graphene, stacks of these sheets – graphite, or cubic lattices – diamond.
Interest in hexagonal silicon dates back to the 1960s due to the possibility of tunable electronic properties that could improve performance beyond the cubic shape.
In 2014, a team at the Carnegie Institution developed a new silicon allotrope, Si₂₄, which consisted of sheets of silicon arranged in rings of five, six, and eight atoms. The breaks in the middle of the rings can form one-dimensional channels for the movement of other atoms. This is useful for storing or filtering energy, scientists say.
In a new study, scientists have developed a method for converting Si₂₄ into another allotrope. Heating the Si₂₄ crystals caused the thin sheets to line up in a hexagonal shape on four repeating layers. By the way, this is why the new structure was named 4H-silicon. It is noted that uncharacteristic stable bulk crystals from such a material were created for the first time.
How exactly should the new silicon structure be applied? Scientists are confident that the discovery will lead to improvements in the operation of transistors or photovoltaic energy systems.
The research is published in the journal Physical Review Letters.