When researchers at the University of Texas at Dallas were heating a material of molybdenum ditelluride, they accidentally created the tiniest US flag ever.
At just a couple of nanometers wide (thousands of times thinner than a human hair), the Old Glory's stars were actually nanowires composed of six atoms of molybdenum surrounded by six atoms of tellurium, which were created from the parent molybdenum-tellurium 2D layer.
From UT Dallas:
“We wanted to understand the thermal stability of this particular material,” Kim said. “We thought it was a good candidate for next-generation nanoelectronics. Out of curiosity, we set out to see whether it would be stable above room temperature.”
When they increased the temperature to above 450 degrees Celsius, two things happened.
“First, we saw a new pattern begin to emerge that was aesthetically pleasing to the eye,” Kim said. Across the surface of the sample, the repeating rows, or stripes, of molybdenum ditelluride layers began to transform into shapes that looked like tiny six-pointed stars, or flowers with six petals.
The material was transitioning into hexa-molybdenum hexa-telluride, a one-dimensional wire-like structure. The cross section of the new material is a structure consisting of six central atoms of molybdenum surrounded by six atoms of tellurium.
As the phase transition progressed, part of the sample was still “stripes” and part had become “stars.” The team thought the pattern looked like a United States flag. They made a false-color version with a blue field behind the stars and half of the stripes colored red, to make a “nanoflag.”
Graduate students Qingxiao Wang (left) and Hui Zhu (right) next to the nanoflag as shown on the computer screens.