Does photoinduced structural change by beta-rhombohedral boron occur at room temperature?

beta-rhombohedral boron (beta-B) is an intriguing solid among the elements. The crystal structure of beta-B is widely accepted as a complex structure based on the B-12 clusters, and with a lot of intrinsic structural defects. In the last decade, beta-B was proved to be the only elemental semiconductor that exhibits the self-compensation property accompanied by changing structural defects during atom doping. Moreover, it is reported that various physical properties of beta-B change discontinuously around 550 K, which may originate from defect diffusion [S. Hoffmann and H. Werheit, Solid State Sciences 14, 1572 (2012)]. We previously reported that a volume expansion of about 1.5% takes place above this temperature (between 650 K and 850 K). On the other hand, this expanded structure is stable in dark conditions for more than 4.5 months. Light irradiation at room temperature reverses the volume back to the initial state, and a possible scenario will be discussed in this paper.

Automated summary

beta-B is an intriguing solid with a complex crystal structure based on B-12 clusters and intrinsic structural defects. It is the only elemental semiconductor that exhibits self-compensation property during atom doping. Various physical properties of beta-B change discontinuously around 550K, possibly due to defect diffusion. We previously found a volume expansion of about 1.5% above this temperature, and it can be reversed by light irradiation at room temperature.