Crystalline Semiconductor Boron Quantum Dots.

Zero-dimensional boron structures have always been the focus of theoretical research owing to their abundant phase structures and special properties. Boron clusters have been reported extensively by combining structure searching theories and photoelectron spectroscopy (PES) experiments; however, crystalline boron quantum dots (BQDs) have rarely been reported. Here, we report the preparation of large-scale and uniform crystalline semiconductor BQDs from the expanded bulk boron powders via a facile and efficient probe ultrasonic approach in the acetonitrile solution. The obtained BQDs have 2.46 nm average lateral size and 2.81 nm thickness. Optical measurements demonstrate that a strong quantum confinement effect occurs in the BQDs, implying the increase of the band gap from 1.80 eV for the corresponding bulk to 2.46 eV for the BQDs. By injecting the BQDs into poly(vinylpyrrolidone) as an active layer, a BQD-based memory device is fabricated that shows a rewriteable nonvolatile memory effect with a low transition voltage of down to 0.5 V and a high on/off switching ratio of 103 as well as a good stability.