Infrared Spectroscopy and Structures of Boron - Doped Silicon Clusters ( Si n B m , n = 3 − 8 , m = 1 − 2 )

Binary nanoclusters are of great interest for understanding fundamental phenomena related to applied materials science. Herein, neutral silicon-rich silicon−boron clusters (SinBm, n = 3−8, m = 1−2) are characterized by means of resonant infrared-ultraviolet two-color ionization (IR-UV2CI) spectroscopy, mass spectrometry, and quantum chemical calculations. Global energy optimizations are employed to find the most stable SinBm structures. By comparing the IR-UV2CI spectrum with the calculated linear IR absorption spectra of the corresponding lowenergy isomers, the geometries of the observed SinBm clusters are determined. Based on this structural information, different physical properties of the detected SinBm clusters such as charge distributions and ionization energies are investigated. Natural bond orbital analysis shows that significant negative charge (∼−1e) is localized at the boron atom(s). As the B−B bond is stronger than the B−Si and Si−Si bonds, boron segregation is observed for SinBm clusters with m = 2.