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In this paper, we report on optimizing the conditions for subsequently growingsingle-phase films of calcium monosilicide (CaSi) and calcium disilicide (CaSi2) on single-crystal silicon by reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). The temperature range for the growth of CaSi films (400–500 °C) was determined, as well as the temperature range (600–680 °C) for the growth of CaSi2 films on silicon with three orientations: (111), (100) and (110). The minimum temperatures for the epitaxial growth of CaSi films by the RDE method and CaSi2 films by the MBE method were determined, amounting to, respectively, T = 475 °C and T = 640 °C. An increase in the ratio of Ca to Si deposition rates to 26 made it possible to grow a large-block CaSi2 epitaxial film with the hR6 structure by the MBE method at T = 680 °C. Raman spectra and reflection spectra from single-phase epitaxial CaSi and CaSi2 films on silicon were recorded and identified for the first time. The correspondence between the experimental reflection spectra and the theoretically calculated reflection spectra in terms of amplitude and peak positions at photon energies of 0.1–6.5 eV has been established. Single-phase CaSi and CaSi2 films retain transparency in the photon energy range 0.4–1.2 eV.

This paper reports the computational study of phosphorus-doped boron clusters PBn/PBn–/PBn+ (n = 4–8). First, a global search and optimization of these clusters were performed to determine the stable structures. We used density functional theory (DFT) methods and ab initio calculations to study the stability of the atomic clusters and to explore the arrangement of stable structures. We found that the lowest energy structures of the smaller phosphorus-doped boron clusters tend to form planar or quasi-planar structures. As additional boron atoms are added to the smallest structures, the boron atoms expand in a zigzag arrangement or in a net-like manner, and the phosphorus atom is arranged on the periphery. For larger structures with seven or eight boron atoms, an unusual umbrella-like structure appears. We calculated the binding energy as well as other energies to study cluster stability. We calculated the ionization energy, electron affinity, and the HOMO–LUMO gaps. In addition, we used the adaptive natural density partitioning program to perform bond analysis so that we have a comprehensive understanding of the bonding. In order to have a suitable connection with the experiment, we simulated the infrared and photoelectron spectra.