ABSTRACTEpitaxial GaN films have been grown at temperatures between 600 and 900 °C by reactive-ion molecular-beam epitaxy. Ga was provided by evaporation from an effusion cell while nitrogen was supplied from a low-energy, single-grid, ion source. The average energy per accelerated N incident at the growing film surface was ≈ 19 eV. Films deposited on Al2O3(0112) and MgO(100)l×l substrates had wurtzite (a-GaN) and metastable zincblende (α-GaN) structures, respectively. The lattice constants were a = 0.3192 nm and c = 0.5196 nm for α;-GaN and a = 0.4531 nm for β -GaN. The room-temperature optical bandgap Eg of zincblende GaN, 3.30 eV, was found to be 0.11 eV lower than that of the hexagonal polymorph α-GaN. All films were n-type with electron carrier concentrations which decreased from 4×1018 to 8×1013 cm−3 with increasing incident N2+/Ga flux ratios between 0.63 and 3.9. Resistivities <106Ω-cm were achieved.
AbstractA combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-xCx alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1-xCx solid solutions were formed up to x = 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1-x,Cx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ∼28% for Ei, = 100 eV and ∼18% for Ei = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.
Tuning the transport and magnetism in a Cr–Bi2Se3topological insulator by Sb doping