SrF2 Films Research Articles

Growth of single crystal SrF2(001)/GaAs(001) structures by molecular beam epitaxy

Epitaxial SrF2 layers were grown onto GaAs (001) at T>250 °C by molecular beam epitaxy. The dominant growth mechanism appears to be by three-dimensional island growth although significant ordering of the surface occurs on annealing the layers at T>400 °C. Growth of epitaxial GaAs (001) at 540 °C by molecular beam epitaxy onto the SrF2 films has also been demonstrated. The results suggest that stacked, single crystal, alternating layers of GaAs (001) and SrF2 (001) should be amenable to growth by molecular beam epitaxy.

Heteroepitaxial Growth of Group-IIa-Fluoride Films on Si Substrates

Growth conditions and structures of vacuum-evaporated heteroepitaxial CaF2, SrF2 and BaF2 films on (111) and (100) oriented Si substrates have been investigated. Single crystal CaF2 films are grown on both Si(111) and (100) substrates at temperatures of 600–800°C and 500–600°C, respectively. CaF2 films on Si(111) have crystal orientations rotated 180° about the normal to the substrate surface. SrF2 and BaF2 films of good crystalline quality are grown on Si(111) at temperatures around 600°C, but are composed of two types of crystallites which have orientations either idential to those of the substrate or rotated 180° on the substrate surface about the surface normal. SrF2 and BaF2 films grown on Si(100) contain (111) oriented crystallites, and, in an extreme case, completely (111) oriented BaF2 films were grown on Si(100).

Epitaxial growth of elemental semiconductor films onto silicide/Si and fluoride/Si structures

Epitaxial growth of Si and Ge films onto silicide/Si and fluoride/Si structures has been reviewed. Growth conditions of epitaxial silicide films such as Pd2Si, CoSi2, and NiSi2 films on Si substrates, as well as heteroepitaxial Si/CoSi2/Si structures, are presented. Crystalline quality and structural properties of the films have been analyzed by Rutherford backscattering and channeling spectroscopy, transmission electron microscopy, optical microscopy, and x-ray diffraction analysis. Growth conditions of fluoride films such as CaF2, SrF2, and BaF2 films on Si substrates are also presented. For the growth of Si and Ge overlayers on the fluoride/Si structure, the lattice matching condition between the semiconductor and fluoride films has approximately been satisfied by use of pure and mixed fluoride films.

Epitaxial relations in group-IIa fluoride/Si(111) heterostructures

CaF2, SrF2, BaF2, and mixed (Ca,Sr)F2 films have been grown epitaxially on Si (111) substrates by vacuum evaporation. The epitaxial relation between these fluoride films and the substrates has been investigated by ion channeling analysis. Both the CaF2 and SrF2 films prefer to have orientations rotated 180° about the normal to the substrate surface. In contrast, the vast majority of (Ca,Sr)F2 films have orientations identical to those of the substrate, and the BaF2 film is composed of a mixture of the two. Analysis was also made on a Si/CaF2/Si(111) double heterostructure, which showed that the top Si film is again rotated 180° about the normal to the underlying CaF2 surface.

Epitaxial Growth of Fluoride Films on Silicon Substrates

ABSTRACTGrowth conditions and structural properties of vacuumevaporated fluoride films on Si(lll) and (100) substrates are reviewed. It has been found that single crystal CaF2 films are grown on both (111) and (100) substrates at temperatures of 600–800°C and 500–600°C, respectively. It has also been found that SrF2 and BaF2 films of good crystalline quality are grown on Si(lll) at temperatures around 600°C, but that the films grown on Si(100) contain (111) oriented crystallites. In epitaxial growth of a Si/CaF2/Si structure, a novel growth method is presented, in which a thin Si layer is deposited at room temperature prior to deposition of a thick Si film at elevated temperature. Investigations on growth of mixed fluoride films, radiation damage in CaF2 films, and epitaxial relations in the fluoride/Si heterostructures are also presented.

Spectra of Electronic Excitations in CaF2, SrF2, and BaF2 in the 8 to 150 eV Range

AbstractThe characteristic energy losses suffered by a 20 keV electron beam through CaF2, SrF2, and BaF2 films have been measured with a magnetic spectrograph. From the energy loss function — Im ε−1, optical constants are calculated by means of Kramers‐Kronig analysis in the 8 to 40 eV range and are compared with the available reflectance data, especially those obtained with synchrotron radiation. The observed structure is tentatively explained for the three compounds, following a band model based upon symmetry considerations. The origin of the energy losses corresponding to the soft X‐ray range is also briefly discussed.