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The properties of bulk contribution to sum-frequency generation reflected and transmitted by a finite layer in a multilayer system are described. The leading term is essentially due to the processes emitting in the transmission geometry, in particular for macroscopic layers. For such transmission processes, phase mismatch leads to the production of interference fringes when the layer thickness or a wavelength is tuned, which may be mistaken for resonant processes inside or at the surface of the material. Experimental evidence of such fringes measured from centrosymmetric bulks is provided for a diamond window in the far infrared and suggested for other materials in previously published data. The existence of a stationary point in the phase mismatch, related to the group velocity mismatch, is shown to be the source of another pseudo-resonant process in centrosymmetric calcium and barium fluorides, for which theoretical predictions reproduce the experimental observations. [ABSTRACT FROM AUTHOR]

Heavy-atom alkaline earth monofluoride molecules are considered as prospective systems to study spatial parity or spatial parity and time-reversal symmetry violating effects such as the nuclear anapole moment or the electron electric dipole moment. A comprehensive and highly accurate theoretical study of the electronic structure properties and transition energies in such systems can simplify the preparation and interpretation of the experiments. However, almost no attempts to calculate quantum electrodynamics (QED) effects' contribution into characteristics of these neutral heavy-atom molecules have been performed. Recently, we have formulated and implemented such an approach to calculate QED contributions to transition energies of molecules [L. V. Skripnikov, J. Chem. Phys. 154, 201101 (2021)]. In this paper, we perform a benchmark theoretical study of the transition energies in the Ba+ cation and BaF molecule. The deviation of the calculated values from the experimental ones is of the order 10 cm−1 and is more than an order of magnitude better than the "chemical accuracy," 350 cm−1. The achievement of such an agreement has been provided, in particular, by the inclusion of the QED effects. The latter appeared to be not less important than the high-order correlation effects beyond the coupled cluster with single, double, and perturbative triple cluster amplitude level. We compare the role of QED effects for transition energies with heavier molecules—RaF and E120F, where E120 is the superheavy Z = 120 homolog of Ra. [ABSTRACT FROM AUTHOR]

A measurement of the magnitude of the electric dipole moment of the electron (eEDM) larger than that predicted by the Standard Model (SM) of particle physics is expected to have a huge impact on the search for physics beyond the SM. Polar diatomic molecules containing heavy elements experience enhanced sensitivity to parity (P) and time-reversal (T)-violating phenomena, such as the eEDM and the scalar–pseudoscalar (S–PS) interaction between the nucleons and the electrons, and are thus promising candidates for measurements. The NL-eEDM collaboration is preparing an experiment to measure the eEDM and S–PS interaction in a slow beam of cold BaF molecules [P. Aggarwal et al., Eur. Phys. J. D 72, 197 (2018)]. Accurate knowledge of the electronic structure parameters, Wd and Ws, connecting the eEDM and the S–PS interaction to the measurable energy shifts is crucial for the interpretation of these measurements. In this work, we use the finite field relativistic coupled cluster approach to calculate the Wd and Ws parameters in the ground state of the BaF molecule. Special attention was paid to providing a reliable theoretical uncertainty estimate based on investigations of the basis set, electron correlation, relativistic effects, and geometry. Our recommended values of the two parameters, including conservative uncertainty estimates, are 3.13 ± 0.12 × 1 0 24 Hz e cm for Wd and 8.29 ± 0.12 kHz for Ws. [ABSTRACT FROM AUTHOR]

The layered van der Waals compounds ( MnBi 2 Te 4)( Bi 2 Te 3) were recently established as the first intrinsic magnetic topological insulators. We report a study on the epitaxial growth of (MnBi 2 Te 4) m (Bi 2 Te 3) n films based on the co-deposition of MnTe and Bi 2 Te 3 on BaF 2 (111) substrates. X-ray diffraction and scanning transmission electron microscopy evidence the formation of multilayers of stacked MnBi 2 Te 4 septuple layers and Bi 2 Te 3 quintuple layers with a predominance of MnBi 2 Te 4. The elemental composition and morphology of the films is further characterized by x-ray photoemission spectroscopy and atomic force microscopy. X-ray magnetic circular and linear dichroism spectra are comparable to those obtained for MnBi 2 Te 4 single crystals and confirm antiferromagnetic order in the films. [ABSTRACT FROM AUTHOR]

Cobalt-metal-fluoride nanogranular films exhibit high electrical resistivity (ρ) and high permittivity (ɛ′) as well as high magnetic moments, making them potentially suitable for applications in low power magnetoelectronic devices at a high-frequency range. Here, we present the DC/AC magnetoelectric effect of high-ρ Cox-(BaF2)1 − x nanogranular films that are constituted of Co nanogranules of about 2 nm in diameter in an insulating BaF2 crystal. Under the application of magnetic field (H), we observed the ρ variations (Δρ/ρ0) of 2.0%–5.9% for x ranging 0.19–0.54 and the ɛ′ variations (Δɛ/ ε 0 ′ ) of 0.7%–6.0% for x ranging 0.19–0.42, respectively. These magnetically controllable ρ and ɛ′ are realized based on the spin-dependent quantum-mechanical charge transfer. The Cox-(BaF2)1 − x film for x = 0.42 possesses high ρ, while remaining in a notably high Δɛ/ ε 0 ′ of 6% at a megahertz frequency range. This study demonstrates a candidate of high-resistive magnetoelectric nanogranular films, which may bring prosperous applications in high-frequency magnetoelectric devices with low power consumption. [ABSTRACT FROM AUTHOR]

The NL-eEDM collaboration is building an experimental setup to search for the permanent electric dipole moment of the electron in a slow beam of cold barium fluoride molecules [NL-eEDM Collaboration, Eur. Phys. J. D 72, 197 (2018)]. Knowledge of the molecular properties of BaF is thus needed to plan the measurements and, in particular, to determine the optimal laser-cooling scheme. Accurate and reliable theoretical predictions of these properties require the incorporation of both high-order correlation and relativistic effects in the calculations. In this work, theoretical investigations of the ground and lowest excited states of BaF and its lighter homologs, CaF and SrF, are carried out in the framework of the relativistic Fock-space coupled cluster and multireference configuration interaction methods. Using the calculated molecular properties, we determine the Franck-Condon factors (FCFs) for the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition, which was successfully used for cooling CaF and SrF and is now considered for BaF. For all three species, the FCFs are found to be highly diagonal. Calculations are also performed for the B 2 Σ 1 / 2 + → X 2 Σ 1 / 2 + transition recently exploited for laser-cooling of CaF; it is shown that this transition is not suitable for laser-cooling of BaF, due to the nondiagonal nature of the FCFs in this system. Special attention is given to the properties of the A′2Δ state, which in the case of BaF causes a leak channel, in contrast to CaF and SrF species where this state is energetically above the excited states used in laser-cooling. We also present the dipole moments of the ground and excited states of the three molecules and the transition dipole moments (TDMs) between the different states. Finally, using the calculated FCFs and TDMs, we determine that the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition is suitable for transverse cooling in BaF. [ABSTRACT FROM AUTHOR]

Four-wave mixing processes are ubiquitous in ultrafast optics and the determination of the coefficients of the χ(3) tensor is thus essential. We introduce a novel time-resolved ultrafast spectroscopic method to characterize the third-order nonlinearity on the femtosecond time-scale. This approach, coined as "nonlinear chirped interferometry," makes use of the variation of the optical group delay of a transmitted probe under the effect of an intense pump pulse in the nonlinear medium of interest. The observable is the spectral interference between the probe and a reference pulse sampled upstream and the metric is the transient swing of the probe group delay. We show that the detected signal is enhanced when the pulses are weakly chirped, and that, although interferometric, the method is intrinsically less sensitive to environmental phase fluctuations and drifts. By chirping adequately the reference pulse, the transient frequency shift of the probe pulses is also detected in the time domain and the detected nonlinear signal is enhanced. Nonlinear phase shifts as low as 10 mrad, corresponding to a frequency shift of 30 GHz, i.e., 0.01% of the carrier frequency, are detected without heterodyne detection or active phase-stabilization. The diagonal and/or non-diagonal terms of reference glasses (SiO2) and crystals (Al2O3, BaF2, CaF2) are characterized. The method is finally applied to measure the soft vibration mode of KTiOAsO4 (KTA). [ABSTRACT FROM AUTHOR]

A cross polarized wave (XPW) generation experiment with double BaF2 crystals in air was demonstrated with 120 µJ input pulse. A circular aperture was used to truncate the near field profile of the input beam and remove the outer part of the beam, and circularly symmetric beam profiles were generated at the BaF2 crystal positions. The measured focal spot size was close to the diffraction limit, and the energy stability of XPW was improved from ∼1.89% (without the aperture) to ∼0.67% (with the aperture). [ABSTRACT FROM AUTHOR]

Structural properties of topological insulator bismuth telluride filmsgrown epitaxially on (111) BaF2 with a fixed Bi2Te3 beam flux were systematically investigated as a function of substrate temperature and additional Te flux. A layer-by-layer growth mode is observed since the early stages of epitaxy and remains throughout the whole deposition. Composition of the epitaxialfilms produced here stays between Bi2Te3 and Bi4Te5, as determined from the comparison of the measured x-ray diffraction curves with calculations. The substrate temperature region, where the growth rate remains constant, is found to be the most appropriate to obtain ordered Bi2Te3films. Line width of the L = 18 Bi2Te3diffraction peaks as low as 140 arcsec was obtained, indicating high crystalline quality. Twinning domains density rises with increasing growth temperature and reducing Te extra flux. X-ray reflectivity curves of pure Bi2Te3films with thickness from 165 to 8 nm exhibited well defined interference fringes, evidencing homogeneous layers with smooth surface. Our results demonstrate that Bi2Te3films with very well controlled structural parameters can be obtained. High structural quality Bi2Te3films as thin as only eight quintuple layers grown here are promising candidates for intrinsic topological insulator. [ABSTRACT FROM AUTHOR]

We investigate the effects of deposition temperature on a crystal structure and electrical and optical properties of PbTe thin films sputtered on BaF2 (111). We observe that with the increase in deposition temperature, the grain size increases, and when it reaches 300 °C, the grain size reaches the maximum, and the preferred orientation begins to change. At 400 °C, the lattice mismatch rate decreases from 4.2% to 3.6% due to lattice contraction caused by reevaporation, and the conduction type changes from p-type dominated by a mismatch strain defect to n-type dominated by a Te vacancy. These changes lead to the interplay of various absorption mechanisms. We find that, in addition to the overall absorption coefficient curve significantly changing with deposition temperature, more importantly, the contribution of various internal absorption mechanisms to the below bandgap absorption spectrum does no longer synchronize. Instead, the contribution of an acoustic phonon to free-carrier absorption (FCA) decreases, while the relative contribution of optical phonon, impurity, two-photon absorption (2PA), and three-photon absorption (3PA) increases. This regulation effect reaches its maximum at 300 °C, which of various absorption mechanisms at 300 °C are 6.3, 11.6, 4.4, and 14.7 times higher than that at 20 °C corresponding to an optical phonon, impurity, 2PA, and 3PA processes, respectively. These results indicate that it should be possible to regulate the FCA, 2PA, and 3PA processes by changing the deposition temperature, thus making them suitable for applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The dependence of X-ray excited luminescence intensity on BaF2 nanoparticle size was studied. A sharp decrease of self-trapped exciton luminescence intensity was observed when the nanoparticle size is less than 80 nm. The main mechanism of the luminescence quenching is caused by the escape of electrons from the nanoparticles. Escape of electrons from nanoparticles is confirmed by the considerable increase of luminescence intensity of the polystyrene scintillator with embedded BaF2 nanoparticles comparing with pure polystyrene scintillator. [ABSTRACT FROM AUTHOR]

The dependence of the amount of the BaF2 flux additive on the luminescence of Y2.95Al5O12:0.05Ce3+ phosphors was investigated. The integrated emission intensity of Y2.95Al5O12:0.05Ce3+ prepared without the flux was enhanced by 29% with the addition of BaF2 flux at the optimum amount of 6 wt. %. Such an enhancement can be attributed to the purer phase of Y3Al5O12 and the morphology change from the irregular shape to spherical shape with the smoother surface due to the flux. The morphology and luminescence of Y2.95Al5O12:0.05Ce3+ prepared with the 6 wt. % BaF2 flux additive (Sample II) were further compared with those of Y2.95Al5O12:0.05Ce3+ prepared with the 7 wt. % H3BO3 flux additive (Sample I). The particle size, particle shape, and integrated emission intensity (λex = 450 nm) of the former were found to be larger, more regular, and 6% higher than those of the latter. The difference in the morphology of Samples I and II, which led to the difference in the emission intensity and the external quantum efficiency, were well explained by the particle growth mechanism. [ABSTRACT FROM AUTHOR]

We study here the p-type doping of PbTe with BaF2. For the investigation, PbTe layers were grown on (111) BaF2 substrates by molecular beam epitaxy. The beam flux ratio between BaF2 and PbTe, defined as the nominal doping level, was varied from 0.02% to 1%. The hole density increases from 5×1017 to 1×1019 cm-3 as the doping level rises from 0.02% to 0.4% and saturates at p∼1019 cm-3 for higher levels. The saturation effect was attributed to self-compensation. The carrier concentration of all samples remained almost constant as the temperature was varied from 10 to 350 K, indicating that no thermal activation is present in the whole doping range. It suggests that the impurity level in PbTe doped with BaF2 remains resonant with the valence band, similar to the native defects behavior. The low-temperature mobility showed a pronounced reduction from 50 000 to 2 000 cm2/V s as the doping level rises from 0.02% to 1%, mainly due to the substantial increase in the hole concentration. For temperatures higher than 80 K, the mobility was essentially limited by phonon scattering. Our results demonstrate that a controlled p-type doping of PbTe with BaF2 can be obtained up to 1019 cm-3. [ABSTRACT FROM AUTHOR]

We study here the p-type doping of PbTe with BaF2. For the investigation, PbTe layers were grown on (111) BaF2 substrates by molecular beam epitaxy. The beam flux ratio between BaF2 and PbTe, defined as the nominal doping level, was varied from 0.02% to 1%. The hole density increases from 5×1017 to 1×1019 cm-3 as the doping level rises from 0.02% to 0.4% and saturates at p∼1019 cm-3 for higher levels. The saturation effect was attributed to self-compensation. The carrier concentration of all samples remained almost constant as the temperature was varied from 10 to 350 K, indicating that no thermal activation is present in the whole doping range. It suggests that the impurity level in PbTe doped with BaF2 remains resonant with the valence band, similar to the native defects behavior. The low-temperature mobility showed a pronounced reduction from 50 000 to 2 000 cm2/V s as the doping level rises from 0.02% to 1%, mainly due to the substantial increase in the hole concentration. For temperatures higher than 80 K, the mobility was essentially limited by phonon scattering. Our results demonstrate that a controlled p-type doping of PbTe with BaF2 can be obtained up to 1019 cm-3. [ABSTRACT FROM AUTHOR]

Physisorption of water on the (111) surface of barium fluoride is investigated using accurate intermolecular potentials. A revised version of the successful ASP-W2 water potential is developed together with a new potential describing the interaction between water and the barium fluoride surface. Isolated water molecules are found to have a binding energy of -39.8 kJ mol[sup -1]. Monolayer and multilayer coverages are also investigated and compared with previous experimental and theoretical work. We find no evidence to support epitaxial growth of ferroelectric ice on this surface and suggest reasons for this. [ABSTRACT FROM AUTHOR]

In this work, we present the results of photoconductivity measurements performed in the temperature range of 12 K–300 K on a 150 nm-thick Bi2Te3 film grown by molecular beam epitaxy on a (111) BaF2 substrate. A transition from negative to positive photoconductivity is found to occur around 125 K. Resistivity and Hall data measured under light and dark conditions qualitatively elucidate the observed phenomena. The Arrhenius plot of recombination times obtained from photoconductivity decay curves measured at different temperatures gives the activation energy associated with the bulk trap level. Using this activation energy as the effective trap potential, we calculated the generation and recombination rates as a function of temperature. The analysis provides a quantitative explanation that predicts the transition effect observed in the experiment. No evidence of contribution from surface states is found from the magnetoresistance curves measured at low temperatures. [ABSTRACT FROM AUTHOR]

When a Ne:BF3 sample is codeposited at approximately 5 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid deposit shows prominent absorptions of BF2. All three vibrational fundamentals and the ν1+ν3 combination band of BF2 isolated in solid neon are identified, and a normal coordinate analysis is conducted. In addition, infrared absorptions of the BF+3, BF+2, and BF-3 molecular ions are assigned, and the processes which occur when the solid deposit is exposed to visible and ultraviolet radiation are considered. [ABSTRACT FROM AUTHOR]

Presents a study of lead telluride on barium fluoride (111) using reflection high-energy electron diffraction (RHEED). Details of the experiment; RHEED intensity oscillations; Information on the substrate temperature dependence; Analysis of the RHEED oscillation data.

Presents a study that investigated the electron-stimulated desorption of fluorine from barium fluoride thin films deposited on silicon substrates. Background on the desorption mechanism; Methodology; Analysis of the Auger electron spectra and slow electron energy loss spectra of the samples.

Examines the epitaxial growth of barium fluoride on oriented gallium arsenide substrates as well as on thin intermediate oriented strontium-fluoride buffers. Use of in situ reflection high-energy electron diffraction and x-ray diffraction; Findings of thickness measurements of cleaved films using a scanning electron microscope; Means to determine directly the amount of misfit in the stacked barium-fluoride/strontium-fluoride layers.

Presents a study which examined the in situ deposition of a buffer layer of barium fluoride and superconducting thin films of yttrium-barium-copper-oxygen by metalorganic chemical vapor deposition on silicon substrates. Experimental details; Results and discussion; Conclusion.

Discusses the preparation of Pb[1-x]Eu[subx]Te films by hot-wall epitaxy, evaporating PbTe, Eu and Te from the same qurtz-tube furnace onto barium fluoride substrates. Description of the hot-wall epitaxy system used to prepare the films; Observation on the optical transmission spectra of the films; Electrical properties of the films.

Fractal and multifractal characteristics of self-affine surfaces of BaF2 thin films, deposited on crystalline Si 〈1 1 1〉 substrate at room temperature, were studied. Self-affine surfaces were prepared by irradiation of 120 MeV Ag9+ ions which modified the surface morphology at nanometer scale. The surface morphology of virgin thin film and those irradiated with different ion fluences are characterized by atomic force microscopy technique. The surface roughness (interface width) shows monotonic decrease with ion fluences, while the other parameters, such as lateral correlation length, roughness exponent, and fractal dimension, did not show either monotonic decrease or increase in nature. The self-affine nature of the films is further confirmed by autocorrelation function. The power spectral density of thin films surfaces exhibits inverse power law variation with spatial frequency, suggesting the existence of fractal component in surface morphology. The multifractal detrended fluctuation analysis based on the partition function approach is also performed on virgin and irradiated thin films. It is found that the partition function exhibits the power law behavior with the segment size. Moreover, it is also seen that the scaling exponents vary nonlinearly with the moment, thereby exhibiting the multifractal nature. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition was employed to deposit epitaxial Ge2Sb2Te5-layers on the (111) plane of BaF2 single crystal substrates. X-ray diffraction measurements show a process temperature window for epitaxial growth between 85 °C and 295 °C. No crystalline growth is observed for lower temperatures, whereas higher temperatures lead to strong desorption of the film constituents. The films are of hexagonal structure with lattice parameters consistent with existing models. X-ray pole figure measurements reveal that the films grow with one single out-of-plane crystal orientation, but rotational twin domains are present. The out-of-plane epitaxial relationship is determined to be Ge2Sb2Te5(0001) || BaF2(111), whereas the in-plane relationship is characterized by two directions, i.e., Ge2Sb2Te5 [-12-10] || BaF2[1-10] and Ge2Sb2Te5[1-210] || BaF2[1-10]. Aberrationcorrected high-resolution scanning transmission electron microscopy was used to resolve the local atomic structure and confirm the hexagonal structure of the films. [ABSTRACT FROM AUTHOR]

Polycrystalline CuCr1-xNixO2 is synthesized and its multiferrocity is characterized in order to enhance the ferromagnetism and ferroelectricity of CuCrO2-based multiferroics. At the optimized doping level x=0.05, we observe not only an enhancement of one order of magnitude in magnetization but also a remarkable increasing of polarization up to ∼50 μC/m2 from ∼35 μC/m2 of polycrystalline CuCrO2. It is argued that the Ni-doping may modulate the antiferromagnetic interactions between Cr3+ ions and probably induce the conical-like spin component responsible for the enhanced ferromagnetism. [ABSTRACT FROM AUTHOR]

Polycrystalline CuCr1-xNixO2 is synthesized and its multiferrocity is characterized in order to enhance the ferromagnetism and ferroelectricity of CuCrO2-based multiferroics. At the optimized doping level x=0.05, we observe not only an enhancement of one order of magnitude in magnetization but also a remarkable increasing of polarization up to ∼50 μC/m2 from ∼35 μC/m2 of polycrystalline CuCrO2. It is argued that the Ni-doping may modulate the antiferromagnetic interactions between Cr3+ ions and probably induce the conical-like spin component responsible for the enhanced ferromagnetism. [ABSTRACT FROM AUTHOR]

The article presents procedures used to successfully fabricate submicron metallic arrays on barium fluoride substrate (BaF2) in both single layer and multiple-layer configurations. Barium fluoride substrate is of interest for infrared (IR) frequency selective surfaces (FSS) applications because of its low refractive index and high IR transparency.

The ferroelectric properties of bulk BaMgF4 are determined by polarization hysteresis measurements. The spontaneous polarization Ps is found to be 6.6 μC/cm2, while the coercive field Ec varies between 4 and 24 kV/cm, depending exponentially on the frequency. Periodical poling of domains, with a 24 μm period, is demonstrated and evidenced by a selective domain etching. [ABSTRACT FROM AUTHOR]

A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF2 and BaF2. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF2, BaF2, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident γ-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs+ relative to Na+, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI. [ABSTRACT FROM AUTHOR]

We perform first-principles calculations for the formation energies of fluorine self-interstitials (F[sub i][sup -]) and fluorine vacancies (V[sub F][sup +]) in CaF[sub 2]–BaF[sub 2] superlattices and in the corresponding bulk compounds. In dislocation-free (strained-layer) superlattices, the calculations show that both the F[sub i][sup -] and the V[sub F][sup +] defects are energetically more stable in the CaF[sub 2] layers than in the BaF[sub 2] layers. If the misfit stress in the superlattices is released (by dislocations, for instance), our results indicate that charge transfer between layers becomes energetically favorable with F[sub i][sup -] in the CaF[sub 2] layers and V[sub F][sup +] in the BaF[sub 2] layers. This is consistent with recent experiments. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Luminescence excitation spectra in barium fluorohalides have been studied using synchrotron radiation of the SIBERIA-I electron storage ring in the energy range from 4 to 35 eV. The energy position of edge and core exciton formation as well as that of the electronic excitation multiplication threshold have been established. These luminophors find their practical application in the novel image-plate technique. [ABSTRACT FROM AUTHOR]

Using blue tunable pulse laser radiation of low fluence, we have investigated laser-induced sputtering from cleaved BaF2 (111) surfaces under ultrahigh vacuum conditions. Time correlated with the laser pulses the positive ions Ba+, Ba++, (BaF)+ and F+ were observed. Practically no negative ions were found. Neutral atomic fluorine (F 0) was desorbed abundantly. A pulse correlation of F 0 as well as the relative amount of F 0 and F+ could not be established at this stage. The emission yield of all positive ions as well as of F 0 was strongly wavelength dependent and showed a broad resonance around 2.9 eV. [ABSTRACT FROM AUTHOR]

Epitaxial (111)CdxPb1-xTe//(111)BaF2 films in the rocksalt structure have been made by codeposition from CdTe and PbTe magnetron targets in an rf discharge onto chemipolished substrates at 320 °C. Films were prepared with x values from 0 to 0.47, well past the range of bulk thermodynamic solubility. Raman spectroscopy, Auger spectroscopy, and transmission electron microscopy showed phase segregation had not occurred. The lattice spacing in the growth direction was observed to be insensitive to x. [ABSTRACT FROM AUTHOR]