Dielectric Properties of the Rubidium Halide Crystals in the Extreme Ultraviolet up to 30 eV

Peimann, C. J.; Skibowski, M.

doi:10.1002/pssb.2220460223

Cited by 18 publications

(5 citation statements)

References 24 publications

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“…The authors calculated the refractive indices in the spectral range of 4.8 eV to 5.7 eV, which is only part of the spectral range of present study. Similarly, the dielectric properties of single crystal RbI were discussed by Peimann and Skibowski in photon energies between 10 to 30 eV [41]. Finally, Roessler and Walker undertook research which was very similar to the present work for both KI and RbI single crystals [42].…”

supporting

confidence: 59%

Optical Properties of Alkali Halides in Ultraviolet Spectral Regions

Bhandari

2019

Optics

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The optical reflectance spectra of alkali halide crystals KI and RbI were measured over the energy range of 4.14 to 6.91 eV. Both single crystal and poly-crystal samples were used to accomplish this task. The phase θ(ω) was computed using the Kramers-Kronig relation between the real and imaginary parts of the complex function, ln r = ln |r| + iθ(ω). Subsequently, the optical constants n and κ were determined from the Fresnel reflectivity equation. The real and imaginary parts of dielectric constants ε 1 and ε 2 were then calculated using n and κ. The optical absorption spectra of the crystal have also been measured in these spectral regions. The spectra agree reasonably well with the current theory concerning exciton peaks. In addition, a shoulder was found in the spectra similar to those previously seen and associated with the band-to-band transition in the alkali iodides.Optics 2020, 1 19 were limited in terms of reflectivity studies and band structures. Before 1970, Baldini et al. studied the reflectivity data of many single-crystal alkali halides such as KI, KCl, KBr, RbI, RbCl, and RbBr in 5 eV to 10 eV [23,24]. Similarly, single-crystal alkali halides CsI [25], , KBr [30], and KCl [31] were also studied to calculate their optical constants. In contrast, studies of thin films of many alkali halides in the UV spectral region were limited in absorption measurements [32][33][34]. In addition, a literature review reveals a few more analyses of alkali halide crystals, such as a study on the influence of surface condition [35], on the strain effects on fundamental absorption [36], and on the effect of the layer thickness or uniaxial stress on the shape/location of exciton bands in RbI [37,38]. The literature on alkali halides has demonstrated that studies on the optical properties of RbI are comparatively limited. Cardona and Lynch studied the optical properties of a thin film of RbI, but their work was concentrated in the extreme ultraviolet region, i.e., from 50 eV to 250 eV [39]. S. Hashimoto and N. Momi-ie studied the interference effect and dispersion in thin RbI crystals [40]. The authors calculated the refractive indices in the spectral range of 4.8 eV to 5.7 eV, which is only part of the spectral range of present study. Similarly, the dielectric properties of single crystal RbI were discussed by Peimann and Skibowski in photon energies between 10 to 30 eV [41]. Finally, Roessler and Walker undertook research which was very similar to the present work for both KI and RbI single crystals [42]. They measured reflectance spectra in the range of 4-11 eV at 300 K and 77 K, respectively. Even though their first exciton peak matched with the present work for single crystal KI, the reflectance spectra for polycrystalline thin films of KI and RbI were not provided. Also, the authors used reflectance data measured at 77 K to calculate the real and imaginary parts of dielectric constants, instead of data measured at room temperature. They also did not calculate the refractive indices and absorption coefficient of th...

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confidence: 59%

Optical Properties of Alkali Halides in Ultraviolet Spectral Regions

Bhandari

2019

Optics

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“…for alkali and halogen atoms as seen in figures 4 and 5. Since the average UV light absorption coefficient for RbI at 400 K can be evaluated as equal to 3 × 10 5 cm −1 [27], we could assume that most of the primary photon energy is deposited down to the depth of 60 nm, which is similar to the penetration depth of 1 keV electrons [28]. Similar desorption yield oscillations have been found previously for electron irradiated alkali halides [24,25].…”

Section: Desorption By Excitation At Threshold Energiesmentioning

confidence: 62%

“…When an electron or a photon with energy higher than the bandgap energy (of the order of 10 eV for halides) reaches the alkali halide crystal, it causes creation of hot electron-hole pairs by inelastic interactions with the crystal lattice [2,7,29,30]. As mentioned in section 3, the penetration depth of 10 eV photons in alkali halides is quite substantial and in fact comparable to the depth of 1 keV electrons [27,28,31]. The electrons and holes could efficiently migrate to the surface via uncorrelated diffusion of the conduction band electron and the hole having an excess of kinetic energy (hot hole [29,30]).…”

Section: Desorption Due To Band-to-band Excitationsmentioning

confidence: 99%

Alkali halide decomposition and desorption by photons—the role of excited point defects and surface topographies

Szymoński

Droba

Goryl

et al. 2006

J. Phys.: Condens. Matter

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Our recent work on photon-stimulated desorption of alkali halide surfaces has been reviewed. Most of the experimental data are presented for the first time. This new material is supplemented with two examples of our work published previously (see Szymonski et al 1996 Surf. Sci. 363 229; 2002 Acta Phys. Pol. 33 2237). The results are discussed and compared with relevant experimental and theoretical work by other authors. In particular, we focus on two aspects of the studies: high resolution AFM imaging of desorbed surfaces, and measurements of mass selected fluxes of the desorbing atoms. It is found that, at initial stages of the UV-photon stimulated desorption, the process is occurring in a ‘layer-by-layer’ mode as a result of growth and linking of monatomic pits on the surface. This results in periodic changes of surface topography from atomically flat to rough with a period equal to the time needed for desorption of 1 ML. Such periodic changes of the surface topography affect the efficiency of the desorption and result in oscillatory dependence of the emitted particle yields versus photon fluence. Careful analysis of the yields reveals that during irradiation there is a substantial number of stable ground state F-centres accumulated under the surface. The number of accumulated defects is changing periodically with the photon fluence in anti-correlation with the desorption yields. Based on the mentioned results, we argue that the production of F-centres and their interaction with the surface are, in fact, the limiting factor for PSD. To test the validity of this statement a series of desorption experiments for the crystal co-irradiated with visible light (with a wavelength corresponding to the F-centre absorption band) and UV photons have been performed. A dramatic increase in the desorption yield, as well as pronounced changes in the surface erosion process, have been found.

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“…The curves were obtained by digitizing the spectra published earlier by several authors. [12][13][14] The KI data are an extension in the VUV of the yield of desorbed iodine presented in previous papers, 15,16 whereas the halogen desorption results from RbI and KBr are presented for the first time, to our knowledge. The insets of Figs.…”

Section: Resultsmentioning

confidence: 77%

Spectroscopic behavior of halogen photodesorption from alkali halidesunder UV and VUV excitation

et al. 1997

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The photostimulated desorption yield of neutral halogen atoms from KI, KBr, and RbI at several temperatures has been measured in the photon energy range between 5 and 30 eV using synchrotron radiation and quadrupole mass spectrometry. The features observed in the desorption yield are slightly correlated with the structures of the absorption spectra of each investigated material. The behavior of the halogen desorption yield is analyzed in the frame of inelastic electron-electron scattering processes, in close analogy with data available from the total photoelectron yield and the luminescence yield. The role played in the desorption mechanism by fundamental excitations, such as valence exciton creation and band-gap electron-hole excitation, is discussed.

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Dielectric Properties of the Rubidium Halide Crystals in the Extreme Ultraviolet up to 30 eV

Cited by 18 publications

References 24 publications

Optical Properties of Alkali Halides in Ultraviolet Spectral Regions

Optical Properties of Alkali Halides in Ultraviolet Spectral Regions

Alkali halide decomposition and desorption by photons—the role of excited point defects and surface topographies

Spectroscopic behavior of halogen photodesorption from alkali halidesunder UV and VUV excitation

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