Optical properties of molybdenum in the ultraviolet and extreme ultraviolet by reflection electron energy loss spectroscopy

Abstract

Optical properties of polycrystalline molybdenum are determined from ultraviolet up to extreme ultraviolet by reflection electron energy loss spectroscopy (REELS). Calculations are performed within the dielectric response theory by means of the quantitative analysis of electron energy losses at surfaces QUEELS-(k, ω)-REELS software [Surf. Interface Anal. 36, 824 ( 2004)] that allows the simulation of inelastic scattering cross sections, using a parametric energy loss function describing the optical response of the material. From this energy loss function, the real and imaginary parts of the dielectric function, the refractive index, and the extinction coefficient are deduced and compared with previously published results.

Determination of optical constants of thin films in the EUV

“…An exception is the value of Diel et al on Ni [32], which is far off our value and the one from CXRO [10]. Pauly et al used reflection electron energy loss spectroscopy on Mo to determine the dielectric constants [31] and determined a value that is also very close to our value. The data set of Soufli et al on Pt [33], who used transmission type measurements on thin, freestanding films, agrees remarkably well with our data.…”

“…When comparing our data at 91.85 eV to the existing literature of direct measurements of the optical constants [30,31,32,33,34,35,36], we find the differences in values, that are summarized in figure 4 alongside those, calculated from atomic scattering factors [10,37,38]. Of those references, the data of Windt et al on Mo, Pt, Ru, and Ta [30], as well as the data of Rodríguez-de Marcos et al on Te [36], Hosoya et al on Ta [35] were obtained from reflection type measurements and are therefore very comparable to ours with respect to methodology and outcome.…”

“…From atomic scattering factors: black triangles[10], green triangles[37,38], from reflectance measurements: blue rectangles[30]. From various other studies: magenta diamonds, Mo[31], Ni[32], Pt[33], Ru[34], Ta[35], Te[36].…”

QUEELS: Software to calculate the energy loss processes in TEELS, REELS, XPS and AES including effects of the core hole

“…Indeed, by calculating a weighted average of over relevant path lengths, it is possible to reproduce energy losses occurring in a REELS experiment by adjusting the ELF parameters and in this way determine the ELF of the material. This procedure was implemented in the QUEELS‐ ε ( k,ω )‐REELS software package, 17 and it has been extensively used to determine the ELF and optical properties for many materials 7,22,23,39,41,43–53 …”

“…This procedure was implemented in the QUEELS-ε(k,ω)-REELS software package, 17 and it has been extensively used to determine the ELF and optical properties for many materials. 7,22,23,39,41,[43][44][45][46][47][48][49][50][51][52][53] F I G U R E 9 K r,Vi eff , K r,Mi eff , K r,Mo eff and K r,Vo eff (see Equation 14) contributions to the effective inelastic scattering cross section K r eff for an electron travelling in gold within a V-type reflection trajectory (E p = 1000 eV, θ i = 20 , θ o = 60 , x 0 = 10 Å). The inset illustrates paths that correspond to the individual contributions to K r eff…”