Preparation and investigation of LaB6 films

Borides in Thin Film Technology

“…The application of triode sputtering (30,32,40), dc (4,5,22,33,38,(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61) and rf magnetron sputtering (31,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43), electron-beam evaporation (20)(21)(22)(23)(24)(25)(26)(27), and arc evaporation (28,29) for the deposition of boride coatings is reported in the literature. Because of the low electrical and thermal conductivity of boron (22) and because of the high reactivity of certain rare-earth metals with oxygen (e.g., lanthanum and cerium), most PVD processes make use of the corresponding boride as the vapor source in...…”

“…1a and 1c). Typical grain sizes for this structure type revealed from X-ray diffraction (XRD) measurements on ZrB -and LaB -based films were found to be below 40 nm for electron-beam evaporation (21) and below 20 nm (21,30,48) for sputtering. In the complementary growth region, i.e., extremely low or high energetic contribution (e.g., high argon pressure, low substrate temperature or high bias voltage, respectively) and due to the addition of nitrogen using reactive PVD processes, the structure of the coatings becomes extremely fine-grained to amorphous (see Figs.…”

“…1b and 1d). Obviously, columnar film growth requiring long-range diffusion processes is not possible at low substrate temperature (23,25,30), with the low energies of condensing target atoms (at high argon pressures (57-59)), during high energy ion bombardment (at high bias voltages (57-59)) or due to the addition of foreign elements (4, 5, 18, 19, 29, 35-39, 46, 47-49, 53, 58, 60, 61).…”

“…Figure 7 shows the spectral reflectivity calculated from ellipsometric data for boride coatings and for the corresponding bulk hexaborides. Due to the highly disordered microstructure of these coatings, their electronic and, consequently, their optical properties differ from those of the bulk values (21,30,(86)(87)(88)(89). Structural defects like interstitials, vacancies, and impurities which are typical for coatings grown by low-temperature PVD processes are expected to affect the shape of the plasma oscillation edge in rare-earth hexaborides (90).…”

Rare Earth Compounds (Oxides, Sulfides, Silicides, Boron, …) as Thin Films and Thin Crystals Physico-Chemical Properties and Applications

“…From resistivity, Hall coefficient , concentration, and mobility measurements, Winsztal et al [376] have shown the metallic nature of conduction in LaB, layers. Compared to the bulk, thin films had a n equivalent carrier concentration, higher resistivity, and lower Hall mobility.…”