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The growth behavior of [B.sub.4] C interlayers deposited at the interfaces of Mo/Si multilayers was investigated using x-ray photoemission spectroscopy, x-ray reflectivity, and x-ray diffraction measurements. We report an asymmetry in the formation of [B.sub.4]C at the [B.sub.4]C-on-Mo interface compared to the [B.sub.4]C-on-Si interface. X-ray photoelectron spectroscopy (XPS) depth profiling shows that for [B.sub.4]C-on-Mo the formed stoichiometry is close to expectation (4 : 1 ratio), while for [B.sub.4]C-on-Si it is observed that carbon diffuses from the [B.sub.4]C interfaces into the multilayer, resulting in nonstochiometric growth (>4 : 1). As a result, there is a discrepancy in the optical response near 13.5 nm wavelength, where [B.sub.4]C-on-Mo behaves according to model simulations, while [B.sub.4]C-on-Si does not. The as-deposited off-stoichiometric [B.sub.4]C-on-Si interface also explains why these interfaces show poor barrier properties against temperature induced interdiffusion. We show that the stoichiometry of [B.sub.4]C at the Mo-Si interfaces is connected to the structure of the layers onto which [B.sub.4]C is grown. Because of enhanced diffusion into the amorphous Si surface, we suggest that deposited boron and carbon atoms form [Si.sub.X][B.sub.Y] and [Si.sub.X][C.sub.Y] compounds. The low formation enthalpy of [Si.sub.X][C.sub.Y] ensures C depletion of any [B.sub.X][C.sub.Y] interlayer. Only after a saturated interfacial layer is formed, does further deposition of boron and carbon atoms result in actual [B.sub.4]C formation. In contrast to the off-stoichiometric [B.sub.4]C growth on top of Si, [B.sub.4]C grown on top of Mo retains the correct stoichiometry because of the higher formation enthalpies for [Mo.sub.X][B.sub.Y] and [Mo.sub.X][C.sub.Y] formation and the limited diffusion depth into the (poly)-crystalline Mo surface. OCIS codes: 230.4170, 310.4165, 340.7480.

Angle resolved x-ray photoelectron spectroscopy (ARXPS) has been employed to determine nondestructively the in-depth interface formation during thin film growth. Buried interfaces underneath the nanometer thick layers are probed by identifying the chemical shift of compound materials in photoelectron spectroscopy and using the angular response to quantify the compound amounts from the measured intensities. The thin interfaces in molybdenum-silicon multilayers grown at ambient temperature are investigated. This system is an example of an almost perfect 1D-system, where the interface region is only a small part of the individual layer thicknesses of 3 to 5 nm. Despite the low growth temperature, both the interfaces of this multilayer show layer thickness dependent interface formation. While the silicon-on-molybdenum interface shows a limited interface thickness of 0.4 nm of Mo5Si3, the molybdenum-on-silicon interface shows a more complex evolution. For this interface, the composition of the first 2.0 nm of deposited layer thickness is best described as a molybdenum-silicon compound layer with a molybdenum rich top and a MoSi2 bottom layer. After 2.5 nm of the deposited layer thickness, the molybdenum rich compound at the top has transformed into polycrystalline molybdenum on top of 1.8 nm MoSi2 at the interface. The formation of the 1.8 nm MoSi2 precedes the formation of polycrystalline molybdenum on top. Angle resolved x-ray photoelectron spectroscopy (ARXPS) is shown to be a good tool to study the interface phenomena beneath the nanometer thick top layers. In the case of Mo/Si multilayer mirrors, this ARXPS study shows that the compound formation at the interface accounts for the majority of the extreme ultraviolet reflectance loss. [ABSTRACT FROM AUTHOR]

The hysteresis, loss, and nonlinearity of the strain and polarization response of an epitaxial PbZr0.55Ti0.45O3 film are experimentally investigated for non‐switching AC excitation fields at a DC bias of 20 kV cm−1 in the 70 Hz to 5 kHz range. The measured strain is hysteretic and linear, whereas the polarization is hysteretic and highly nonlinear with excitation amplitude. Furthermore, compared to the case with zero bias, the effective piezoelectric coefficient that is extracted from the strain response is almost not changed for the investigated field range. In contrast, the loss tangent and nonlinearity of the polarization response are strongly reduced. The observations can not be explained by the Rayleigh model and its extensions, but are very well explained by the recently proposed polarization rotation model through addition of a non‐zero bias field term to the model. This model describes the film properties as the result of the nonlinear rotation of the polarization vector within the unit‐cell in response to the applied field, which is accompanied with viscous domain interaction. These results demonstrate that the polarization rotation model can describe the film response in a broad range of excitation frequencies and amplitudes, which far the applicable range of the Rayleigh model. [ABSTRACT FROM AUTHOR]

The role of the Mo2C/oxide interface on multi-layer graphene (MLG) nucleation during a chemical vapor deposition (CVD) process is investigated. During the CVD process, MLG growth is only observed in the presence of a Mo2C/SiO2 interface, indicating that the chemical reactions occurring at this interface trigger the nucleation of MLG. The chemical reaction pathway is explained in four steps as (1) creation of H radicals, (2) reduction of the oxide surface, (3) formation of C–C bonds at O–H sites, and (4) expansion of graphitic domains on the Mo2C catalyst. Different Mo2C/oxide interfaces are investigated, with varying affinity for reduction in a hydrogen environment. The results demonstrate a catalyst/oxide bifunctionality on MLG nucleation, comprising of CH4 dehydrogenation by Mo2C and initial C–C bond formation at the oxide interface. [ABSTRACT FROM AUTHOR]

The phenomena of hysteresis, ferroelectric loss, and nonlinearity are investigated for the strain and polarization of a monoclinic, epitaxial Pb(Zr,Ti)O3 film over the 70 Hz to 5 kHz frequency range at sub‐coercive excitation fields and zero electrical bias. For the strain, a linear hysteretic behavior is found, whereas the polarization shows a strongly nonlinear hysteretic behavior. In contrast to polycrystalline structures (for instance in ceramics or chemical solution deposited thin films), the commonly referred Rayleigh model cannot explain the observed behavior. A new model is presented, based on the rotation of the polarization vector within the monoclinic or rhombohedral unit cell under an applied electric field, with the viscous interaction of domains accompanying the unit cell deformation. The model explains the amplitude and frequency scaling of the strain, polarization, and loss tangent as well as the observed higher harmonics of polarization in the measured epitaxial Pb(Zr,Ti)O3 films. It is concluded that the nonlinear response and the hysteretic loss originate from two separate physical processes. The nonlinear response is attributed to the nonlinear angular rotation of the polarization vector, whereas the hysteresis and ferroelectric loss are due to a viscous interaction of domains while the polarization vector is rotating. [ABSTRACT FROM AUTHOR]

Ion sputtering yields for Ru, Mo, and Si under Ar+ ion bombardment in the near-threshold energy range have been studied using an in situ weight-loss method with a Kaufman ion source, Faraday cup, and quartz crystal microbalance. The results are compared to theoretical models. The accuracy of the in situ weight-loss method was verified by thickness-decrease measurements using grazing incidence x-ray reflectometry, and results from both methods are in good agreement. These results provide accurate data sets for theoretical modeling in the near-threshold sputter regime and are of relevance for (optical) surfaces exposed to plasmas, as, for instance, in extreme ultraviolet photolithography. [ABSTRACT FROM AUTHOR]