RESUMEN
The spatial resolution and high sensitivity of tip-enhanced Raman spectroscopy allows the characterization of surface features on a nano-scale. This technique is used to visualize silicon-based structures, which are similar in width to the transistor channels in present leading-edge CMOS devices. The reduction of the intensive far-field background signal is crucial for detecting the weak near-field contributions and requires beside a careful alignment of laser polarization and tip axis also the consideration of the crystalline sample orientation. Despite the chemical identity of the investigated sample surface, the structures can be visualized by the shift of the Raman peak positions due to the patterning induced change of the stress distribution within lines and substrate layer. From the measured peak positions the intrinsic stress within the lines is calculated and compared with results obtained by finite element modeling. The results demonstrate the capability of the tip-enhanced Raman technique for strain analysis on a sub-50nm scale.
RESUMEN
A large electric field at the surface of a ferromagnetic metal is expected to appreciably change its electron density. In particular, the metal's intrinsic magnetic properties, which are commonly regarded as fixed material constants, will be affected. This requires, however, that the surface has a strong influence on the material's properties, as is the case with ultrathin films. We demonstrated that the magnetocrystalline anisotropy of ordered iron-platinum (FePt) and iron-palladium (FePd) intermetallic compounds can be reversibly modified by an applied electric field when immersed in an electrolyte. A voltage change of -0.6 volts on 2-nanometer-thick films altered the coercivity by -4.5 and +1% in FePt and FePd, respectively. The modification of the magnetic parameters was attributed to a change in the number of unpaired d electrons in response to the applied electric field. Our device structure is general and should be applicable for characterization of other thin-film magnetic systems.
RESUMEN
Ni80Nb20-MgO multilayers with d spacing that varies from 2.50 to 3.07 nm were prepared by pulsed laser deposition under conditions of ultrahigh vacuum (UHV) and argon. The morphological and atomic structure in the multilayers was determined by hard-x-ray scattering. It was found that the interface roughness in both cases, UHV and argon deposition, is <0.4 nm, whereas the lateral and longitudinal correlation lengths in the case of argon deposition, 5.0 and 1.0 nm, respectively, are an order of magnitude lower. This is due to a reduction in kinetic energy of the condensing species in argon by orders of magnitude due to multiple collisions, which reduces the lateral relaxation probability. Hence the soft-x-ray reflectance of [Ni80Nb20-MgO]10 multilayers deposited in argon was determined at 413 eV (3.00 nm), middle of the water window. The reflectance has a peak at approximately 35.2 degrees with a half-width of 3.5 degrees and 0.19% maximum value. These results agree well with the simulation results performed by use of the structural parameters obtained from hard-x-ray scattering. The atomic structure determined by high-angle x-ray diffraction shows that both Ni80Nb20 and MgO are amorphous in the as-deposited condition.