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When a nominally flat surface is bombarded with a broad ion beam at oblique incidence, nanoscale ripples often develop on the surface. For high angles of incidence, surfaces typically develop into a terraced form at the late stages of their time evolution. In the present work, this process is exploited to prevent unwanted smoothing of ordered terraced substrates during the deposition of thin films. A Si surface prepatterned with a 500 nm pitch binary grating structure was bombarded at oblique incidence by a low energy Xe + ion beam to establish an ordered terraced topography. Subsequently, Si/SiO2 bilayers were deposited on the surface, and further oblique incidence Xe+ bombardment was performed following the deposition of each Si layer to re-establish the ordered terraced topography. Self-organized processes, such as in the present work, that only require exposure of a surface to a plasma or ion source have the potential to provide a simple and inexpensive route for fabricating large-area nanostructured surfaces. The presented procedure has potential applications in the fabrication of multilayer blazed gratings for use in the extreme ultraviolet or soft x-ray regimes. [ABSTRACT FROM AUTHOR]

The genomics approach to materials, heralded by increasingly accurate density functional theory (DFT) calculations conducted on thousands of crystalline compounds, has led to accelerated material discovery and property predictions. However, so far, amorphous materials have been largely excluded from this as these systems are notoriously difficult to simulate. Here, we study amorphous Ta2O5 thin films mixed with Al2O3, SiO2, Sc2O3, TiO2, ZnO, ZrO2, Nb2O5, and HfO2 to identify their crystalline structure upon post-deposition annealing in air both experimentally and with simulations. Using the Materials Project open database, phase diagrams based on DFT calculations are constructed for the mixed oxide systems and the annealing process is evaluated via grand potential diagrams with varying oxygen chemical potential. Despite employing calculations based on crystalline bulk materials, the predictions agree well with the experimentally observed crystallized phases of the amorphous thin films. In the absence of ternary phases, the dopant acts as an amorphizer agent increasing the thermal stability of Ta2O5. The least efficient amorphizer agent is found to be Nb2O5, for which the cation has similar chemical properties to those of Ta in Ta2O5. These results show that DFT calculations can be applied for the prediction of crystallized structures of annealed amorphous materials. This could pave the way for accelerated in silico material discovery and property predictions using the powerful genomic approach for amorphous oxide coatings employed in a wide range of applications such as optical coatings, energy storage, and electronic devices. [ABSTRACT FROM AUTHOR]

A simple, highly sensitive technique for measuring absorbed power in thin film dielectrics based on thermal lensing is demonstrated. Absorption of an amplitude modulated or pulsed incident pump beam by a thin film acts as a heat source that induces thermal lensing in the substrate. A second continuous wave collimated probe beam defocuses after passing through the sample. Determination of absorption is achieved by quantifying the change of the probe beam profile at the focal plane using a four-quadrant detector and cylindrical lenses to generate a focus error signal. This signal is inherently insensitive to deflection, which removes noise contribution from point beam stability. A linear dependence of the focus error signal on the absorbed power is shown for a dynamic range of over 105. This technique was used to measure absorption loss in dielectric thin films deposited on fused silica substrates. In pulsed configuration, a single shot sensitivity of about 20 ppm is demonstrated, providing a unique technique for the characterization of moving targets as found in thin film growth instrumentation. [ABSTRACT FROM AUTHOR]

A defect tolerant method of printing periodic structures with submicron resolution is presented. This technique is based on the self-imaging effect produced when a periodic semi-transparent mask is illuminated with coherent light. An analytical description of the effect, numerical simulations, and experimental evidence that is in good agreement with the theoretical analysis is presented. To explore the extent of defect tolerance, masks with different defect layouts were designed and tested. [ABSTRACT FROM AUTHOR]

Films of tantalum pentoxide (Ta2O5) with thickness of 10–100 nm were deposited on Si wafers and have been compared using spectroscopic ellipsometry (SE) and x-ray reflectivity (XRR). (Ta2O5) was chosen for comparison work based on various criterions for material selection outlined in this article. Measurements were performed at six positions across the sample area to take into consideration thickness and composition inhomogeneity. SE and XRR fitted curves required the incorporation of a linearly graded interface layer. SE systematically measured higher values of film thickness as compared to XRR. A linear equation was established between the thickness measurements using SE and XRR. The slope of the linear equation established was found to be 1.02±0.01. However, the intercepts were found to be 1.7±0.2 and 2.6±0.3 when the interface was excluded and included, respectively. These differences in the values of intercepts were attributed to the uncertainties in the determination of the interface layer. [ABSTRACT FROM AUTHOR]

The laser induced breakdown threshold of HfO2 films is studied with single pairs of pulses of variable delay and 50 fs and 1 ps pulse duration. Two distinct transient regimes are observed that can be related to the relaxation of the electron density from the conduction band via an intermediate state to the valence band. The experimental results are in good agreement with a theoretical model that assumes occupation of mid gap states after the first pulse on a time scale of several tens of picoseconds and subsequent decay of this population via recombination with holes in the valence band on a time scale of several tens of milliseconds. [ABSTRACT FROM AUTHOR]

We report on electron emission from cesiated GaN n-p junctions in forward bias. Surface electric fields ∼3 V/µm caused a fivefold increase in emission current. Initial maximum currents in excess of 200 nA degrade to 50 nA due to charge trapping but are quickly recovered at zero bias. Energy spectra confirm negative electron affinity 80 h after cesiation, indicate resistive losses limit the emission current, and reveal significant emission at energies above the Fermi level of the injecting contact. [ABSTRACT FROM AUTHOR]

A compact nanofabrication system that combines Talbot lithography and a table-top extreme ultraviolet laser is presented. The lithographic method based on the Talbot effect provides a robust and simple experimental setup that is capable to print periodic structures over millimeter square areas free of defects. Test structures were printed and transferred into metal layers showing a complete coherent extreme ultraviolet lithographic process in a table-top system. [ABSTRACT FROM AUTHOR]