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Due to its appreciable electro-optical properties, potassium tantalate niobate (KTN) thin films of high quality are expected to enhance the functionality of integrated photonics optical modulators. Unfortunately, they are inherently hard to synthesize. Herein, the authors present atomic layer deposition (ALD) of oriented KTN for the first time. They study the variability in phase content with respect to potassium concentration across a variety of substrates. Films grown with a slight overstoichiometry in potassium show excellent crystal quality of a pure perovskite phase. Highly oriented films were obtained on substrates of a similar lattice constant to bulk potassium tantalate niobate. Nearly stoichiometric potassium contents yield films with similar quality, albeit with trace amounts of pyrochlore. Potassium deficient films consist of an overwhelming amount of pyrochlore. Phase control and orientation control are essential when considering device integration of optical modulators. The authors believe that ALD is an ideal technique to obtain KTN thin films with high growth control. [ABSTRACT FROM AUTHOR]

Measurements have been made near normal incidence of the two-dimensional spatial coherence of the acoustic field scattered from the lakebed in Seneca Lake, New York. In the test region, the lakebed consists of a series of sediment layers created by a sequence of distinct depositional processes. The spatial coherence length of the scattered field is shown to be dependent on the structure of the underlying sediment sequences. Significant ping-to-ping variability in the spatial coherence surface was also observed for each sediment sequence. This variability is quantified by a two-dimensional spatial coherence metric that measures the coherence lengths and asymmetric coherence surface orientation. The ping-to-ping variation of the surface asymmetry appears to be linked to the spatial isotropy of the sediment scattering strength. The scattering strength of the deepest observed sequence in the sub-bottom is the most spatially isotropic and the ping-to-ping variability of the coherence lengths and surface orientations are random. The scattering strength of the shallower sequences is spatially anisotropic and the coherence lengths and surface orientations show intervals of non-random ping-to-ping behavior. [ABSTRACT FROM AUTHOR]

We have successfully deposited Fe4N thin films with (111) out-of-plane orientation on thermally oxidized Si substrates using a facing-target-sputtering system. A Ta/Ru composite buffer layer was adopted to improve the (111) orientation of the Fe4N thin films. The N2 partial pressure and substrate temperature during sputtering were optimized to promote the formation of the Fe4N phase. Furthermore, we measured the transport spin polarization of (111) oriented Fe4N by the point contact Andreev reflection (PCAR) technique. The spin polarization ratio was determined to be 0.50 using a modified BTK model. The film thickness dependence of the spin polarization was also investigated. The spin polarization of Fe4N measured by PCAR does not show degradation as the sample thickness was reduced to 10nm. [ABSTRACT FROM AUTHOR]

The selective epitaxial growth of Si1-xGex and the related strain properties were studied. Epitaxial Si1-xGex films were deposited on (100) and (110) orientation wafers and on patterned Si wafers with recessed source and drain structures via ultrahigh vacuum chemical vapor deposition using different growing steps and Ge concentrations. The stepwise process was split into more than 6 growing steps that ranged in thicknesses from a few to 120 nm in order to cover the wide stages of epitaxial growth. The growth rates of SiGe on the plane and patterned wafers were examined and a dependence on the surface orientation was identified. As the germanium concentration increased, defects were generated with thinner Si1-xGex growth. The defect generation was the result of the strain evolution which was examined for channel regions with a Si1-xGex source/drain (S/D) structure. [ABSTRACT FROM AUTHOR]

Two high-k dielectric materials (Al2O3 and HfO2) were deposited on n-type (100) and (110) InAs surface orientations to investigate physical properties of the oxide/ semiconductor interfaces and the interface trap density (Dit). X-ray photoelectron spectroscopy analyses (XPS) for native oxides of (100) and (110) as-grown n-InAs epi wafers show an increase in As-oxide on the (100) surface and an increase in InOx on the (110) surface. In addition, XPS analyses of high-k (Al2O3 and HfO2) on n-InAs epi show that the intrinsic native oxide difference between (100) and (110) epi surfaces were eliminated by applying conventional in-situ pre-treatment (TriMethyAluminium (TMA)) before the high-k deposition. The capacitance-voltage (C-V) characterization of HfO2 and Al2O3 MOSCAPs on both types of n-InAs surfaces shows very similar C-V curves. The interface trap density (Dit) profiles show Dit minima of 6.1 × 1012/6.5 × 1012 and 6.6 × 1012/7.3 × 1012 cm-2 eV-1 for Al2O3 and HfO2, respectively for (100) and (110) InAs surfaces. The similar interface trap density (Dit) on (100) and (110) surface orientation were observed, which is beneficial to future InAs FinFET device with both (100) and (110) surface channel orientations present. [ABSTRACT FROM AUTHOR]

The authors report the compositional dependence of the direct and indirect band gaps of pseudomorphic Ge1−x−ySixSny alloys on Ge and GaAs with (001) surface orientation determined from deformation potential theory and spectroscopic ellipsometry measurements. The effects of alloying Ge with Si and Sn and the strain dependence of the band gaps at the Γ, Δ, and L conduction band minima are discussed. Deformation potential theory predicts an indirect to direct crossover in pseudomorphic Ge1−y−xSixSny alloys on Ge or GaAs only for very high Sn concentrations between 15% and 20%. No indirect to direct cross-over in pseudomorphic Ge1−ySny alloys (x = 0) on Ge or GaAs was found for practically approachable Sn compositions (y < 25%). The predictions for the compositional dependence of the E0, E1, and E1 + Δ1 band gaps were validated for pseudomorphic Ge1−ySny alloys on Ge using spectroscopic ellipsometry. The complex pseudodielectric functions of pseudomorphic Ge1−ySny alloys grown on Ge by molecular beam epitaxy were determined from Fourier transform infrared and ultraviolet-visible ellipsometry in the 0.1–6.6 eV energy range of Sn contents up to 11%, to investigate the compositional dependence of the band gaps. Critical point energies and related parameters were obtained by analyzing the second derivative spectra of the dielectric function of the Ge1−ySny epilayers. Sn composition, thickness, and strain of the Ge1−ySny epilayers on Ge were characterized by high resolution x-ray diffraction. The E0, E1, and E1 + Δ1 band gaps of pseudomorphic Ge1−ySny alloys on Ge obtained from ellipsometry are in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]