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Abstract: In the present work, we report the growth of wurtzite InN epilayers on GaN/Si (111) substrate by plasma-assisted molecular beam epitaxy (PAMBE). The growth parameters such as indium flux, substrate temperature and RF power affect the crystallographic and morphological properties of InN layers, which were evaluated using high resolution X-ray diffraction (HRXRD) analysis and atomic force microscopy (AFM). It is found that excess indium (In) concentrations and surface roughness were increased with increase in In flux and growth temperature. The intensity of HRXRD (0002) peak, corresponding to c-axis orientation has been increased and full width at half maxima (FWHM) has decreased with increase in RF power. It was found that highly c-axis oriented InN epilayers can be grown at 450°C growth temperature, 450W RF power and 1.30×10−7 mbar In beam equivalent pressure (BEP). The energy gap of InN layers grown by optimizing growth conditions was determined by photoluminescence and optical absorption measurement. [Copyright &y& Elsevier]

Abstract: Zinc–Tin-Oxide (ZTO) thin films were deposited on glass substrate with varying concentrations (ZnO:SnO2; 100:0, 90:10, 70:30 and 50:50wt.%) at room temperature by flash evaporation technique. These deposited ZTO films were annealed at 450°C in vacuum. These films were characterized to study the effect of annealing and addition of SnO2 concentration on the structural, chemical and electrical properties. The XRD analysis indicates that crystallization of the ZTO films strongly depends on the concentration of SnO2 and post annealing where annealed films showed polycrystalline nature. Atomic force microscopy (AFM) images manifest the surface morphology of these ZTO thin films. The XPS core level spectra of Zn(2p), O(1s) and Sn(3d) have been deconvoluted into their Gaussian component to evaluate the chemical changes, while valence band spectra reveal the electronic structures of these films. A small shift in Zn(2p) and Sn(3d) core level towards higher binding energy and O(1s) core level towards lower binding energy have been observed. The minimum electrical resistivity (ρ ≈3.69×10−2 Ω-cm), maximum carrier concentration (n ≈3.26×1019 cm−3) and Hall mobility (μ ≈5.2cm2 v−1 s−1) were obtained for as-prepared ZTO (50:50) film thereafter move towards lowest resistivity (ρ ≈1.12×10−3 Ω-cm), highest carrier concentration (n ≈2.96×1020 cm−3) and mobility (μ ≈18.8cm2 v−1 s−1) for annealed ZTO (50:50) thin film. [Copyright &y& Elsevier]

This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50 nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp 3 /sp 2 ratio accompanied with the highest hardness of ∼18.34 GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak ( A D / A G ) and the highest conductivity (∼2.23 S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27 × 10 −7 S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport. [ABSTRACT FROM AUTHOR]

• Explored the linear and nonlinear optical interaction in the Bi2Se3 single-crystal cleaved flake. • Kramer's Kronig approach and DFT calculations confirm the prominent 2 eV OBT from the Ɛ1 and Ɛ2 simulations. • Concurrently, the TRUS measurements are done to explore the excited-state dynamics of the states populating due to the Moss-Burstein shifts. • With the same excitation, probing in the NIR region shows the occurrence of the Pauli blocking. • The low temperature study give a clear evidence of presence of second surface state and a broad absorbance of 1.2 eV can be easily seen through TRUS. [Display omitted] We report the optical response and temperature-dependent excited-state carrier dynamics in the flake of Bi 2 Se 3 , which is cleaved from its single crystal. The optical properties are explored using the visible-near infrared (VIS-NIR), infrared (IR), and photoluminescence (PL) spectroscopies. The VIS-NIR spectra are then used to find the Ɛ 1 and Ɛ 2 using Kramer's Koning relations, confirming OBT of 2 eV and 1.4 eV. The DFT (density functional theory) calculations are also carried out to confirm the experimental optical transitions (OBT). To probe these OBT in the bismuth selenide, we have studied the temperature, fluence, and excitation dependent ultrafast transient reflectance over a wide spectral range from 2.58–0.77 eV (VIS-NIR) with different excitation energies 3.02 eV, 2.61 eV, 1.9 eV, and 1.4 eV to explore several previously unseen transitions that do not appear in PL spectroscopy and room temperature carrier analysis. The temperature-dependent excited-state dynamics are investigated at 5–300 K. This study clearly indicates the existence of Moss-Burstein shift in the visible region and Pauli blocking effect in the NIR region in the Bi 2 Se 3 topological insulator. Moreover, the low-temperature TRUS confirms the transition to the second surface state present in bismuth selenide. [ABSTRACT FROM AUTHOR]