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<jats:p>In continuation of our recent report on molybdates [<jats:italic>Appl. Phys. A</jats:italic> <jats:bold>124</jats:bold>, 44 (2018)], the structural, electronic, elastic, and optical properties of <jats:italic>Z</jats:italic>MoO<jats:sub>3</jats:sub> (<jats:italic>Z</jats:italic> = Ba and Sr) molybdates are investigated under pressure (10 GPa–50 GPa) comprehensively by deploying the density functional theory. Our investigations show that the studied compounds exhibit stable cubic phase with metallic attributes. The thermodynamic parameters such as enthalpy of formation, Debye, and melting temperatures of the compounds are observed to increase with pressure. While the Grüninsen parameter and the coefficient of super-plastic deformation decrease as the pressure increases. Mechanical properties elucidate an increase in measured values of hardness, bulk, shear, and youngʼs moduli with pressure. Our results suggest that the studied compounds are useful in high pressure optoelectronic devices. The optical properties of BaMoO<jats:sub>3</jats:sub> (BMO) and SrMoO<jats:sub>3</jats:sub> (SMO) are computed for the radiation of up to 35 eV. The present compounds show beneficial optical applications in the anti-reflection coating, lenses, and the high avoiding solar heating applications in the variant applied pressure.</jats:p>

<jats:p>High-quality bulk boron carbide (B<jats:sub>4</jats:sub>C) is successfully prepared at high pressure and high temperature (HPHT) by using B<jats:sub>4</jats:sub>C powder as a precursor. The as-synthesized B<jats:sub>4</jats:sub>C possesses a nanosheet structure with a thickness value of 15 nm and a length of several dozen micrometers. Its Vickers hardness value and fracture toughness value are 42.4 GPa and <jats:inline-formula> <jats:tex-math><?CDATA $4.51\,\mathrm{MPa}\cdot {{\rm{m}}}^{1/2}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>4.51</mml:mn> <mml:mspace width="0.25em" /> <mml:mi>MPa</mml:mi> <mml:mo>·</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo stretchy="false">/</mml:mo> </mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_6_066201_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, respectively, which are superior to those of B<jats:sub>4</jats:sub>C obtained from spark plasma sintering due to its high densification and nanosheet structure. Additionally, it shows good property of oxidation resistance. In air, its oxidation resistance temperature is 1100 °C which is higher than that of diamond under the same test condition.</jats:p>

<jats:p>A theoretical analysis of the cross-plane lattice thermal conduction in graphite is performed by using first-principles calculations and in the single-mode relaxation time approximation. The out-of-plane phonon acoustic mode ZA and optical mode <jats:inline-formula> <jats:tex-math><?CDATA $\mathrm{ZO}^{\prime} $?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ZO</mml:mi> <mml:mo>′</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_6_066301_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> have almost 80% and 20% of contributions to cross-plane heat transfer, respectively. However, these two branches have a small part of total specific heat above 300 K. Phonons in the central 16% of Brillouin zone contribute 80% of cross-plane transport. If the group velocity angle with respect to the graphite layer normal is less than 30°, then the contribution is 50% at 300 K. The ZA phonons with long cross-plane mean free path are focused in the cross-plane direction, and the largest mean free path is on the order of several micrometers at room temperature. The average value of cross-plane mean free path at 300 K is 112 nm for ZA phonons with group velocity angle with respect to the layer normal being less than 15°. The average value is dropped to 15 nm when phonons of all branches in the whole Brillouin zone are taken into account, which happens because most phonons have small or even no contributions.</jats:p>

<jats:p>The <jats:italic>ρ</jats:italic>(NH<jats:sub>2</jats:sub>) infrared (IR) frequencies and the corresponding full width at half maximum (FWHM) values for (CH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>NH<jats:sub>2</jats:sub>Fe<jats:sup>III</jats:sup> <jats:italic>M</jats:italic> <jats:sup>II</jats:sup>(HCOO)<jats:sub>6</jats:sub> (DMFe<jats:italic>M</jats:italic>, <jats:italic>M</jats:italic> = Ni, Zn, Cu, Fe, and Mg) are analyzed at various temperatures by using the experimental data from the literature. For the analysis of the IR frequencies of the <jats:italic>ρ</jats:italic>(NH<jats:sub>2</jats:sub>) mode which is associated with the structural phase transitions in those metal structures, the temperature dependence of the mode frequency is assumed as an order parameter and the IR frequencies are calculated by using the molecular field theory. Also, the temperature dependence of the IR frequencies and of the damping constant as calculated from the models of pseudospin (dynamic disorder of dimethylammonium (DMA<jats:sup>+</jats:sup>) cations)–phonon coupling (PS) and of the energy fluctuation (EF), is fitted to the observed data for the wavenumber and FWHM of the <jats:italic>ρ</jats:italic>(NH<jats:sub>2</jats:sub>) IR mode of the niccolites studied here. We find that the observed behavior of the IR frequencies and the FWHM of this mode can be described adequately by the models studied for the crystalline structures of interest. This method of calculating the frequencies (IR and Raman) and FWHM of modes which are responsible for the phase transitions can also be applied to some other metal organic frameworks.</jats:p>

<jats:p>High pressure structural phase transition of monoclinic paraotwayite type <jats:italic>α</jats:italic>-Ni(OH)<jats:sub>2</jats:sub> nanowires with a diameter of 15 nm–20 nm and a length of several micrometers were studied by synchrotron x-ray diffraction (XRD) and Raman spectra. It is found that the <jats:italic>α</jats:italic>-Ni(OH)<jats:sub>2</jats:sub> nanowires experience an isostructural phase transition associated with the amorphization of the H-sublattice of hydroxide in the interlayer spaces of the two-dimensional crystal structure at 6.3 GPa–9.3 GPa. We suggest that the isostructural phase transition can be attributed to the amorphization of the H-sublattice. The bulk moduli for the low pressure phase and the high pressure phase are 41.2 (4.2) GPa and 94.4 (5.6) GPa, respectively. Both the pressure-induced isostructural phase transition and the amorphization of the H-sublattice in the <jats:italic>α</jats:italic>-Ni(OH)<jats:sub>2</jats:sub> nanowires are reversible upon decompression. Our results show that the foreign anions intercalated between the <jats:italic>α</jats:italic>-Ni(OH)<jats:sub>2</jats:sub> layers play important roles in their structural phase transition.</jats:p>

<jats:p>The adsorption configurations of molecules adsorbed on substrates can significantly affect their physical and chemical properties. A standing configuration can be difficult to determine by traditional techniques, such as scanning tunneling microscopy (STM) due to the superposition of electronic states. In this paper, we report the real-space observation of the standing adsorption configuration of phenylacetylene on Cu (111) by non-contact atomic force microscopy (nc-AFM). Deposition of phenylacetylene at 25 K shows featureless bright spots in STM images. Using nc-AFM, the line features representing the C–H and C–C bonds in benzene rings are evident, which implies a standing adsorption configuration. Further density functional theory (DFT) calculations reveal multiple optimized adsorption configurations with phenylacetylene breaking its acetylenic bond and forming C–Cu bond(s) with the underlying copper atoms, and hence stand on the substrate. By comparing the nc-AFM simulations with the experimental observation, we identify the standing adsorption configuration of phenylacetylene on Cu (111). Our work demonstrates an application of combining nc-AFM measurements and DFT calculations to the study of standing molecules on substrates, which enriches our knowledge of the adsorption behaviors of small molecules on solid surfaces at low temperatures.</jats:p>

<jats:p>Kerfless technology is a promising alternative for reducing cost and providing flexible thin crystals in silicon-based semiconductors. In this work we propose a protruded seed substrate technology to prepare flexible monocrystalline Si thin film economically. Grooved seed substrate is fabricated by using SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> thin film as a mask for the wet-etching and thermal oxidation process. After the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> layer on the wedged strip is removed by hot phosphoric acid, the pre-defined structured substrate is achieved with the top of the strip serving as the seed site where there is no oxide layer. And a preferred growth of epitaxial Si on the substrate is performed by introducing an intermittent feed method for silicon source gas. The technique in this paper obviously enhances the mechanical stability of the seed structure and the growth behavior on the seed sites, compared with our previous techniques, so this technique promises to be used in the industrial fabrication of flexible Si-based devices.</jats:p>

<jats:p>Based on the microscopic nonlocal optical response theory, the resonant radiation force exerted on a semiconductor-coupled quantum well nanostructure (CQWN), induced by the nonlocal interaction between lasers and electrons in conduction bands, is investigated for two different polarized states. The numerical results show that the spatial nonlocality of optical response can cause a radiation shift (blue-shift) for the spectrum of the resonant radiation force, which is dependent on the CQWN width ratio, the barrier height, and polarized states sensitively. It is also confirmed that the resonant radiation force is steerable by the incident and polarized directions of incident light. This work may provide an advantageous method for detecting internal quantum properties of nanostructures, and open novel and raising possibilities for optical manipulation of nano-objects using laser-induced radiation force.</jats:p>

<jats:p>We have investigated the temperature-dependent effective mobility characteristics in impurity band and conduction subbands of n-doped silicon junctionless nanowire transistors. It is found that the electron effective mobility of the first subband in 2-fold valleys is higher than that of the second subband in 4-fold valleys. There exists a maximum value for the effective subband mobilities at low temperatures, which is attributed to the increase of thermally activated electrons from the ionized donors in the impurity band. The experimental results indicate that the effective subband mobility is temperature-dependent on the electron interactions by thermal activation, impurity scattering, and intersubband scattering.</jats:p>

<jats:p>The hybrid graphene-quantum dot devices can potentially be used to tailor the electronic, optical, and chemical properties of graphene. Here, the low temperature electronic transport properties of bilayer graphene decorated with PbS colloid quantum dots (CQDs) have been investigated in the weak or strong magnetic fields. The presence of the CQDs introduces additional scattering potentials that alter the magnetotransport properties of the graphene layers, leading to the observation of a new set of magnetoconductance oscillations near zero magnetic field as well as the high-field quantum Hall regime. The results bring about a new strategy for exploring the quantum interference effects in two-dimensional materials which are sensitive to the surrounding electrostatic environment, and open up a new gateway for exploring the graphene sensing with quantum interference effects.</jats:p>