Search

The emergent van der Waals semiconductor GaPS4 is heralding frontiers for gallium-based semiconductors. Despite its potential, the intricacies of its Raman spectrum and phonon heat transport remain elusive. In this research, experimental and theoretical methods are employed to give a comprehensive portrayal. The Raman spectra and phonon calculations obtained were cross-validated, affirming the study's credibility. A total of 28 Raman peaks were identified, with all phonon irreducible representations delineated. Advanced calculations unveiled notable shifts in the transition of GaPS4 from bulk to monolayer. During this process, phonons undergo a red shift, and the vibration contributions of different atoms change. The lifetime and group velocity of low wavenumber phonons are markedly reduced, suppressing the thermal conductivity in the monolayer. The thermal conductivity of GaPS4 bulk at 300 K is 0.5 W/m K, and 0.13 W/m K for monolayer, while the thermal conductivity in the cleavage direction is lower. These findings offer a detailed account of the complex Raman spectra and phonon thermal transport properties of GaPS4, setting the stage for its subsequent exploration and prospective applications in electronic and thermal devices, and contributing to enriching condensed matter theory of phonon thermal transport in van der Waals materials. [ABSTRACT FROM AUTHOR]

Spintronics devices have been a research hotspot due to their rich theoretical and application value. The widebandgap semiconductor β-Ga2O3 has excellent application potential in spintronics due to the controllability of its electron behavior via ultraviolet light. This paper employs first-principles calculations and the Wenzel–Kramers–Brillouin (WKB) approximation to comprehensively investigate spin transport based on magnetic tunnel junctions (MTJs) comprising β-Ga2O3 nanosheets. The magnetic moment of the ferromagnetic layer in β-Ga2O3 MTJs is found to be positively correlated with tunnel magnetoresistance (TMR). Interestingly, layer-number parity-dependent oscillation of TMR in β-Ga2O3 MTJs is observed, which is explained by the non-equilibrium Green function and the WKB approximation. TMR reaches a maximum of 1077% at five layers, and bias-dependent stability is observed in the monolayer model under biases of 0–20 mV. This study not only expands the application potential of β-Ga2O3 and predicts its superiority in spintronics but also enriches the related condensed matter theory. [ABSTRACT FROM AUTHOR]

The emergent van der Waals semiconductor GaPS4 is heralding frontiers for gallium-based semiconductors. Despite its potential, the intricacies of its Raman spectrum and phonon heat transport remain elusive. In this research, experimental and theoretical methods are employed to give a comprehensive portrayal. The Raman spectra and phonon calculations obtained were cross-validated, affirming the study's credibility. A total of 28 Raman peaks were identified, with all phonon irreducible representations delineated. Advanced calculations unveiled notable shifts in the transition of GaPS4 from bulk to monolayer. During this process, phonons undergo a red shift, and the vibration contributions of different atoms change. The lifetime and group velocity of low wavenumber phonons are markedly reduced, suppressing the thermal conductivity in the monolayer. The thermal conductivity of GaPS4 bulk at 300 K is 0.5 W/m K, and 0.13 W/m K for monolayer, while the thermal conductivity in the cleavage direction is lower. These findings offer a detailed account of the complex Raman spectra and phonon thermal transport properties of GaPS4, setting the stage for its subsequent exploration and prospective applications in electronic and thermal devices, and contributing to enriching condensed matter theory of phonon thermal transport in van der Waals materials. [ABSTRACT FROM AUTHOR]

Periodic gold dimer nanoantennas on a one-atomic-layer graphene sheet elevated above Si cavities were fabricated to systematically study the effects of the cavity depth on surface-enhanced Raman scattering (SERS). The periodic trend of Raman intensity as a function of the cavity depth resulting from the interference effect between the plasmonic resonance of the gold dimer and the cavity resonance of the underlying Si cavity was observed, and the electric field was greatly enhanced compared with the non-suspended system. The finite-difference time-domain method was used to simulate the interaction between the electromagnetic wave and the suspended system and to verify the observed SERS response in experiments. Our work has the advantages of combining the superior properties of graphene with suspended metallic nanostructures to result in the enhanced electric field for SERS applications. [ABSTRACT FROM AUTHOR]

Extreme-ultraviolet (EUV) light is used to inspect the Si photomask by analyzing the reflective photons. We demonstrated the re-emitting EUV photons from the flat Si surface and a two-dimensional semicircular Si defect by using the Monte Carlo method with a Gaussian phase function, respectively. The results of a model based on the Feynman path integral matches those of the Monte Carlo method very well by multiplying a correction function. The intensity of re-emitting photons from the defect can offer enough signals at the angle intersecting the surface less than 20°. [ABSTRACT FROM AUTHOR]

We demonstrate functional field transformation in irregular waveguide structures having strong scatter from a stepped conducting wall geometry. The resulting degrees of freedom and significant evanescent field content make it possible to accomplish virtually perfect transformation in a distance of several wavelengths. A microwave experiment verifies frequency-dependent transformation, suggesting that wavelength division multiplexing based on this principle is possible. A mode-selective transformation, which exhibits disparate reflectivities for different modes at the same frequency, may find application in multimode laser cavities. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]