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Effect of surface modification and laser repetition rate on growth, structural, electronic and optical properties of GaN nanorods on flexible Ti metal foil
摘要： The effect of flexible Ti metal foil surface modification and laser repetition rate in laser molecular beam epitaxy growth process on the evolution of GaN nanorods and their structural, electronic and optical properties has been investigated. The GaN nanostructures were grown on bare- and pre-nitridated Ti foil substrates at 700 °C for different laser repetition rates (10–30 Hz). It is found that the low repetition rate (10 Hz) promotes sparse growth of three-dimensional inverted-cone like GaN nanostructures on pre-nitridated Ti surface whereas the entire Ti foil substrate is nearly covered with film-like GaN consisting of large-sized grains for 30 Hz growth. In case of the GaN growth at 20 Hz, uniformly-aligned, dense (～8 × 109 cm?2) GaN nanorods are successfully grown on pre-nitridated Ti foil whereas sparse vertical GaN nanorods have been obtained on bare Ti foil under similar growth conditions for both 20 and 30 Hz. X-ray photoemission spectroscopy (XPS) has been utilized to elucidate the electronic structure of GaN nanorods grown under various experimental conditions on Ti foil. It confirms Ga–N bonding in the grown structures, and the calculated chemical composition turns out to be Ga rich for the GaN nanorods grown on pre-nitridated Ti foil. For bare Ti substrates, a preferred reaction between Ti and N is noticed as compared to Ga and N leading to sparse growth of GaN nanorods. Hence, the nitridation of Ti foil is a prerequisite to achieve the growth of dense and aligned GaN nanorod arrays. The X-ray diffraction, high resolution transmission electron microscopy and Raman studies revealed the c-axis growth of wurtzite GaN nanorods on Ti metal foil with good crystallinity and structural quality. The photoluminescence spectroscopy showed that the dense GaN nanorod possesses a near band edge emission at 3.42 eV with a full width at half maximum of 98 meV at room temperature. The density-controlled growth of GaN nanorods on a flexible substrate with high structural and optical quality holds promise for potential applications in futuristic flexible GaN based optoelectronics and sensor devices.
关键词： Ti metal foil,laser molecular beam epitaxy,optical properties,GaN nanorods,structural properties,surface modification,electronic properties,laser repetition rate
更新于2025-09-23 15:19:57
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Epitaxial growth and determination of the band alignment for NixMg1-xO/MgO interface by laser molecular beam epitaxy
摘要： By laser molecular beam epitaxy, single crystalline NixMg1-xO films have been successfully synthesized on MgO(100) surface. The in situ reflection high-energy electron diffraction patterns show that the induced O2 background gas with at least 1.0 × 10?3 Pa is necessary to the epitaxial growth of NixMg1-xO films. The X-ray diffraction patterns reveal the single-phase growth along (200) direction. The energy band alignment at the interface is investigated by employing in situ X-ray photoelectron spectroscopy. The valence band offsets are determined to be from 1.47 eV to 1.50 eV with the decrease of Ni content (0.39 / 0.35). Furthermore, the work function is evaluated by using in situ ultraviolet photoemission spectroscopy, indicating the values from 4.33 eV to 4.64 eV. This study provides a promising guidance for the solar-blind device design and fabrication.
关键词： Work function,X-ray photoelectron spectroscopy,Band alignment,Ultraviolet photoemission spectroscopy,Laser molecular beam epitaxy
更新于2025-09-19 17:13:59
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Spin excitations in laser-molecular-beam epitaxy grown nanosized YIG films: towards low relaxation and desirable magnetization profile
摘要： We describe synthesis of nanosized Y3Fe5O12 (YIG) films grown by laser-molecular-beam epitaxy on Gd3Ga5O12 (GGG) and Nd3Ga5O12 (NdGG) substrates with (111) orientation and present results of ferromagnetic resonance (FMR) and spin wave propagation studies in these heterostructures. It is found that magnetic parameters of YIG films grown on NdGG and GGG substrates are considerably different. FMR spectra of YIG/NdGG structures are characterized by a large number of narrow peaks, while FMR spectra of YIG/GGG structures consist of a small number of peaks or one peak. The effective magnetization of YIG films grown on NdGG substrates is less than that of YIG films grown on GGG and is more sensitive to the growth conditions. A lateral inhomogeneity of YIG/NdGG structures is observed in spin wave propagation experiments. For YIG/NdGG and YIG/GGG structures the FMR linewidth ?H of a single peak sharply increases with temperature decrease from 298 to 67 K. The observed increase of ?H is explained by typical relaxation processes caused by the presence of Fe2+ ions. From the spin-wave propagation study it is also found that relaxation of spin-waves explains only a minor part of the FMR single peak linewidth in YIG/NdGG structures. On the basis of obtained results, YIG/GGG/semiconductor- and YIG/NdGG/semiconductor-heterostructures with expected low spin-wave relaxation and desirable effective magnetization profile are proposed.
关键词： magnetization profile,ferromagnetic resonance,spin wave propagation,laser-molecular-beam epitaxy,YIG films
更新于2025-09-19 17:13:59
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Magnetization reversal in NiFe <sub/>2</sub> O4/SrTiO <sub/>3</sub> nanoheterostructures grown by laser molecular beam epitaxy
摘要： NiFe2O4/SrTiO3(001) nanoheterostructures have been fabricated by laser molecular beam epitaxy method. Surface morphology and crystal structure of Ni-ferrite films were analysed by atomic force microscopy (AFM), reflection of high energy electron diffraction (RHEED), X-ray diffraction (XRD). X-ray methods prove the presence of inverse spinel crystal structure of films that was confirmed by measurements of spectral dependence of optical polar Kerr (PMOKE) effect. Study of magnetization reversal for different orientations of magnetic field carried out by vibration sample magnetometry (VSM) and longitudinal magneto-optical Kerr effect (LMOKE) are presented. In-plane magnetization loops exhibit 90 period indicating presence of biaxial magnetic anisotropy. Asymmetry of LMOKE hysteresis loops is related to manifestation of quadratic in magnetization effects in reflection of light.
关键词： nanoheterostructures,NiFe2O4/SrTiO3,biaxial magnetic anisotropy,laser molecular beam epitaxy,magnetization reversal
更新于2025-09-12 10:27:22