- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Raman and photoluminescence spectral studies in double perovskite epitaxial Nd2CoMnO6 thin films deposited by pulse laser deposition
摘要： The detailed temperature dependent optical properties in double perovskite type Nd2CoMnO6-SrTiO3 (NCMO-STO) thin films have been investigated the experimentally grown epitaxial thin films on STO substrates using pulsed laser deposition technique. At first order room temperature, a Raman spectrum of NCMO/STO thin films are measured in unpolarized geometry using 488 nm laser excitation and confirms its monoclinic bulk like crystal structure. Temperature dependent Raman spectra confirms the appearance of a sharp, intense phonon mode below magnetic ordering, signifies structural phase transition accompanied by magnetic transition. The phonon mode position and line-width are fitted by anharmonic model and found to be strongly softened phonon mode position below TC and strong spin-phonon coupling in the system. The excitation spectrum and the bandgap in NCMO film confirms the yellow emission resulting from energy transfer within the non- centrosymmetric structure.
关键词： Optical properties,Thin films,Photoluminescence spectroscopy,Raman spectroscopy
更新于2025-09-23 15:21:01
-
Epitaxial Growth of Monolayer MoS <sub/>2</sub> on SrTiO <sub/>3</sub> Single Crystal Substrates for Applications in Nanoelectronics
摘要： Monolayer molybdenum disulfide (MoS2) crystals grown on amorphous substrates such as SiO2 are randomly oriented. However, when MoS2 is grown on crystalline substrates, the crystal shapes and orientations are also influenced by their epitaxial interaction with the substrate. In this paper we present the results from chemical vapor deposition growth of MoS2 on three different terminations of single crystal strontium titanate (SrTiO3) substrates. On SrTiO3(111) the monolayer MoS2 crystals form equilateral triangles with two main orientations, in which they align their <21?1?0>-type directions (i.e., the sulfur-terminated edge directions) with the <11?0>-type directions on SrTiO3. This arrangement allows near perfect coincidence epitaxy between seven MoS2 unit cells and four SrTiO3 unit cells. On SrTiO3(110) the MoS2 crystals tend to align their edges with both <11?0> and <11?2?> directions on SrTiO3 as these both provide favorable coincidence lattice registry. This distorts the crystal shapes and introduces an additional strain detectable by photoluminescence. When triangular MoS2 crystals are grown on SrTiO3(001), they again show a preference to align their edges with the <11?0> directions on SrTiO3. Our observations can be explained if the interfacial van der Waals (vdW) bonding between MoS2 monolayers and SrTiO3 is greatest when the maximum commensuration between the lattices is achieved. Therefore, a key finding of this paper is that the vdW interaction between MoS2 and SrTiO3 substrates determines the supported crystal shapes and orientations by the epitaxial relations. Controlled crystal orientations make the growth of large sheets of MoS2 possible when there are multiple nucleation sites. This minimizes the number of grain boundaries and optimizes electronic properties of the material, e.g., charge mobility, which is crucial for the application of monolayer MoS2 in next-generation nanoelectronic devices.
关键词： Raman spectroscopy,van der Waals epitaxy,scanning tunneling microscopy,SrTiO3,2D materials,chemical vapor deposition,MoS2,photoluminescence spectroscopy
更新于2025-09-23 15:21:01
-
Inkjet-Printed Organohalide 2D Layered Perovskites for High-Speed Photodetectors on Flexible Polyimide Substrates
摘要： The synthesis of solution-processed two-dimensional organohalide layered (CH3(CH2)3NH3)2(CH3NH3)n?1PbnI3n+1 (n = 2, 3, and 4) perovskites is presented, where inkjet printing was used to fabricate heterostructure flexible photodetector (PD) devices on polyimide (PI) substrates. Inks for the n = 4 formulation were developed to inkjet-print PD devices that were photoresponsive to broadband incoming radiation in the visible regime, where the peak photoresponsivity R was calculated to be ～0.17 A/W, which is higher compared to prior reports, while the detectivity D was measured to be ～3.7 × 1012 Jones at a low light intensity F ≈ 0.6 mW/cm2. The ON/OFF ratio was also high (～2.3 × 103), while the response time τ on the rising and falling edges was measured to be τ ≈ 24 ms and τ ≈ 65 ms, respectively. Our strain-dependent measurements, conducted here for the first time for inkjet-printed perovskite PDs, revealed that the Ip decreased by only ～27% with bending (radius of curvature of ～0.262 cm?1). This work demonstrates the tremendous potential of the inkjet-printed, composition-tunable, organohalide 2D perovskite heterostructures for high-performance PDs, where the techniques are readily translatable toward flexible solar cell platforms as well.
关键词： organohalide 2D perovskites,flexible photodetector,inkjet printing,photoluminescence spectroscopy,strain dependency
更新于2025-09-23 15:19:57
-
Temperature dependence of inter-dot electron-spin transfer among laterally coupled excited states in high-density InGaAs quantum dots
摘要： The temperature dependence of interdot spin-transfer dynamics at laterally coupled excited states (ESs) in high-density InGaAs quantum dots (QDs) was studied using spin- and time-resolved photoluminescence spectroscopy. At low temperatures below 100 K, temporary suppression of electron-spin polarization decay due to selective relaxation of minority spins from emissive ESs to lower-energy states in neighboring QDs was observed. In the temperature range from 20 K to 140 K, thermal activation of electron spins from lower-energy QD states to higher-energy states via interdot transfer prevents the aforementioned selective relaxation of minority spins, leading to a faster decay of electron-spin polarization during light emission. At high temperatures above 140 K, reinjection of depolarized electron spins from barriers after thermal escape from QD ESs accelerates the further decay of the electron-spin polarization, wherein the electron spins can be activated via ladderlike interdot transfer. These findings indicate that the suppression of reinjection of electron spins from barriers in a high-density QD system is crucial for maintaining high electron-spin polarization during light emission at high temperatures.
关键词： electron-spin polarization,InGaAs quantum dots,interdot spin-transfer dynamics,spin- and time-resolved photoluminescence spectroscopy,temperature dependence
更新于2025-09-19 17:13:59
-
Crystal defects in monocrystalline silicon induced by spot laser melting
摘要： Laser processing of monocrystalline silicon has become an important tool for a wide range of applications. Here, we use microsecond spot laser melting as a model experiment to investigate the generation of crystal defects and residual stress. Using Micro-Raman spectroscopy, defect etching, and transmission electron microscopy, we find no dislocations in the recrystallized volume for cooling rates exceeding jdT=dtj ? 2 (cid:2) 107 K/s, and the samples remain free of residual stress. For cooling rates less than jdT=dtj ? 2 (cid:2) 107 K/s, however, the experiments show a sharp transition to a defective microstructure that is rich in dislocations and residual stress. Moreover, transmission electron microscopy indicates dislocation loops, stacking-fault tetrahedra, and voids within the recrystallized volume, thereby indicating supersaturation of intrinsic point defects during recrystallization. Complementing photoluminescence spectroscopy indicates even three regimes with decreasing cooling rate. Spectra of regime 1 do not contain any defect related spectral lines. In regime 2, spectral lines appear related to point defect clusters. In regime 3, the spectral lines related to point defect clusters vanish, but dislocation-related ones appear. We propose a quantitative model explaining the transition from dislocation-free to dislocation-rich recrystallization by means of the interaction between intrinsic point defects and dislocations.
关键词： monocrystalline silicon,transmission electron microscopy,laser melting,micro-Raman spectroscopy,crystal defects,residual stress,photoluminescence spectroscopy
更新于2025-09-16 10:30:52
-
Interfacial charge transfer between CsPbBr <sub/>3</sub> quantum dots and ITO nanoparticles revealed by single-dot photoluminescence spectroscopy
摘要： The interfacial charge transfer between single CsPbBr3 perovskite quantum dots (QDs) and indium tin oxide (ITO) is investigated by single-dot photoluminescence spectroscopy. It is found that when the Fermi level of single perovskite QDs aligns with that of ITO nanoparticles, the QD surface cannot be charged by the ITO through interfacial electron transfer. Therefore, the QD/ITO system with Fermi level alignments can exclude exciton nonradiative recombination processes involving the additional surface electrons, such as the exciton Auger recombination and the valence band hole transfer processes. Hence the photovoltaic devices based on perovskite QD/ITO system with the Fermi level alignments have the improved photoelectric conversion efficiency.
关键词： Fermi level alignments,single-dot photoluminescence spectroscopy,photoelectric conversion efficiency,interfacial charge transfer,CsPbBr3 quantum dots,ITO nanoparticles
更新于2025-09-11 14:15:04
-
Green coloring of GaN single crystals introduced by Cr impurity
摘要： In this study unintentionally doped GaN grown by hydride vapor phase epitaxy that exhibits a sharply delimited region of green color was investigated. Optical analysis was performed by absorption and photoluminescence spectroscopy. An absorption band between 1.5 and 2.0 eV was found to be responsible for the green color and was related to a sharp emission at 1.193 eV by luminescence and excitation spectroscopy. The appearance of both optical signatures in the region of green color was related to an increase of Cr contamination detected by secondary ion mass spectrometry. We propose that the origin of green color as well as the emission line at 1.193 eV is attributed to internal transitions of Cr4+.
关键词： Crystal impurities,Photoluminescence spectroscopy,Bulk GaN,Hydride vapor phase epitaxy,Absorption spectroscopy
更新于2025-09-10 09:29:36
-
Er-doped antimonite Sb2O3?PbO?ZnO/ZnS glasses studied by low-temperature photoluminescence spectroscopy
摘要： Antimonite glasses Sb2O3?PbO?ZnO/ZnS doped with ErCl3 within the range of 0.25-1.0% were prepared and investigated by means of transmission, photoluminescence excitation and photoluminescence (PL) spectroscopy. In the studied glasses, the wavelength of 522 nm was found to be the most suitable for PL excitation of Er3+ ions doped in both the NIR and VIS spectral ranges. The PL spectra excited by wavelengths at 522 and/or 514.5 nm were measured at room and low temperatures (4 K) in the wavelength range of 400–1700 nm. Low-temperature PL spectroscopy allowed us to observe both the broad luminescence of the host glass centered at around 1050 nm and the narrow emissions caused by Er3+ ions. Special attention was given to the wavelengths where the broad-band luminescence of the host overlaps with 4f–4f transitions within Er3+ ions. A broad PL band of the host glass was observed together with a superimposed narrow emission band at 985 nm (4I11/2? 4I15/2) and a narrow absorption dip at about 970 nm (4I15/2? 4I11/2). This absorption dip is a direct experimental evidence of energy transfer from the electronic structure of the host glass to 4f states of doped-in Er3+ ions. The strongest PL band at 1530 nm, representing transition from the lowest excited manifold 4I13/2 to the ground state manifold 4I15/2 was measured at 300 K and 4 K. The broadening at elevated temperature occurs primarily in the high energy part of the spectrum due to thermal excitation of electrons within the 4I13/2 manifold.
关键词： photoluminescence excitation spectroscopy,broad-band luminescence,low-temperature photoluminescence spectroscopy,erbium,antimonite glasses
更新于2025-09-09 09:28:46
-
Radiative lifetime of localized excitons in transition-metal dichalcogenides
摘要： Disorder derived from defects or local strain in monolayer transition-metal dichalcogenides (TMDs) can lead to a dramatic change in the physical behavior of the interband excitations, producing inhomogeneous spectral broadening and localization leading to radiative lifetime increase. In this study, we have modeled the surface disorder of a monolayer TMD sample through a randomized potential in the layer plane. We show that this model, applied to a monolayer of WSe2, allows us to simulate the spectra of localized exciton states as well as their radiative lifetime. In this context, we give an in depth study of the in?uence of the disorder potential parameters on the optical properties of these defects through energies, density of states, oscillator strengths, photoluminescence (PL) spectroscopy, and radiative lifetime at low temperature (4 K). We demonstrate that localized excitons have a longer emission time than free excitons, in the range of tens of picoseconds or more, the radiative decay time depending strongly on the disorder parameter and dielectric environment. Finally, in order to prove the validity of our model, we compare it to available experimental results of the literature.
关键词： disorder potential,localized excitons,radiative lifetime,transition-metal dichalcogenides,photoluminescence spectroscopy
更新于2025-09-09 09:28:46
-
Photoluminescence Imaging for Buried Defects Detection in Silicon: Assessment and Use-cases
摘要： In this work, the innovative photoluminescence imaging technique is described for applications to buried defect detection in silicon devices. The validity of this emerging technique is first assessed in comparison with well-established characterization techniques (defect selective etching of silicon, X-Ray diffraction topography, cross-sectional transmission electron microscopy imaging and photoluminescence spectroscopy). The paper then describes specific applications illustrating the use of the photoluminescence imaging technique for common processes of the CMOS semiconductor industry. The benefit of this fast, high resolution and non-destructive technique is demonstrated: this includes industrial use of the technique for in-line production control on product wafers.
关键词： photoluminescence imaging,dislocations,non-visual defects,X-Ray diffraction topography,photoluminescence spectroscopy,buried defects
更新于2025-09-04 15:30:14