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Remote Phonon Scattering in Two-Dimensional InSe FETs with High-κ Gate Stack
摘要： This work focuses on the effect of remote phonon arising from the substrate and high-κ gate dielectric on electron mobility in two-dimensional (2D) InSe field-effect transistors (FETs). The electrostatic characteristic under quantum confinement is derived by self-consistently solving the Poisson and Schr?dinger equations using the effective mass approximation. Then mobility is calculated by the Kubo–Greenwood formula accounting for the remote phonon scattering (RPS) as well as the intrinsic phonon scatterings, including the acoustic phonon, homopolar phonon, optical phonon scatterings, and Fr?hlich interaction. Using the above method, the mobility degradation due to remote phonon is comprehensively explored in single- and dual-gate InSe FETs utilizing SiO2, Al2O3, and HfO2 as gate dielectric respectively. We unveil the origin of temperature, inversion density, and thickness dependence of carrier mobility. Simulations indicate that remote phonon and Fr?hlich interaction plays a comparatively major role in determining the electron transport in InSe. Mobility is more severely degraded by remote phonon of HfO2 dielectric than Al2O3 and SiO2 dielectric, which can be effectively insulated by introducing a SiO2 interfacial layer between the high-κ dielectric and InSe. Due to its smaller in-plane and quantization effective masses, mobility begins to increase at higher density as carriers become degenerate, and mobility degradation with a reduced layer number is much stronger in InSe compared with MoS2.
关键词： two-dimensional material,indium selenide,mobility,phonon scattering,high-κ dielectric,field effect transistor
更新于2025-09-19 17:15:36
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Fabrication of ZnSe/InP Heterojunctions on Flat and Shaped Surfaces of InP Laser Crystals
摘要： We have studied the growth of zinc selenide layers on flat and shaped indium phosphide surfaces. The growth rate of zinc selenide has been shown to depend on substrate orientation. It has been shown that the present results can be useful in designing mesa stripe structures for quantum electronic instruments. We have fabricated mesa stripe laser diodes operating on the absorption band of methane and suitable for producing fiber-optic signal transmission systems.
关键词： methane,semiconductor heterostructures,zinc selenide,laser diodes
更新于2025-09-19 17:13:59
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Hierarchical Ni-MoSex@CoSe2 core-shell nanosphere as highly active bifunctional catalyst for efficient dye-sensitized solar cell and alkaline hydrogen evolution
摘要： Core-shell structured nanocomposites based on transition metal selenides have a broad development prospect as Pt-free electrocatalyst in energy conversion due to large surface area, rich edge sites, as well as synergistic interactions between the core and shell. Herein, the preparation of core-shell structured transition metal selenides nanospheres was achieved through a facile wrapping process using zeolitic imidazolate framework (ZIF-67) as the cobalt source, which assembled on glycerol precursor nanospheres. After a selenization treatment, this formed core-shell structure had a Ni-MoSex inner core, supporting the CoSe2 outer shell (denoted as Ni-MoSex@CoSe2 CSNs). And the resultant Ni-MoSex@CoSe2 CSNs not only had a large number of active sites, but also was good for adsorbing/transferring iodine and hydrogen ions. Therefore, Ni-MoSex@CoSe2 delivered superior performance in dye-sensitized solar cells (DSSCs) and alkaline hydrogen evolution reactions (HERs). DSSCs based on Ni-MoSex@CoSe2 CSNs performed an outstanding power conversion efficiency (PCE) of 9.58% which was much higher than that of Pt (8.32%). A lower onset potential of 37.5 mV and a smaller Tafel slope of 68.9 mV dec?1 were achieved by Ni-MoSex@CoSe2 as electrocatalysts for HER in 1.0 M KOH. This work affords a new idea for the design of cut-price core-shell nanomaterials with high efficiency and can be extended to the synthesis of other electrocatalysts substituting Pt-based catalysts.
关键词： Hydrogen evolution,Core-shell nanosphere,Bifunctional catalyst,Dye-sensitized solar cell,Ni-MoSex@CoSe2,Transition metal selenide
更新于2025-09-19 17:13:59
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Wafer-size growth of 2D layered SnSe films for UV-Visible-NIR Photodetector Arrays with High Responsitivity
摘要： Due to its excellent electrical and optical property, tin selenide (SnSe), a typical candidate of two-dimentional (2D) semiconductors, has attracted great attention in the field of novel optoelectronics. However, the large-area growth of high-quality SnSe films still remain a great challenge which limit its practical applications. Here, wafer-size SnSe ultrathin films with high uniformity and crystallization are deposited via a scalable magnetron sputtering method. The results show that the SnSe photodetector is highly sensitive to a broad wavelength in the UV-Visible-NIR range, especially showing an extremely high responsivity of 277.3 A W -1 with the corresponding external quantum efficiency of 8.5×104% and detectivity of 7.6×1011 Jones. These figures-of-merits are among the best performance for the sputter-fabricated 2D photodetector devices. The photodetecting mechanisms based on a photogating effect induced by the trapping effect of the localized defects are discussed in details. The results indicate that the few-layered SnSe films from the sputtering growth would have great potential in designing high-performance photodetector arrays.
关键词： tin selenide,detectivity,responsivity,optoelectronics,SnSe,UV-Visible-NIR,2D semiconductors,external quantum efficiency,photodetector,magnetron sputtering
更新于2025-09-19 17:13:59
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Optoelectronic Impacts of Particle Size in Water-Dispersible Plasmonic Copper Selenide Nanoparticles
摘要： There is significant interest in earth-abundant plasmonic materials, but whether or not their performance can match or even surpass their noble metal counterparts remains to be established. An important step in determining the extent of their versatility is to understand basic aspects of their plasmonic features. In this work, we measure near-infrared plasmonic molar extinction coefficients of water-dispersible copper selenide nanoparticles of different diameters. Obtaining molar extinction coefficients of these materials has traditionally been challenging because particles could not be synthesized at size ranges that avoid convoluting factors such as carrier density anomalies, surface depletion, and quantum confinement effects. Here, we report a straightforward synthesis that can control particle diameter within a size range that mitigates these convolutions, and then use these materials to establish their molar extinction coefficients. Importantly, we determine that size-dependent increases in molar extinction coefficients are likely a result of increases only in scattering cross-section, much like their noble metal analogues. Further, we show that the size-dependent trends in molar extinction coefficient follow the trends predicted by Mie theory well. These results suggest a promising outlook for the future implementation of earth-abundant and alternative plasmonic technologies from this material class.
关键词： plasmonic materials,copper selenide nanoparticles,molar extinction coefficients,earth-abundant materials,Mie theory
更新于2025-09-19 17:13:59
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Nonradiative Energy Transfer in a??Colloidal Quantum Dot Nanoclustera??Dyea?? Hybrid Nanostructures: Computer Experiment
摘要： A computer model of nonradiative electronic excitation energy transfer from nanoclusters of colloidal quantum dots of cadmium selenide to the meso-tetra(3-pyridyl)porphyrin molecule in hybrid nanostructures nanocluster–dye has been constructed and analyzed. The model uses the experimental luminescence and absorption spectra of quantum dots and the dye, takes into account heterogeneity of the properties of quantum dots in nanoclusters and the different location of the dye in the hybrid structure. It has been shown that, in the ideal case, due to such energy transfer, the intensity of the luminescent signal of the dye can be increased by five orders of magnitude. However, this value is significantly reduced due to nonluminescent particles, the presence of a protective ligand shell, a large size distribution of the particles, and the non-optimal geometric structure of the hybrid system.
关键词： porphyrin dye,colloidal quantum dots,F?rster resonance energy transfer,hybrid systems,cadmium selenide,computer simulation
更新于2025-09-19 17:13:59
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Microwave assisted synthesis of CuInGaSe2 quantum dots and spray deposition of their composites with graphene oxide derivatives
摘要： In this contribution, we explore a spray deposition technique to prepare thin films based on nanocomposites of graphene oxide (GO) or reduced graphene oxide (rGO) with CuInGaSe2 quantum dots (QD) synthesized by a microwave-assisted method. Small nanocrystals in the tetragonal phase and emitting light at 650 nm were obtained. Water-based solutions of the nanocomposites were sprayed onto transparent conductive glass substrates using an automated ultrasonic spray system and the resulting thin films were evaluated with respect to their morphological and electrochemical properties. The distribution and organization of the graphene sheets in the composites were affected by the interaction between the nanocrystals and GO or rGO, which also interfered on the electronic properties. In addition, we demonstrated a possible application of the thin film based on the rGO-QD composite as a counter electrode in dye-sensitized solar cells.
关键词： copper indium gallium selenide,dye-sensitized solar cell,graphene oxide,microwave assisted synthesis,spray deposition,reduced graphene oxide
更新于2025-09-16 10:30:52
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Effect of CdSe thickness deposited by electrophoretic deposition for quantum-dot-sensitized solar cell
摘要： Cadmium selenide (CdSe) and titanium dioxide (TiO2) nanoparticles in chloroform were deposited on fluorine-doped tin oxide (FTO) conducting glass-substrate by the electrophoretic deposition (EPD) method at varying voltages and deposition times. Firstly, TiO2 nanoparticles were deposited on FTO conducting glass-substrate at 150 V for 30 s by EPD method. After that, CdSe was deposited on TiO2 layer at 100 V for 60 s, 90 s, and 120 s by EPD method. The CdSe/TiO2 films were characterized using UV-visible spectroscopy (UV-vis) and scanning electron microscope (SEM). A complete quantum-dots-sensitized solar cells (QDSSCs) were assembled using polysulfide electrolyte and Cu2S counter electrodes. Polysulfide electrolyte was prepared with mixture of sulphur, sodium hydroxide and methanol/deionized water. The power conversion efficiency of 2% was achieved using a CdSe/TiO2 (100 V, 120 s) electrode, under simulated AM 1.5, 100 mW cm-2 illumination.
关键词： Cadmium selenide nanoparticles,quantum dots sensitized solar cell,electrophoretic deposition,titanium dioxide nanoparticles
更新于2025-09-16 10:30:52
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Impact of Post-Deposition Recrystallization by Alkali Fluorides on Cu(In,Ga)Se2Thin-Film Materials and Solar Cells
摘要： Using thermal evaporation, Cu(In,Ga)Se2 (CIGS) layers were deposited at low temperature (350 °C) and high rate (10 μm/h) using a single stage process. They were then recrystallized using a variety of alkali fluorides: NaF, KF, RbF and CsF. To ensure that the substrate would not influence the study (via alkali diffusion), the samples were deposited on silicon wafers. The chemical, physical and electrical properties of the films were then characterized, demonstrating that all alkali fluorides behave as fluxing agents to enhance recrystallization and conductivity, and induce a (112) preferential orientation. Secondary ion mass spectrometry analysis showed that no modification of the elements' distribution occurs because of recrystallization. Solar cells were also fabricated and characterized, indicating that NaF can double the efficiency of solar cells compared to the as-deposited layers. This enhancement is accompanied by the disappearance of a rollover, voltage dependent current collection and shunt from the current density-voltage curves. However, even for the best recrystallization, the current is still limited to 28 mA/cm2, indicating that only a portion (0.75 μm) of the full device (2 μm) is activated.
关键词： Recrystallization,Copper indium gallium selenide,Alkali-fluorides,Solar cells
更新于2025-09-16 10:30:52
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Investigation on Surface Properties of Mn-Doped CdSe Quantum Dots Studied by X-ray Photoelectron Spectroscopy
摘要： In this work, we report on the effects of incorporating manganese (Mn) dopant into different sizes of cadmium selenide (CdSe) quantum dots (QDs), which improves the electronic and optical properties of the QDs for multiple applications such as light-emitting diodes, lasers, and biological labels. Furthermore, the greener inverse Micelle method was implemented using organic ligand, which is oleic acid. This binding of the surface enhanced the QDs’ surface trap passivation of Mn-doped CdSe, which then increased the quantity of the output. In addition, the inverse Micelle technique was used successfully to dope Mn into CdSe QDs without the risk of Mn dopants being self-purified as experienced by wurtzite CdSe QDs. Also, we report the X-ray photoelectron spectroscopy (XPS) results and analysis of zinc blended manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs), which were synthesized with physical sizes that varied from 3 to 14 nm using the inverse Micelle method. The XPS scans traced the existence of the Se 3d and Cd 3d band of CdSe crystals with a 54.1 and 404.5 eV binding energy. The traced 640.7 eV XPS peak is proof that Mn was integrated into the lattice of CdSe QDs. The binding energy of the QDs was related to the increase in the size of the QDs.
关键词： quantum dots,semiconductor,chemical synthesis,cadmium selenide,X-ray photoelectron spectroscopy,manganese doped
更新于2025-09-16 10:30:52