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Coherent and incoherent bands in La and Rh doped
摘要： In Sr2IrO4 and Sr3Ir2O7, correlations, magnetism, and spin-orbit coupling compete on similar energy scales, creating a new context to study metal-insulator transitions (MIT). We use here angle-resolved photoemission to investigate the MIT as a function of hole and electron doping in Sr3Ir2O7, obtained respectively by Ir/Rh and Sr/La substitutions. We show that there is a clear reduction as a function of doping of the gap between a lower and upper band on both sides of the Fermi level, from 0.2 to 0.05 eV. Although these two bands have a counterpart in band structure calculations, they are characterized by a very different degree of coherence. The upper band exhibits clear quasiparticle peaks, while the lower band is very broad and loses weight as a function of doping. Moreover, their ARPES spectral weights obey different periodicities, reinforcing the idea of their different nature. We argue that a very similar situation occurs in Sr2IrO4 and conclude that the physics of the two families is essentially the same.
关键词： coherence,Sr3Ir2O7,metal-insulator transitions,incoherence,angle-resolved photoemission,doping
更新于2025-09-09 09:28:46
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Room-temperature synthesis of Mn2+-doped cesium lead halide perovskite nanocrystals via a transformation doping method
摘要： Currently, Mn2+-doped cesium lead halide perovskite nanocrystals have attracted research interests. Here, we report a novel room-temperature transformation doping method for the synthesis of Mn2+-doped CsPbCl3 and CsPb(Br/Cl)3 nanocrystals. Innovatively, the transformation of Cs4PbX6 (X=Cl, Br) phase which has no excitation emission to CsPbX3 phase which has strong luminescence was used in this mechanism. Simply injecting MnCl2 precursor into Cs4PbX6 solution could result in the full transformation of Cs4PbX6 phase to CsPbX3 phase and Mn2+-doped CsPbCl3 or CsPb(Br/Cl)3 were obtained. The basic idea for the transformation doping method is that MnCl2 can not only drive the transformation of the two structures but also Mn2+ can substitute Pb2+. In this reaction, the concentration of Mn precursor is a key influence factor. Moreover, instead of the ligand of OA, the acetic acid was used in our method. Through the adjustment of the ligand in precursor, not just the photoluminescence quantum yields of as-prepared Mn2+-doped CsPbCl3 nanocrystals were improved from 7.8 to 32.6% (Mn2+-doped CsPb(Br/Cl)3 nanocrystals even could reach to 42.7%), the nanocrystals also retained outstanding stability. We propose a combination of structure transformation and ion doping as a perovskite doping mechanism. Our doping method is a novel strategy for lead halide perovskite nanocrystals doping project and it could provide more possibilities in the future.
关键词： photoluminescence quantum yields,Cs4PbX6,Mn2+-doped cesium lead halide perovskite nanocrystals,CsPbX3,room-temperature transformation doping method
更新于2025-09-09 09:28:46
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Formation of ultra-low resistance contact with nickel stanogermanide/heavily doped <i>n</i> <sup>+</sup> -Ge <sub/> 1? <i>x</i> </sub> Sn <sub/><i>x</i> </sub> structure
摘要： We examined the formation of Ni(Ge1?xSnx)/n+-Ge1?xSnx contacts with Sb- and P-doped Ge1?xSnx epitaxial layers with various electron concentrations and investigated the crystalline structure and contact resistivity. The fully maintained strain and no serious degradation of the crystallinity were confirmed in the Sb-doped Ge1?xSnx layer after Ni stanogermanidation, while the Sn content slightly decreased. The contact resistivity of Ni(Ge1?xSnx)/Sb-doped Ge1?xSnx interface achieved a value lower than the P-doped samples, in spite of high Sn contents with a Ni germanidation temperature of 350 °C. The ultra-low contact resistivity as low as 10?9 Ω cm2 was obtained with the Ni(Ge1?xSnx)/Sb-doped Ge0.935Sn0.065 sample with an electron concentration of 1.8×1020 cm?3.
关键词： contact resistivity,n-type doping,GeSn
更新于2025-09-09 09:28:46
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Characterization of electron charging and transport properties of Si-QDs with phosphorus doped Ge core
摘要： We formed high-density Si quantum dots (Si-QDs) with undoped and P-doped Ge cores on thermally-grown SiO2 by controlling low pressure chemical vapor depositions of Si and Ge. Doping into the Ge core was carried out during selective-growth of Ge on pre-grown Si-QDs. From hard x-ray photoelectron spectroscopy measurements, we con?rmed phosphorus incorporation into the Ge core, where phosphorus donor concentration in the Ge core was roughly estimated to be ～0.09 at%. When the surfaces of Si-QDs with undoped and P-doped Ge cores were scanned with an Rh-coated tip biased at 0 V, the surface potential of Si-QDs with P-doped Ge cores were increased by ～30 mV, while that of Si-QDs with undoped Ge cores remained unchanged. These results indicate that an electron was extracted from the conduction band of the Ge core due to a phosphorus donor. In the current images measured with the Rh-coated tip, the current level of Si-QDs with P-doped Ge cores on n-Si(100) substrates was higher than that of Si-QDs with undoped Ge cores. This result indicates that phosphorus donor can contribute to an increase in the electron injection rate from the Si-substrate.
关键词： Ge core,Si quantum dot,surface potential,doping,electron transport
更新于2025-09-09 09:28:46
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Rare Earth and Transition Metal Doping of Semiconductor Materials || Gadolinium-doped gallium-nitride
摘要： The race toward a dilute magnetic semiconductor (DMS) that exhibits room-temperature (RT) ferromagnetism has been in progress for about 15 years, sparked by the theoretical prediction that the two wide band-gap semiconductors GaN and ZnO would show a Curie temperature (TC) above 300 K if doped with 5% of Mn and a large hole concentration of 1 (cid:1) 1020/cm3 (Dietl et al., 2000). Despite apparent experimental evidence that RT magnetic order was already reported by many groups shortly after the theoretical prediction, the subject remained unusually controversial in the following years. Dietl (2010) summarizes that after 10 years of research the existence of ferromagnetism is well established for GaAs:Mn and related systems but it remains the major goal in the ?eld to achieve TCs at or above 300 K. Around the same time a review of a large group of theorists summarize: “The results of ab initio calculations seem to suggest that it is rather unlikely to obtain TC values as high as room temperature or above in this range” (Sato et al., 2010). Nonetheless persistent experimental claims of TCs above 300 K for a range of DMS materials can be found up to today. Thus it is worth trying to get a broader view on a given materials systems and compare a range of samples from different sources to elucidate whether these reports are characteristic of the DMS material itself (system-speci?c) or if only peculiarities of a given specimen are reported (sample-speci?c). Only in the former case can we consider those ?ndings to be useful for future potential applications in spintronic devices that have to be operational at ambient conditions.
关键词： ferromagnetism,room-temperature,GaN,Gd doping,dilute magnetic semiconductor
更新于2025-09-09 09:28:46
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Atomic-Level Doping of Metal Clusters
摘要： Atomically precise noble metal (mainly silver and gold) nanoclusters are an emerging category of promising functional materials for future applications in energy, sensing, catalysis, and nanoelectronics. These nanoclusters are protected by ligands such as thiols, phosphines, and hydride and have sizes between those of atoms and plasmonic nanoparticles. In metallurgy, the properties of a pure metal are modified by the addition of other metals, which often offers augmented characteristics, making them more utilizable for real-life applications. In this Account, we discuss how the incorporation of various metal atoms into existing protected nanoclusters tunes their structure and properties. The process of incorporating metals into an existing cluster is known as doping; the product is known as a doped cluster, and the incorporated metal atom is called a dopant/foreign atom. We first present a brief historical overview of protected clusters and the need for doping and explain (with examples) the difference between an “alloy” and a “doped” cluster, which are two frequently confused terms. We then discuss several commonly observed challenges in the synthesis of doped clusters: (i) doping produces a mixture of compositions that prevents the growth of single crystals; (ii) doping with foreign atoms sometimes changes the overall composition and structure of the parent cluster; and (iii) doping beyond a certain number of foreign atoms decomposes the doped cluster. After delineating the challenges, we review a few potential synthetic methods for doped clusters: (i) the co-reduction method, (ii) the galvanic exchange method, (iii) ligand-induced conversion of bimetallic clusters to doped clusters, and (iv) intercluster reactions. As a foreign atom is able to occupy different positions within the structure of the parent cluster, we examine the structural relationship between the parent clusters and their different foreign-atom-doped clusters. We then show how doping enhances the stability, luminescence, and catalytic properties of clusters. The enhancement factor highly depends on the number and nature of the foreign atoms, which can also alter the charge state of the parent cluster. Atomic-level doping of foreign atoms in the parent cluster is confirmed by high-resolution electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry techniques and single-crystal X-ray diffraction methods. The photophysical properties of the doped clusters are investigated using both time-dependent and steady-state luminescence and optical absorption spectroscopies. After presenting an overview of atomic-level doping in metal clusters and demonstrating its importance for enriching the chemistry and photophysics of clusters and extending their applications, we conclude this Account with a brief perspective on the field’s future.
关键词： applications,doping,properties,atomically precise,noble metal nanoclusters,alloy,synthesis,structure
更新于2025-09-09 09:28:46
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Influence of Iodine Doping on the Structure, Morphology and Physical Properties of Manganese Phthalocyanine Thin Films
摘要： Doping with halide ions is a popular method to alter the properties of metal phthalocyanines (MPcs), particularly magnetic and electrical nature of organic semiconductors for applications in spintronic or electronic devices. Doping can cause a structural rearrangement in MPc packing and the physical properties may be correlated with molecular packing. Films of a planar and magnetic MPc, manganese(II)phthalocyanine (MnPc) is chosen for iodine doping study. The optical, magnetic and the electrical properties of pristine and iodine doped MnPc thin films are investigated and can be directly associated with their molecular structure. 2D grazing incidence Synchrotron X-ray diffraction reveals structural disorder in MnPc films upon iodine infusion induced by the reorientation of ordered, edge-on molecular configuration to tilted and face-on configurations in a random fashion. The film morphology changes accordingly, where in the uniform crystallites reorganize in a disordered manner. The ferromagnetic nature of the pristine film gets weakened due to iodine species and favors antiferromagnetic coupling. The study of electrical properties at room temperature by conducting atomic force microscopy reveals that the conductance is enhanced independently of the film thickness due to disorder induced by iodine inclusion.
关键词： Thin Films,Electrical properties,Structural rearrangement,Manganese Phthalocyanine,Iodine doping,Magnetic properties
更新于2025-09-09 09:28:46
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Band Engineering of SrTiO <sub/>3</sub> : Effect of Synthetic Technique and Site Occupancy of Doped Rhodium
摘要： It is well known that doping of Rh into the SrTiO3 lattice introduces 4d donor levels within the band gap which causes reduction in the gap and extends the photocatalytic activity to the visible region of solar spectrum. The mid gap states formed also act as recombination centers and diminishes the efficiency of the material. Herein, we present a combined theoretical and experimental approach to avoid the formation of the so called acceptor mid gap states. For the first time, we study the effect of occupancy of Rh in the Sr site. First principles calculations reveal that mixed occupancies of Rh into Sr and Ti sites lead to the introduction of acceptor levels within the band gap leading to decrease in photocatalytic efficiency. A facile one pot solvothermal approach by avoiding high temperature calcinations is reported to obtain Rh doped SrTiO3 nanoparticles in Rh3+ states suppressing the formation of Rh4+ states by directing Rh towards Sr sites. The photocatalytic activity of Rh doped SrTiO3 nanoparticles is studied in the case of degradation of methylene blue wherein 1.0 Rh sample was found to be highly efficient.
关键词： solvothermal synthesis,SrTiO3,photocatalysis,band engineering,Rh doping
更新于2025-09-09 09:28:46
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Hierarchical Ta-Doped TiO2 Nanorod Arrays with Improved Charge Separation for Photoelectrochemical Water Oxidation under FTO Side Illumination
摘要： TiO2 is one of the most attractive semiconductors for use as a photoanode for photoelectrochemical (PEC) water oxidation. However, the large-scale application of TiO2 photoanodes is restricted due to a short hole diffusion length and low electron mobility, which can be addressed by metal doping and surface decorating. In this paper we report the successful synthesis of hierarchical Ta doped TiO2 nanorod arrays, with nanoparticles on the top (Ta:TiO2), on F-doped tin oxide (FTO) glass by a hydrothermal method, and its application as photoanodes for photoelectrochemical water oxidation. It has been found that the incorporation of Ta5+ in the TiO2 lattice can decrease the diameter of surface TiO2 nanoparticles. Ta:TiO2-140, obtained with a moderate Ta concentration, yields a photocurrent of ～1.36 mA cm?2 at 1.23 V vs. a reversible hydrogen electrode (RHE) under FTO side illumination. The large photocurrent is attributed to the large interface area of the surface TiO2 nanoparticles and the good electron conductivity due to Ta doping. Besides, the electron trap-free model illustrates that Ta:TiO2 affords higher transport speed and lower electron resistance when under FTO side illumination.
关键词： hierarchical TiO2,photoelectrochemical water oxidation,Ta doping,charge separation
更新于2025-09-09 09:28:46
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Electrically and optically tunable responses in graphene/ transition metal dichalcogenide heterostructures
摘要： Heterostructures involving layered two dimensional (2D) transitional metal dichalcogenides (TMDCs) are not only fundamentally interesting to explore emerging properties at atomically thin limit, but also technically important to achieve novel optoelectronic devices. However, achieving tunable optoelectronic properties and clarifying interlayer processes (charge transfer, energy transfer) in 2D heterostructures remain to be part of the key challenges so far. Here, by fabricating heterostructures of graphene and monolayer TMDCs (n-type MoS2 and p-type WSe2), we demonstrate both electrically and optically tunable responses of the heterostructures, revealing the critical interface processes between graphene and TMDCs. In MoS2/graphene heterostructure, electron transfer from MoS2 to graphene is observed and gate-tunable interface relaxation induces the electrically controlled photoluminescence (PL). While in WSe2/graphene heterostructure, electron transfer from graphene to WSe2 is observed and the PL is tuned by carrier density, which can be controlled by the gate voltage. The interlayer process can also be modulated by laser intensity, which enables photo-induced doping on graphene and optically tunable electrical characteristics of graphene. Combining the tunable Fermi level of graphene and strong light-matter interaction of monolayer TMDCs, our demonstrations are important to the design of multifunctional and efficient optoelectronic devices with TMDCs/graphene heterostructures.
关键词： photo-induced doping,heterostructure,charge transfer,optoelectronic,electrically tunable,transition metal dichalcogenides
更新于2025-09-09 09:28:46