We apply a stochastic version of an optimally tuned range-separated hybrid functional to provide insight on the electronic properties of P- and B- doped Si nanocrystals of experimentally relevant sizes. We show that we can use the range-separation parameter for undoped systems to calculate accurate results for dopant activation energies. We apply this strategy for tuning functionals to study doped nanocrystals up to 2.5 nm in diameter at the hybrid functional level. In this confinement regime, the P- and B- dopants have large activation energies and have strongly localized states that lie deep within the energy gaps. Structural relaxation plays a greater role for B-substituted dopants and contributes to the increase in activation energy when the B dopant is near the nanocrystal surface.
Electron conduction through bare metal oxide nanocrystal (NC) films is hindered by surface depletion regions resulting from the presence of surface states. We control the radial dopant distribution in tin-doped indium oxide (ITO) NCs as a means to manipulate the NC depletion width. We find in films of ITO NCs of equal overall dopant concentration that those with dopant-enriched surfaces show decreased depletion width and increased conductivity. Variable temperature conductivity data shows electron localization length increases and associated depletion width decreases monotonically with increas…
Co-doped with calcium, europium and erbium ions lanthanum vanadate crystalline nanoparticles are synthesized and investigated with a goal to clarify the mechanisms of calcium and erbium impurities effects on europium ions luminescence and to find compositions with enhanced luminescence intensity. The XRD analysis reveals dependence of crystal structure on dopants concentration: monoclinic crystal phase is observed for low dopant concentrations and content of tetragonal crystal phase increases with dopant concentrations increase. The SEM investigation reveals formation of nanoparticles with two…
Robust control over the carrier type is fundamental for the fabrication of nanocrystal-based optoelectronic devices, such as the p-n homojunction, but effective incorporation of impurities in semiconductor nanocrystals and its characterization is highly challenging due to their small size. Herein, InAs nanocrystals, post-synthetically doped with Cd, serve as a model system for successful p-type doping of originally n-type InAs nanocrystals, as demonstrated in field-effect transistors (FETs). Advanced structural analysis, using atomic resolution electron microscopy and synchrotron X-ray absorpt…
Anisotropic Dopant and Strain Architectures in WS$_2$ Nanocrystals Driven by Growth Kinetics
Universidade Federal de São Carlos（圣卡洛斯联邦大学）；Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM)（巴西同步辐射光实验室（LNLS），巴西能源与材料研究中心（CNPEM））；Universidade Federal de Ouro Preto（欧鲁普雷图联邦大学）；The Pennsylvania State University（宾夕法尼亚州立大学）
Metal-halide perovskite nanocrystals have demonstrated excellent optoelectronic properties for light-emitting applications. Isovalent doping with various metals (M2+) can be used to tailor and enhance their light emission. Although crucial to maximize performance, an understanding of the universal working mechanism for such doping is still missing. Here, we directly compare the optical properties of nanocrystals containing the most commonly employed dopants, fabricated under identical synthesis conditions. We show for the first time unambiguously and supported by first principles calculations …
Nanocrystals based on metal-halide perovskites offer a promising material platform for highly efficient lighting. Using transient optical spectroscopy, we study excitation recombination dynamics in manganese-doped CsPb(Cl,Br)3 perovskite nanocrystals. We find an increase in the intrinsic excitonic radiative recombination rate upon doping, which is typically a challenging material property to tailor. Supported by ab initio calculations, we can attribute the enhanced emission rates to increased exciton localization through lattice periodicity breaking from Mn dopants, which increases exciton eff…
Structural, magnetic, and optical properties of zinc- and copper- substituted nickel ferrite nanocrystals
铁氧体纳米晶由于其丰富的物理性质而成为人们感兴趣的材料。在这里，我们将掺杂剂Zn和Cu添加到镍铁氧体纳米晶体Ni 1-xMxFe 2 O 4（0<=x<=1，M{ \in }{Cu，Zn}）中，并表征样品的相关性质如何相应地改变。基本上，这些掺杂导致Fe+3离子重排到两个预先存在的八面体和四面体位置。事实上，这，我们表明，诱导相关的磁性掺杂样品。在Cu掺杂的情况下，Jahn-Teller效应也出现了，我们通过样品的FTIR光谱来识别。此外，我们发现掺杂样品的晶格参数增加，以及掺杂样品的超顺磁性行为，而Jahn-Teller效应排除了CuFe 2 O 4纳米晶体中类似的行为。采用室温光致发光法研究了Zn和Cu掺杂对镍铁氧体纳米晶光学性质的影响。
Si nanocrystals have been extensively studied because of their novel properties and their potential applications in electronic, optoelectronic, photovoltaic, thermoelectric and biological devices. These new properties are achieved through the combination of the quantum confinement of carriers and the strong influence of surface chemistry. As in the case of bulk Si the tuning of the electronic, optical and transport properties is related to the possibility of doping, in a controlled way, the nanocrystals. This is a big challenge since several studies have revealed that doping in Si nanocrystals…
Precursor stoichiometry controls dopant structure, defect chemistry, and valence in Mn-doped ZnGa$_2$O$_4$ nanocrystals
HUN-REN Wigner Research Centre for Physics（匈牙利科学院维格纳物理研究中心）；Institute for Solid State Physics and Optics（凝聚态物理与光学研究所）；Budapest University of Technology and Economics（布达佩斯科技经济大学）；University of Notre Dame（圣母大学）
Modulation of structural short-range order due to chemical patterning in multi-component amorphous interfacial complexions
University of California, Irvine（加州大学尔湾分校）；Johns Hopkins University（约翰斯·霍普金斯大学）；Irvine Materials Research Institute, University of California, Irvine（加州大学尔湾分校欧文材料研究所）
To fully deploy the potential of semiconductor nanocrystal films as low-cost electronic materials, a better understanding of the amount of dopants required to make their conductivity metallic is needed. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is described by the Mott criterion. Here, we theoretically derive the critical concentration $n_c$ for films of heavily doped nanocrystals devoid of ligands at their surface and in direct contact with each other. In the accompanying experiments, we investigate the conduction mechanism in films of p…
Tuning of the electronic properties of pre-synthesized colloidal semiconductor nanocrystals (NCs) by doping plays a key role in the prospect of implementing them in printed electronics devices such as transistors, and photodetectors. While such impurity doping reactions have already been introduced, the understanding of the doping process, the nature of interaction between the impurity and host atoms, and the conditions affecting the solubility limit of impurities in nanocrystals are still unclear. Here, we used a post-synthesis diffusion based doping reaction to introduce Ag impurities into I…
Yb3+-doped inorganic metal-halide perovskites (Yb3+:CsPbX3, X = Cl, Br) have recently been discovered to display highly efficient quantum cutting, in which the energy from individual blue or UV photons absorbed by the material is re-emitted in the form of pairs of near-infrared photons by Yb3+ dopants. Experimental photoluminescence quantum yields approaching 200{%} have been reported. As the first quantum-cutting materials that combine such high photoluminescence quantum yields with strong, broadband absorption in the visible, these materials offer unique opportunities for enhancing the effic…
