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Graphene Nucleation Preference at CuO Defects Rather Than Cu2O on Cu(111): A Combination of DFT Calculation and Experiment
摘要： It is well-known that reducing the nucleation density is an effective way to enhance the growth quality of graphene. In this work, we explore the mechanism of graphene nucleation and growth around CuO defects on a Cu(111) substrate by using density functional theory (DFT) combined with the nudged elastic band (NEB) method. The defect formation mechanism at the initial nucleation stage is also studied. Our calculation results of the C adsorption energy and the reaction barrier of C–C dimer formation illustrate that the initial nucleation of graphene could be promoted by artificially introducing CuO defects on a Cu(111) surface and the nucleation on the clean Cu(111) substrate could thus be suppressed. These conclusions have been verified by graphene growth experiments using a chemical vapor deposition (CVD) method. Further studies showed that graphene grown around CuO “seed crystals” could maintain its structural integrity without significantly producing defective carbon rings. This work provides fundamental understanding and theoretical guidance for controllable preparing large dimension and high quality graphene by artificially introducing CuO seeds.
关键词： CuO,Cu2O,Graphene,DFT,Nucleation
更新于2025-09-23 15:21:21
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General synthesis of uniform three-dimensional metal oxides/reduced graphene oxide aerogels by a nucleation-inducing growth strategy for high-performance lithium storage
摘要： Three-dimensional (3D) transition metal oxides/reduced graphene oxide aerogels (TMOs/rGO-G) have received great attention for boosting the performance of alkali-ion batteries owing to abundant active sites and short lithium ion diffusion path. In this paper, we design a general self-assembly strategy for preparing uniform 3D porous TMOs/rGO-G (TMOs = CoO, MnO, Fe2O3) hybrids even with very high TMOs content (especially > 80% for CoO/rGO-G and Fe2O3/rGO-G). This strategy contains successive self-assembly processes: self-assembly nucleation of TMOs on GO nanosheets in N,N-Dimethylformamide (DMF)/H2O mixed solvent, and 3D reduction-assembly of the obtained precursor for hybrid hydrogels along with nucleation-inducing growth of TMOs. Benefitting from the 3D porous network for fast ion/electron transport, and uniform hybrid between TMOs and rGO with high TMO content, the 3D TMOs/rGO-G demonstrates an impressive lithium storage performance with both outstanding rate capability and excellent cycling stability. Specifically, the 3D CoO/rGO-G delivers a reversible capacity of 1142.8 mAh g-1 after 100 cycles at 0.5 A g-1, and high pseudocapacitive lithium storage behavior with 93.1% at 2 mV s-1 leading to outstanding rate capability with 624.7 mAh g-1 at 8 A g-1, as well as excellent stability with 493.3 mAh g-1 over 800 cycles at 4 A g-1. This general strategy demonstrates a general method in design and synthesis of uniform 3D porous TMOs/rGO-G for the energy storage.
关键词： nucleation-inducing growth,aerogels,3D transport channels,uniform hybrids,lithium storages
更新于2025-09-23 15:21:21
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Nucleation of Three-Dimensional Ge Islands on a Patterned Si(100) Surface
摘要： The nucleation of three-dimentional Ge islands formed on a pre-patterned Si substrate with an array of round pits is studied. It is found that the Ge islands nucleate within pits with pointed bottoms and along the perimeters of pits with flat bottoms. This effect is determined by the difference between the distributions of elastic strains at the Ge/Si interface for differently shaped pit bottoms. The results of the simulation of growth show that, in the case of pits with pointed bottoms, the most relaxed regions are at the centers of the pit bottoms and the nucleation of islands takes place just in these regions. At the same time, in the case of pits with flat bottoms, the most relaxed regions are shifted from the pit bottoms to the pit edges, resulting in the nucleation of islands along the pit perimeters.
关键词： three-dimensional Ge islands,patterned Si substrate,elastic strains,nucleation,Ge/Si interface
更新于2025-09-23 15:21:01
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Ferroelectricity of Hf <sub/>x</sub> Zr <sub/>1?x</sub> O <sub/>2</sub> Thin Films Fabricated Using TiN Stressor and ZrO <sub/>2</sub> Nucleation Techniques
摘要： We studied the ferroelectricity and the leakage current (J) properties of the TiN/ZrO2/HfxZr1?xO2/ZrO2/TiN capacitor (D-ZrO2) with the ZrO2 nucleation layers, comparing to the TiN/HfxZr1?xO2/TiN capacitor (D-TiN) with the TiN stressor layers. The larger ferroelectric phase ratio was achieved by the epitaxial like grain growth of the HfxZr1?xO2 film on the surface of the top- and bottom-ZrO2 nucleation layers. Thus, the larger remanent polarization (2Pr = 29 μC/cm2) of D-ZrO2 was obtained compared to that (24 μC/cm2) of D-TiN. Moreover, the J value of D-ZrO2 was approximately one order of magnitude lower than that of D-TiN. Therefore, these results suggest that the superior ferroelectricity of HZO film can be obtained using the ZrO2 nucleation technique instead of the TiN stressor technique.
关键词： HfxZr1?xO2,Thin Films,Ferroelectricity,ZrO2 Nucleation,TiN Stressor
更新于2025-09-23 15:21:01
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Nucleation-controlled growth of superior lead-free perovskite Cs3Bi2I9 single-crystals for high-performance X-ray detection
摘要： The organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. However, the issues raised by the toxic lead element and marginal stability due to the volatile organic components have severely limited their potential applications. In this work, we develop a nucleation-controlled solution method to grow large size high-quality Cs3Bi2I9 perovskite single crystals (PSCs). Using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. We ?nd that X-ray detectors based on PSCs exhibit high sensitivity of 1652.3 μC Gyair?1 cm?2 and very low detectable dose rate of 130 nGyair s?1, both desired in medical diagnostics. In addition, its outstanding thermal stability inspires us to develop a high temperature X-ray detector with stable response at up to 100 °C. Furthermore, PSCs exhibit high X-ray imaging capability thanks to its negligible signal drifting and extremely high stability.
关键词： nucleation-controlled growth,high sensitivity,X-ray detection,lead-free,perovskite single crystals
更新于2025-09-23 15:21:01
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Fragmentation of Magica??Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures
摘要： Colloidal small-size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic-size clusters (MSC). Here, we report our synthesis of small-size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1-octadecene (ODE), we show that after the formation of the PC in the pre-nucleation stage, the addition of tri-n-octylphosphine oxide (TOPO) facilitates the production of small-size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small-size QDs even at room temperature. Our findings introduce a new approach to making small-size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two-pathway model proposed for the pre-nucleation stage of colloidal binary QDs, the present study aids in the advance of non-classical nucleation theory.
关键词： crystal growth,nucleation,cadmium sulfide,magic-size clusters,quantum dots
更新于2025-09-23 15:21:01
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Fragmentation of Magica??Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures
摘要： Colloidal small-size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic-size clusters (MSC). Here, we report our synthesis of small-size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1-octadecene (ODE), we show that after the formation of the PC in the pre-nucleation stage, the addition of tri-n-octylphosphine oxide (TOPO) facilitates the production of small-size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small-size QDs even at room temperature. Our findings introduce a new approach to making small-size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two-pathway model proposed for the pre-nucleation stage of colloidal binary QDs, the present study aids in the advance of non-classical nucleation theory.
关键词： crystal growth,nucleation,cadmium sulfide,magic-size clusters,quantum dots
更新于2025-09-23 15:21:01
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Development of Synthetic Methods to Grow Long-Wavelength Infrared-Emitting HgTe Quantum Dots in Dimethylformamide
摘要： Most successful syntheses of long wavelength infrared (IR) absorbing/emitting Hg-chalcogenide quantum dots (QDs) use either aqueous or organic solvent-based methods. Accounts of IR QD growth in aprotic solvents such as dimethyl sulfoxide (DMSO) or dimethyl formamide (DMF) are much less common, and yet producing QDs in such solvents can be useful from the perspective of further reactions to conjugate or incorporate the QDs with other materials since such solvents can be a useful meeting ground for both organic and ionic solutes. Here we start by demonstrating long wavelength infrared emission (across the wide spectral range up to 4500 nm) in HgTe QDs grown in DMF under basic conditions. Whilst many existing synthetic approaches use soluble chalcogen precursors in adduct, salt or organo-chalcogenide forms, we have opted to take the approach of using slow addition of gaseous H2Te generated under programmed control, which allowed us to investigate the growth kinetics in order to manipulate the different competing processes, and to obtain larger HgTe QDs with the best size distributions on a repeatable and controlled basis. We demonstrate how the nucleation process of HgTe QDs can be carried out analogously to how it occurs in classic hot injection syntheses, but in our case at a far lower (sub-ambient) temperature owing to the use of a much more labile Te precursor. We also demonstrate the use of a two stage, seeded QD growth process which allows the synthesis conditions for the initial nucleation step and the subsequent enlargement stage to be decoupled, in other words the QD concentration during the enlargement phase need not be forced to be excessively large by the choice of nucleation conditions. This approach should eventually be extendable to making >5000 nm emitting HgTe QD based materials, and the use of aprotic solvents will offer compatibility with other nanomaterial chemistries, e.g. oxide glass formers etc., for the synthesis of composites. By comparing the emission spectra of HgTe QDs grown in DMF with those grown in DMSO, we show that polaron mediated coupling to ligand and solvents, previously seen when using DMSO, can be substantially suppressed using our new synthetic method.
关键词： nucleation,dimethylformamide,synthetic methods,growth kinetics,HgTe quantum dots,infrared emission
更新于2025-09-23 15:19:57
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Controlling Nucleation Process of InP/ZnS Quantum Dots Using Zeolite as A Nucleation Site
摘要： As a representative of III-V semiconductor materials, InP/ZnS quantum dots are regarded as the star material in the field of light-emitting devices due to their low toxicity and suitable luminescence range. However, there are still some major problems in the preparation process of InP/ZnS QDs, such as phosphine precursors are expensive and difficult to preserve and the nucleation time of short wavelength InP/ZnS QDs is too short and the size distribution is too large. In this paper, we'll replace the traditional tris(trimethylsilyl)phosphine with the tris(diethylamino)phosphine as a cheaper phosphine precursor and propose a novel and convenient method for adjusting the luminescence wavelength of InP/ZnS QDs. Different from the traditional method to adjust the emission wavelength by changing the nucleation time, the emission wavelength of InP/ZnS QDs was regulated by changing the number of initially formed cores. Zeolites do duty for providing a nucleation site for the InP cores. The InP/ZnS QDs emitted from 522 nm to 589 nm were obtained. Moreover, the obtained InP/ZnS QDs has good monochromaticity, the minimum half-width (half-full width) up to 48 nm. This method provides a new way to adjust the size of quantum dots with good performance.
关键词： Zeolites,Indium phosphide,Color tunable,Quantum dots,nucleation site
更新于2025-09-23 15:19:57
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Different role of graphene for nonisothermal crystallization behavior of graphene filled poly(ether ether ketone) by different perparation methods
摘要： The nonisothermal crystallization investigation on different contents of graphene filled PEEK nanocomposites by ball milling and solution dispersed was performed on differential scanning calorimetry. Jeziorny and Mo's methods were selected to evaluate the result, so as to investigate the nonisothermal crystallization kinetics of pure PEEK and two kinds of PEEK/GE nanocomposites. Mo's method was demonstrated to be the most appropriate model to represent the crystallization behavior for neat PEEK and PEEK/GE nanocomposites under nonisothermal condition. The result showed that the absolute degree of crystallinity of both PEEK/GE nanocomposites decreased with increasing the content of graphene, but increased the nucleation activity for the nanocomposites. When the addition of graphene was 1 wt%, the dispersed method affected the crystallization mechanisms obviously, either promoting or hindering the polymer matrix crystallization. Overall, the method that filling graphene to PEEK matrix had influence on the nonisothermal crystallization process, hence affected the properties of nanocomposites.
关键词： dispersed methods,nonisothermal crystallization kinetics,nucleation activity,graphene,PEEK
更新于2025-09-23 15:19:57