Junhua Meng

Controlled Growth of Few-Layer Hexagonal Boron Nitride on Copper Foils Using Ion Beam Sputtering Deposition

Ion beam sputtering deposition (IBSD) is used to synthesize high quality few-layer hexagonal boron nitride (h-BN) on copper foils. Compared to the conventional chemical vapor deposition, the IBSD technique avoids the use of unconventional precursors and is much easier to control, which should be very useful for the large-scale production of h-BN in the future.

Enhanced efficiency of graphene-silicon Schottky junction solar cells by doping with Au nanoparticles

We have reported a method to enhance the performance of graphene-Si (Gr/Si) Schottky junction solar cells by introducing Au nanoparticles (NPs) onto the monolayer graphene and few-layer graphene. The electron transfer between Au NPs and graphene leads to the increased work function and enhanced electrical conductivity of graphene, resulting in a remarkable improvement of device efficiency. By optimizing the initial thickness of Au layers, the power conversion efficiency of Gr/Si solar cells can be increased by more than three times, with a maximum value of 7.34%. These results show a route for fabricating efficient and stable Gr/Si solar cells.

Plasmon enhanced polymer solar cells by spin-coating Au nanoparticles on indium-tin-oxide substrate

To enhance light absorption in polymer solar cells, the Au nanoparticles (NPs) with different sizes were incorporated to the devices by spin-coating Au colloid solution on the indium-tin-oxide substrates prior to deposition of buffer layer. It has been found that the power conversion efficiency of bulk heterojunction cells can be increased from 3.50% to 4.07% after incorporating the 60 nm Au NPs, corresponding to an improvement of 16%. The improved device performance is ascribed to the localized surface plasmon excitation of the Au NPs. The method we report herein is a kind of simple and quick solution process.

High efficiency Schottky junction solar cells by co-doping of graphene with gold nanoparticles and nitric acid

We have reported an effective method to enhance the efficiency of graphene-on-Si (Gr/Si) Schottky junction solar cells by co-doping of graphene with Au nanoparticles (NPs) and HNO3. Both Au NPs decoration and HNO3 treatment lead to p-type doping of graphene, and their combination is confirmed to be a more effective approach for achieving the higher work function and enhanced electrical conductivity of graphene. Consequently, the power conversion efficiency of Gr/Si solar cells is increased by 2.6 times, with a maximum value of 10.20%. This work suggests that the co-doping might be a promising way to realize high performance Gr/Si solar cells.

Synthesis of Large-Sized Single-Crystal Hexagonal Boron Nitride Domains on Nickel Foils by Ion Beam Sputtering Deposition

Large-sized single-crystal h-BN domains with a lateral size up to 100 μm are synthesized on Ni foils by ion-beam sputtering deposition. The nucleation density of h-BN is dramatically decreased by reducing the concentrations of both active sites and species on the Ni surface through a brief in situ pretreatment of the substrate and optimization of the growth parameters, enabling the growth of large-sized domains.

Ferrimagnetic and half-metallic CaCu3Fe4O12: Prediction from first principles investigation

The structural stability and physical properties of CaCu3Fe4O12 were studied by the use of the full-potential linearized augmented plane wave method. The authors’ calculated result indicates that the title compound is stable both thermodynamically and mechanically. It is ferrimagnetic and half-metallic. The calculated magnetic structure reveals that the coupling of Cu–Fe is antiferromagnetic, while those of Cu–Cu and Fe–Fe are ferromagnetic.

Efficiency enhancement of polymer solar cells by localized surface plasmon of Au nanoparticles

We demonstrate the improvement of power conversion efficiency (PCE) in bulk heterojunction polymer solar cells based on blended poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester by introducing 40 nm Au nanoparticles (NPs) with various concentrations. The Au NPs were deposited on indium-tin-oxide (ITO) substrates by spin-coating from colloidal solution prior to deposition of poly (3,4-ethylene dioxythiophene:poly (styrene sulfonate) (PEDOT:PSS) buffer layer. It has been found that both short-circuit current density and PCE increase after incorporating Au NPs between ITO and PEDOT:PSS layer, and a suitable area density of Au NPs is required to achieve a maximum enhancement of device efficiency. The PCE of solar cells has been increased from 3.50% to 3.81% with 0.9 wt. % Au NPs. The PCE enhancement is attributed to the localized surface plasmon excitation of Au NPs. The method employed herein is a kind of simple and convenient solution process, and it has great potential in future practical a...

Aligned Growth of Millimeter-Size Hexagonal Boron Nitride Single-Crystal Domains on Epitaxial Nickel Thin Film

Atomically thin hexagonal boron nitride (h-BN) is gaining significant attention for many applications such as a dielectric layer or substrate for graphene-based devices. For these applications, synthesis of high-quality and large-area h-BN layers with few defects is strongly desirable. In this work, the aligned growth of millimeter-size single-crystal h-BN domains on epitaxial Ni (111)/sapphire substrates by ion beam sputtering deposition is demonstrated. Under the optimized growth conditions, single-crystal h-BN domains up to 0.6 mm in edge length are obtained, the largest reported to date. The formation of large-size h-BN domains results mainly from the reduced Ni-grain boundaries and the improved crystallinity of Ni film. Furthermore, the h-BN domains show well-aligned orientation and excellent dielectric properties. In addition, the sapphire substrates can be repeatedly used with almost no limit. This work provides an effective approach for synthesizing large-scale high-quality h-BN layers for electronic applications.

One-step synthesis of graphene-Au nanoparticle hybrid materials from metal salt-loaded micelles

In this study, we present a facile one-step method to synthesize graphene-Au nanoparticle (NP) hybrid materials by using HAuCl4-loaded poly(styrene)-block-poly(2-vinylpyridine) (PS-P2VP) micelles as solid carbon sources. N-doped graphene with controllable thickness can be grown from PS-P2VP micelles covered by a Ni capping layer by an annealing process; simultaneously, the HAuCl4 in the micelles were reduced into Au NPs under a reductive atmosphere to form Au NPs on graphene. The decoration of Au NPs leads to an obviously enhanced electrical conductivity and a slightly increased work function of graphene due to the electron transfer effect. The graphene-Au NP hybrid materials also exhibit a localized surface plasmon resonance feature of Au NPs. This work provides a novel and accessible route for the one-step synthesis of graphene-Au NP hybrid materials with high quality, which might be useful for future applications in optoelectronic devices.

Synthesis of atomic layers of hybridized h-BNC by depositing h-BN on graphene via ion beam sputtering

We report the deposition of hexagonal boron nitride (h-BN) on graphene by ion beam sputtering deposition. Both graphene domains and films synthesized by chemical vapor deposition were used as substrates. In the case of graphene domains, it was found that the h-BN domains were preferentially grown on the baked Cu surface instead of graphene due to the highly catalytic activity of Cu. On the other hand, the higher ejection energy of sputtered particles leads to the mixing of boron/nitrogen atoms and carbon atoms. Consequently, the h-BNC films consisting of the hybrid atomic layers of h-BN and graphene domains were formed when the graphene films were used as substrates. This work provides a promising and accessible route for the synthesis of hybridized h-BNC material.