Jianyun Zheng

A Near‐Frictionless and Extremely Elastic Hydrogenated Amorphous Carbon Film with Self‐Assembled Dual Nanostructure

A highly crosslinking network combined with a fullerene-like structure is disclosed in a hydrogenated amorphous carbon film. The very soft carbon film exhibits super-low friction and excellent wear resistance even under a Hertzian contact pressure comparable to its hardness under vacuum, which is an extraordinary tribological behavior in the filed of solid lubrication films or coatings.

Vanadium Dioxide Nanoparticle-based Thermochromic Smart Coating: High Luminous Transmittance, Excellent Solar Regulation Efficiency, and Near Room Temperature Phase Transition

An annealing-assisted preparation method of well-crystallized VxW1-xO2(M)@SiO2 core-shell nanoparticles for VO2-based thermochromic smart coatings (VTSC) is presented. The additional annealing process reduces the defect density of the initial hydrothermally prepared VxW1-xO2(M) nanoparticles and enhances their crystallinity so that the thermochromic film based on VxW1-xO2(M)@SiO2 nanoparticles can exhibit outstanding thermochromic performance with balanced solar regulation efficiency (ΔTsol) of 17.3%, luminous transmittance (Tlum) up to 52.2%, and critical phase transition temperature (Tc) around 40.4 °C, which is very promising for practical application. Furthermore, it makes great progress in reducing Tc of VTSC to near room temperature (25.2 °C) and simutaneously maintaining excellent optical properties (ΔTsol = 14.7% and Tlum = 50.6%). Such thermochromic performance is good enough to make VTSC applicable to practical architecture.

Natural Hydrophobicity and Reversible Wettability Conversion of Flat Anatase TiO2 Thin Film

Flat anatase TiO2 thin film deposited at room temperature shows the natural hydrophobicity, which is destroyed by 400 °C vacuum annealing. On the basis of the analysis of surface composition and structure, the origin of hydrophobicity of the flat TiO2 film can be identified as (1) approximately fully stoichiometric TiO2 and (2) hydrocarbon adsorbates on the film surface. We further validate that interfacial water molecules near the surface of the as-prepared TiO2 film are oriented in the hydrophobic hydration structure via Fourier transform infrared/attenuated total reflection. Moreover, the as-prepared TiO2 film also shows a smart surface reversibly switched between hydrophobicity and super-hydrophilicity. During the recovery process of hydrophobicity, the irradiated films show the wettability with water contact angle of 107 ± 1.7, 72 ± 2.5, 80 ± 1.1, and 17 ± 1.3° corresponding to after a week of exposure to ambient air, O2, CF4, and Ar, respectively. It can be strongly reinforced that the stoichiometry and the adsorbates both play an important role in forming the hydrophobic TiO2 films.

Anatase TiO2 Films with Dominant {001} Facets Fabricated by Direct-Current Reactive Magnetron Sputtering at Room Temperature: Oxygen Defects and Enhanced Visible-Light Photocatalytic Behaviors

A TiO2 film with dominant anatase {001} facets is directly prepared by direct-current reactive magnetron sputtering at room temperature without using morphology-controlling agents. The formation mechanism of anatase TiO2 films with dominant {001} facets is explained by the competition between thermodynamics and ion impinging in the deposition process. The crystalline TiO2 film shows a superior photocatalytic efficiency for the degradation of Rhodamine B under UV-visible (λ > 250 nm) lights. Furthermore, a comparable photodegradation of Rhodamine B is also found on the TiO2 film surface by using visible (λ > 420 nm) lights. During film growth, the surface bombarded by high energy of ions yields plenty of oxygen defects, which can enhance the photocatalytic activity of the films irradiated under visible light.

Properties of TiN/TiCN multilayer films by direct current magnetron sputtering

In this work, a TiN/TiCN multilayer film was deposited by direct current magnetron sputtering. Its thickness was about 9675 nm and the bilayer numbers were 10. The composition, crystalline structure and amorphous carbon (a-C) phase of the film were investigated by x-ray photoelectron spectroscopy, x-ray diffraction and Raman spectroscopy. Field emission scanning electron microscopy was employed to observe the inner structure of the film. The TiCN layer exhibited a glass-like structure and the TiN layer presented a columnar structure. The adhesion force between the film and the substrate was 37.8 N determined by scratch tests. The hardness of the uppermost TiCN layer and the total film was 34.22 GPa and 27.22 GPa obtained by nano-indentation tests, respectively. In addition, the TiN/TiCN multilayer thick film showed different types of tribological behaviour against Si3N4 balls and steel balls. The mean coefficient of friction and the wear rate of the film were about 0.14 and 1.15 × 10−6 mm3 N−1 m−1 when the film slid against Si3N4 balls for 1 h.

Achieving high-performance planar perovskite solar cells with co-sputtered Co-doping NiOx hole transport layers by efficient extraction and enhanced mobility

Perovskite solar cells are some of the most promising photovoltaic devices and they have experienced extraordinary progress in efficiency and fabricating technologies. Herein, we explore the effect of Co-doped NiOx hole transport layers on the electronic structure and photovoltaic properties of PSCs, which were deposited onto FTO substrates via DC magnetron sputtering at room temperature. Appropriate Co-doping can slightly regulate the optical band gap and the Fermi level position, leading to an increased potential cell performance. By virtue of continuously adjusting the power loaded onto the Co target, we can obtain the optimal atomic ratio of the Co:NiOx hole transport layer, and the PSC based on Co:NiOx exhibited a 25% higher efficiency than its undoped counterparts (from 9.46% to 12.61%). Therefore, these results demonstrate that Co is an appropriate dopant and the PSCs based on Co:NiOx layers have a good performance.

The optical properties of low infrared transmittance WO3−x nanocrystal thin films prepared by DC magnetron sputtering under different oxygen ratios

Low infrared transmittance WO3−x (0 < x < 1) ratios, as transparent conductors with high transmittance in the visible range and UV blocking. The infrared shielding properties could be adjusted by tuning the oxygen ratio during the sputtering process. The intrinsic defects, such as oxygen vacancy () and special atom (W5+), determine the main optical properties by localized states originated from the electron caused by interband transition and the surface dipole of the plasmon oscillation of the nanoparticle with optical scattering. The structures, morphology, defects and chemical states were investigated. With respect to oxygen ratio, it has little effect on the structure and morphology, yet the optical shielding performance, defects and chemical states can be controlled linearly by considering the oxygen ratio during the sputtering process. The WO3−x thin films have great potential for application in infrared shielding and energy conservation.

Strong visible and infrared photoluminescence from Er-implanted silicon nitride films

Silicon nitride films were deposited by plasma-enhanced chemical-vapour deposition. The films were then implanted with erbium ions to a concentration of 8 x 10(20) cm(-3). After high temperature annealing, strong visible and infrared photoluminescence (PL) was observed. The visible PL consists mainly of two peaks located at 660 and 750 nm, which are considered to originate from silicon nanocluster (Si-NCs) and Si-NC/SiNx interface states. Raman spectra and HRTEM measurements have been performed to confirm the existence of Si-NCs. The implanted erbium ions are possibly activated by an energy transfer process, leading to a strong 1.54 mu m PL.

Preparation of superior lubricious amorphous carbon films co-doped by silicon and aluminum

Silicon (Si) and aluminum (Al) co-doped amorphous carbon films ((Si, Al)–C:H) were deposited on Si and stainless steel substrates by radio frequency (13.56 MHz) magnetron sputtering. The Al and Si were found to jointly regulate the hybridized carbon bonds. Mechanical properties of the films were detected by nano-indention and scratch tests. The nano-indention results revealed that all the samples exhibited good elastic recovery rate, among which the highest one was beyond 84%. Besides co-regulating the hybridizations of carbon, the co-doped Si and Al also had a common regulation on the mechanical and tribological properties. Especially, the film containing 1.6 at. % of Si and 0.9 at. % of Al showed a super-low friction (< 0.01) and a superior wear resistance in ambient air.

Activation and Enhancement of Room-Temperature Ferromagnetism in Cu-Doped Anatase TiO2 Films by Bound Magnetic Polaron and Oxygen Defects

Cu-doped anatase TiO2 films grown by magnetron sputtering at room temperature showed the unexpected observation of room-temperature ferromagnetism, which was enhanced or destroyed corresponding to low or high impurity concentration via vacuum annealing. On the basis of the analysis of composition and structure, the most important factor for activating ferromagnetism can be identified as the creation of grain boundary defects. In addition, oxygen defects can be the dominating factor for increasing the saturation moment of the 0.19 at. % Cu-doped TiO2 film from 0.564 to 26.41 emu/cm(3). These results help elucidate the origin of ferromagnetism and emphasize the role of oxygen defects for the application of ferromagnetic films.