Search

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs). With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope, we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) have been grown directly on a Si substrate without a diffusion barrier in ethanol diffusion flame using Ni as the catalyst after a photoresist-assisted catalyst annealing process. The growth mechanism of as-synthesized CNTs is confirmed by scanning electron microscopy, high resolution transmission-electron microscopy and energy-dispersive spectroscopy. The photoresist is the key for the formation of active catalyst particles during annealing process, which then result in the growth of CNTs. The catalyst annealing temperature has been found to affect the morphologies and field electron emission properties of CNTs significantly. The field emission properties of as-grown CNTs are investigated with a diode structure and the obtained CNTs exhibit enhanced characteristics. This technique will be applicable to a low-cost fabrication process of electron-emitter arrays. [Copyright &y& Elsevier]

Abstract: Nickel oxide thin films were deposited on fused silica and Si(100) substrates at different substrate temperatures ranging from room temperature to 400°C using radio frequency reactive magnetron sputtering from a Ni metal target in a mixture of O2 and Ar. With the increase of substrate temperature, nickel oxide films deposited on the Si substrates exhibit transition from amorphous to poly-crystalline structures with different preferred orientations of NiO(200) and (111). The films deposited at higher temperature exhibit higher Ni2+/Ni3+ ratio. With substrate temperature increasing from room temperature to 400°C, the electrical resistivities of nickel oxide films increase from (2.8±0.1)×10−2 to (8.7±0.1)Ωcm, and the optical band-gap energies increase from 3.65 to 3.88eV. A p-nickel oxide/n-zinc oxide heterojunction was fabricated to confirm the p-type conduction of nickel oxide thin film, which exhibited a steadily rectifying behavior. [Copyright &y& Elsevier]

Abstract: Hafnium nitride (Hf-N) thin films were deposited on fused silica at different N2 flow ratio (N2/N2 +Ar) using a reactive DC magnetron sputtering system. A gradual evolution in the composition of the films from Hf3N2, HfN, to higher nitrides was found through X-ray diffraction (XRD). Films of Hf3N2 and HfN show positive temperature coefficients of resistivity, while higher nitride has a negative one. Highly oriented growth of (001) Hf3N2 and NaCl-structure (100) HfN films were fabricated on fused silica substrate at relatively lower temperature of 300°C. The electrical resistivity values of both as-deposited and post-deposition annealed films were measured by a four-point probe method. The obtained minimum resistivity of as-deposited film is 20μΩcm, and this result shows potential application of HfN films as electrode materials in electronic devices. [Copyright &y& Elsevier]

Abstract: Vertically well-aligned single crystal ZnO nanorod arrays were synthesized and enhanced field electron emission was achieved after radio-frequency (rf) Ar plasma treatment. With Ar plasma treatment for 30min, flat tops of the as-grown ZnO nanorods have been etched into sharp tips without damaging ZnO nanorod geometrical morphologies and crystallinity. After the Ar ion bombardment, the emission current density increases from 2 to 20μAcm−2 at 9.0Vμm−1 with a decrease in turn-on voltage from 7.1 to 4.8Vμm−1 at a current density of 1μAcm−2, which demonstrates that the field emission of the as-grown ZnO nanorods has been efficiently enhanced. The scanning electron microscopy (SEM) results, in conjunction with the results of transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence observation, are used to investigate the mechanisms of the field emission enhancement. It is believed that the enhancements can be mainly attributed to the sharpening of rod tops, and the decrease of electrostatic screening effect. [Copyright &y& Elsevier]

Abstract: A type of optical degradation of aluminium-doped zinc oxide (AZO) films due to water electrolysis-induced reduction reaction was reported. An experiment was designed in which AZO films were immersed in a 0.01M NaOH aqueous solution as cathode to electrolyze water. Significant decreases in the optical transmission of the treated samples were observed. Studies by X-ray diffraction and scanning electron microscope showed that the degradation of AZO films was due to compositional and structural changes with the treatment of water electrolysis, which resulted from the reduction reaction of atomic hydrogen generated in the electrolysis of water. This optical degradation reflects the stability degradation of AZO films under water electrolysis environment. [Copyright &y& Elsevier]

Abstract: In this study, highly transparent conductive Ga-doped Zn0.9Mg0.1O (ZMO:Ga) thin films have been deposited on glass substrates by pulsed laser deposition (PLD) technique. The effects of substrate temperature and post-deposition vacuum annealing on structural, electrical and optical properties of ZMO:Ga thin films were investigated. The properties of the films have been characterized through Hall effect, double beam spectrophotometer and X-ray diffraction. The experimental results show that the electrical resistivity of film deposited at 200°C is 8.12×10−4 Ωcm, and can be further decreased to 4.74×10−4 Ωcm with post-deposition annealing at 400°C for 2h under 3×10−3 Pa. In the meantime, its band gap energy can be increased to 3.90eV from 3.83eV. The annealing process leads to improvement of (002) orientation, wider band gap, increased carrier concentration and blue-shift of absorption edge in the transmission spectra of ZMO:Ga thin films. [Copyright &y& Elsevier]

Abstract: Highly transparent conductive Al2O3 doped zinc oxide (AZO) thin films have been deposited on the glass substrate by pulsed laser deposition technique. The effects of substrate temperature and post-deposition annealing treatment on structural, electrical and optical properties of AZO thin films were investigated. The experimental results show that the electrical resistivity of films deposited at 240°C is 6.1×10−4 Ωcm, which can be further reduced to as low as 4.7×10−4 Ωcm by post-deposition annealing at 400°C for 2h in argon. The average transmission of AZO films in the visible range is 90%. The optical direct band gap of films was dependent on the substrate temperature and the annealing treatment in argon. The optical direct band gap value of AZO films increased with increasing annealing temperature. [Copyright &y& Elsevier]

Preferred crystal orientation and low electrical resistivity are required for ZrNx films applied in electronic devices. In this paper, effects of N2:(N2+Ar) flow ratio (F(N2)) and substrate temperature on the properties of the films deposited on glass substrate by reactive dc sputtering are investigated. In a wide range of F(N2) (4–24%), the films show fcc NaCl structure. While for F(N2) in the ranges of 5–12, 12–24 and >24%, the films show (1 1 1)/(2 0 0), (1 1 1) only and amorphous structures, respectively. The electrical resistivity increases with F(N2) from 5 to 24%, and can be controlled to some extent by changing the substrate temperature. [Copyright &y& Elsevier]

Ni 2 P nanosheets were fabricated on carbon fiber using the hydrothermal method and subsequent phosphatization process. The highly conductive Ni 2 P nanosheet arrays could not only facilitate electron transport but also shorten the ion diffusion path. The in-situ grown Ni 2 P nanosheet arrays could be applied as the cathode in Zn battery without any additives and binder. The Ni 2 P//Zn battery based on Ni 2 P nanosheet arrays and metal Zn electrode exhibits excellent electrochemical performance, such as high operating voltage (1.78 V), specific capacity of 231 mAh g−1, and energy density of 318 Wh Kg−1. In addition, the Ni 2 P//Zn battery can maintain a specific capacity retention ~ 80% after 1500 continuous cycles. In view of the excellent electrochemical properties of Ni 2 P//Zn battery, the Ni 2 P will be a potential material for next-generation energy storage devices. • Ni 2 P nanosheet arrays are synthesized on carbon fiber by a two-step procedure. • The Ni 2 P electrode exhibits high specific capacity and good cyclic performance. • A novel Ni 2 P//Zn battery with Zn on carbon fiber as anode was assembled successfully. • The battery with high operating potential shows an energy density of 318 Wh kg−1. [ABSTRACT FROM AUTHOR]

ZnO thin films have been prepared by atomic layer deposition for ultraviolet photodetection with metal-semiconductor-metal (MSM) structure. The innovation of rapid thermal annealing treatment can modulate the carrier concentration of the ZnO thin films, a lowest carrier concentration of 4.4 × 1014 cm−3 was obtained after annealing at 450 °C, resulting in the minimum dark current of 4.5 × 10−8 A at 5 V. Furthermore, these photodetectors demonstrated respectable responsivity of up to 27 A/W, and the detectivity was enhanced to a fairly high value of 8.5 × 1013 Hz1/2/W together with an extremely rapid response of <80 μs. These performance metrics are far superior compared with the records in the existing literature based on ZnO thin films, and are even on a par with nano-structural ZnO devices, while remain the key features of thin film devices, including high reproducibility and facile preparation. • ALD provides thickness control and uniformity. • Annealing can removes defects. • Response time of < 80 µs, respectively. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO 2 ) film with high mobility and good transmittance has been reported as a promising semiconductor material for high performance perovskite solar cells (PSCs). In this study, ultrathin SnO 2 film synthesized by radio frequency magnetron sputtering (RFMS) method at room temperature was employed as hole blocking layer for planar PSCs. The room-temperature sputtered SnO 2 film not only shows favourable energy band structure but also improves the surface topography of fluorine doped SnO 2 (FTO) substrate and perovskite (CH 3 NH 3 PbI 3 ) layer. Thus, this SnO 2 hole blocking layer can efficiently promote electron transport and suppress carrier recombination. Furthermore, the best efficiency of 13.68% was obtained for planar PSC with SnO 2 hole blocking layer prepared at room temperature. This research highlights the room-temperature preparation process of hole blocking layer in PSC and has a certain reference significance for the usage of flexible and low-cost substrates. [ABSTRACT FROM AUTHOR]

Doping-induced visible-light adsorption is often considered as the main reason for the enhanced photocatalytic activity of TiO 2 . However, this work provides a new understanding on the effect of doping on the photocatalytic activity of TiO 2 . The investigation on the C–F codoped anatase TiO 2 {0 0 1} surface reveals that the impurity C and F atoms prefer to substitute for the outmost O atoms in the TiO 2 {0 0 1} surface rather than those in the bulk TiO 2 . The exhibited vectorial doping of C and F atoms in TiO 2 {0 0 1} surface produces a conducting layer with low electric resistance, which can promote the charge transfer in the photocatalytic reaction. This effectively inhibits the undesirable bulk recombination of photogenerated electron and hole. Hence, the optimized charge transfer in the C–F codoped TiO 2 {0 0 1} surface makes a great contribution to the enhanced photocatalytic activity of TiO 2 . Further, the surface doping treatment is a potential method to improve the performance of photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Zn0.95−x Co0.05Cu x O (ZCCO, where x =0, 0.005, 0.01 and 0.015) thin films were deposited on Si (100) substrates by pulsed laser deposition technique. Crystal structures, surface morphologies, chemical compositions, bonding states and chemical valences of the corresponding elements for ZCCO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). XRD and FESEM results indicate that crystallite sizes of the highly (002)-oriented ZCCO films slightly decrease with increasing Cu content. When the Cu content increases from 0 to 0.015, Zn 2p 3/2, Co 2p, Cu 2p 3/2 and O 1s peaks of the ZCCO film shift towards higher or lower binding energy regions, and the reasons for these chemical shifts are investigated by fitting the corresponding XPS narrow-scan spectra. Both in-plane and out-of-plane magnetization-magnetic field hysteresis loops of the ZCCO films reveal that all the films have room temperature ferromagnetisms (RTFMs). The conceivable origin of the RTFM is ascribed to the combined effects of the local structural disorder resulted from (Co2+, Cu2+, Cu1+)-cations which substitute Zn2+ ions in the ZnO matrices, ferromagnetic coupling between coupled dopant atoms caused by Co2+ (3d 74s 0) and Cu2+ (3d 94s 0) spin states, and exchange interactions between the unpaired electron spins originating from lattice defects induced by Cu doping in the Zn0.95Co0.05O matrices. [Copyright &y& Elsevier]

Abstract: Ba0.9Sr0.1TiO3 (BST) thin films were deposited on fused quartz and Pt/TiN/Si3N4/Si substrates by radio frequency magnetron sputtering technique. Microstructure and chemical bonding states of the BST films annealed at 700°C were characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and Raman spectrum. Optical constants including refractive indices, extinction coefficients and bandgap energies of the as-deposited BST film and the BST films annealed at 650, 700 and 750°C, respectively, were determined from transmittance spectra by envelope method and Tauc relation. Dielectric constant and remnant polarization for the BST films increase with increasing annealing temperature. Leakage current density-applied voltage (J–V) data indicate that the dominant conduction mechanism for all the BST capacitors is the interface-controlled Schottky emission under the conditions of 14V< V <30V and −30V< V <−14V. Furthermore, the inequipotential J–V characteristics for the BST films annealed at various temperatures are mainly attributed to the combined effects of the different thermal histories, relaxed stresses and strains, and varied Schottky barrier heights in the BST/Pt and Pt/BST interfaces. [Copyright &y& Elsevier]

Abstract: Highly transparent conductive Dy2O3 doped zinc oxide (ZnO)1–x (Dy2O3) x nanocrystalline thin films with x from 0.5% to 5% have been deposited on glass substrate by pulsed laser deposition technique. The structural, electrical and optical properties of Dy2O3 doped thin films were investigated as a function of the x value. The experimental results show that the Dy concentration in Dy-doped ZnO thin films has a strong influence on the material properties especially electrical properties. The resistivity decreased to a minimum value of 5.02×10−4 Ωcm with x increasing from 0.5% to 1.0%, then significantly increased with the further increasing of x value. On the contrary, the optical direct band gap of the (ZnO)1–x (Dy2O3) x films first increased, then decreased with x increasing. The average transmission of Dy2O3 doped zinc oxide films in the visible range is above 90%. [Copyright &y& Elsevier]