The binding energy spectra and the momentum distributions of the outer valence orbitals of W(CO) ₆ have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-orbital relativistic DFT-B3LYP calculations. The experimental momentum profiles of the outer valence orbitals obtained with the impact energies of 1200 eV and 2400 eV were compared with various theoretical calculation results. The relativistic calculations could provide better descriptions for the experimental momentum distributions than the non-relativistic ones. Moreover, a new ordering of orbitals 10t _1u, 3t _2g, and 7e _g, i.e., 10t _1u < 3t _2g < 7e _g < 10a _1g, is established in this work.

We report on a tunneling study of underdoped submicron Bi ₂Sr _{2− x}La _x CuO _6+δ (La-Bi2201) intrinsic Josephson junctions (IJJs), whose self-heating is sufficiently suppressed. The tunneling spectra are measured from 4.2 K up to the pseudogap opening temperature of T* = 260 K. The gap value found from the spectral peak position is about 35 meV and has a weak temperature dependence both below and above the superconducting transition temperature of T _c = 29 K. Since the superconducting gap should have a value of 10–15 meV, our results indicate that the pseudogap (~35 meV) plays an important role in the underdoped La-Bi2201 intrinsic tunneling spectroscopy down to the lowest temperature of 4.2 K. However, the contribution of the superconducting gap can be separated by normalizing the spectra to the one near and above T _c, which shows that the IJJs can be a useful tool for the study of the el...

The rate and cycling performances of the electrode materials are affected by many factors in a practical complicated electrode process. Learning about the limiting step in a practical electrochemical reaction is very important to effectively improve the electrochemical performances of the electrode materials. Li ₄Ti ₅O ₁₂, as a zero-strain material, has been considered as a promising anode material for long life Li-ion batteries. In this study, our results show that the Li ₄Ti ₅O ₁₂ pasted on Cu or graphite felt current collector exhibits unexpectedly higher rate performance than on Al current collector. For Li ₄Ti ₅O ₁₂, the electron transfer between current collector and active material is the critical factor that affects its rate and cycling performances.

Density functional theory (DFT) calculations are employed to explore the NO ₂-sensing mechanisms of pure and Ti-doped WO ₃ (002) surfaces. When Ti is doped into the WO ₃ surface, two substitution models are considered: substitution of Ti for W _6c and substitution of Ti for W _5c. The results reveal that substitution of Ti for 5-fold W forms a stable doping structure, and doping induces some new electronic states in the band gap, which may lead to changes in the surface properties. Four top adsorption models of NO ₂ on pure and Ti-doped WO ₃ (002) surfaces are investigated: adsorptions on 5-fold W (Ti), on 6-fold W, on bridging oxygen, and on plane oxygen. The most stable and likely NO ₂ adsorption structures are both N-end oriented to the surface bridge oxygen O _1c site. By comparing the adsorption energy and the electronic population, it is found that Ti doping can enhance the adsorption of...

A method of measuring the thermoelectric power of nano-heterostructures based on four-probe scanning tunneling microscopy is presented. The process is composed of the in-situ fabrication of a tungsten-indium tip, the precise control of the tip-sample contact and the identification of thermoelectric potential. When the temperature of the substrate is elevated, while that of the tip is kept at room temperature, a thermoelectric potential occurs and can be detected by a current—voltage measurement. As an example of its application, the method is demonstrated to be effective to measure the thermoelectric power in several systems. A Seebeck coefficient of tens of μV/K is obtained in graphene epitaxially grown on Ru (0001) substrate and the thermoelectric potential polarity of this system is found to be the reverse of that of bare Ru (0001) substrate.

This paper reports the fabrication of J-shaped bent-waveguide superluminescent diodes utilizing an InAlGaAs/AlGaAs quantum dot active region. The emission spectrum of the device is centred at 884 nm with a full width at half maximum of 37 nm and an output power of 18 mW. By incorporating an Al composition into the quantum dot active region, short-wavelength superluminescent diode devices can be obtained. An intersection was found for the light power-injection current curves measured from the straight-waveguide facet and the bent-waveguide facet, respectively. The result is attributed to the conjunct effects of the gain and the additional loss of the bent waveguide. A numerical simulation is performed to verify the qualitative explanation. It is shown that bent waveguide loss is an important factor that affects the output power of J-shaped superluminescent diode devices.

In this work, the thermal properties of a single-walled carbon nanotube (SWCNT) crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak (658 W/mK) is found at a temperature of about 100.0 K. The thermal conductivity decreases gradually to a value of 480 W/mK and keeps almost a constant in the temperature range from 100.0 K to 300.0 K. Meanwhile, the specific heat shows an obvious linear relationship with temperature in the temperature range from 1.9 K to 300.0 K. We discuss the possible mechanisms for these unique thermal properties of the single-walled carbon nanotube crystal.

Self-assembly and growth of manganese phthalocyanine (MnPc) molecules on an Au(111) surface is investigated by means of low-temperature scanning tunneling microscopy. At the initial stage, MnPc molecules preferentially occupy the step edges and elbow sites on the Au(111) surface, then they are separately adsorbed on the face-centered cubic and hexagonal closely packed regions due to a long-range repulsive molecule—molecule interaction. After the formation of a closely packed monolayer, molecular islands with second and third layers are observed.

Two strain-state samples of GaN, labelled the strain-relief sample and the quality-improved sample, were grown by hydride vapour phase epitaxy (HVPE), and then characterized by high-resolution X-ray diffraction, photoluminescence and optical microscopy. Two strain states of GaN in HVPE, like 3D and 2D growth modes in metal-organic chemical vapour deposition (MOCVD), provide an effective way to solve the heteroepitaxial problems of both strain relief and quality improvement. The gradual variation method (GVM), developed based on the two strain states, is characterized by growth parameters' gradual variation alternating between the strain-relief growth conditions and the quality-improved growth conditions. In GVM, the introduction of the strain-relief amplitude, which is defined by the range from the quality-improved growth conditions to the strain-relief growth conditions, makes the strain-relief control concise and effective. The 300-μm thick bright and crack-free GaN film grown...