Yingjie Xing

Optical properties of the ZnO nanotubes synthesized via vapor phase growth

A large quantity of nanosized ZnO tubular structures was prepared using a very simple thermal evaporation of mixed Zn–ZnO powders under a wet oxidation condition. The ZnO nanotubes have a hollow core with crystalline wall of 8–20 nm in thickness. Optical properties of ZnO nanotubes were studied at room temperature. Raman peaks arising from the ZnO nanotubes were analyzed, which correspond well to that of the bulk ZnO sample. The photoluminescence measurements of ZnO nanotubes revealed an intensive UV peak at 377 nm corresponding to the free exciton emission, and a broad peak at about 500 nm arising from defect-related emission.

Electrical conductivity of a single C60 nanotube

Electrical conductivity measurements were carried out on a single C60 nanotube fabricated via template growth technique. High resistance was observed from untreated C60 nanotubes. The I-V characteristics of the annealed C60 nanotubes indicate that a Schottky barrier exists between the electrode and the nanotube, which can be modified via annealing in vacuum. The activation energy of the annealed samples is close to the value of single C60 crystal. It was found that the C60 nanotube shows a large photoconductivity under light illumination and is an excellent candidate for optical switch. Our results suggest that the semiconducting C60 nanotube can be used as a rational building block in the construction of hierarchical architectures.

Microstructural and compositional characterization of a new silicon carbide nanocables using scanning transmission electron microscopy

Abstract Composite nanocables with peculiar structure were synthesized using a solid–liquid–solid mechanism. Each of the nanocables consists of a crystalline core sheathed with an amorphous layer ( 40 nm in average diameter). The crystalline core of the nanocables is so fine (1– 6 nm in diameter), that it is nearly impossible to characterize them using other methods. Fortunately, the powerful high resolution electron energy loss spectroscopy (EELS) technique (with minimum beam size nm ) allowed us to analyze this peculiar nanomaterial. The fine crystalline core was proved to be a hexagonal silicon carbide, while the sheathing layer was silicon oxide. High angle dark field technique was employed to map the nanocable structures. Our results show that the EELS is powerful in nanometric regime characterization, while the SiC nanocables reported here may be useful in future nanotechnology.

Quantum interference effect in single Pt(Ga)∕C nanowire

The electron transport behavior in single Pt(Ga)∕C nanowire fabricated using focused ion beam was studied. The Pt(Ga)∕C nanowire consists of <3nm Pt particles, which are sheathed with Ga+-doped amorphous carbon layers. The temperature dependence of the nanowire resistivity measured under four-probe method indicated the weak localization effect resulting from large disorder in the system. Moreover, low temperature resistivity of the nanowire increased with decrease of its temperature, following a −T law, which could be interpreted by electron-electron interaction in weak localization regime. An anomalous positive magnetoresistance was observed as well, which was ascribed to quantum interference effect arising from Coulomb interactions and weak localization in the strong spin-orbit scattering limit.

Analytical investigations on the thermal properties of microscale inorganic light-emitting diodes on an orthotropic substrate

The microscale inorganic light-emitting diodes (μ-ILEDs) create novel opportunities in biointegrated applications such as wound healing acceleration and optogenetics. Analytical expressions, validated by finite element analysis, are obtained for the temperature increase of a rectangular μ-ILED device on an orthotropic substrate, which could offer an appealing advantage in controlling the heat flow direction to achieve the goal in thermal management. The influences of various parameters (e.g., thermal conductivities of orthotropic substrate, loading parameters) on the temperature increase of the μ-ILED are investigated based on the obtained closed-form solutions. These results provide a novel route to control the temperature distribution in the μ-ILED system and provide easily interpretable guidelines to minimize the adverse thermal effects.

Growth of High Material Quality Group III-Antimonide Semiconductor Nanowires by a Naturally Cooling Process

We report on a simple but powerful approach to grow high material quality InSb and GaSb nanowires in a commonly used tube furnace setup. The approach employs a process of stable heating at a high temperature and then cooling down naturally to room temperature with the nanowire growth occurred effectively during the naturally cooling step. As-grown nanowires are analyzed using a scanning electron microscope and a transmission electron microscope equipped with an energy-dispersive X-ray spectroscopy setup. It is shown that the grown nanowires are several micrometers in lengths and are zincblende InSb and GaSb crystals. The FET devices are also fabricated with the grown nanowires and investigated. It is shown that the grown nanowires show good, desired electrical properties and should have potential applications in the future nanoelectronics and infrared optoelectronics.

Generic technique to grow III-V semiconductor nanowires in a closed glass vessel

Crystalline III-V semiconductor nanowires have great potential in fabrication of nanodevices for applications in nanoelectronics and optoelectronics, and for studies of novel physical phenomena. Sophisticated epitaxy techniques with precisely controlled growth conditions are often used to prepare high quality III-V nanowires. The growth process and cost of these experiments are therefore dedicated and very high. Here, we report a simple but generic method to synthesize III-V nanowires with high crystal quality. The technique employs a closed evacuated tube vessel with a small tube carrier containing a solid source of materials and another small tube carrier containing a growth substrate inside. The growth of nanowires is achieved after heating the closed vessel in a furnace to a preset high temperature and then cooling it down naturally to room temperature. The technique has been employed to grow InAs, GaAs, and GaSb nanowires on Si/SiO2 substrates. The as-grown nanowires are analyzed by SEM, TEM and Raman spectroscopy and the results show that the nanowires are high quality zincblende single crystals. No particular condition needs to be adjusted and controlled in the experiments. This technique provides a convenient way of synthesis of III-V semiconductor nanowires with high material quality for a wide range of applications.

Tunable Low Loss 1D Surface Plasmons in InAs Nanowires

Due to the ability to manipulate photons at nanoscale, plasmonics has become one of the most important branches in nanophotonics. The prerequisites for the technological application of plasmons include high confining ability (λ0 /λp ), low damping, and easy tunability. However, plasmons in typical plasmonic materials, i.e., noble metals, cannot satisfy these three requirements simultaneously and cause a disconnection to modern electronics. Here, the indium arsenide (InAs) nanowire is identified as a material that satisfies all the three prerequisites, providing a natural analogy with modern electronics. The dispersion relation of InAs plasmons is determined using the nanoinfrared imaging technique, and show that their associated wavelengths and damping ratio can be tuned by altering the nanowire diameter and dielectric environment. The InAs plasmons possess advantages such as high confining ability, low loss, and ease of fabrication. The observation of InAs plasmons could enable novel plasmonic circuits for future subwavelength applications.

Growth of InAs NWs with controlled morphology by CVD

We report on the growth of single crystal InAs NWs on Si/SiOx substrates by chemical vapor deposition (CVD). By adjusting growth parameters, the diameters, morphology, length and the proportion of superlattice ZB InAs NWs (NWs) can be controlled on a Si/SiOx substrate. Our work provides a low-cost route to grow and phase-engineer single crystal InAs NWs for a wide range of potential applications.

THERMAL EVAPORATION SYNTHESIS OF ZnO MICROSHELLS

We demonstrate the synthesis of zinc oxide microshells by thermal evaporation of ZnO and Zn powders. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) observations reveal that the products are ZnO microshells with hollow cores, of which the wall thickness is about several hundred nanometers. The possible growth process is discussed.