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Controlled synthesis surface-clean monolayer graphene was achieved. Monolayer Graphene was achieved by mechanical exfoliation (ME) and chemical vapor deposition (CVD),and then transferred to SiO2 (300nm)/Si substrates. There were tape residues left on the surface of the ME graphene, and poly (methyl methacrylate) (PMMA)/photoresist residues left on the surface of the CVD graphene after the transferring and lithography process. Annealing method was used to clean all these kinds of residues. Annealing processes were performed at different temperatures in both vacuum and N2/H2. It is conclude that N2/H2 is crucial for the removing of residues, and 400°C is favorable for removing the residues. Atomic force microscope (AFM) images and Raman spectra were taken to confirm the effect of the annealing.

The high-quality phosphorus-doped ZnO nanocombs were synthesized by the simple chemical vapor deposition method without use of any catalyst. The images of field-emission scanning electron microscopy show that the phosphorus-doped ZnO nanocombs have a uniform length of 8 μm with the diameter of 70 nm and the cusp of the teeth of 20 nm. The measurement results of selected-area electron diffraction pattern indicate that the phosphorus-doped ZnO nanocombs are single crystalline structure. The phosphorus related acceptor emission was observed in the photoluminescence spectra of phosphorus-doped ZnO nanocombs at 11 K. The acceptor binding energy is estimated to be ∼127 meV.

Gallium oxide (Ga2O3) has five crystalline polymorphs, i.e. corundum (α-phase), monoclinic (β-phase), spinel (γ-phase), bixbite (δ-phase) and orthorhombic (ε-phase). Among these phases, the monoclinic structured β-Ga2O3 is the most stable form, and is a ultraviolet (UV) transparent semiconductor with a wide band gap of 4.9 eV. It is a promising candidate for applications in UV transparent electrodes, solar-blind photodetectors, gas sensors and optoelectronic devices. In recent years, one-dimensional (1D) nanoscale semiconductor structures, such as nanowires, nanobelts, and nanorods, have attracted considerable attention due to their interesting fundamental properties and potential applications in nanoscale opto-electronic devices.Numerous efforts have been made to fabricate such devices in 1D nanostructures such as nanowires and nanorods. Comparing with the thin film form, the device performance in the 1D form is significantly enhanced as the surface-to-volume ratio increases. In order to realize β-Ga2O3 based nano-optoelectronic devices, it is necessary to obtain controlled-synthesis and the high-quality β-Ga2O3 nanomaterials. According to the present difficulties in synthesizing β-Ga2O3 nanomaterials, in this paper, the grid-like β-Ga2O3 nanowires are prepared on sapphire substrates via electric field assisted chemical vapor deposition method.High-purity metallic Ga (99.99%) is used as Ga vapor source. High-purity Ar gas is used as carrier gas. The flow rate of high-purity Ar carrier gas is controlled at 200 sccm. Then, oxygen reactant gas with a flow rate of 2 sccm enters into the system. The temperature is kept at 900℃ for 20 min. The effect of the external electric voltage on the surface morphology, crystal structure and optical properties of β-Ga2O3 nanowires are investigated. It is found that the external electric voltage has a great influence on the surface morphology of the sample. The orientation of the β-Ga2O3 nanowires grown under the action of an applied electric field begins to improve. Only a grid composed of three different growth directions appears. And with the increase of applied voltage, the distribution of nanowires becomes denser and the length increases significantly. In addition, it is found that the chemical vapor deposition method assisted by this external electric field can significantly improve the crystallization and optical quality of the samples.

Aligned trumpet-shaped zinc oxide microtube arrays have been successfully prepared on silicon (100) substrates via the chemical vapour deposition method with a mixture of ZnO and active carbon powders as reactants. The results show that two types of trumpet-shaped ZnO microtubes can be obtained. A plausible growth mechanism based on the studies of scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and room-temperature photoluminescence spectroscopy is proposed and discussed. The initial metastable zinc-rich ZnOx embryos play a key role in the formation of trumpet-shaped ZnO microtubes. On the different surfaces of metastable zinc-rich ZnOx (x

Composite arrays of multi-wall carbon nanotubes (MWNTs) and silicon nanowires (SiNWs) are fabricated by means of the chemical vapour deposition method in porous anodic aluminium oxide (AAO) templates. The results of the scanning electron microscopy, high-resolution transmission electron microscopy, and transmission electron microscopy have shown that SiNWs are successful nested or filled in the hollow cavities of synthesized MWNT arrays in AAO templates to form MWNT-SiNW composite arrays. The photoluminescence (PL) intensity degradation and a blueshift of PL peak position, usually created from the chemical instability of the SiNW surfaces, are decreased and eliminated clearly in the composite arrays. The composite arrays of MWNTs-SiNWs exhibit more enhanced intensity and stability of PL performance than the SiNW arrays deposited in AAO templates.

Arsenic-doped petal-like zinc oxide microrods are grown on silicon (100) substrates by the chemical vapor deposition method without the use of catalysts. Scanning electron microscopy shows that As-doped petal-like ZnO microrods with a preferred c-axial orientation are obtained, which is well in accordance with x-ray diffraction analysis. The obtained ZnO microrods have uniform lengths of about 2 μm and side lengths of about 100 nm. As-related acceptor emissions are observed from photoluminescence spectra of the ZnO microrods at a temperature of 11 K. The acceptor binding energy is estimated to be 128 meV.