Chemical vapor deposition synthesis and Raman scattering investigation of quasi-one-dimensional ZrS_(3)nanoflakes

Quasi-one-dimensional ZrS_(3)nanoflakes attract intense interest attributed to their superior electrical and optical anisotropy,stemming from the low symmetry in the crystal structure.However,the conventional chemical vapor transport method for synthesizing bulk ZrS_(3)is limited by morphology and size controllability.It is highly desirable to propose a facile way to precisely synthesize ZrS_(3)nanoflakes.In this work,the chemical vapor deposition method is proposed as a feasible way to synthesize ZrS_(3)nanoflakes.The effects of various substrates and temperatures on ZrS_(3)synthesis have been investigated.For the as-grown ZrS_(3),good crystallinity is confirmed with X-ray diffraction and transmission electron microscopy.The structure and interlayer coupling are investigated with Raman scattering spectroscopy.The strong in-plane anisotropy and interlayer coupling of the ZrS_(3)nanoflakes are illustrated with angle-resolved Raman spectroscopy and temperature-dependent Raman characterization,respectively.This study demonstrates a feasible way for the synthesis of transition metal trisulfides,which may shed new light on the research of other two-dimensional anisotropic transition metal materials.

Study on the Pyrolytic Carbon Generated by the Electric Heating CVD Method

A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon source with nitrogen as dilution gas, and the pyrolytic carbon started to deposit on the carbon fiber surface when the deposition temperature was reached. The morphology of pyrolytic carbon was characterized by SEM, and the surface properties of carbon fibers before and after CVD were characterized by Raman spectroscopy. The experimental results show that the electric heating method is a novel method to fabricate C/C composite materials, which can form a dense C/C composite material in a short time. The order degree and the average crystallite size of the carbon fiber surface were decreased after the experiment.

Synthesis of Large-Area, Few-Layer Graphene on Iron Foil by Chemical Vapor Deposition

We demonstrate a simple and controllable way to synthesize large-area, few-layer graphene on iron substrates by an optimized chemical vapor deposition （CVD） method using a mixture of methane and hydrogen. Based on an analysis of the Fe-C phase diagram, a suitable procedure for the successful synthesis of graphene on Fe surfaces was designed. An appropriate temperature and cooling process were found to be very important in the synthesis of highly crystalline few-layer graphene. Graphene-based field-effect transistor （FET） devices were fabricated using the resulting few-layer graphene, and showed good quality with extracted mobilities of 300-1150 cm2/（V.s）.

Safe growth of graphene from non-flammable gas mixtures via chemical vapor deposition

Chemical vapor deposition has emerged as the most promising technique for the growth of graphene.However, most reports of this technique use either flammable or explosive gases, which bring safety concerns and extra costs to manage risk factors. In this article, we demonstrate that continuous monolayer graphene can be synthesized via chemical vapor deposition technique on Cu foils using industrially safe gas mixtures. Important factors, including the appropriate ratio of hydrogen flow and carbon precursor,pressure, and growth time are considered to obtain graphene films. Optical measurements and electrical transport measurements indicate graphene films are with comparable quality to other reports. Such continuous large area graphene can be synthesized under non-flammable and non-explosive conditions, which opens a safe and economical method for mass production of graphene. It is thereby beneficial for integration of graphene into semiconductor electronics.