اثر زیرلایه روی جوانه زنی و رشد نانو ورق های عمودی گرافن

Influence of substrate on nucleation and growth of

verticalgraphene nanosheets

اثر زیرلایه روی جوانه زنی و رشد نانو ورق های عمودی گرافن

ABSTRACT

The present study reports the role of substrate on nucleation and growth of vertical graphene nanosheets (VGNs) under electron cyclotron resonance chemical vapor deposition (ECR-CVD). The VGNs are grown on Pt, Ni, Au, Cu, Si(100), Si(111), SiO2 and quartz substrates simultaneously. The morphology of VGNs is found to vary significantly with substrate. VGNs on Pt have the highest aerial density of vertical sheets while quartz have the lowest. The structural defects in VGNs vary with substrate as evidenced from Raman spectroscopy. The observation of defect related Raman bands such as D'' and D* at 1150 and 1500 cm-1, respectively revealed the existence of pentagon-heptagon rings or carbon onions in VGNs. Formation of such defects at early stage of nucleation dictates the growth mechanism and hence the morphology. A phenomenological four stage model is discussed, to substantiate the nucleation and growth mechanism of VGNs on different substrates, by evoking substrate - plasma interaction during growth.

 

رشد ورقه های گرافن روی نانوسیم های سیلیکا با دانسیته بالا

Catalyst-free approach for growth of graphene sheets on

high-density silica nanowires byCVD

روش بدون کاتالیزور برای رشد ورقه های گرافن روی نانوسیم های سیلیکا

با دانسیته بالا توسط CVD 

ABSTRACT

A novel “two-step annealing” method is proposed for the direct synthesis of graphene sheets on high-density dielectric silica nanowires without using metal catalysts. During the first annealing at 1000 °C, the extremely thin SiO2 layer on Si substrate shrinks and forms dense nanoparticles. Using these silica nanoparticles as templates, graphene sheets and silica nanowires are synthesized simultaneously after the second annealing process at 800–850 °C. The experiment results suggest that the graphene sheets grow along the nanowires and its crystalline quality and domain size are determined by the temperature and duration of the second annealing process.

 

تولید، خواص و قابلیت‌های گرافن Production, properties and potential of graphene

Production, properties and potential of graphene

تولید، خواص و قابلیت‌های گرافن

ABSTRACT

This review on graphene, a one-atom thick, two-dimensional sheet of carbon atoms, starts with a general description of the graphene electronic structure as well as a basic experimental toolkit for identifying and handling this material. Owing to the versatility of graphene properties and projected applications, several production techniques are summarized, ranging from the mechanical exfoliation of high-quality graphene to the direct growth on carbides or metal substrates and from the chemical routes using graphene oxide to the newly developed approach at the molecular level. The most promising and appealing properties of graphene are summarized from an exponentially growing literature, with a particular attention to matching production methods to characteristics and to applications. In particular, we report on the high carrier mobility value in suspended and annealed samples for electronic devices, on the thickness-dependent optical transparency and, in the mechanical section, on the high robustness and full integration of graphene in sensing device applications. Finally, we emphasize on the high potential of graphene not only as a post-silicon materials for CMOS device application but more ambitiously as a platform for post-CMOS molecular architecture in electronic information processing.