[Reminder] MSE PhD Dissertation Defense: Sangwon Lee (Tomorrow, 10am)

Sangwon Lee sangwon at stanford.edu
Sun Feb 12 08:38:33 PST 2012

>  Department of Materials Science & Engineering
> University PhD Dissertation Defense
> Graphene: Synthesis, Structure & Properties
> Sangwon Lee
> Advisor: Prof. Alberto Salleo
> Date: Monday, February 13th, 2012
> Time: 10 am (Refreshments served at 9:45 am)**
> Location: Jerry Yang and Akiko Yamazaki Environment and Energy Building
> (Y2E2)
> Conference room # 299 (Bechtel conference room)
> (http://campus-map.stanford.edu/index.cfm?ID=04-070)
> <http://cis.stanford.edu/directions/>
> Abstract
> The discovery of free-standing graphene in 2004 has attracted wide
> attention in both scientific communities and industries because of its
> unusual electronic structure and properties. Due to the possible
> applications of graphene, many attempts to produce high-quality wafer-scale
> graphene films have been actively tried in the materials science and other
> scientific communities. Thermal decomposition of silicon carbide (SiC) is
> considered as one of the most promising routes toward the synthesis of
> well-controlled and characterized graphene films.
> Since the argon (Ar) atmosphere produced higher quality graphene films on
> SiC than in vacuum, the inert-gas mediated thermal decomposition of SiC is
> regarded so far as the most effective method for the controlled epitaxial
> graphene (EG) growth. Most studies and progresses have been demonstrated
> with the Si-face of basal plane oriented SiC substrates because of its
> slower reaction kinetics, which results from higher surface energy than the
> C-face. Nevertheless, there is significant interest in obtaining
> few-layer, smooth EG on the C-face of SiC due to its superior electrical
> properties as compared to EG on the Si-face. The first part of the
> presentation will focus on the structural properties of EG layers grown on
> the C-face of 4H-SiC in vacuum or Ar environments by X-ray diffraction
> using synchrotron radiation. The qualities and characteristics of layers
> will be also correlated with carrier mobilities from Hall measurements.
> The high temperatures required in this method (~ 1400°C) are not
> compatible with large-scale device integration where different materials
> must be deposited and patterned prior to the formation of the semiconductor
> layers and limit the synthesis to single-crystal SiC substrates. In the
> second part of the presentation, an alternative low-temperature, spatially
> controlled and scalable epitaxial graphene synthesis technique based on
> laser-induced surface decomposition of SiC will be proposed. This technique
> is compatible and amenable to large-scale device integration. Furthermore,
> laser synthesis of graphene offers the advantage of combining synthesis and
> patterning in one step as the process can be designed to form graphene
> devices in predetermined locations on the substrate. Our results in this
> research show that epitaxial graphene (EG) forms on SiC as a result of
> laser irradiation. Various characterization techniques such as RHEED,
> synchrotron-based X-ray diffraction, Raman, TEM and STM were used to
> confirm the graphitization of SiC and to measure the properties of graphene
> films.
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