Synthesis of High Quality GO & rGO by E-Beam Evaporator

(Performed by Ji hoon Kang)

(Courtesy of Mr. Jae Heo at NDnMP)

Project description

✔ Deposition of High quality GO with E-beam evaporator.
✔ Using GO's functional groups to give proper properties for device applications
✔ Finding an effective and optimized GO reduction method to obtain high performance rGO
✔ Enhancing the materials & devices properties by applying GO & rGO

Why? The reasons for the research

✔ A differentiated Method
- Existing methods using chemical reactions cause degradating of the materials properties.
- E-beam evaporator uses only physical deposition, because of this defects can be reduced.

✔ Overcoming Graphene's Limitations
- It is possible to assign chemical functionalizations that are not in graphene.
- It can open the band gap of GO & rGO using oxygen's functional group.

✔ Next Generation Semiconductor
- It has superior properties compared to Silicon.
- It can improve the performance of materials and devices by replacing Silicon.

Why is the project important?

✔ Large area and high quality GO & rGO synthesis by E-beam evaporator, a more advanced method compared to the current method
✔ Application of high efficiency and high performance devices using high quality GO & rGO
✔ The importance of Nano-Technology using 2D materials as a key paradigm in the future.

2D Materials Heterostructure

(Performed by Yongteng Qian)

(Courtesy of Mr. Yongteng Qian at ASDNL)

Project description

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ High-quality large-area graphene/h-BN vertical heterostructures are promising building blocks for many viable applications such as energy harvesting/conversion, electronics and optoelectronics.
✔ We successfully grew high-quality large-area graphene/h-BN vertical heterostructures on Pt foils by one batch low-pressure chemical vapor deposition (LPCVD).
✔ This work was supported by the National Research Foundation of Korea grant funded by the Korean government (NRF-2014R1A2A1A11052965 and 2017R1D1A1B03034847).

Main findings

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ We found that using a single-layer h-BN/Pt foil as a substrate not only presents an ideal platform for obtaining continuous graphene/h-BN vertical heterostructures but also enables to realize desirable electrical characteristics of graphene.

✔ Direct growth of graphene on h-BN films retains the pristine properties of graphene by avoiding the interfacial contamination, thus yielding a clean interface between the graphene and the h-BN film.

✔ Our graphene/h-BN heterostructure exhibits high carrier mobility, in the 2,000–8,000 cm2V−1s−1 range.

Why? The reasons for the research

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ One plausible strategy for producing graphene/h-BN vertical heterostructures is based on layer-by-layer transfer of separately exfoliated 2D layers via a two-step process. However, such a two-step process has some drawbacks during the transfer process, such as unwanted charge trapping that originates from any transfer-induced contaminants and defects, and poor surface fatness during the transfer; all of these are undesirable for obtaining high quality graphene/h-BN vertical heterostructures.
✔ Develop a new method for synthesis of continuous, large-area graphene/h-BN vertical heterostructures on recyclable Pt foils.

What was found?

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ h-BN film is continuous without impurities and wrinkles.
✔ Graphene/h-BN film on the SiO2/Si substrate is continuous and large area.
✔ Monolayer graphene film direct grown on monolayer layer h-BN film.

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ The h-BN surface is continious.
✔ The continuous graphene flm is grown on the h-BN film.
✔ The graphene/h-BN heterostructure was observed with the rotation angle of about 5.5°.

Why is the project important?

(Courtesy of Mr. Yongteng Qian at ASDNL)
✔ We found that using a single layer h-BN flm as the substrate allows us to obtain high quality, larger area graphene/h-BN heterostructures.

✔ The field efect mobility of the fabricated graphene/h-BN heterostructures based feld effect transistors is as high as 7,200 cm2V−1s−1 at room temperature.

Analysis of thermal characteristics of large-area rGO ultra thin films

(Performed by Yongwoo Song)

(Courtesy of Mr. Yong Woo Song at NDnMP)

❖ Project description

Manuel Bogner et al. Cross- and in-plane thermal conductivity of AlN thin films measured using differential 3-omega method Surface and coatings technology 2017
Paula A. A. P. Marques et al. Functionlaized Graphene Nanocomposites. Advances in nanocomposite technology 2011
✔ Precise measurement of physical properties using 3𝜔 method
✔ Comparing the physical properties of graphene and r-GO
✔ Study of thermal properties of r-GO with surface functionalization

Main findings

(Courtesy of Mr. Yong Woo Song at NDnMP)
✔ Measurement of thermal properties of large-area r-GO with a few nm thickness
✔ Accurate thermal and electrical conductivity measurement using 3𝜔 method
✔ Determination of Seebeck coefficient and ZT from thermal and electrical conductivity

Why? The reason for the research

✔ Physical properties of large area r-GO
• The physical properties of r-GO and graphene are expected to be similar
• As the area increases, the reliability of the measured value increases
✔ Absence of thermal characteristics study of r-GO
• Most of the experiments are consisted of studies on electrical conductivity and no study of thermal properties was done
• To use a substance as a material, the physical properties of the substance should be analyzed priority

Why is the project important?

✔ Determining the ZT of the r-GO
• It is possible to confirm that r-GO is an alternative material to graphene
✔ Controlling the charge carrier density and thermal properties by utilizing chemical bonding of oxygen functional group of r-GO
• Confirming the possibility of development of high efficiency thermoelectric material with high ZT