Category Archives: Publications

Single-step growth of graphene and graphene-based nanostructures by plasmaenhanced chemical vapor deposition

Our latest review article by Professor Nai-Chang Yeh, Chen-Chih Hsu, Jacob Bagley and
Wei-Shiuan Tseng
The realization of many promising technological applications of graphene and graphene-based
nanostructures depends on the availability of reliable, scalable, high-yield and low-cost synthesis
methods. Plasma enhanced chemical vapor deposition (PECVD) has been a versatile technique
for synthesizing many carbon-based materials, because PECVD provides a rich chemical
environment, including a mixture of radicals, molecules and ions from hydrocarbon precursors,
which enables graphene growth on a variety of material surfaces at lower temperatures and faster
growth than typical thermal chemical vapor deposition. Here we review recent advances in the
PECVD techniques for synthesis of various graphene and graphene-based nanostructures.
Pdf Publication Link
https://iopscience.iop.org/article/10.1088/1361-6528/aafdbf

Vertically-aligned graphene nanowalls grown via plasma-enhanced chemical vapor deposition as a binder-free cathode in Li–O2 batteries

Vertically-aligned graphene nanowalls grown via plasma-enhanced chemical vapor deposition as a binder-free cathode in Li–O2 batteries Chih-Pin Han, Vediyappan Veeramani, Chen-Chih Hsu, Anirudha Jena, Ho Chang, Nai-Chang Yeh, Shu-Fen Hu, and Ru-Shi Liu
https://doi.org/10.1088/1361-6528/aae362

In the present report, vertically-aligned graphene nanowalls are grown on Ni foam (VA-G/NF) using plasma-enhanced chemical vapor deposition method at room temperature. Optimization of the growth conditions provides graphene sheets with controlled defect sites. The unique architecture of the vertically-aligned graphene sheets allows sufficient space for the ionic movement within the sheets and hence enhancing the catalytic activity. Further modification with ruthenium nanoparticles (Ru NPs) drop-casted on VA-G/NF improves the charge overpotential for lithium–oxygen (Li–O2) battery cycles. Such reduction we believe is due to the easier passage of ions between the perpendicularly standing graphene sheets thereby providing ionic channels.

High-yield single-step catalytic growth of graphene nano-strips by plasma enhanced chemical vapor deposition

“High-yield single-step catalytic growth of graphene nano-strips by plasma enhanced chemical vapor deposition”, Chen-Chih Hsu, Jacob D. Bagley, Marcus L. Teague, Wei-Shiuan Tseng, Kathleen L, Yang, Yiran Zhang, Yiliang Li, Yilun Li, James M. Tour, and N.-C. Yeh, Carbon 129, 527 –536 (2018).

https://www.sciencedirect.com/science/article/pii/S0008622317312915

Atomic-Scale Structural and Chemical Characterization of Hexagonal Boron Nitride Layers Synthesized at the Wafer-Scale with Monolayer Thickness Control

Hexagonal boron nitride (h-BN) is a promising two-dimensional insulator with a large band gap and low density of charged impurities that is isostructural and isoelectronic with graphene. Here we report the chemical and atomic-scale structure of CVD-grown wafer-scale (~25 cm2) h-BN sheets ranging in thickness from 1-20 monolayers. Atomic-scale images of h-BN on Au and graphene/Au substrates obtained by scanning tunneling microscopy (STM) reveal high h-BN crystalline quality in monolayer samples. Further characterization of 1-20 monolayer samples indicates uniform thickness for wafer-scale areas; this thickness control is a result of precise control of the precursor flow rate, deposition temperature and pressure. Raman and infrared spectroscopy indicate the presence of B-N bonds and reveal a linear dependence of thickness with growth time. X-ray photoelectron spectroscopy (XPS) shows the film stoichiometry, and the B/N atom ratio in our films is 1 ± 0.6% across the range of thicknesses. Electrical current transport in metal/insulator/metal (Au/h-BN/Au) heterostructures indicates that our CVD-grown h-BN films can act as excellent tunnel barriers with a high hard-breakdown field strength. Our results suggest that large-area h-BN films are structurally, chemically and electronically uniform over the wafer scale, opening the door to pervasive application as a dielectric in layered nanoelectronic and nanophotonic heterostructures.

http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.7b00183

Mn-doping induced ferromagnetism and enhanced superconductivity in Bi4−xMnxO4S3 (0.075 ≤ x ≤ 0.15)

Mn-doping induced ferromagnetism and enhanced superconductivity in Bi4−xMnxO4S3 (0.075 ≤ x ≤ 0.15) Zhenjie Feng, Xunqing Yin, Yiming Cao, Xianglian Peng, Tian Gao, Chuan Yu, Jingzhe Chen, Baojuan Kang, Bo Lu, Juan Guo, Qing Li, Wei-Shiuan Tseng, Zhongquan Ma, Chao Jing, Shixun Cao, Jincang Zhang, and N.-C. Yeh Phys. Rev. B 94, 064522 (2016). arXiv:1608.04410
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.064522