Arc discharge synthesis of exotic Group IV allotropes

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Arc Discharge Synthesis of Exotic Group IV Allotropes

Karen Ficenec

1,2

_{, Erich Meinig}

1

_{, Reuben T. Collins}

1

_{, & Lakshmi Krishna}

1

1- Physics Department, Colorado School of Mines, Golden, CO. 2- Physics Department, College of William and Mary, Va.

Group IV Allotropes

Arc Discharge Technique

Arc Chamber Set-Up

Evidence of C

₆₀

Synthesis

Acknowledgements

I would like to thank my advisor Lakshmi Krishna for the breadth of knowledge she taught me, as well as the NSF and REMRSEC for sponsoring this research.

In the arc discharge process, high-density carbon clusters can form in the hot plasma zone between graphite electrodes.

Anode & Cathode After Arc

Future Directions

- 3 main fullerene peaks are present (marked by red dots) - 2 unidentified peaks that disappear on re-run (marked by x's)

XRD characterization from deposition on anode

- Fullerenes still present (red dots) -unidentified peaks have disappeared: potentially an unstable allotrope broke down.

1- Ulloa, Eulises. "Fullerenes and Their Applications in Science and Technology." Introduction to Nanoscience (2013): 1-5. Web. 25 July 2016.

2- L.Krishna et al., CrystEngComm, 16, 3940-3949 (2014) 3-www.gl.ciw.edu/static/users/tstrobel/si24.html 4-worldofnanoscience.weebly.com/nanotube--carbon-fiber-overview.html

Fullerene

Clathrates

C601 M136(M = Si, Ge, Sn) Si24

Semiconducting group IV allotropes - composed of earth abundant elements - have promise as new semiconducting materials with exciting electronic and optical properties.

Synthesis Challenges: Semiconducting Si Clathrates for PV & Carbon Clathrates (predicted to be the hardest material)

Eg(Si136) =1.7 eV2 Eg(Si24) =1.3 eV3

Carbon Nanotubes

Parameters of Arc: -Electrode Material -Electrode Geometry -Gas (H, He, Ar) -Gas Pressure (100-1000 Torr) -Current (25-125 A)

Arc Discharge Technique has been used to successfully synthesize - graphite, graphene, carbon nanotubes, fullerenes, Si nano-dots, & Si nano rods.

Arc in Action

Top-Down View of Arc Chamber

Anode Cathode

Experimental Parameters: Graphite Electrodes, 1 mm gap, 300 Torr Helium, 100 A current, with & without Nickel catalyst.

Carbon sample collected during arc discharge

X-ray diffraction phase analysis was performed on arc samples with Graphite electrodes containing a Nickel catalyst. Depositions on the glass slide were measured immediately post-arc (figure A) and after 5 days (figure B).

& a New Allotrope?

A

B

SEM Observations

- XRD peak is shifted from graphite, giving evidence of Carbon nanotubes

Left: Soot observed in Carbon arc with no Ni catalyst. Right: Broccoli-like structures observed in Carbon arc with catalyst.

Multiwalled Carbon Nanotube4

-Possible electrode configurations for synthesis of exotic Group IV Clathrates

-Develop a system for cathode and chamber cooling

-Si arc in Neon Gas for sythesizing semiconducting clathrates with Ne guest