Advanced

Water assisted CO intercalation underneath Ir(111) supported graphene studied with scanning tunneling microscopy

Mevada, Kaivalya LU (2018) FYSM60 20162
Synchrotron Radiation Research
Department of Physics
Abstract
Graphene have attracted attention recently due to its unique properties and opportunities for development of high performance carbon based devices. The intercalation, absorption and reactions processes of small molecules above and below the graphene islands hold the key for new perspectives in catalysis, molecular sensors and other technologies. The present master thesis is focused on the investigation of the process for the intercalation of small molecules, such as Carbon Monoxide (CO), below graphene islands under Ultra High Vacuum conditions using Scanning Tunneling Microscopy (STM). It has been proven that the intercalation is facilitated with the presence of water under graphene islands. The water is formed underneath graphene by... (More)
Graphene have attracted attention recently due to its unique properties and opportunities for development of high performance carbon based devices. The intercalation, absorption and reactions processes of small molecules above and below the graphene islands hold the key for new perspectives in catalysis, molecular sensors and other technologies. The present master thesis is focused on the investigation of the process for the intercalation of small molecules, such as Carbon Monoxide (CO), below graphene islands under Ultra High Vacuum conditions using Scanning Tunneling Microscopy (STM). It has been proven that the intercalation is facilitated with the presence of water under graphene islands. The water is formed underneath graphene by sequentially dosing of oxygen and hydrogen molecules. The formed water is visible with STM and preferentially located in the graphene edges and across the graphene islands grown on Ir(111) step edges. This phase raised the height of graphene by approximately 100 pm leading the graphene areas to be elevated from the Ir substrate. Furthermore, different amount of CO were dosed and STM was used to study the intercalation process. On saturating the surface with CO, digital CO intercalation was achieved below water phased graphene islands at room temperature and low pressures (in the range of 10-5mbar). Digital intercalation means graphene areas where fully intercalated by CO molecules or not at all. The graphene corrugation (ripples) was also decreased by one order of magnitude, as compared to pristine graphene. Finally the intercalation at 1 × 10-8 mbar CO exposure was also studied using STM. Irregular shaped CO channels were formed under graphene islands crossing over Ir(111) step edge suggested a possible mechanism for the CO intercalation. The STM studies gained from this intercalation method and the proposed edge mechanism can give an insight on the design of new graphene interfaces. (Less)
Popular Abstract
Tent for atoms and molecules

Graphene is the thinnest two-dimensional material discovered, with the thickness of 0.34 nm, made up of single layer of carbon atoms arranged in a honeycomb structure in a plane. To get an idea how thin it is, consider a coin of 1.5mm thickness, graphene is 4.5 million times thinner than that. Historically, graphene was extracted by isolating a single layer of graphite with sticky tape, since it is the building block of graphite. One can imagine a book as graphite then a single sheet of paper is graphene.

Today graphene is grown in laboratories on metal substrate by extracting carbon atoms from hydrocarbon gas. It has gained popularity among researcher due to its unique properties; very high electron and... (More)
Tent for atoms and molecules

Graphene is the thinnest two-dimensional material discovered, with the thickness of 0.34 nm, made up of single layer of carbon atoms arranged in a honeycomb structure in a plane. To get an idea how thin it is, consider a coin of 1.5mm thickness, graphene is 4.5 million times thinner than that. Historically, graphene was extracted by isolating a single layer of graphite with sticky tape, since it is the building block of graphite. One can imagine a book as graphite then a single sheet of paper is graphene.

Today graphene is grown in laboratories on metal substrate by extracting carbon atoms from hydrocarbon gas. It has gained popularity among researcher due to its unique properties; very high electron and heat conductivity. However, little is known on how its properties are modified upon interaction with other atoms and molecules. In this work, we study graphene by introducing atoms and molecules between graphene and its substrate. This process is called intercalation.

Intercalation of graphene is similar to the process of setting up a tent. Your cloth lying on the ground resembles graphene on its substrate. Next step in setting up a tent is to elevate the cloth from the ground with the help of a pole. In my experiments, water is formed beneath graphene by sequential dosing of oxygen and hydrogen and this water acts as a pole and elevates graphene from its substrate.

Now that the tent is ready a person can easily enter in the tent. We use carbon monoxide, CO molecules, to intercalate graphene. We propose a mechanism for how CO intercalation starts. The CO molecules enter beneath graphene from the region where there is water trapped below graphene. Similarly, a person enters the tent from where it is elevated by the pole and not from where the cloth is fixed to the ground.

Instead of water if xenon atoms are used to elevate graphene then CO molecules are not able to intercalate graphene. Thus, CO intercalation of graphene is highly dependent on the atoms or molecules that elevate graphene from its substrate. (Less)
Please use this url to cite or link to this publication:
author
Mevada, Kaivalya LU
supervisor
organization
course
FYSM60 20162
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Graphene, Intercalation, STM, CVD, TPG
language
English
id
8962681
date added to LUP
2018-11-06 14:14:31
date last changed
2018-11-06 14:14:31
@misc{8962681,
  abstract     = {Graphene have attracted attention recently due to its unique properties and opportunities for development of high performance carbon based devices. The intercalation, absorption and reactions processes of small molecules above and below the graphene islands hold the key for new perspectives in catalysis, molecular sensors and other technologies. The present master thesis is focused on the investigation of the process for the intercalation of small molecules, such as Carbon Monoxide (CO), below graphene islands under Ultra High Vacuum conditions using Scanning Tunneling Microscopy (STM). It has been proven that the intercalation is facilitated with the presence of water under graphene islands. The water is formed underneath graphene by sequentially dosing of oxygen and hydrogen molecules. The formed water is visible with STM and preferentially located in the graphene edges and across the graphene islands grown on Ir(111) step edges. This phase raised the height of graphene by approximately 100 pm leading the graphene areas to be elevated from the Ir substrate. Furthermore, different amount of CO were dosed and STM was used to study the intercalation process. On saturating the surface with CO, digital CO intercalation was achieved below water phased graphene islands at room temperature and low pressures (in the range of 10-5mbar). Digital intercalation means graphene areas where fully intercalated by CO molecules or not at all. The graphene corrugation (ripples) was also decreased by one order of magnitude, as compared to pristine graphene. Finally the intercalation at 1 × 10-8 mbar CO exposure was also studied using STM. Irregular shaped CO channels were formed under graphene islands crossing over Ir(111) step edge suggested a possible mechanism for the CO intercalation. The STM studies gained from this intercalation method and the proposed edge mechanism can give an insight on the design of new graphene interfaces.},
  author       = {Mevada, Kaivalya},
  keyword      = {Graphene,Intercalation,STM,CVD,TPG},
  language     = {eng},
  note         = {Student Paper},
  title        = {Water assisted CO intercalation underneath Ir(111) supported graphene studied with scanning tunneling microscopy},
  year         = {2018},
}