Exfoliated, Epitaxial, or Chemical Vapor Deposited Graphene: Guided Research

STEP-UP Lesson Plan 2012

Candice R. Henry, MPH Learning Facilitator

Title

Exfoliated, Epitaxial, or Chemical Vapor Deposited (CVD) Graphene: Guided Research

Problem

As graphene continues to be studied for its unique properties there is a need to produce a high quality product consistently and in large quantities. There are currently three ways to fabricate graphene, but which one offers the promise of a high quality and consistent product?

Abstract

The lesson focuses on the Habits of Mind and Common Core standards of reading technical texts. These standards are addressed using Graphene as the subject matter. Students while focusing on the elucidation of fabrication techniques for exfoliated, epitaxial, and chemical vapor deposited graphene from various sources will answer the question:

As graphene continues to be studied for its unique properties there is a need to produce a high quality product consistently and in large quantities. There are currently three ways to fabricate graphene, but which one offers the promise of a high quality and consistent product?

Thereby summarizing information to gain procedural understanding, as well as, analyzing the information gathered to develop hypotheses and draw conclusions.

Alignment with National, State, and Common Core Standards

o Georgia Performance Standards o SCSh3. Students will identify and investigate problems

scientifically. a. Suggest reasonable hypotheses for identified problems. d. Graphically compare and analyze data points and/or summary statistics. e. Develop reasonable conclusions based on data collected. f. Evaluate whether conclusions are reasonable by reviewing the process and checking against other available information.

o Common Core 9-10 o ELACC9-10RST2: Determine the central ideas or conclusions of a

text; trace the text’s explanation or depiction of a complex process, phenomenon, or concept provide an accurate summary of the text.

o ELACC9-10RST1: Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions. data) with qualitative analysis in print or digital text.

o ELACC9-10RST7: Translate quantitative or technical

information expressed in words in a text into visual form (e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into words.

o ELACC9-10RST10: By the end of grade 10, read and comprehend

science/technical texts in the grades 9–10 text complexity band

independently and proficiently. o Common Core 11-12

o RST.11-12.2. Determine the central ideas or conclusions of a text; summarize complex concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms.

o RST.11-12.9. Synthesize information from a range of sources

(e.g., texts, experiments, simulations) into a coherent understanding of a process, phenomenon, or concept, resolving conflicting information when possible.

o RST.11-12.8. Evaluate the hypotheses, data, analysis, and

conclusions in a science or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information.

o RST.11-12.10. By the end of grade 12, read and comprehend science/technical texts in the grades 11–12 text complexity band

independently and proficiently.

Objectives At the end of the guided research lesson students will proficiently:

o Utilize strategies to read and comprehend complex texts o Utilize multiple sources of information to summarize key ideas o Utilize multiple sources of information to develop hypotheses and draw

conclusions citing textual evidence o Compare and analyze graphs to draw conclusions

Anticipated learner outcomes At the end of the lesson, students will:

o Gain knowledge about graphene and its potential future in electronics o Deduce the procedure of epithelial graphene from reading a technical

text o Deduce the procedure of epitaxial graphene from reading a technical

text o Deduce the procedure of chemical vapor deposited graphene from

reading a technical text o Analyze the methods of retrieving graphene for product consistency o Analyze multiple Raman Shift Graphs and create hypotheses about what

the graphical images are depicting

Assessment Please find the answer key with the lesson materials

Background Graphene is a novel material that surged to scientific popularity when the 2010

Nobel Prize in Physics was given to Andre Geim and Konstantin Novoselov for their work on exfoliated graphene. Their technique is depicted below.

However, work on graphene had been going on for a while resulting in varying opinions about the methodology for producing graphene and if Geim and Novoselov should have received the Nobel Prize. However, beyond that controversy graphene’s conductivity (currently the fastest conductivity at room temperature of any known material), transparence, strength, and flexibility make it very interesting as a material for new technologies in electronics. However, the exfoliated scotch tape method is considered crude by some scientists and is not the only method for the production of graphene (single layer of carbon atoms that can be stacked to form multiple layers… not to be confused to graphite, which is formed from multiple layers of carbon bonded to each other. The other two methods for fabricating graphene are epitaxial graphene and chemical vapor deposited (CVD). Epitaxial graphene involves using a silicon carbide wafer and exposing it to extremely high temperatures within a vacuum. CVD fabricated graphene involves using a hydrocarbon gas at elevated temperatures and pressure on a metal catalyst to produce the graphene. For additional and up-to-date information on graphene please visit the Georgia Tech Materials Research Science and Engineering Center’s Website www.mrsec.gatech.edu.

Materials and Supplies o Computer

o Projector o Articles o Lesson Materials

Plan (See appendix for student resources)

1. I find that it is important prior to reading to have some level of background knowledge; due to the very technical nature of the readings below are some suggested videos that give some level of background knowledge to the students about graphene. Dependent upon your comfort level and students’ at home resources the videos can be viewed as a class or as a homework assignment prior to the reading activity.

a. “Introducing Graphene” YouTube Video: (Cartoon explanation of exfoliated graphene and graphenes properties) http://www.youtube.com/watch?v=dTSnnlITsVg

b. “Dream Touch Screens from Graphene at Rice University” YouTube Video: (A researchers describes an application of graphene in touch screen flexible technology) http://www.youtube.com/watch?v=d-P6_BMsHSw

c. “Materials Marvel with Ainissa Ramirez-Graphene” YouTube Video: (A Professor describes the basics of graphene, its properties, and molecular structure and includes other carbon

molecules) http://www.youtube.com/watch?v=SsEr4JVPX7U 2. Engage students in a classroom discussion about graphene:

a. What is graphene? b. Why is graphene an important material in science and

technology? c. How is graphene related to the material within your pencil? d. How is graphene different from the graphite in your pencil?

3. Next, introduce the Lesson’s Problem : As graphene continues to be studied for its unique properties there is a need to produce a high quality product consistently and in large quantities. There are currently three ways to fabricate graphene, but which one offers the promise of a high quality and consistent product? The videos discuss exfoliated graphene, which is obtained/fabricated using scotch tape on graphite. This procedure while producing very thin layers of graphene is problematic due to issues of mass production . Tell students, you will be using multiple sources to research and find an answer to the problem. (Dependent upon your students’ reading levels you might want to let them know that the readings are complex and challenging but decipherable using the strategies that they are going to learn.)

4. Hand out the student materials worksheet and go over what information that students will be looking for in their research; fabrication procedure for exfoliated, epitaxial, and CVD graphene, their properties, as well as, pros and cons for each method.

5. Prior to handing out the articles go over various reading and comprehension strategies; see lesson materials “Things to Remember when Reading”

6. Pass out the following Articles: a. “Carbon Wonderland” (11.2 – 11.9 Flesch-Kincaid Readability)

http://www.condmat.physics.manchester.ac.uk/fullpub/17%20Sci.%20Am.%20298,%2090-97%20(2008).pdf

b. “Controlling Silicon Evaporation Improves Quality of Graphene” (12 Flesch-Kincaid Readability) http://www.cos.gatech.edu/news/Controlling-Silicon-Evaporation-Improves-Quality-of-Graphene

c. “Continuous Wafer-Scale Graphene Films Prepared by Chemical Vapor Deposition: Production and Applications” (12 Flesch-Kincaid Readability) http://www.graphene-supermarket.com/images/XC/CVD%20graphene/Continuous%20Wafer-Scale%20Graphene%20Films%20Prepared%20by%20Chemical%20Vapor%20Deposition-Production%20and%20Applications.pdf

d. “Graphene: Synthesis and Application” (12 Flesch-Kincaid Readability) http://www.sciencedirect.com/science/article/pii/S1369702112700445

7. On the student materials following the articles students will evaluate 4 graphs. They are Raman Shift graphs depicting graphene grown on silicon carbide wafers or just silicon carbide. Students will be asked to qualitatively describe what the graphs are depicting. Then qualitatively describe what the graphs are depicting; ultimately coming to the conclusion that graph A is only depicting silicon carbide; graph B has a

silicon carbide peak and a graphene peak, graph C has a silicon carbide peak with less graphene, and graph D has a silicon carbide peak with even less graphene. The Y-Axis is intensity; which varies from Graph A to D, but the shape of the silicon carbide peak remains the same so how can the quantitative relationship of more or less graphene be determined? The easiest conclusion is to determine a ratio of the highest silicon carbide peak to the graphene peak.

Graph A n/a n/a

Graph B 5660/3550= 1.6 3550/5660= 0.63

Graph C 1420/450= 3 450/1420 = 0.32

Graph D 3600/390= 9 390/3600= 0.10

Assuming that the silicon carbide wafers are the same for all of the samples ; graph D has the least amount of graphene with silicon carbide having an intensity 9 times greater than graphene, OR graph D has the least amount of graphene with its peak being only 10% of the silicon carbide peak.

Extension Activity Students can then utilize the information that they have gathered and write

an essay utilizing the Research Problem as a prompt. As graphene continues to be studied for its unique properties there is a need to produce a high quality product consistently and in large quantities. There are currently three ways to fabricate graphene, but which one offers the promise of a high quality and consistent product?

*** You can try the Calibrated Peer Review as a tool to grade essays. After registering and logging your students into the system, students can upload their essay. They then have to grade three essays that you either write or select to CALIBRATE their grading process based upon your rubric. Then they are given peer essays to review/grade. Below is the home page for the free version of the service. There is a new version but it is not free.

http://cpr.molsci.ucla.edu/cpr/cpr_info/index.asp

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Use the Headings Articles like textbooks will often have heading titles, bold and italicized key terms that organize the writing and help the reader know what a

particular section is going to be about… When you are trying to find specific information using the headings can be very helpful in shortening your search.

Use Context Clues When encountering a word that you do not know, take a moment and

reread the phrase, sentence, or paragraph. Focus on the words around the unknown word to decipher the word and figure out its meaning.

Use a Dictionary when it is needed A dictionary is a resource that should be used after figuring it out using

context clues has been exhausted; simply, because as you begin reading more

complex texts the time it would take to look up every word you do not know would TAKE TOO LONG. However, when you feel that the understanding of a sentence or phrase would become clear if only you knew the definition of a word, pull out your dictionary.

Every word doesn’t need to be defined Some words are proper nouns: people, places, or specific things and they don’t necessarily have a definition that aids in comprehension of the sentence. Identifying this type of word and moving past it is key to not getting stuck. Read with Your Pen As you are reading a complex text use your pen or pencil as a tool. You can underline key phrases that are pertinent to your research. When you have an ah-hah moment/ the light bulb of understanding goes off write it over to the side so you will not forget it as you continue reading.

Pertinent Information Only The people who are responsible for writing an article probably needed to include all of the information present. However, if you are looking for specific information more than likely you will not need all of the information they have provided. Being aware of information that is out of the scope of your research will save you time.

Name __________________________ Date________ Per ___

Exfoliated, Epitaxial, or Chemical Vapor Deposited (CVD) Graphene: Guided Research

Problem: As graphene continues to be studied for its unique properties there is a

need to produce a high quality product consistently and in large quantities. There are currently three ways to fabricate graphene, but which one offers the promise of a high quality and consistent product?

Instructions: Read the assigned articles to complete the graphic organizer

below, then use the gathered information to answer questions 1 and 2.

Exfoliated Epitaxial CVD Fabrication Procedure

Question 1: Identify the Pros and Cons of each Graphene Fabrication Procedure.

Exfoliated Epitaxial CVD Pros

Cons

Question 2: Based on your current knowledge of graphene explain which of the three protocols will offer a high quality and consistent product.

The Identification of Graphene on a Silicon Carbide Substrate

Below you will find four different graphs that were produced from a Raman Spectroscope. This machine uses a laser technology to ultimately identify materials that are on the surface. Following all three graphene fabrication methods the Raman can be used to identify if there is graphene present, as well as the quality of the graphene and the amount. The samples below all have a silicon carbide wafer as the substrate. Instructions: After looking at the graphs make qualitative and quantitative observations to describe what the graphs are depicting.

Graph A

Graph B

Graph C

Graph D

Question 3: Qualitatively Describe what each graph is depicting

Graph A

Graph B

Graph C

Graph D

Question 4: Quantitatively Describe what each graph is depicting

Graph A

Graph B

Graph C

Graph D

Question 5: What conclusions can be made about the amount of

graphene in each sample based upon your qualitative and quantitative observations?

Answer Key: The letter appearing after the statement in parentheses corresponds to the article in the lesson plan

Exfoliated Epitaxial CVD Fabrication Procedure

Step 1: Stick a flake of graphite onto plastic adhesive tape Step 2: Fold the sticky side of the tape over the flake Step 3: Pull the tape apart Step 4: Repeat the process (A)

Step1: Heat a silicon carbide wafer to approximately 1500 degrees Celsius under high vacuum or inert gas (B)

Step 1: Allow hydrogen and methane gas to flow over a metal catalyst (copper or nickel) at 1000 degrees Celsius Step 2: The methane decomposes to leave just carbon (graphene) on the metal Step 3: Transfer the graphene to a substrate like glass or silicon (C)

Question 1: Identify the Pros and Cons of each Graphene Fabrication

Procedure. Exfoliated Epitaxial CVD

Pros Simple and low budget (D)

Templated growth creates graphene that does not need to be cut (when it is cut it leaves

ragged edges which decreases conductivity), can make very small to

the nanometer templated structures,

protects graphene from surface contaminants while being fabricated

(B) Allows better control of graphene layers when

grown on Silicon face (side) (D)

Grows very thin layers and at large scales (D)

Method produces large scale and high quality

product (C)

Cons Crude fabrication process (A), irregularly shaped and has limited

commercial and electronic applications

(D)

Has not yet been scaled up to grow large scaled sheets (B) Growth on

carbon face is uncontrolled (D)

Has to be transferred from the metal to

another substrate to be tested which leads to

wrinkles, folding, tearing (D)

Question 2: Based on your current knowledge of graphene explain which of the three protocols will offer a high quality and consistent product.

Choices should either be epitaxial or CVD with a supported explanation

Question 3: Qualitatively Describe what each graph is depicting

Graph A

Graph B

Graph C

Graph D

Question 4: Quantitatively Describe what each graph is depicting

Graph A

Graph B

Graph C

Graph D

Graph A n/a n/a

Graph B 5660/3550= 1.6 3550/5660= 0.63

Graph C 1420/450= 3 450/1420 = 0.32

Graph D 3600/390= 9 390/3600= 0.10

Question 5: What conclusions can be made about the amount of graphene in each sample based upon your qualitative and quantitative observations?

Assuming that the silicon carbide wafers are the same for all of the samples ; graph D has the least amount of graphene with silicon carbide having an intensity 9 times greater than graphene, OR graph D has the least amount of graphene with its peak being only 10% of the silicon carbide peak. Etc…