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Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.ORCID iD: 0000-0002-8222-3157
KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. Chalmers Institute of Technology, Sweden.
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2017 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 663, p. 23-30Article in journal (Refereed) Published
Abstract [en]

We present dispersion-corrected density functional calculations of water and carbon dioxide molecules adsorption on graphene residing on silica and sapphire substrates. The equilibrium positions and bonding distances for the molecules are determined. Water is found to prefer the hollow site in the center of the graphene hexagon, whereas carbon dioxide prefers sites bridging carbon-carbon bonds as well as sites directly on top of carbon atoms. The energy differences between different sites are however minute - typically just a few tenths of a millielectronvolt. Overall, the molecule-graphene bonding distances are found to be in the range 3.1-3.3 (A) over circle. The carbon dioxide binding energy to graphene is found to be almost twice that of the water binding energy (around 0.17 eV compared to around 0.09 eV). The present results compare well with previous calculations, where available. Using charge density differences, we also qualitatively illustrate the effect of the different substrates and molecules on the electronic structure of the graphene sheet.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 663, p. 23-30
Keywords [en]
Graphene, DFT, Sensor, Humidity, Carbon dioxide
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-211313DOI: 10.1016/j.susc.2017.04.009ISI: 000405043300004Scopus ID: 2-s2.0-85018431677OAI: oai:DiVA.org:kth-211313DiVA, id: diva2:1129300
Funder
Swedish e‐Science Research CenterSwedish Research Council, VR 2015-04605The Royal Swedish Academy of SciencesKnut and Alice Wallenberg FoundationCarl Tryggers foundation , CTS 14:105 CTS KF16:2Swedish Energy Agency, STEM P40147-1Swedish Foundation for Strategic Research , SSF EM11-0002
Note

QC 20170802

Available from: 2017-08-02 Created: 2017-08-02 Last updated: 2018-01-18Bibliographically approved
In thesis
1. Density Functional Theory Calculations for Graphene-based Gas Sensor Technology
Open this publication in new window or tab >>Density Functional Theory Calculations for Graphene-based Gas Sensor Technology
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nowadays, electronic devices span a diverse pool of applications, especially when getting smaller and smaller satisfying the more than Moore paradigm. To further develop this, studies focusing on material design toward electronic devices are crucial. Accordingly, we present a theoretical study investigating the possibility of graphene as a promising material for such electronic devices design. We focus on graphene and graphene-based sensors. Graphene is known to have outstanding electronic and mechanical properties making it a game changer in the electronic design in the so-called 'post-silicon' industry. It is stronger than steel yet the thinnest material ever known while overstepping copper regarding electronic conductivity.

In this thesis, we perform first-principle ab-initio density functional theory (DFT) calculations of graphene in different sensing ambient conditions, which allows fast, accurate and efficient investigations of the electronic structure properties. Principally, we centre our attention on the arising interactions between the adsorbates on top of the graphene sheet and the underlying substrates' surface defects. The combined effect of the impurity bands arising from these defects and the adsorbates reveals a doping influence within the graphene sheet. This doping behaviour is responsible for different equilibrium distances and binding energies for different adsorbate types as well as substrates. Moreover, we briefly investigate the same effect on double layered graphene under the same ambient conditions.

We extend the studies to involve various types of substrates with different surface conditions and different adhesion nature to graphene. We take into consideration the governing van der Waals interactions in describing the electronic structure properties taking place at the graphene sheet interfacing both with the substrates below and the adsorbates above. Furthermore, we investigate the possibility of passivating such action of graphene sensing towards adsorbates to inhibit the graphene's sensing action as devices passivation becomes a necessity for the ultimate purpose of achieving more than Moore applications. Which in turn result in the optimal integration of graphene-based devices with different other devices functionalities on the same resultant chip.

In summary, graphene, by means of first-principle calculations verification, shows a promising behaviour in the sensor functionality enabling more than Moore applications for further advances.

Abstract [sv]

Elektroniska komponenter används i allt vidare utsträckning, och deras användning ökar i takt med att de blir mindre och mindre samtidigt som deras prestanda ökar, enligt det paradigm som brukar kallas ''more than Moore''. För att att göra ytterligare framsteg i denna riktning är grundläggande studier som fokuserar på materialdesign och tillverkning av nya typer av elektroniska komponenter avgörande. I den här avhandlingen presenteras teoretiska studier av grafen-baserade komponenter. Grafen är ett mycket intressant material för framtidens elektroniska komponenter. Specifikt fokuserar vi på grafenbaserade gas-sensorer. Grafen är känt för att ha mycket ovanliga elektroniska och mekaniska egenskaper som gör det till ett unikt material för "post-silicon"-design av elektronik. Det är starkare än stål och är samtidigt världens tunnaste material. Samtidigt har det bättre elektrisk ledningsförmåga än koppar.

Täthetsfunktionalsteori (DFT) har använts för att beräkna hur den elektroniska strukturen hos grafen ändras som funktion av substratmaterial och typ av molekyler som adsorberats på grafenets yta. DFT är en beräkningsmetod som medger simuleringar med hög precision samtidigt som den är relativt snabb. I studierna har DFT kombinerats med olika modeller för van der Waals-interaktionen.En viktig aspekt i de studier vi presenterar här är interaktionen mellan adsorbat-molekylerna ovanpå grafenet och ytdefekterna hos det underliggande substratet. De orenhetsband som härrör från defekterna, i kombination med adsorbat-molekylerna, skapar en slags dopningseffekt som ändrar elektronstrukturen hos grafenet. Därmed kan även de elektriska transportegenskaperna ändras hos grafenet, vilket möjliggör elektrisk detektion av molekylerna.

Vi har även studerat sensorer byggda med dubbelskiktad grafen. Dessutom har vi gjort en systematisk studie av hur grafen binder till ett stort antal substrat samt även hur man kan passivisera grafen så att den elektriska ledningsförmågan inte ändras vid molekyladsorption. Detta sista är viktigt för "more than Moore"-tillmämpningar, där ett centralt designkriterium är att kunna integrera många funktioner på samma chip.

Place, publisher, year, edition, pages
Stockholm, Sweden, 2018: KTH Royal Institute of Technology, 2018. p. 75
Series
TRITA-SCI-FOU ; 2018:01
Keywords
graphene, ab-initio, humidity, carbon dioxide, substrate, DFT, vdW, first-principle, simulation, calculations
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-221639 (URN)978-91-7729-660-7 (ISBN)
Public defence
2018-02-09, Ka-Sal C (Sal Sven-Olof Öhrvik), Electrum 229 16440 Kista, Stockholm, Stockholm, 09:00 (English)
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Supervisors
Note

QC 20180118

Available from: 2018-01-18 Created: 2018-01-18 Last updated: 2018-01-19Bibliographically approved

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