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Resistive graphene humidity sensors with rapid and direct electrical readout
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.ORCID iD: 0000-0003-4637-8001
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. (Anna Delin Group)ORCID iD: 0000-0002-8222-3157
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.ORCID iD: 0000-0002-0525-8647
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, School of Electrical Engineering (EES), Micro and Nanosystems. KTH, Centres, SeRC - Swedish e-Science Research Centre.ORCID iD: 0000-0001-7788-6127
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2015 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 45, p. 19099-19109Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N-2), oxygen (O-2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. The interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO(2)d substrate leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical readout and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2015. Vol. 7, no 45, p. 19099-19109
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-179618DOI: 10.1039/c5nr06038aISI: 000364852500035PubMedID: 26523705Scopus ID: 2-s2.0-84947265250OAI: oai:DiVA.org:kth-179618DiVA, id: diva2:892726
Funder
Swedish Research Council, E0616001 D0575901Knut and Alice Wallenberg FoundationSwedish Energy Agency
Note

QC 20160111

Available from: 2016-01-11 Created: 2015-12-17 Last updated: 2018-01-18Bibliographically approved
In thesis
1. Density Functional Theory Calculations of Graphene based Humidity and Carbon Dioxide Sensors
Open this publication in new window or tab >>Density Functional Theory Calculations of Graphene based Humidity and Carbon Dioxide Sensors
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Graphene has many interesting physical properties which makes it useful for plenty of applications. In this work we investigate the possibility of using graphene as a carbon dioxide and humidity sensor. Carbon dioxide and water adsorbates are modeled on top of the surface of a graphene sheet, which themselves lie on one of two types of silica substrates or sapphire substrate. We evaluate the changes in the electronic and structural properties of the graphene sheet in the presence of the described adsorbates as well as the accompanying substrate. We perform the study using ab-initio calculations based on density functional theory (DFT), that allows fast, accurate and efficient investigations. In particular, we focus our attention on investigating the effects of defects in the substrate and how it influences the properties of the graphene sheet. The defects of the substrate contribute with impurity bands leading to doping effects on the graphene sheet, which in turn together with the presence of the adsorbates result in changes of the electronic charge distribution in the system. We provide charge density difference plots to visualize these changes and also determine the relaxed minimum distances of the adsorbates from the graphene sheet together with the respective minimum energy configurations. We also include the density of states, Löwdin charges and work functions for further investigations.

Abstract [sv]

Grafen har många intressanta fysikaliska egenskaper, vilket gör det användbart för många  tillämpningar. I detta arbete har vi teoretiskt undersökt möjligheten att använda grafen som gassensor för koldioxid och fukt. Adsorberade koldioxid- och vattenmolekyler modelleras ovanför ytan av ett lager grafen, som i sig ligger ovanpå en av två typer av kiseldioxidsubstrat eller ett aluminiumoxidsubstrat. Vi har utvärderat förändringar i de elektroniska och strukturella egenskaperna hos grafenlagret i närvaro av de beskrivna molekylerna samt åtföljande substrat. Vi utför studien med ab-initio beräkningar baserade på täthetsfunktionalteori (DFT), som möjliggör snabba, korrekta och effektiva elektronstruktursberäkningar. Framför allt fokuserar vi på effekten av defekter i underlaget, och hur dessa påverkar egenskaperna hos grafenlagret. Defekter i underlaget bidrar genom att införa elektroniska band som leder till dopningseffekter i grafenlagret, vilket i sin tur tillsammans med närvaron av adsorbatmolekylerna leder till förändringar av den elektroniska laddningsfördelningen i systemet. Vi tillhandahåller s.k. laddningsdensitet-skillnadsfigurer som visualiserar dessa förändringar. Vi har även beräknat jämviktsavståndet mellan adsorbatmolekylerna och grafenlagret  tillsammans med respektive minimienergikonfigurationer för molekylerna, Vi åksa tillhandahåller täthet av stater, Löwdin laddningar och arbetsfunktion för fortsatta undersökningar.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. p. xi, 20
Series
TRITA-ICT ; 2016:02
Keywords
DFT, graphene, sensors, Quantum Espresso, ab-initio
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-180761 (URN)978-91-7595-817-0 (ISBN)
Presentation
2016-02-19, Sal/hall 205, Elektrum 229, Isafjordsgatan 22, KTH-ICT, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center
Note

QC 20160218

Available from: 2016-01-28 Created: 2016-01-22 Last updated: 2016-02-12Bibliographically approved
2. Graphene-based Devices for More than Moore Applications
Open this publication in new window or tab >>Graphene-based Devices for More than Moore Applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Moore's law has defined the semiconductor industry for the past 50 years. Devices continue to become smaller and increasingly integrated into the world around us. Beginning with personal computers, devices have become integrated into watches, phones, cars, clothing and tablets among other things. These devices have expanded in their functionality as well as their ability to communicate with each other through the internet. Further, devices have increasingly been required to have diverse of functionality. This combination of smaller devices coupled with diversification of device functionality has become known as more than Moore. In this thesis, more than Moore applications of graphene are explored in-depth.

Graphene was discovered experimentally in 2004 and since then has fueled tremendous research into its various potential applications. Graphene is a desirable candidate for many applications because of its impressive electronic and mechanical properties. It is stronger than steel, the thinnest known material, and has high electrical conductivity and mobility. In this thesis, the potentials of graphene are examined for pressure sensors, humidity sensors and transistors.

Through the course of this work, high sensitivity graphene pressure sensors are developed. These sensors are orders of magnitude more sensitive than competing technologies such as silicon nanowires and carbon nanotubes. Further, these devices are small and can be scaled aggressively.

Research into these pressure sensors is then expanded to an exploration of graphene's gas sensing properties -- culminating in a comprehensive investigation of graphene-based humidity sensors. These sensors have rapid response and recovery times over a wide humidity range. Further, these devices can be integrated into CMOS processes back end of the line.

In addition to CMOS Integration of these devices, a wafer scale fabrication process flow is established. Both humidity sensors and graphene-based transistors are successfully fabricated on wafer scale in a CMOS compatible process. This is an important step toward both industrialization of graphene as well as heterogeneous integration of graphene devices with diverse functionality. Furthermore, fabrication of graphene transistors on wafer scale provides a framework for the development of statistical analysis software tailored to graphene devices.

In summary, graphene-based pressure sensors, humidity sensors, and transistors are developed for potential more than Moore applications. Further, a wafer scale fabrication process flow is established which can incorporate graphene devices into CMOS compatible process flows back end of the line.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. p. xxvi, 79
Series
TRITA-ICT ; 2016:17
Keywords
Graphene, Humidity Sensor, Pressure Sensor, GFET, CMOS, BEOL, More than Moore, Integration, Statistics
National Category
Engineering and Technology Nano Technology
Identifiers
urn:nbn:se:kth:diva-188134 (URN)978-91-7729-024-7 (ISBN)
Public defence
2016-08-26, Sal C, Isafjordsgatan 22, Electrum 229, 164-40, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20160610

Available from: 2016-06-10 Created: 2016-06-06 Last updated: 2016-06-10Bibliographically approved
3. 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)
Opponent
Supervisors
Note

QC 20180118

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

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Smith, Anderson D.Elgammal, KarimNiklaus, FrankDelin, AnnaFischer, Andreas C.Vaziri, SamForsberg, FredrikRåsander, MikaelHugosson, HåkanBergqvist, LarsSchröder, StephanÖstling, MikaelLemme, Max C.
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