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Graphene Field Effect Transistor Properties Modulation Via Mechanical Strain Induced By Micro-Cantilever
Brodský, Jan
This work presents a new method, which enables the electrical characterization ofgraphene monolayer with induced mechanical strain. The device is a combination oftwo-dimensional field effect transistor (2DFET) and a MEMS cantilever, both of which can be usedto alter graphene properties. The first method applies external electric field to the graphenemonolayer. The second method is based on mechanical bending of the cantilever by external force,which induces mechanical strain in the characterized layer. By sweeping the gate voltage (VGS) inrange from – 50 V to + 50 V and measuring the current between drain and source (IDS) with fixeddrain-source voltage (VDS) at 1 V, Dirac point of graphene is found at ≈ 9.3 V of VGS. After bendingof the cantilever, the sweep is performed again. The induced strain shifts the position of the Diracpoint by ≈ 1.3 V to VGS = 8 V. Because the fabrication process is compatible with silicon technology,this method brings new possibilities in graphene strain engineering.
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Detection of biochemical substance using graphene sensor
Supalová, Linda ; Šimšíková, Michaela (referee) ; Bartošík, Miroslav (advisor)
Tato bakalářská práce studuje interakci biochemických látek s grafénem pomocí senzorů v uspořádání polem řízeného tranzistoru. Adsorbované atomy nebo molekuly mohou vyvolat dopování grafénové vrstvy, což může být experimentálně určeno pozorováním změny pozice Diracova bodu. Je studována závislost polohy Diracova bodu na přidané látce a stejně tak i časová odezva na přidání kapalného vzorku. Je pozorována citlivost na odlišné molekuly a jsou dikutovány důsledky výsledků pro adsorpci různých molekul.
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Electrical characterization of a unipolar transistor with a graphene channel
Žeravík, František ; Lednický, Tomáš (referee) ; Gablech, Imrich (advisor)
This work deals with basic properties of graphene, methods of its synthesis, doping, transfer, characterization and description of basic properties and fabrication of field-effect transistor with graphene channel. The practical part focuses on electrical characterization of a field-effect transistor with graphene channel. Concretely on measuring the channel resistance, its dependence on gate voltage, finding the Dirac point and determining the dependence of the channel conductivity on the annealing lenght. Lastly, the shift of the Dirac point and the change of the electrical properties of graphene during bending of a MEMS structure with a unipolar transistor with a graphene channel are investigated.
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Measurement of graphene transport properties
Nečesal, Daniel ; Procházka, Pavel (referee) ; Kormoš, Lukáš (advisor)
In order to create electronic devices utilizing graphene, it is necessary to manu- facture large sheets of high quality graphene which can be achieved by chemical vapor deposition (CVD). Mobility plays an important role in determining quality of graphene sheet because it is inversely proportional to concentration of defects. In this work, CVD graphene samples were fabricated, and their transport properties were characterized by van der Pauw and Hall bar methods. Graphene was transferred to samples either by using Fe(NO3)3 solution or via electrolytic delamination process. Both methods yiel- ded highly p-doped graphene. The electrolytic delamination transfer process resulted in a higher mobility of the graphene sheet and the Dirac point was observed due to a significant doping decrease.
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Influence of electron beam on graphene field effect transistors
Mareček, David ; Čech,, Vladimír (referee) ; Čechal, Jan (advisor)
This diploma thesis deals with electrical conductivity of a graphene sample, preparation of a graphene field-effect transistor and his irradiation by electron beam. In the theoretical part of the thesis, we describe electronic properties of graphene, preparation of graphene by CVD and its transfer to Si substrate with SiO_2 layer. Experimental part of this thesis is focused on the preparation of a graphene field-effect transistor for use in UHV conditions. Futher describes electron beam scanning over the transistor and creation of current maps of tranzistor. In the last part, the thesis deals with influence of electron beam on transport properties of graphene layer and doping of graphene layer by electron beam.
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Preparation of graphene samples for experiments under UHV conditions
Mareček, David ; Mach, Jindřich (referee) ; Čechal, Jan (advisor)
This bachelor thesis deals with electrical conductivity of a graphene sample and preparation of a graphene field-effect transistor. In the theoretical part of the thesis, we describe electronic properties of graphene, preparation of graphene by CVD and its transfer to SiO_2. Experimental part of this thesis is focused on the preparation of a graphene field-effect transistor with long distance between Source and Drain electrodes. Thesis deals with a design of a chip expander for contact of graphene in UHV conditions. The last part describes measurement of dependency of graphene layer conductivity on the gate voltage with emphasis on the position of Dirac point during adjustments of the sample in UHV conditions.
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