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Characterization of graphene electrical properties on MEMS structures
Brodský, Jan ; Pekárek, Jan (referee) ; Gablech, Imrich (advisor)
This work presents basic properties of graphene, methods for its synthesis and methods for its characterization by Raman spectroscopy, two-point probe, four-point probe and van der Pauw measurements. The experimental part of this work describes the process of graphene oxide, reduced graphene oxide and graphene sample preparation and measurement of its current-voltage characteristic by two-point probe method. Subsequently, sample annealing in vacuum furnace is described in this work. The annealing is important for acquiring good electrical contact between the 2D material and electrodes. Sample analysis by Raman spectroscopy is performed. The last chapters of this work describe design and fabrication of MEMS structure. Such structure serves for characterization of graphene and other 2D materials.
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Gas sensors based on 1D and 2D materials
Brodský, Jan ; Glowacki, Eric Daniel (referee) ; Gablech, Imrich (advisor)
In this work, general properties of fundamental gas sensors are described. Thesis is mainly focused on chemoresistive and ChemFET types, which are further used in experimental part. Subsequently, properties, preparation and transfer methods of chosen 1D and 2D materials are described. Experimental part of this work describes design and fabrication of chips, which combine the sensing principals mentioned above for utilization of 1D and 2D materials as an active layer. Transfer methods of individual materials on fabricated chips are described and these materials are characterized by Raman spectroscopy and field effect transistor characteristics measurements. Finally, the response of chosen materials to oxidative and reductive gases is measured.
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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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Wet Etching Of Sio2 As Sacrificial Layer With Infinite Selectivity To Al
Brodský, Jan
This work presents an unusual method for releasing microelectromechanical systems which contain an Al layer. This is done by wet etching of SiO2 as a sacrificial layer. Mixture of 49% HF acid and 20% H2SO4∙SO3 (oleum) is used. Oleum keeps the solution water-free and subsequently prevents the attack of Al layer. Exceptional etch rate (≈ 1 μm·min−1) of thermally grown SiO2 is achieved by this method. The infinite selectivity to Al layer is verified by measuring the thickness of layer before and after etching. The etching itself is done in an ordinary fume hood in polytetrafluorethylene (PTFE) beaker.
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Gas sensors based on 1D and 2D materials
Brodský, Jan ; Glowacki, Eric Daniel (referee) ; Gablech, Imrich (advisor)
In this work, general properties of fundamental gas sensors are described. Thesis is mainly focused on chemoresistive and ChemFET types, which are further used in experimental part. Subsequently, properties, preparation and transfer methods of chosen 1D and 2D materials are described. Experimental part of this work describes design and fabrication of chips, which combine the sensing principals mentioned above for utilization of 1D and 2D materials as an active layer. Transfer methods of individual materials on fabricated chips are described and these materials are characterized by Raman spectroscopy and field effect transistor characteristics measurements. Finally, the response of chosen materials to oxidative and reductive gases is measured.
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Characterization Of Electrical Properties Of Graphene-Based Materials On Mems Structures
Brodský, Jan
This work presents characterization of basic electrical properties of graphene and graphene oxide. Graphene was prepared by chemical reduction of graphene oxide. The experimental part of this work describes the process of graphene oxide and reduced graphene oxide sample preparation and measurement of its current-voltage characteristic by two-point probe method. Measurement is carried out on MEMS structure, which can be used for mechanical bending. Such structure will serve for utilization of graphene and other 2D materials.
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Characterization of graphene electrical properties on MEMS structures
Brodský, Jan ; Pekárek, Jan (referee) ; Gablech, Imrich (advisor)
This work presents basic properties of graphene, methods for its synthesis and methods for its characterization by Raman spectroscopy, two-point probe, four-point probe and van der Pauw measurements. The experimental part of this work describes the process of graphene oxide, reduced graphene oxide and graphene sample preparation and measurement of its current-voltage characteristic by two-point probe method. Subsequently, sample annealing in vacuum furnace is described in this work. The annealing is important for acquiring good electrical contact between the 2D material and electrodes. Sample analysis by Raman spectroscopy is performed. The last chapters of this work describe design and fabrication of MEMS structure. Such structure serves for characterization of graphene and other 2D materials.
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