National Repository of Grey Literature 51 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
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.
In-Situ Sem Characterization Of Lithium-Ion Battery Created On Mems Chip
Klvač, Ondřej
The aim of the work is to develop an in-situ method for electrode nanostructure investigationby scanning electron microscopy. In the first part, the preparation of a model battery using FIBSEMsystem is described, which consists of lithium titanate oxide (LTO) and metallic lithium materialcutting by the focused ion beam, transport to the MEMS chip, and contacting by carbon deposition.After that the electrodes were soaked by the electrolyte, the voltage changes were measured ontwo created battery systems. Finally, a current was applied to the cell. However, cycling failed dueto technological problems. Challenges connected with battery preparation are described and possiblesolutions for future testing are proposed. The work is evolved in cooperation with Thermo FisherScientific Brno.
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.
Development localization board
Szabó, Michal ; Novotný, Radovan (referee) ; Levek, Vladimír (advisor)
This document describes a device capable to determine geographical position thanks to its GNSS module and measure the change of movement with the help of an accelerometer and gyroscope. Outputs of these integrated circuits are combined, data are processed and fused thanks to a numerical integration and mathematical filters. Results are stored on a memory card. The whole development is described from a concept, through the making of the device and software algorithms to the testing of its functions.
Simulation And Fabrication Of Piezoelectric Mems Resonators
Klempa, Jaroslav
This paper presents FEM analyses and fabrication of piezoelectric MEMS resonators. Modal and harmonic analyses were made using Ansys® Workbench. These simulations showed the influence of resonators geometry on their out-of-plane displacement and corresponding resonant frequencies. Piezoelectric resonators were fabricated by standard microfabrication processing compatible with complementary metal-oxide-semiconductor (CMOS) technology.
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.
Laboral task of variables measurement by position MEMS sensor
Jarůšek, Jakub ; Vančík, Silvester (referee) ; Hubálek, Jaromír (advisor)
MEMS technology and her products are very used today. One of these products are accelerometers, which are highly used for determining orientation, wear measurement or seismology. Their functions are used for consumer electronics, even for development or diagnostics. For more demanding applications, especially for determining orientation, are used components named gyroscopes (alone or with cooperation with accelerometers).
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.
Gas Flow measurement
Majvald, František ; Kunz, Jan (referee) ; Beneš, Petr (advisor)
This bachelor's thesis is focussed on thermal flow meters. There are shortly described basic characteristics of flow and basic terms in flow measurement and its opportunities. The principles of operation of thermal flow meters and its implementation is described closely. With sensors developed by the company of IST AG called FS2 and FS7 was done series of measurements, like measurement of time responses, supply demands, and measurements in the view of determining of mathematical models of the sensors. Mathematical models were determined in a few different ways and its dependence on ambient temperature was found. Thanks to measurement were designed universal electric circuit controlled by microcontroller Arduino Mega 2560. Microcontroller keeps sensors in constant temperature difference mode. There were made trial measurements with designed electronics and the suppression of temperature was checked.
MEMS based energy harvesting
Klempa, Jaroslav ; Prášek, Jan (referee) ; Gablech, Imrich (advisor)
This work is dedicated to principles of energy harvesting or scavenging from free energy around us. Energy harvesting principles are described in the first part. Following chapter is devoted to description of piezoelectricity and piezoelectric materials. Next part researches already reported results on piezoelectric energy harvesters. Following chapter shows simulations on designed structures in ANSYS® Workbench. Next the fabrication of the structures is described. Measurement are made regarding to maximum generated power.

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