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The graphene structures suitable for field effect transistors
Kurfürstová, Markéta ; Bartošík, Miroslav (referee) ; Mach, Jindřich (advisor)
This bachelor’s thesis is focused on preparation of graphene structures suitable for field effect transistors. In the first section, graphene is characterized in terms of its properties and prepataion methods. The second part sums up semiconductor technology, focusing on transistors with graphene layer. Next, electron beam litography method is presented, which had been used for preparation of the structures. Finally, an experimental procedure of graphene structures manufacture is described.
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Interaction of low-energy electrons with graphene field effect transistors
Vysocký, Filip ; Kunc, Jan (referee) ; Čechal, Jan (advisor)
This diploma thesis is focused on fabrication of graphene field-effect transistors, characterisation of their transport properties and investigation of low-energy electron beam influence on the devices' properties under UHV conditions. The theoretical part of this work describes graphene fabrication methods, options of graphene transfer onto the substrates for graphene field-effect transistor manufacture. Furthermore, model of graphene doping via electrostatic interaction or photon, resp. electron beam exposition is explained. The experimental part of this work consist of manufacture of the graphene field-effect transistor in order to examine the change of its transport properties induced by doping of the graphene via low-energy electron beam exposition.
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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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Analysis of the transport properties of graphene nanostructures
Novák, Martin ; Bartošík, Miroslav (referee) ; Lišková, Zuzana (advisor)
Graphene transport properties are analysed in this thesis. They are strongly dependent on doping with charge carriers. The number of charge carriers can be influenced by electric field, substrate or surface adsorbates. The graphene field-effect transistor (FET) has been prepared. Graphene made by chemical vapor deposition (CVD) has been con tacted through gold structures made by electron beam lithography (EBL). Dependences on electrode configuration, gate voltage and used substrate are observed.
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Basic measurement of bipolar and unipolar transistor
Kaňa, Leoš ; Šebesta, Jiří (referee) ; Dřínovský, Jiří (advisor)
In terms of the better effectiveness in the sphere of transistor characteristics measuring, no matter unipolar (FET) or bipolar (BJT), in laboratory conditions and their better understanding in terms of thrash out a subject matter is desirable have to available workplace let us say preparation enabling this kind of measuring with modifiability wiring and with possibility to change measured component. This thesis isn‘t focused only on development of this kind of universal component for measuring but simultaneously contains brief summary about the theory and parameters of transistors. Next aim is the development and realisation of static characteristic measuring program in VEE 8.0 Pro environment. Finally the complex laboratory exercise has to be done for measuring of bipolar and unipolar transistor’s static characteristics include programs for automatic measuring. For developing of DPS was used developing system named Eagle which gives us instrument with sufficiently accuracy. In thesis is contained theory needed for measuring and programming. Except possibility of measured component change we can change transistor connection in circuit on the board. This change is available for BJT (CE, CB, CC) and unipolar JFET (CS, CG, CD) transistor’s.
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Electrical transport properties of molecular materials for smart applications
Ivancová, Anna ; Vala, Martin (referee) ; Přikryl, Radek (advisor)
This master´s thesis deals with possibilities of application of new organic molecular materials for electronic devices. Nowadays it is a very attractive field of research, because of the tendencies in industry to miniaturize, reduce production costs and develop new, eco-friendlier, processes of production. The theoretical part of the thesis provides a short overview of organic materials suitable for smart applications and thin films issues including their characterization. The experimental part is dedicated to means how to prepare thin-film electronic components to silicon wafers for thin films field effect transistors. The obtained results in the last part of thesis are discussed about properties of prepared thin films, in the concrete about the electrical transport properties, in the connection with the condition of preparation.
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Study of optoelectrical properties of organic semiconductor thin film layers of phtalocyanines
Miklíková, Zdeňka ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
Diploma thesis is focused on the study of optoelectric properties of thin layers of organic materials based on phthalocyanines, which can be used as an active layer of photovoltaic cells. Especially are studied the properties of the thin active layers of PdPc and PdPc + IL on the glass or ceramic substrates with aluminium contact, which are prepared by material printing here. On the prepared samples were first measured current-voltage characteristics in the dark and in the light and then were measured impedance spectrums in the dark. The received results will be used to improve the properties and structures of photovoltaic cells.
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Graphene doping by low-energy electrons
Stará, Veronika ; Kunc, Jan (referee) ; Čechal, Jan (advisor)
Tato diplomová práce se zabývá dotováním grafenu nízkoenergiovými elektrony. Na křemíkový substrát pokrytý vrstvou SiO2 jsou pomocí litograficky vyrobené masky nadeponované kovové kontakty z titanu a zlata. Grafen vyrobený pomocí metody depozice z plynné fáze je přenesen na substrát a slouží jako vodivé spojení kovových elektrod, které vytvářejí kolektor a emitor. Na křemík je ze spodu přivedeno napětí, které tak vytváří spodní hradlo. Takto vytvořený grafenový tranzistor je ozařován nízkoenergiovými elektrony, které mění dotování grafenu. Z polohy maxima v závislosti odporu grafenu na hradlovém napětí lze vyčíst typ dotování. Toto maximum udává napětí, při kterém Fermiho meze grafenu prochází Diracovým bodem v pásové struktuře grafenu. Velikost hradlového napětí, primární energie elektronového svazku a proud svazku jsou tři parametry, které mají velký vliv na změny dotování. Při ozařování transistoru dochází ke změně typu dotování právě tehdy, když odpor grafenu v závislosti na hradlovém napětí dosáhne maxima. Vývoj této změny je zkoumán pro různé energie a proudy primárního svazku v závislosti na hradlovém napětí i v čase. Typ dotování je také prozkoumán při zastavení ozařování v různých fázích smyčky hradlového napětí. Dopování grafenu nízkoenergiovými elektrony je popsáno v teoretickém modelu.
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CMOS compatible piezoelectric resonator with FET structure for graphene monolayer properties modulation
Gablech, Imrich ; Frank,, Otakar (referee) ; Husák,, Miroslav (referee) ; Pekárek, Jan (advisor)
Práce je zaměřena na výzkum nové struktury umožňující charakterizaci fyzikálních vlastností grafenu při přesně řízených podmínkách. Návrh spojuje MEMS piezoelektrický rezonátor spolu s Hall Bar/FET strukturou. Tento přístup umožňuje měnit vlastnosti grafenu odděleně nebo společně dvěma metodami. Mechanický způsob je založen na relativní deformaci způsobené rezonátorem, na kterém je umístěna grafenová monovrstva. Navrhovaná struktura umožňuje měřit vlastnosti grafenu vyvolané pouze změnou mechanického pnutí a frekvencí nucených kmitů bez vlivu vnějšího elektrického pole. Druhý přístup přidává možnost ovládat fyzikální vlastnosti grafenu pomocí elektrického pole FET struktury. Tato technika využívá grafenovou monovrstvu jako laditelný sensor pro molekulární detekci. Měření koncentrace v jednotkách ppb není konstrukčně ničím limitováno. Realizované frekvenčně laditelné piezoelektrické MEMS rezonátory s monovrstvou grafenu budou využitelné v mnoha oblastech pro detekci na molekulové úrovni. Výsledné struktury budou vyrobeny v souladu s požadavky na bio- a CMOS kompatibilitu.
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