Emrah Birinci

Transfer-free fabrication of graphene transistors

The authors invented a method to fabricate graphene transistors on oxidized silicon wafers without the need to transfer graphene layers. To stimulate the growth of graphene layers on oxidized silicon, a catalyst system of nanometer thin aluminum/nickel double layer is used. This catalyst system is structured via liftoff before the wafer enters the catalytic chemical vapor deposition (CCVD) chamber. In the subsequent methane-based growth process, monolayer graphene field-effect transistors and bilayer graphene field-effect transistors are realized directly on oxidized silicon substrate, whereby the number of stacked graphene layers is determined by the selected CCVD process parameters, e.g., temperature and gas mixture. Subsequently, Raman spectroscopy is performed within the channel region in between the catalytic areas and the Raman spectra of five-layer, bilayer, and monolayer graphene confirm the existence of graphene grown by this silicon-compatible, transfer-free and in situ fabrication approach. The...

CVD assisted fabrication of graphene layers for field effect device fabrication

In this paper, we report on the fabrication and characterization of graphene layers for graphene field effect devices. After the graphene layers are fabricated by means of chemical vapor deposition using a methane feedstock, the band gap is engineered confining the lateral dimensions of graphene in order to obtain graphene nanoribbons. Contacting the graphene nanoribbons with appropriate metallic materials will lead to field effect devices suitable for various applications.

In-Situ CCVD Grown Bilayer Graphene Transistor

In this paper we report on a novel method to fabricate graphene transistors directly on oxidized silicon wafers without the need to transfer graphene. By means of catalytic chemical vapor deposition (CCVD) the in-situ grown monolayer graphene field-effect transistors (MoLGFETs) and bilayer graphene field-effect transistors (BiLGFETs) are realized directly on oxidized silicon substrate. In-situ CCVD grown MoLGFETs exhibit the expected Dirac point together with the typical low on/off-current ratios of 16. In addition, however, in-situ CCVD grown BiLGFETs possess unipolar p-type device characteristics with an extremely high on/off-current ratio up to 1x10 7 exceeding previously reported values by several orders of magnitude. With this novel fabrication method hundreds of large scale in-situ CCVD grown graphene FETs are realized simultaneously on one 2’’ wafer. Besides the excellent device characteristics, the complete CCVD fabrication process is silicon CMOS compatible. This will allow a simple and low-cost integration of graphene devices for nanoelectronic applications in a hybrid silicon CMOS environment.

In-Situ CCVD Grown Graphene Transistors with Ultra-high On/Off-Current Ratio in Silicon CMOS Compatible Processing

We invented a novel method to fabricate graphene transistors on oxidized silicon wafers without the need to transfer graphene layers. By means of catalytic chemical vapor deposition (CCVD) the in-situ grown monolayer graphene field-effect transistors (MoLGFETs) and bilayer graphene transistors (BiLGFETs) are realized directly on oxidized silicon substrate, whereby the number of stacked graphene layers is determined by the selected CCVD process parameters. In-situ grown MoLGFETs exhibit the expected Dirac point together with the typical low on/off-current ratios between 16 (hole conduction) and 8 (electron conduction), respectively. In contrast, our BiLGFETs possess unipolar p-type device characteristics with an extremely high on/off-current ratio up to 1E7 exceeding previously reported values by several orders of magnitude. We explain the improved device characteristics by a combination of effects, in particular graphene-substrate interactions, hydrogen doping and Schottky-barrier effects at the source/drain contacts as well. Besides the excellent device characteristics, the complete CCVD fabrication process is silicon CMOS compatible. This will allow the usage of BiLGFETs for digital applications in a hybrid silicon CMOS environment.

On/off-current ratios of transfer-free bilayer graphene FETs as a function of temperature

In this paper we report on a novel method to fabricate graphene transistors directly on oxidized silicon wafers without the need to transfer graphene. By means of catalytic chemical vapor deposition (CCVD) the in-situ grown bilayer graphene transistors (BiLGFETs) are realized directly on oxidized silicon substrate. These BiLGFETs possess unipolar p-type device characteristics with an extremely high on/off-current ratio between 1×106 and 1×107 at room temperature [1, 2], exceeding previously reported values by several orders of magnitude. Furthermore, when increasing the ambient temperature to 200°C, the on/off-current ratio only degrades by one order of magnitude for BiLGFETs. Besides the excellent device characteristics, the complete CCVD fabrication process is silicon CMOS compatible. This will allow a simple and low-cost integration of graphene devices for nanoelectronic applications in a hybrid silicon CMOS environment.