Sarcasm is a pervasive phenomenon in today's social media platforms such as Twitter and Reddit. These platforms allow users to create multi-modal messages, including texts, images, and videos. Existing multi-modal sarcasm detection methods either simply concatenate the features from multi modalities or fuse the multi modalities information in a designed manner. However, they ignore the incongruity character in sarcastic utterance, which is often manifested between modalities or within modalities. Inspired by this, we propose a BERT architecture-based model, which concentrates on both intra and inter-modality incongruity for multi-modal sarcasm detection. To be specific, we are inspired by the idea of self-attention mechanism and design intermodality attention to capturing inter-modality incongruity. In addition, the co-attention mechanism is applied to model the contradiction within the text. The incongruity information is then used for prediction. The experimental results demonstrate that our model achieves state-of-the-art performance on a public multi-modal sarcasm detection dataset.

No abstract

We report the dc and rf performance of graphene rf field-effect transistors, where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates. Composite materials, benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics. The observation of n-and p-type transitions verifies the ambipolar characteristics in the graphene layers. While the intrinsic carrier mobility of CVD graphene is extracted to be 1200 cm 2 /V•s, the parasitic series resistances are demonstrated to have a serious impact on device performance. With a gate length of 1 µm and an extrinsic transconductance of 72 mS/mm, a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors, illustrating the potential of the CVD graphene for rf applications.

No abstract

We report on a demonstration of top-gated graphene field-effect transistors (FETs) fabricated on epitaxial SiC substrate. Composite stacks, benzocyclobutene and atomic layer deposition Al 2 O 3 , are used as the gate dielectrics to maintain intrinsic carrier mobility of graphene. All graphene FETs exhibit n-type transistor characteristics and the drain current is nearly linear dependence on gate and drain voltages. Despite a low field-effect mobility of 40 cm 2 /(V s), a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency of 1.5 GHz were obtained for the graphene devices with a gate length of 1 μm. Graphene, consisting of one or a few carbon atomic layers packed into a two dimensional (2D) hexagonal lattice, has attracted enormous attention over the last few years [1]. Graphene exhibits impressive transport properties, including high carrier mobility and saturation velocity [2]. As a result, it is a good candidate for radio-frequency (RF) field-effect transistor (FET) applications. So far, high quality graphene device with a maximum cutoff frequency (f T ) of 300 GHz has been obtained on thin exfoliated films of graphite [3].Although an excellent method to obtain single devices for scientific research, exfoliation is impractical for large-scale manufacturing of graphene sheets. However, mass production can be solved by epitaxial growth on SiC or metalcatalyzed chemical vapor deposition (CVD) [4,5]. To date, graphene FETs with f T beyond 100 GHz have also been achieved using graphene films synthesized by both methods [6,7]. Graphene by epitaxy on SiC is directly obtained on semi-insulating SiC substrates, so that no transfer is required before processing devices, as compared with the CVD method. Recently, graphene integrated circuits have been realized on SiC wafers [8], showing potential in practical applications. Nevertheless, the graphene on SiC substrates is still cost ineffective and not compatible with Si technologies.In this work, we present DC and RF performance of graphene FETs developed on SiC substrates. The graphene transistors are fabricated by the conventional top-down approach, holding the potential of compatibility with other semiconductor materials. An organic polymer film is introduced between graphene and regular gate dielectrics to minimize mobility degradation in top-gated graphene FETs. The output characteristics are nearly linear without clear current saturation before device breakdown. With a gate length of 1 μm and a low field-effect mobility of 40 cm 2 /(V s), a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency (f MAX ) of 1.5 GHz were measured.The graphene was epitaxially grown on SiC. From the intensity ratio of the G peak to SiC substrate peaks and the shape of the 2D peak in the measured Raman spectrum of the graphene [9,10], it can be determined that most of the surface was covered by monolayer graphene, and only in few regions associated with pits bilayers started forming;