The growth of graphene on Ni–Cu alloy thin films at a low temperature and its carbon diffusion mechanism

Carbon solid solubility in metals is an important factor affecting uniform graphene growth by chemical vapor deposition (CVD) at high temperatures. At low temperatures, however, it was found that the carbon diffusion rate (CDR) on the metal catalyst surface has a greater impact on the number and uniformity of graphene layers compared with that of the carbon solid solubility. The CDR decreases rapidly with decreasing temperatures, resulting in inhomogeneous and multilayer graphene. In the present work, a Ni–Cu alloy sacrificial layer was used as the catalyst based on the following properties. Cu was selected to increase the CDR, while Ni was used to provide high catalytic activity. By plasma-enhanced CVD, graphene was grown on the surface of Ni–Cu alloy under low pressure using methane as the carbon source. The optimal composition of the Ni–Cu alloy, 1:2, was selected through experiments. In addition, the plasma power was optimized to improve the graphene quality. On the basis of the parameter optimization, together with our previously-reported, in-situ, sacrificial metal-layer etching technique, relatively homogeneous wafer-size patterned graphene was obtained directly on a 2-inch SiO2 /Si substrate at a low temperature (~600◦ C)

Mechanisms of Creativity Differences Between Art and Non-art Majors: A Voxel-Based Morphometry Study

Creativity is considered the ability to generate new ideas or behaviors, an ability that have diverse expressions in different human groups, such as painters and non-painters. Art major students require more creative activities than non-art students do. In this study, we plan to explore the figural creativity abilities of art major students and whether these students exhibited higher figural creativity scores and why their brain structure of gray matter are lower which may benefit from their professional training relative to non-art majors. Therefore, in this study, we use voxel-based morphometry (VBM) to identify different behavioral and brain mechanisms between art major students and non-art major students by using the figural Torrance Test of Creative Thinking. Our results showed that the TTCT-figural (TTCT-F) scores of art majors were higher than those of non-art majors. The TTCT-F score of art major students and practicing and study time have positive correlations which means art major’s figural creativity score benefit from there art professional training in some degree. Subsequently, the interaction analysis revealed that the TTCT-figural scores of art majors and non-majors exhibited significant correlations with the gray matter volumes (GMV) of the left anterior cingulate cortex (ACC) and the left medial frontal gyrus (MFG). While the simple slope analysis showed that art majors, compared with non-art majors, exhibited a marginal significantly positive association with the left ACC and MFG, non-art majors exhibited a significantly negative association with the left ACC and MFG. Overall, our study revealed that people who major in artistic work are more likely to possess enhanced figural creative skills relative to non-artistic people. These results indicated that professional artistic programs or training may increase creativity skills via reorganized intercortical connections

Monolithic heterogeneous integration of Si photodetector and Van der Waals heterojunction with photocurrent enhancement

Two-dimensional material has many novel features, which can be used to significantly improve the performance of traditional photonic and electronic devices. Therefore, the development of silicon/two-dimensional material monolithic heterogeneous integrated photodetector has attracted extensive attention worldwide. In this paper, we present a method to enhance the response of photocurrent of silicon-based PN junction photodetectors by using two-dimensional material Van der Waals heterostructures. The MoS _2 /graphene/N+ silicon monolithic heterogeneous integrated Van der Waals heterostructure is used as an NPN-type phototransistor to realize the amplification of photocurrent. When the device is irradiated, the photogenerated electron hole pairs in the semiconductor are separated by the applied electric field. However, graphene has a low density of defect states, and only a few electrons from N+ silicon can be recombined in graphene. Meanwhile, the graphene layer is very thin, and the positively biased graphene/N+ silicon junction and reversed-biased MoS _2 /graphene junction will accelerate the electrons to across the graphene layer and directly into MoS _2 . Using MXenes as the contact electrode of the MoS _2 can eliminate the Fermi level pinning effect. The experimental results show that the photoresponsivity and photocurrent gain increase with the bias voltage, in the range of 0 to 5 V bias voltage. And the optical I _on /I _off ratio increases by nearly 50 times. This research provides new insights for the detection of weak light and design for the photon computing device

Highly Compressible and Sensitive Flexible Piezoresistive Pressure Sensor Based on MWCNTs/Ti3C2Tx MXene @ Melamine Foam for Human Gesture Monitoring and Recognition

Flexible sensing devices provide a convenient and effective solution for real-time human motion monitoring, but achieving efficient and low-cost assembly of pressure sensors with high performance remains a considerable challenge. Herein, a highly compressible and sensitive flexible foam-shaped piezoresistive pressure sensor was prepared by sequential fixing multiwalled carbon nanotubes and Ti3C2Tx MXene on the skeleton of melamine foam. Due to the porous skeleton of the melamine foam and the extraordinary electrical properties of the conductive fillers, the obtained MWCNTs/Ti3C2Tx MXene @ melamine foam device features high sensitivity of 0.339 kPa−1, a wide working range up to 180 kPa, a desirable response time and excellent cyclic stability. The sensing mechanism of the composite foam device is attributed to the change in the conductive pathways between adjacent porous skeletons. The proposed sensor can be used successfully to monitor human gestures in real-time, such as finger bending and tilting, scrolling the mouse and stretching fingers. By combining with the decision tree algorithm, the sensor can unambiguously classify different Arabic numeral gestures with an average recognition accuracy of 98.9%. Therefore, our fabricated foam-shaped sensor may have great potential as next-generation wearable electronics to accurately acquire and recognize human gesture signals in various practical applications

Theoretical study of terahertz active transmission line oscillator based on RTD-gated HEMT

In this paper, a new kind of terahertz oscillator is presented using plasma wave excitation in a resonant tunnel diode (RTD) gated high electron mobility transistor (HEMT). The plasma wave arising from the RTD-gated HEMT is equivalent to active transmission lines and induces negative differential conductance (NDC) of the oscillator. The proposed RTD-gated HEMT oscillator is more compact and has higher oscillation frequency than the transmission line loaded traditional RTD oscillator duo to plasma wave effect. This paper analyses and calculates the oscillation conditions, the relationships between device structures, oscillation frequency and the output power of the oscillator. The presented work may provide a new concept for fabricating terahertz oscillator