Laser-Scribing Technology for Wafer-Scale Graphene Devices

Graphene has attracted a lot of attention due to its amazing properties. A huge number of novel devices, covering the electric, acoustic, photonic, magnetic and mechanical domains, can be developed with graphene. Its ultrahigh mobility can enable ultra-fast transistors or photodetectors. However, the natural zero bandgap of graphene, with insufficient on/off ratio, limits its practical applications. In this chapter, we introduce laser-scribing technology that enables wafer-scale production of graphene devices. Moreover, such laser-scribed graphene (LSG) is, infact, semi-reduced graphene oxide with a finite bandgap, which is suitable for practical applications. We show five kinds of representative LSG devices and their integration. These devices are a resistive memory, an earphone, a strain sensor, a pressure sensor and a light-emitting device. These LSG devices are high-performance, flexible and low cost, which demonstrates the practical nature of laser-scribed graphene-based materials. Finally, an outlook is presented regarding how laser scribing, a serial patterning method, may lead to similar developments in various other serial lithography techniques, such as ion beam lithography

Graphene Acoustic Devices

In 2011, Ren’s group has developed the first graphene sound source device in the world. This is the first time that the graphene applications have been extended into acoustic area. The graphene sound source can produce sound in a wide sound frequency range from 100 Hz to 50 kHz. After that, we have innovated the first graphene earphone, which can be used both for human and animals. In 2017, both the sound detection and sound emission have been integrated into one graphene device, which is called graphene artificial throat. In this book chapter, more details for developing those graphene acoustic devices will be introduced, which can help to boost the real applications of graphene devices

3D Stretchable Arch Ribbon Array Fabricated via Grayscale Lithography.

Microstructures with flexible and stretchable properties display tremendous potential applications including integrated systems, wearable devices and bio-sensor electronics. Hence, it is essential to develop an effective method for fabricating curvilinear and flexural microstructures. Despite significant advances in 2D stretchable inorganic structures, large scale fabrication of unique 3D microstructures at a low cost remains challenging. Here, we demonstrate that the 3D microstructures can be achieved by grayscale lithography to produce a curved photoresist (PR) template, where the PR acts as sacrificial layer to form wavelike arched structures. Using plasma-enhanced chemical vapor deposition (PECVD) process at low temperature, the curved PR topography can be transferred to the silicon dioxide layer. Subsequently, plasma etching can be used to fabricate the arched stripe arrays. The wavelike silicon dioxide arch microstructure exhibits Young modulus and fracture strength of 52 GPa and 300 MPa, respectively. The model of stress distribution inside the microstructure was also established, which compares well with the experimental results. This approach of fabricating a wavelike arch structure may become a promising route to produce a variety of stretchable sensors, actuators and circuits, thus providing unique opportunities for emerging classes of robust 3D integrated systems

Hippocampal Neurons’ Alignment on Quartz Grooves and Parylene Cues on Quartz Substrate

Alignment and patterning of neurons have great importance in some research fields, especially for regenerative medicine and for the formation of artificial neural networks. Alignment of neurons on quartz grooves and parylene cues on quartz substrate was evaluated in this work. The neurons’ alignment on quartz grooves is considered to be topographical alignment, while the neurons’ alignment on parylene cues on quartz substrate is considered to be chemical alignment. Both quartz grooves’ and parylene cues’ widths were fabricated in a range from 2 µm to 8 µm; quartz grooves’ heights were in a range from 0.25 µm to 4 µm, while parylene cues’ heights were only 0.25 µm. Neurons were dissociated hippocampal neurons from rat E18. Neurons were cultivated on test substrates for 7 days before alignment evaluation. As expected, neurons aligned according to the direction of grooves and cues; however, transversal growth direction was also observed with much smaller tendency. Chemical alignment was found to be more effective than topographical alignment. If parylene cues are thin and distanced enough, then neurons have a tendency to follow the direction of individual parylene cues; however, neurons on quartz grooves have a tendency just to follow a preferable direction than individual quartz grooves

Application of Ferrite Nanomaterial in RF On-Chip Inductors

Several kinds of ferrite-integrated on-chip inductors are presented. Ferrite nanomaterial applied in RF on-chip inductors is prepared and analyzed to show the properties of high permeability, high ferromagnetic resonance frequency, high resistivity, and low loss, which has the potential that will improve the performance of RF on-chip inductors. Simulations of different coil and ferrite nanomaterial parameters, inductor structures, and surrounding structures are also conducted to achieve the trend of gains of inductance and quality factor of on-chip inductors. By integrating the prepared ferrite magnetic nanomaterial to the on-chip inductors with different structures, the measurement performances show an obvious improvement even in GHz frequency range. In addition, the studies of CMOS compatible process to integrate the nanomaterial promote the widespread application of magnetic nanomaterial in RF on-chip inductors

Hafnium isotope fractionation during continental weathering: Implications for the generation of the seawater Nd-Hf isotope relationships

To investigate the mechanisms of the offset of seawater radiogenic Nd-Hf isotope compositions from those of the upper continental crust rocks, combined Nd-Hf isotope compositions of desert and loess samples from northern China (which integrate a wide range of lithologies and ages of continental rocks) are presented in this study. The results show significant and systematic fractionation of Hf isotopes between finegrained detritals/leachates (<5 mm) and coarser fractions (<75 mm) of the same samples. A small but systematic difference of Nd isotope compositions between leachates and detrital silicates is also revealed. Overall, the leaching data either plot along or slightly above the Nd-Hf seawater array, providing strong direct support that the seawater Nd-Hf isotope relationship is predominantly generated by weathering of upper continental crust. Our study supports the application of dissolved Hf isotopes as a proxy for different modes of weathering regimes rather than for continental source provenances