Jiebin Zhong

Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors

In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO2 nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g−1, areal capacitance: 1.11 F cm−2) which leads to an exceptionally high energy density of 39.28 Wh kg−1 and power density of 128.01 kW kg−1. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.

Heterogeneous Graphene Nanostructures: ZnO Nanostructures Grown on Large‐Area Graphene Layers

In this work, the synthesis and characterization of three-dimensional hetergeneous graphene nanostructures (HGN) comprising continuous large-area graphene layers and ZnO nanostructures, fabricated via chemical vapor deposition, are reported. Characterization of large-area HGN demonstrates that it consists of 1-5 layers of graphene, and exhibits high optical transmittance and enhanced electrical conductivity. Electron microscopy investigation of the three-dimensional heterostructures shows that the morphology of ZnO nanostructures is highly dependent on the growth temperature. It is observed that ordered crystalline ZnO nanostructures are preferably grown along the <0001> direction. Ultraviolet spectroscopy and photoluminescence spectroscopy indicates that the CVD-grown HGN layers has excellent optical properties. A combination of electrical and optical properties of graphene and ZnO building blocks in ZnO-based HGN provides unique characteristics for opportunities in future optoelectronic devices.

Molecular absorption and photodesorption in pristine and functionalized large-area graphene layers

We studied the photodesorption behavior of pristine and nitric acid (HNO(3)) treated graphene layers fabricated by chemical vapor deposition (CVD). The decrease in electrical conductivity and a negative shift of the Dirac point in graphene layers illuminated with ultraviolet light are caused by molecular photodesorption, while the UV illumination does not degrade the carrier mobility of graphene layers. When graphene layers were treated with concentrated HNO(3), the photodesorption-induced current decrease became less significant than for pristine graphene layers. We suggest this is due to the passivation of oxygen-bearing functionalities to CVD grown graphene structural defects by HNO(3) functionalization, which prevents the further absorption of gas molecules. Our results provide a new strategy for stabilizing the electrical performance of CVD grown large-area graphene layers for applications ranging from nanoelectronics to optoelectronics.

Electrochemical supercapacitor based on flexible pillar graphene nanostructures

Here we report the fabrication of high conductive and large surface-area 3D pillar graphene nanostructures (PGN) films from assembly of vertically aligned CNT pillars on flexible copper foils and directly employed for the application in electrochemical double layer capacitance (EDLC) supercapacitor. The fabricated supercapacitor based on PGN films with excellent mechanical flexibility and electrical conductivity has high energy storage capability. The PGN films which were one-step synthesized on flexible copper foil (25 um) by CVD process exhibit high conductivity with sheet resistance as low as 1.6 ohm per square and high mechanical flexibility. The fabricated EDLC supercapacitor based on high surface-area PGN electrodes (563m2/g) shows high performance with high specific capacitance of 330F/g and energy density as high as 45.8Wh/kg. All of these make this 3D graphene/CNTs hybrid carbon nanostructures highly attractive material for high performance supercapacitor and other energy storage material.

Data transmission performance of CVD grown sub-20 nm indium antimonide nanowires

We investigated the data transmission performance of indium antimonide (InSb) nanowires (NWs) synthesized on InSb (100) substrate using chemical vapor deposition (CVD) having diameters below 20 nm. The data transmission measurement was accomplished over the NW field effect transistors (NWFETs) fabricated on Si/SiO2 substrates. Digital data stream is randomly generated and then uploaded to a waveform generator which generates the stream and transmits it repeatedly with the desired frequency. The signal was applied on the sources of the NWFETs and collected from the drains of the same devices. Collected data was first filtered with a low pass filter (LPF), and then the output of the filter was used to create the eye diagrams of the NWs. Bit error rate (BERs), attenuation , quality factor (Q-factor) and maximum data transmission are extracted from eye diagrams. The results indicate that the data transmission performance of NWs suffer from low mobility values on the order of 10-to-15 cm2V-1s-1 because of their small diameters, crystal defects and oxidation occurs during growth and cooling. 20 nm NWs can sustain data rates up to 10 mega bits per second (Mbps) and the data rate is directly proportional to the diameter of the NWs.

InSb nanowire based field effect transistor

InSb nanowire field effect transistors (NWFET) were fabricated using electrochemically synthesized nanowires. To accurately extract transistor parameters, we introduced a model which takes into account the often ignored ungated nanowire segments. A significant improvement in extracted device parameters was observed which demonstrated that conventional models tend to underestimate the gate effect and therefore lead to lower carrier mobilities. Based on the model, we obtained a NWFET ON current of 11.8uA, an ION/IOFF ratio of 63.5 and hole mobility of 292.84 cm2V-1s-1.