Graphene composite structure based optical absorption pressure sensor.

In this paper, a graphene composite structure based optical absorption pressure sensor is proposed. First, a composite structure which is composed of PDMS micro-pyramid structure, graphene film, and waveguide is introduced. The sensitive mechanism and dynamic working state of the pressure sensor are analyzed continuously. Second, the mapping between the pressure on PDMS and its contact area with the graphene film is deeply analyzed, as well as the optical transmission properties of graphene combined with waveguides, followed by a series of simulations about the optical power output performance facing different pressure conditions. Finally, the designed sensor samples are prepared and a series of performance verification experiments were carried out. The experimental results show that the range of the pressure sensor is 0-870kPa. The sensitivity in the pressure range of 0-100kPa is 2.83×10-1µW/kPa. The experimental results effectively prove that the designed graphene composite structure based optical absorption pressure sensor has high sensitivity and good repeatability, which further verifies the feasibility of the design and analysis method.

Tunable giant magnetoresistance ratio in bilayer CuPc molecular devices.

We investigate the influence of the distance between the buffer layer and the central molecule on the electrical transport, spin-filter transport, magnetoresistance effects and thermoelectric properties of a bilayer CuPc molecular device with V-shaped zigzag-edged graphene nanoribbon (VZGNR) electrodes by combining density functional theory and the non-equilibrium Green's function. The results show that the spin-dependent total conductance and spin filter efficiency of the bilayer CuPc molecular device reach a maximum with a parallel spin configuration (PC) when the carbon atom at the edge of the electrode is in the center of the carbon atom at the edge of the bilayer molecules due to the stronger coupling interaction between the double-layer molecules and the leads. Moreover, the spin polarization of the bilayer CuPc molecular device is reversed at certain distances; there is a minimum spin filter efficiency (SFE) of -99.93448% and a maximum SFE of 97.91% observed in the anti-parallel spin configuration (APC) of the device and there is a minimum SFE of -26.03175% and a maximum SFE of 99.99996% observed with the PC at zero bias. The SFE oscillates with increasing considered bias voltage in the PC and APC when the distances are d = 0 Å and d = -1.06 Å, and a negative differential resistance (NDR) effect was observed. For the PC and APC, there is a giant magnetoresistance (MR) effect and the MR ratio exceeds 5.21 × 107% (99.9996%), and the MR ratio oscillates with increasing considered bias voltage when d = 0 Å. The MR ratio could be reserved by applying a certain bias voltage. These transport behaviors can be well understood by analyzing the transmission spectra, projected density of states and scattering states. There are pure spin Seebeck coefficients and pure charge Seebeck coefficients at certain temperatures when the distances are certain values, which means that the corresponding temperature differences could produce pure spin current and pure charge current, respectively. Our results provide new ideas for designing ultrahigh-performance spintronic molecular devices.

Design and modeling of a graphene-based composite structure optical pressure sensor.

In this paper, a novel graphene-based composite structure optical pressure sensor is designed and built with the aid of modeling. A PDMS force-sensitive structural mechanics model is established to optimize the size of the pyramid array distributed on the PDMS layer so that to support high levels of sensitivity and stability. Meanwhile, a graphene waveguide optical model is established to obtain the optimized interference length (L), arm spacing (H) and core width (W), with the objectives of advanced sensitivity, low propagation loss, high resolution. The experimental results show that the pressure sensitivity of the proposed sensor is 17.86 nm/kPa and the maximum pressure that can be detected is 3.40 kPa, which is consistent with the theoretical analysis and verifies the feasibility of the design, also the modeling methods of the graphene-based composite structure optical pressure sensor.

Use of Ambipolar Dual-Gate Carbon Nanotube Field-Effect Transistor to Configure Exclusive-OR Gate.

As the physical scaling limit of silicon-based integrated circuits is approached, new materials and device structures become necessary. The exclusive-OR (XOR) gate is a basic logic gate performed as a building block for digital adder and encrypted circuits. Here, we suggest that using the ambipolar property of carbon nanotubes and the threshold modulation ability of dual-gate field-effect transistors, an XOR gate can be constructed in only one transistor. For a traditional XOR gate, 4 to 6 transistors are needed, and this low-footprint topology could be employed in the future for hyperscaling and three-dimensional logic and memory transistor integration.

Ultrahigh Spin Filter Efficiency, Giant Magnetoresistance and Large Spin Seebeck Coefficient in Monolayer and Bilayer Co-/Fe-/Cu-Phthalocyanine Molecular Devices.

The spin related electrical and thermoelectric properties of monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices in a parallel spin configuration (PC) and an anti-parallel spin configuration (APC) between the V-shaped zigzag-edged graphene nanoribbon electrodes and the center bilayer MPc molecules are investigated by combining the density functional theory and non-equilibrium Green's function approaches. The results show that there is an ultrahigh spin filter efficiency exceeding 99.99995% and an ultra-large total conductance of 0.49996G0 for FePc-CoPc molecular devices in the PC and a nearly pure charge current at high temperature in the APC and a giant MR ratio exceeding 9.87 × 106% at a zero bias. In addition, there are pure spin currents for CuPc and FePc molecular devices in the PC, and an almost pure spin current for FePc molecular devices in the APC at some temperature. Meanwhile, there is a high SFE of about 99.99585% in the PC and a reserved SFE of about -19.533% in the APC and a maximum MR ratio of about 3.69 × 108% for the FePc molecular device. Our results predict that the monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices possess large advantages in designing high-performance electrical and spintronic molecular devices.

High performance GaN-based LEDs on patterned sapphire substrate with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 DBR backside reflector.

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with patterned composite SiO(2)/Al(2)O(3) passivation layers and TiO(2)/Al(2)O(3) distributed Bragg reflector (DBR) backside reflector have been proposed and fabricated. Highly passivated Al(2)O(3) layer deposited on indium tin oxide (ITO) layer with excellent uniformity and quality has been achieved with atomic layer deposition (ALD) technology. With a 60 mA current injection, an enhancement of 21.6%, 59.7%, and 63.4% in the light output power (LOP) at 460 nm wavelength was realized for the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers, the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers and Ag mirror + 3-pair TiO(2)/SiO(2) DBR backside reflector, and the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layer and Ag mirror + 3-pair ALD-grown TiO(2)/Al(2)O(3) DBR backside reflector as compared with the conventional LED only with a single SiO(2) passivation layer, respectively.