Zongchen Liu

A new potentiometric SO2 sensor based on Li3PO4 electrolyte film and its response characteristics

A potentiometric SO2 gas sensor based on Li3PO4 solid electrolyte has been developed using Au as the reference electrode and Li2SO4/V2O5 as the sensing electrode. The Li3PO4 film was deposited on Al2O3 substrate by resistance heating evaporation. Two Au films with designed patterns were formed on the Li3PO4 film by micro-fabrication technologies. The sensing electrode covers one electrode partly using thick-film technology. The electromotive force values between the sensing electrode and the reference electrode were measured and various characteristics were studied including sensitivity, response characteristics, and stability and selectivity. According to the results, we conclude that an optimal working temperature of the SO2 sensor is 500 °C, the measurement range is 0-100 ppm, the sensitivity is about 32.47 mV/dec, the response and the recovery time is about 5 min and 10 min, respectively. And the stability and the selectivity of the sensor are good, making it have potential in SO2 measurement of living environment.

Diamond based field-effect transistors of Zr gate with SiN x dielectric layers

Investigation of Zr-gate diamond field-effect transistor with SiNx dielectric layers (SD-FET) has been carried out. SD-FET works in normally on depletion mode with p-type channel, whose sheet carrier density and hole mobility are evaluated to be 2.17 × 1013 cm-2 and 24.4 cm2ċV-1ċs-1, respectively. The output and transfer properties indicate the preservation of conduction channel because of the SiNx dielectric layer, which may be explained by the interface bond of C-N. High voltage up to -200 V is applied to the device, and no breakdown is observed. For comparison, another traditional surface channel FET (SC-FET) is also fabricated.

Second-order self-imaging with parametric amplification four-wave mixing

By modulating the emission characteristics of a twin-correlated bright beam in a parametric amplification of the four-wave mixing process, a nondestructive and lensless imaging scheme to image ultra-cold atoms or molecules is proposed. The optical lattice state, which is induced via the coupling between ultra-cold atoms and a standing wave, is used to effectively modulate the dressing-suppressed/enhanced nonlinear susceptibility, and an emission-intensity-modulated grating of a correlated bright beam is formed. The intensity fluctuations of the correlated bright beam are taken as the imaging light to implement second-order coincidence measurement. As an important complementary scheme to a previous self-imaging scheme with spontaneous parametric down-conversion, our scheme has the characteristic of an efficient generation and detection rate. In addition, the visibility of the imaging can be significantly improved by enhanced nonlinear susceptibility. Our work may offer a nondestructive and lensless way to image ultra-cold atoms or molecules.

A finite element analysis of the effects of geometrical shape on the elastic properties of chemical vapor deposited diamond nanowire

We report the effect of geometrical shape of diamond nanowire on its mechanical properties. Finite element modeling using COMSOL Multiphysics software is used to simulate various diamond nanowire with circular, square, rectangular, hexagonal and triangular cross-sections. A bending test under concentrated load applied at one of the free ends is simulated using FEM. The force response of the nanowire under different loading is studied for the various cross-sections. The dimensions of each cross-section is chosen so that material properties such as Young’s modulus can be kept constant for comparison in all the cross-sections. It is found out that the bending capability of a triangular nanowire is higher compared to other cross-sections due to its lowest second moment. Circular and hexagonal cross-section show highest stiffness. The study of mechanical property of diamond nanowires is useful for optimal nanomechanical designs where the effect of cross-section has to be taken into account.

Investigation of the occupancy ratio dependence for microlens arrays on diamond

Diamond microlens arrays with a high occupancy ratio were fabricated by an improved thermal reflow method. Our resultes show that the occupancy ratio of a photoresist mask could be improved with optimizing the reflow temperature, time and photoresist thickness during the reflow process. The fabricated microlens arrays exhibited a uniform arrangement and good optical performance.

Hybrid three-mode correlation and squeezing in a Pr3+:YSO crystal

We report the generation of three-mode hybrid intensity-noise correlation and intensity-difference squeezing of spontaneous parametric four-wave mixing (SP-FWM) and fourth-order fluorescence (FL) signals in the heteronuclear-like (three-level Λ-type) molecular structure of a Pr3+:Y2SiO5 (Pr3+:YSO) crystal using the nonlinear cross-Kerr effect under a polarized dressing effect. In the semi-classical view of a Kerr nonlinear medium, the amplitude of two-mode hybrid correlations of this kind is subject to a limit determined by the hybrid maximally entangled state. Whereas the degree of correlation and squeezing is determined by the dressing effects of the input laser fields participating in the SP-FWM process. We also find that the variations in magnitude of three-mode hybrid intensity-noise correlation and intensity-difference squeezing are consistent with nonlinear cross-Kerr processes. Such a three-mode hybrid signal may have potential applications in long-distance communication, dense coding, all-optical communication and quantum storage on photonic chips.

Ohmic contact between iridium film and hydrogen-terminated single crystal diamond

Investigation of ohmic contact between iridium (Ir) film and hydrogen-terminated single crystal diamond has been carried out with annealing temperature from 300 to 600 °C in argon (Ar) and hydrogen ambient. Electrodes were deposited on hydrogen-terminated single crystal diamond by electron beam evaporation technique, and specific contact resistivity has been measured by transmission line model. The interface between Ir film and hydrogen-terminated single crystal diamond was characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy. Theoretical calculation value of barrier height between Ir film and hydrogen-terminated single crystal diamond was around −1.1 eV. All results indicate that an excellent ohmic contact could be formed between Ir film and hydrogen-terminated single diamond.

FEM thermal analysis of Cu/diamond/Cu and diamond/SiC heat spreaders

The effects of thermal stress resulting from thermal cooling in copper/diamond/copper heat spreader is investigated using finite element method. A similar model of diamond/SiC heat spreader is compared without addition of interlayer. The effect of carbide interlayer in reduction of interfacial thermal stress is investigated. The results show that the carbide interlayer film thickness is critical in stress reduction for a copper/diamond/copper heat spreader device. Diamond/SiC device has lower interfacial stress without interlayer. The study of mechanical and thermal property of diamond heat spreader is useful for optimal designs of efficient heat spreader for electronic components.

Effect of thermoelastic damping on silicon, GaAs, diamond and SiC micromechanical resonators

The effect of thermoelastic damping as a main dissipation mechanism in single crystalline silicon, GaAs, diamond, SiC and SiO2 micromechanical resonators are studied. Numerical simulation is performed to compare quality factors of the given materials. Results using Zener’s well-known approximation and recent developments of Lifshitz and Roukes models were used to model thermoelasticity effects. In the later model, the effect of thermal diffusion length is taken into account for determination of thermoelastic damping. Our results show that larger discrepancy is obtained between the two models for SiO2. The difference is pronounced when beam aspect ratio (L/w) is smaller. Such progresses will find potential applications in optimal design of high quality factor micrometer- and nanometer-scale electromechanical systems.

Lifetime Autler-Townes Splitting of Dressed Multi-Order Fluorescence in Pr3+:YSO

HIGHLIGHTS • We observed Autler-Townes splitting of single peak into two and three peaks in two-level, and three-level systems, respectively. • We reported primary and secondary Autler-Townes splitting are caused by double cascaded dressing in time domain. • WeobservedAutler-Townessplittingofmulti-orderfluorescenceintimedomainismore obvious than that of in spectral domain. For first time, we study primary and secondary Autler-Townes (AT) splitting of multi-order fluorescence (FL) in time domain. The AT-splitting of multi-order FL signals are controlled by changing power, detuning, and polarization of single and double dressing in a heteronuclear-like molecule system of Pr C3 :YSO. The primary and secondary AT-splitting are caused by double cascaded dressing in time domain. The AT-splitting of multi-order FL in time domain is more sensitive than that of in spectral domain. Such results have potential applications in quantum communication and optical information processing on photonic chip.