Search

Using multi-step deposition mode, we developed an innovational strategy of homogenously multilayered (HM) structure to tailor the roughening kinetics of sputtered W films. Dynamic scaling analysis showed that all sublayers of HM W films exhibited the same anomalous roughening behavior, which originated from the limited surface diffusion. Intriguingly, different from its single-layered counterpart, the HM W films exhibited a suppression effect of kinetic roughening, which could be well manipulated by film modulation period. Detailed experimental characterization and phenomenological model analysis suggested that this roughening suppression arises from the multi-interruption of the continuous film roughening process, forming an interlayer interface after every interruption and restarting the sublayer roughening on the pre-sublayer surface. [ABSTRACT FROM AUTHOR]

Local disordering has been analyzed in ordered intermetallic CoAl films epitaxially grown on GaAs(001) substrates by molecular beam epitaxy. Transmission electron microscopy investigations demonstrate the appearance of the bcc phase in the CoAl epilayer, which is the disordered version of the B2 crystal lattice type. Variations in the growth temperature between 100 and 300 °C reveal that the degree of thermal disordering and the volume fraction of the disordered bcc phase increase with increasing temperature. Interface reactions were observed in the sample fabricated at 300 °C resulting in the formation of CoAs precipitates at the interface. These precipitates contribute to the plastic relaxation of the 1.2% lattice mismatch between the CoAl film and the GaAs substrate affecting the strain-induced order–disorder transition. The impact of disordering is discussed in connection to the high diffusivity of vacancies and Co atoms existing in the intermetallic alloy. [ABSTRACT FROM AUTHOR]

Single-crystal dendritic ZnO nanostructures in appearance of macroscale in mass production have been synthesized via the vapor-phase transport method with Cu catalyst at 930 °C. The hierarchical ZnO dendrites with a long central trunk and lots of multilevel branches are composed of well-oriented nanorods whose diameters range from 60 to 800 nm. Gas sensors based on as-synthesized ZnO products exhibit high sensitivity and selectivity to H2S gas at room temperature through detecting various gases. The large modulation of the energy barrier of contact between nanorods in ZnO dendrites by H2S gas at room temperature might be the origin of the high sensitivity. The results demonstrate that the ZnO dendrites, with macroscopical appearance and properties of nanomaterials, are potential to develop effective and high performance gas sensors. Moreover, the detailed humidity characteristics of the sensor have also been investigated in the relative humidity range of 5%-97.6%. [ABSTRACT FROM AUTHOR]

ZnGa2O4 nanowires were grown via a low-pressure chemical vapor deposition method, and the electrical transport properties of these nanowires were investigated. It was found that the current across individual nanowires was several picoamperes at a bias of 30 V, and the current was insensitive to oxygen and temperature. These behaviors still maintained as the ZnGa2O4 nanowires were exposed to below-band-gap irradiation. In contrast, upon exposure to 254 nm ultraviolet light, the current across the nanowire increased a lot. With decreasing oxygen pressure or increasing temperature, the photocurrent increased evidently; this could be understood from the Langmuir model and the adsorption isobar, respectively. The present results demonstrate that surface-related processes especially oxygen chemisorption have significant effects on the photoelectric properties of nanostructures. The optically driven oxygen and temperature sensing as found in the ZnGa2O4 nanowires may find promising applications in functional devices. [ABSTRACT FROM AUTHOR]

The effects of constant bias stress and electric field on the electromechanical behavior of <001>-oriented Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN–0.32PT) relaxor ferroelectric single crystals have been investigated. Both unipolar and bipolar responses are considered. Obtained results show that compressive bias stress with appropriate magnitude can significantly increase the piezoelectric constant. It is also found that bias electric field in the poling direction stabilizes the microstructure of PMN–0.32PT and reduces the hysteresis loss. The observed effects of bias stress and bias electric field on the electromechanical properties of <001>-oriented PMN–0.32PT single crystals can be interpreted in terms of phase-transformation-induced polarization rotation through intermediate phases. [ABSTRACT FROM AUTHOR]

Silicon on insulator (SOI)-based transistors gated by nanogranular SiO2 proton conducting electrolytes were fabricated to mimic synapse behaviors. This SOI-based device has both top proton gate and bottom buried oxide gate. Electrical transfer properties of top proton gate show hysteresis curves different from those of bottom gate, and therefore, excitatory post-synaptic current and paired pulse facilitation (PPF) behavior of biological synapses are mimicked. Moreover, we noticed that PPF index can be effectively tuned by the spike interval applied on the top proton gate. Synaptic behaviors and functions, like short-term memory, and its properties are also experimentally demonstrated in our device. Such SOI-based electronic synapses are promising for building neuromorphic systems. [ABSTRACT FROM AUTHOR]

High-performance Y2O3/In2O3-based transparent thin-film transistors were processed featuring low thermal budget. The device shows a field-effect mobility of 43.5 cm2 V-1 s-1, a subthreshold swing of 0.28 V/decade, and an on/off current ratio of 108. These results are attributed to the high dielectric constant of Y2O3 and unique electronic structure of In2O3. Furthermore, the cubic phases of crystalline Y2O3 and In2O3 films have the identical crystal structure with a small lattice mismatch, which provides a well-defined dielectric/semiconductor interface for the optimal performance. [ABSTRACT FROM AUTHOR]

Polarized in-plane and cross-sectional Raman spectra have been used to determine the crystal orientation of m-plane GaN grown on γ-LiAlO2(100) (LAO) using a three-step metalorganic vapor phase epitaxy process. The epitaxial relationship is found to be GaN(1100)∥LAO(100) and GaN[1120]∥LAO[001]. However, the stripes on the GaN surface are oriented parallel to [0001], i.e., perpendicular to the one found on striated m-plane GaN surfaces in previous studies. This unusual orientation is attributed to the changes in the Ga adatom kinetics due to the presence of a 2-nm-thick interlayer observed at the GaN/LAO interface in transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The authors report on surface-depletion controlled gas sensing ZnO nanorods. These nanorods were synthesized through a simple wet chemical route at room temperature. The diameter of nanorods is about 15 nm, which is close to two times of the Debye length of ZnO. In contrast to the previous report, the sensing is surface-depletion controlled rather than contact controlled and the sensitivity is up to 29.7 against 100 ppm ethanol. Such high sensitivity is due to an almost complete depletion of the rods in air, which is confirmed from photoluminescence spectrum and x-ray photoelectron spectroscopy. The gas sensing mechanism controlled by surface depletion provides another approach to realize high-performance gas sensors. [ABSTRACT FROM AUTHOR]

Vertically aligned tin-doped indium oxide (ITO) single-crystalline nanowire arrays are epitaxially grown on ITO/yttrium stabilized zirconia substrates by vapor transport method. Vacuum electron field emission properties of the aligned ITO nanowires are investigated. The turn-on electrical field at a current density of 1 μA/cm2 is about 2.0 V/μm, and the lowest vacuum for an obvious emission is 1×10-1 Pa. The good performance of field emission is attributed to the vertically aligned morphology, which has a stronger local electric field due to their orientation parallel to the electric-field direction. [ABSTRACT FROM AUTHOR]

The authors report a route to realize very quick oxygen response and demonstrate it by using individual β-Ga2O3 nanowires. The current across the nanowire is at a low level and varies slightly with changing the oxygen pressure. In contrast, under 254 nm ultraviolet illumination, the current increases rapidly to a value that reflects the level of the oxygen pressure around the nanowire. The illumination gives rise to the oxygen sensing. This optically driven oxygen sensing is the origin of the fast response. The results demonstrate a promising approach to realize fast-response gas sensors. [ABSTRACT FROM AUTHOR]

ZnO films doped with manganese (Mn) and phosphorus (P) are grown on (0001) sapphire substrates by pulsed laser deposition at different temperatures and oxygen pressures. The structural and magnetic properties of the codoped ZnO films are carefully investigated. Experimental results demonstrate that p-type conduction is necessary for the observation of ferromagnetism in Mn+P codoped ZnO films at room temperature. A distinct aging effect is observed, which is likely due to the instability of p-type conduction of Mn+P codoped ZnO films. [ABSTRACT FROM AUTHOR]

In order to improve the field emission properties of screen-printed carbon nanotube films, ZnO nanostructures were deposited on multiwall carbon nanotubes (MWNTs) using vapor phase transport method. Based on the combined effect of geometrical structure of MWNT/ZnO, a low turn-on field of ∼0.7 V/μm at current density of 0.1 μA/cm2, a low threshold field of ∼2.3 V/μm at current density of 1 mA/cm2, a high field enhancement factor of 8.2×103, and a homogeneous emission image with emission spot density of ∼105 cm-2 were obtained from ZnO nanomultipods grown on MNWT film. [ABSTRACT FROM AUTHOR]

Contact-controlled sensing is realized from flowerlike ZnO structures composed of rods. The rods are around 150 nm in diameter and up to a few micrometers in length. When they are exposed to air, a depletion region formed below the surface of the rods arising from the adsorption of oxygen. Surface depletion does not greatly reduce either the carrier density or the mobility in the rods but significantly modify the potential barrier of the contacts between the rods. Both the large diameter and the long length result in a low sensor resistance down to 104 kΩ in air at 300 °C. The exponential increase of the tunneling rate with the thickness and height of the contact barrier leads to a high sensitivity up to 14.6 for 100 ppm ethanol. These results indicate that contact-controlled sensing can be used to fabricate high-performance sensors with both high sensitivity and low resistance. [ABSTRACT FROM AUTHOR]

SnO2 nanowires synthesized by thermal evaporation method are investigated as a possible anode electrode for Li-ion batteries. In the first discharge process, the capacity of Li ions is 2133 mA h g-1, which is much more than the theoretical total capacity of the bulk SnO2, 1494 mA h g-1. During the successive 15 cycles, the reversible capacity stays in the range of 1250–700 mA h g-1 with a capacity fading of 3.89% per cycle at a constant current density of 0.5 mA cm-2. These results demonstrate that SnO2 nanowires are a promising anode material for Li-ion battery applications. [ABSTRACT FROM AUTHOR]

The photocatalytic characteristics of the tetrapod-branched ZnO nanostructures synthesized by thermal evaporation method are investigated. The fitting of absorbance maximum plot versus time indicates an exponential decay, suggesting the photodegradation of Rhodamine B catalyzed by the ZnO nanotetrapod is a pseudo first-order reaction. These results demonstrate that the photocatalytic activity of ZnO nanotetrapod is much better than that of P25 TiO2 and ZnO powders. The slow electron/hole recombine rate due to the abundant surface states, as well as the high surface-to-volume ratio will effectively enhance the photocatalytic activity of the ZnO nanotetrapod. [ABSTRACT FROM AUTHOR]

We observe an anomalous electrorheological (ER) behavior of suspensions composed of ZnO nanowires and silicone oil. In contrast to the usual ER behavior, a decrease in viscosity of the suspensions is observed. Such an anomalous behavior results from the migration of ZnO nanowires to the electrodes under a dc electric field. The migration leads to a relatively pure silicone oil zone between the electrodes, as confirmed by optical microscope observations. The occurrence of the electrophoresis is proposed as the origin of the decrease in shear stress. [ABSTRACT FROM AUTHOR]

Positive temperature coefficient of resistance is observed on single Cd-doped ZnO nanowires. The current along the nanowire increases linearly with the bias and saturates at large biases. The conductance is greatly enhanced either by ultraviolet illumination or infrared illumination. However, the conductance decreases with increasing temperature, in contrast to the reported temperature behavior either for ZnO nanostructures or for CdO nanoneedles. The increase of the conductance under illumination is related to surface effect and the decrease with increasing temperature to bulk effect. These results show that Cd doping does not change surface effect but affects bulk effect. Such a bulk effect could be used to realize on-chip temperature-independent varistors. [ABSTRACT FROM AUTHOR]

Individual ZnO nanowire transistors are fabricated, and their sensing properties are investigated. The transistors show a carrier density of 2300 μm-1 and mobility up to 6.4 cm2/V s, which are obtained from the ISD-VG curves. The threshold voltage shifts in the positive direction and the source-drain current decreases as ambient oxygen concentration increases. However, the opposite occurs when the transistors are under illumination. Surface adsorbates on the ZnO nanowires affect both the mobility and the carrier density. Our data are helpful in understanding the sensing mechanism of the gas sensors. [ABSTRACT FROM AUTHOR]

An in situ doping approach was adopted to synthesize single-crystalline Sn-doped In2O3 [indium tin oxide (ITO)] nanowhiskers. Similar synthesis strategy could be used in the production of various doped metal oxide nanowhiskers. The growth mode of ITO nanowhiskers was discussed based on a self-catalytic vapor-liquid-solid growth mechanism. At room temperature, a photoluminescence peak at 510 nm was observed, which was likely related to the surface defects of ITO nanowhiskers. In air ambient, the resistivity of individual ITO whisker was measured to be 0.40 Ω cm, which was much higher than that of ITO films. A possible explanation for the high resistivity was proposed based on the influence of surface oxygen absorption. [ABSTRACT FROM AUTHOR]

Thin film transistors are fabricated by in situ growth of SnO2 nanobelts on Au/Pt electrodes. A linear correlation in the output characteristics is observed at zero gate voltage, indicating Ohmic contacts between the nanobelts and the electrodes. The transistors exhibit n-type behaviors and have a mobility of 1.85 cm2/V s with a current on/off ratio above 103. The conductance increases as the pressure in the device chamber is reduced, which indicates that the transistors are promising for oxygen detecting. [ABSTRACT FROM AUTHOR]

Stable field emission is realized from well-separated tetrapod-like ZnO nanostructures with high purity. The ZnO nanostructures are painted on a highly doped silicon substrate covered by a Au layer with a thickness of 300 nm. An emission current density of 18 mA/cm2 is obtained and degradation was not observed over a three day period. The fluctuations of the emission current are less than 2%. These experimental results indicate that tetrapod-like ZnO nanostructures are promising materials as cold cathodes for mass production. [ABSTRACT FROM AUTHOR]

Electronic transport through individual ZnO nanowires has been investigated. The current increases linearly with the bias and the conductance jumps upon ultraviolet illumination. The increase rate upon the illumination is much faster than the decrease rate as the light is off. The decrease rate under vacuum is slower than that in air. These phenomena are related to the surface oxygen species and further confirmed by in situ current–voltage measurements as a function of oxygen pressure at room temperature. Also, the conductance increases greatly as the temperature is raised. These results demonstrate that the surface oxygen species dominate the transport process through individual ZnO nanowires, which indicates their potential application to room temperature gas sensors. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited high sensitivity and fast response to ethanol gas at a work temperature of 300 °C. Our results demonstrate the potential application of ZnO nanowires for fabricating highly sensitive gas sensors. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on the microwave response properties of the ZnO nanowire-polyester composites fabricated into a planar plate with the area of 180×180 mm2 and the thickness of about 1 mm. Strong microwave absorption has been observed in X band and the maximum absorption is enhanced as the concentration of the nanowires increases in the composites. Both the low complex permittivity and the low dissipation of the pure nanowires demonstrate the pure nanowires are low-loss materials for microwave absorption in X band. The strong absorption is related to interfacial multipoles at the interface between the polyester and the ZnO nanowires, a high surface-to-volume ratio and a similar shape of the nanowires to antenna. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Cd-doped ZnO nanowires in mass production were synthesized by evaporating metal zinc (Zn) and cadmium (Cd) at 900 °C. Devices using the synthesized nanowires were fabricated on microstructured substrates. Cd-doped ZnO nanowires show a clear positive temperature coefficient of resistance effect, which is quite abnormal as compared to pure ZnO nanowires. At room temperature, resistance change of more than three orders of magnitude was measured when Cd-doped ZnO nanowire device was exposed to a moisture pulse of 95% relative humidity. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Massive ZnO nanowires with the mean diameter of 20 nm have been rapid synthesized by evaporation of metal zinc at 900 °C in the quartz tube. Metal catalyst, graphite additive, and vacuum are not necessary, and, more importantly, it is very convenient and effective for large-scale industrialization. The hydrogen storage characteristics of the synthesized ZnO nanowires are investigated at room temperature. The highest storage capacity of 0.83 wt% is achieved under the pressure of about 3.03 Mpa, and about 71% of the stored hydrogen can be released under ambient pressure at room temperature. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Tetrapod-like zinc oxide (ZnO) nanostructures can be synthesized by rapid heating metal zinc pellet at 900 °C under air ambient. Catalyst, vacuum, and carrying gas are not necessary, and more importantly, it is a volcanic process for rapid and mass production. The turn-on field of the synthesized tetrapod-like ZnO nanostructures is found to be as low as 1.6 V/μm at the current density of 1 μA/cm[sup 2]. These ZnO nanostructures are technologically useful for vacuum electron devices because they can be easily and economically synthesized and deposited on large substrates. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Metal-insulator-semiconductor (MIS) structures containing Ge nanocrystals embedded in high permittivity dielectrics (ZrO[SUB2]/Al[SUB2]O[SUB3]) are fabricated by electron-beam evaporation method. Capacitance-voltage (C - V) and I - V characteristics of the fabricated MIS structures are investigated in the dark and under illumination. Charge storing and negative photoconductivity effects of the Ge nanocrystals are experimentally demonstrated by the hysteresis in the C - V curves and the decrease of the current under illumination at a given voltage, respectively. [ABSTRACT FROM AUTHOR]

Structural and electrical characteristics of the metal-insulator-semiconductor (MIS) structures of Al/Al[SUB2]O[SUB3]/Si containing Ge nanoclusters are experimentally demonstrated. Secondary ion mass spectroscopy results indicate the out-diffusion of Ge after annealing at 800 °C in N[SUB2] ambient for 30 min. An increment of leakage current is observed due to the out-diffusion of Ge. Capacitance-voltage studies indicate that annealing can effectively passivate the negatively charged trapping centers. Memory effect of the Ge nanoclusters is verified by the hysteresis in the C - V curves in the annealed sample. [ABSTRACT FROM AUTHOR]

Amorphous germanium (α-Ge) nanoclusters embedded in Al[SUB2]O[SUB3] matrix are synthesized on fused-quartz glass substrate at room temperature by vacuum electron-beam coevaporation. Linear optical transmittance measurements reveal an indirect optical absorption edge with a blueshift as large as 1.6 eV due to the quantum confinement effects. The Z-scan method is used to study the third-order nonlinear absorption process of the synthesized samples, which clearly show a two-photon nonlinear process. Results also suggest that Ge nanocluster density or size is of great influence to the value of nonlinear absorption coefficient β. [ABSTRACT FROM AUTHOR]

Vacuum electron-beam coevaporation of Fe and Si followed by annealing in N[SUB2] ambient is used to synthesize beta iron disilicide (β-FeSi[SUB2]) nanocrystals. The reason for β-FeSi[SUB2] nanocrystal formation is discussed based on the principle of minimization of the interface energy. X-ray diffraction studies suggest that β-phase FeSi[SUB2] nanostructures turn into the a phase when the annealing temperature is 1000 °C. The optical transmission measurements indicate that the β-FeSi[SUB2] nanocrystals have a direct-band structure with the energy gap in the range of 0.84 -0.88 eV. A sharp photoluminescence peak of the β-FeSi[SUB2] nanocrystals located at 1.5 μm is measured at 77 K. [ABSTRACT FROM AUTHOR]

High-vacuum electron-beam evaporation was used to synthesize germanium (Ge) cone-arrays on N[sup +]-type (100) Si. The surface morphology of Ti nanocrystals' catalyst and Ge cone-arrays was investigated by scanning electron microscopy and atomic force microscopy. The lattice constant of the Ge cones determined from x-ray diffraction was nearly identical to that of bulk Ge. The mechanism of Ge cone-arrays' formation was investigated. The electron field emission properties of the as-prepared Ge cone-arrays were studied based on current-voltage measurements and the Fowler-Nordheim equation. [ABSTRACT FROM AUTHOR]

High vacuum electron-beam co-evaporation, followed by N[sub 2] annealing at 500 °C is used for preparing of silicon nanocrystals (Si NCs) embedded in Al[sub 2]O[sub 3] dielectric matrix. X-ray diffraction and transmission electron microscopy are used to investigate the structures of Si+ Al[sub 2]O[sub 3] films and estimate the mean diameter of the Si NCs. The electrical properties of the diode containing Si NCs embedded in Al[sub 2]O[sub 3] are studied at room temperature and resonant tunneling effect with large voltage gap is observed. A circuit model based on resonant tunneling is proposed to simulate the measured I-V curve. [ABSTRACT FROM AUTHOR]

In a recent letter, Cao et al. [Appl. Phys. Lett. 88, 251116 (2006)] reported the growth of In+N codoped p-type ZnO films with a low resistivity of 1.58×10-1 Ω cm by a simple sol-gel spin coating method. Unfortunately, this low resistivity value is doubtful based on Hall effect measurement analysis. If the values of carrier concentration and Hall mobility are correct in their experiment, the resistivity value should be 10.62 Ω cm, but not 1.58×10-1 Ω cm. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "A transparent metal: Nb-doped anatase TiO2," by Q. Wan and T. H. Wang published in the previous issue.

Methane (CH4) oxidation is an important reaction to reduce the greenhouse effect caused by incomplete combustion of CH4. Here, we explored the mechanism of CH4 oxidation catalyzed by CeO2 and Ni-doped CeO2, focusing on the redox properties of these catalyst surfaces, using density functional theory (DFT). We found that the barriers for CH4* activation and H2O* formation are correlated with the surface redox capacity, which is enhanced by Ni doping. Furthermore, the complete reaction mechanism is explored by DFT calculations and microkinetic simulations on bare and Ni-doped CeO2 surfaces. Our calculations suggest that the doping of Ni leads to a much higher overall reactivity, due to a balance between the CH4* activation and H2O* formation steps. These results provide insights into the CH4 oxidation mechanism and the intrinsic relationship between redox properties and the activity of CeO2 surfaces., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Eccentric error is a vital part of high-precision optical encoder error. An automatic error compensation system is designed to lower the eccentric error of the encoder. On the periphery of the fan-shaped code path of the traditional encoder disk, a set of radial code paths is drawn. This radial code path is composed of several concentric circles with alternating light and dark lines. The direction of the radial code path is perpendicular to the direction of the fine code path. When the encoder rotates, the eccentricity of the encoder disk is measured by the moiré fringe signal output from the radial code channel. Based on the eccentricity error compensation algorithm, the eccentricity error of the encoder disk is compensated in real time to enhance the accuracy of the encoder. The experimental results of an encoder show that the mean square error of the encoder before the eccentricity error compensation is 21.25 arc seconds, and it is 3.66 arc seconds after compensation by this algorithm. The algorithm can significantly compensate the error caused by the eccentricity of the encoder and greatly improve the accuracy of the encoder., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Due to the potential difference between two neurons and that between the inner and outer membranes of an individual neuron, the neural network is always exposed to complex electromagnetic environments. In this paper, we utilize a hyperbolic-type memristor and a quadratic nonlinear memristor to emulate the effects of electromagnetic induction and electromagnetic radiation on a simple Hopfield neural network (HNN), respectively. The investigations show that the system possesses an origin equilibrium point, which is always unstable. Numerical results uncover that the HNN can present complex dynamic behaviors, evolving from regular motions to chaotic motions and finally to regular motions, as the memristors' coupling strength changes. In particular, coexisting bifurcations will appear with respect to synaptic weights, which means bi-stable patterns. In addition, some physical results obtained from breadboard experiments confirm Matlab analyses and Multisim simulations.

Phononic crystal is a type of acoustic material, and the study of phononic crystals has attracted great attention from national research institutions. Meanwhile, noise reduction in the low-frequency range has always encountered difficulties and troubles in the engineering field. In order to obtain a unique and effective low-frequency noise reduction method, in this paper a low frequency noise attenuation system based on phononic crystal structure is proposed and demonstrated. The finite element simulation of the band gap is consistent with the final test results. The effects of structure parameters on the band gaps were studied by changing the structure parameters and the band gaps can be controlled by suitably tuning structure parameters. The structure and results provide a good support for phononic crystal structures engineering application.

Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.