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The use of diamond as a semiconductor for the realization of transistor structures, which can operate at high temperatures (>700 K), is of increasing interest. In terms of bipolar devices, the growth of n-type phosphorus doped diamond is more efficient on the (111) growth plane; p-type boron-doped diamond growth has been most usually grown in the (100) direction and, hence, this study into the electronic properties, at high temperatures, of boron-doped diamond (111) homoepitaxial layers. It is shown that highly doped layers (hole carrier concentrations as high as 2×1020 cm-3) can be produced without promoting the onset of (unwanted) hopping conduction. The persistence of valance-band conduction in these films enables relatively high mobility values to be measured (∼20 cm2/V s) and, intriguingly, these values are not significantly reduced at high temperatures. The layers also display very low compensation levels, a fact that may explain the high mobility values since compensation is required for hopping conduction. The results are discussed in terms of the potential of these types of layers for use with high temperature compatible diamond transistors. [ABSTRACT FROM AUTHOR]

4D printing enables 3D printed structures to change shape over "time" in response to environmental stimulus. Because of relatively high modulus, shape memory polymers (SMPs) have been widely used for 4D printing. However, most SMPs for 4D printing are thermosets, which only have one permanent shape. Despite the efforts that implement covalent adaptable networks (CANs) into SMPs to achieve shape reconfigurability, weak thermomechanical properties of the current CAN-SMPs exclude them from practical applications. Here, we report reconfigurable 4D printing via mechanically robust CAN-SMPs (MRC-SMPs), which have high deformability at both programming and reconfiguration temperatures (>1400%), high Tg (75°C), and high room temperature modulus (1.06 GPa). The high printability for DLP high-resolution 3D printing allows MRC-SMPs to create highly complex SMP 3D structures that can be reconfigured multiple times under large deformation. The demonstrations show that the reconfigurable 4D printing allows one printed SMP structure to fulfill multiple tasks.. [ABSTRACT FROM AUTHOR]

An important development in the field of diamond electronics has been the production of n-type electrical characteristics following homoepitaxial diamond growth on (111) diamond in the presence of phosphorus-containing gases. Several studies have reported that a phosphorus donor level forms with an activation energy in the range of 0.43–0.6 eV; the ground state for the donor level is considered to be at 0.6 eV. Little is currently known about other electrically active defects that may be produced alongside the donor state when phosphorus is introduced. In this paper we report upon the use of impedance spectroscopy, which can isolate the differing components that contribute to the overall conductivity of the film. In Cole-Cole plots, two semicircular responses are observed for all temperatures above 75 °C; a single semicircle being seen at temperatures below this. The results suggest the presence of two conduction paths with activation energies of 0.53 and 0.197 eV. The former can be attributed to the phosphorus donor level, being lower than 0.6 eV due to reduced mobility within the film at elevated temperatures. The latter is discussed in terms of defects in the P+-doped region under the Ohmic contacts being used. [ABSTRACT FROM AUTHOR]

Nanocrystalline diamond films were synthesized by microwave plasma-enhanced chemical vapor deposition using Ar/H[sub 2]/CH[sub 4] gas mixtures. A Fluke PM6306 RCL meter was used to study the electrical impedance of these diamond films in the frequency range 50 Hz to 1 MHz. The impedance dispersion measurement yields the real and imaginary parts in the form of a Cole-Cole plot in the complex plane. A single semicircular response of the impedance of nanocrystalline diamond films was observed at temperatures below 250 °C, with a second semicircular response appearing at low frequencies at temperatures above this. The semicircular responses were found to fit a double resistor-capacitor parallel circuit model. Physical mechanisms likely to be responsible for these observations are discussed in this paper. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The impedance spectroscopy measurements were used to investigate the separated contributions of diamond grains and grain boundaries (GBs), giving an insight into p-type to n-type conductivity conversion in O+-implanted ultrananocrystalline diamond (UNCD) films. It is found that both diamond grains and GBs promote the conductivity in O+-implanted UNCD films, in which GBs make at least half contribution. The p-type conductivity in O+-implanted samples is a result of H-terminated diamond grains, while n-type conductive samples are closely correlated with O-terminated O+- implanted diamond grains and GBs in the films. The results also suggest that low resistance of GBs is preferable to obtain high mobility n-type conductive UNCD films. [ABSTRACT FROM AUTHOR]

LCR measurements have been performed on type IIa and type Ib single crystal diamonds, in an attempt to identify any differences in their dielectric characteristics. It is found that the type IIa diamond, which contains little nitrogen, behaves as an ideal insulator, with the dielectric loss appearing to be frequency independent at low temperatures, whilst assuming a frequency dependence at high temperatures. In contrast, the type Ib diamond samples exhibited a dielectric loss peak in the temperature-dependent data, from which a thermal activated process with an Ea of 1.67 eV can be determined using a simple Debye law relationship. However, the data suggests that a dielectric relaxation constant (nitrogen-induced dipole) of 1017 Hz is evident in the Ib system, which is much higher than that predicted by the Debye model, as such it is unlikely due to the dipole moment itself. A possible physical mechanism responsible for this phenomena is simply the ionization of a nitrogen centre with a defect level lying at 1.7 eV below the conduction band. [ABSTRACT FROM AUTHOR]

The development of simple and highly controllable fabrication methods for the β-Ga2O3, especially for the nanowire structure, has been a challenge. The slanted Ga2O3 nanowires are favorable for increasing the optical contact area and improving photon flux through nanoparticle scattering, leading to an increase in the photogenerated carrier yield. Herein, obliquely oriented and uniformly distributed β-Ga2O3 nanowires are fabricated on Si substrates by a radio frequency magnetron sputtering using the strategy of Au nanoparticles as an intermediate catalyst. By depositing Ti and Au electrodes, the metal-semiconductor-metal Ga2O3-based photodetectors are fabricated with a simple structure. Remarkably, the photodetector based on the β-Ga2O3 nanowires outperforms the one based on the β-Ga2O3 film, demonstrating higher responsivity and an exceptional photocurrent-to-dark current ratio (Iphoto/Idark) of 1.43 x 104 @5 V. This work presents a promising approach to enhance the utilization of incident light and maximize the generation of photoinduced carriers in the Ga2O3-based photodetectors. [ABSTRACT FROM AUTHOR]

In this study, an epoxy resin, YZ-05, designed specifically for carbon fiber reinforced polymer prepregs, was characterized and modeled. A degassing method for the highly viscous YZ-05 was established for specimen preparation. To numerically model the behavior of YZ-05 in curing, several components, including the heat transfer, curing kinetics, and viscoelastic constitutive law ones, were developed, and the corresponding material properties to be input were tested. As YZ-05 shows severe creep at high temperature under mechanical loading, the combination of digital image correlation (DIC) and thermography technique was utilized to obtain its thermal expansion and chemical shrinkage. In the aspects of viscoelastic behavior, stress relaxation tests were performed based on time-temperature superposition principle with a numerical method to calculate shift factors. After development and input identification, these modeling components for YZ-05 resin were integrated and the modeling results were validated using experiments, where bending of resin beams was induced during curing. [ABSTRACT FROM AUTHOR]

The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n=5 layered phase, while donor substitution produced nanoscale intergrowths of n=3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as ∼20%. Pure La2Ti2O7 has a thermal conductivity value of ∼1.3W/m K which dropped to a value of ∼1.12W/m K for Sr doped La2Ti2O7 and ∼0.93 W/m K for Ta doped La2Ti2O7 at 573K. [ABSTRACT FROM AUTHOR]

[Objectives] To study responses of Houttuynia cordata Thunb. to tetracycline (TC) stress in a sterile environment. [Methods] Aseptic H. cordata seedlings were cultured in the medium which added the different concentrations of TC, and then the contents of chlorophyll and malondialdehyde (MDA), and activity of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) of H. cordata leaves were measured. [Results] Compared with the CK, the contents of chlorophyll of H. cordata leaves decreased, and the accumulation of MDA, and the activity of CAT, POD and SOD in H. cordata leaves increased when H. cordata was stressed by different concentration of TC. [Conclusions] The growth, metabolism and physiology of H. cordata were affected by the stress of TC. More importantly, this proved an insight into the effect or harm of undegraded antibiotics in the soil and water in the natural environment to plant growth all the time. [ABSTRACT FROM AUTHOR]

[Objectives] To understand the content changes of fatty acid compositions and seedling growths during seed germinations of Cassia obtusifolia L. [Methods] The fatty acid compositions of germinations and seedling growths of C. obtusifolia seeds treated with different concentrations of gibberellin（GA3） and naphthalene acetic acid（NAA） were analyzed using gas chromatograph-mass spectrometer（GC-MS）, and the germination rates, root lengths, plant heights and fresh weights of their seedlings were analyzed. [Results] The contents of eicosenoic acid, α-linoleic acid, arachidic acid, eicosadienoic acid and eicosapentaenoic acid of C. obtusifolia seeds treated with different concentrations of GA3 and NAA decreased with germination time. There were significant differences between the ratios of germinations of C. obtusifolia seeds treated with different concentrations of GA3 and NAA. GA3 and NAA of different ratio treatments could promote seedling heights and fresh weights of C.obtusifolia, but increases of seedling heights and fresh weights were different. Eicosenoic acid, α-linoleic acid, arachidic acid, eicosadienoic acid and eicosapentaenoic acid were remarkably negative correlation with seedling heights and fresh weights. [Conclusions] The fatty acid components of C. obtusifolia seed germination and growth of their seedlings were affected. It indicated that GA3 and NAA treatments can affect fatty acid metabolism, the germination rates, root lengths, plant heights and fresh weights of C. obtusifolia. It is intended to provide a theoretical basis and technological reference for standardized cultivated techniques of C. obtusifolia. [ABSTRACT FROM AUTHOR]

A facile solvothermal method followed by a postannealing process is used to prepare NiO@NiCo2O4 core-shell nanosheet arrays supported on Ni foam substrate for a high-performance supercapacitor. The hybrid electrode possesses a three-dimensional structure with the "shell" of NiCo2O4 nanoflakes anchored on the "core" of ordered NiO nanosheets. It shows high specific capacitance of 1623.6 F g-1 (or specific capacity of 225.5 mAh g-1) at 2 A g-1 and excellent rate performance with a 96% capacitance retention rate at 20 A g-1. The high cycling stability is proved by nearly 90% capacitance retention at 10 A g-1 after 10000 cycles. Its asymmetric supercapacitor, assembled with NiO@NiCo2O4/Ni foam and the activated carbon/Ni foam as the positive and negative electrode, respectively, displays the specific energy of 52.5 W h kg-1 at 387.5 W kg-1. The excellent electrochemical performance of NiO@NiCo2O4 electrode indicates its great potential in applications of energy storage devices. [ABSTRACT FROM AUTHOR]

A high-dielectric constant (high-k) TiOx thin layer was fabricated on hydrogen-terminated diamond (H-diamond) surface by low temperature oxidation of a thin titanium layer in ambient air. The metallic titanium layer was deposited by sputter deposition. The dielectric constant of the resultant TiOx was calculated to be around 12. The capacitance density of the metal-oxide-semiconductor(MOS) based on the TiOx/H-diamond was as high as 0.75 µF/cm² contributed from the high-k value and the very thin thickness of the TiOx layer. The leakage current was lower than 10-13 A at reverse biases and 10-7A at the forward bias of -2 V. The MOS field-effect transistor based on the high-k TiOx/H-diamond was demonstrated. The utilization of the high-k TiOx with a very thin thickness brought forward the features of an ideally low subthreshold swing slope of 65 mV per decade and improved drain current at low gate voltages. The advantages of the utilization high-k dielectric for diamond metal-oxide semiconductor field effect transistors are anticipated. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy (IS) analysis is carried out to investigate the electrical properties of the metal-oxide-semiconductor (MOS) structure fabricated on hydrogen-terminated single crystal diamond. The low-temperature atomic layer deposition Al2O3 is employed as the insulator in the MOS structure. By numerically analysing the impedance of the MOS structure at various biases, the equivalent circuit of the diamond MOS structure is derived, which is composed of two parallel capacitive and resistance pairs, in series connection with both resistance and inductance. The two capacitive components are resulted from the insulator, the hydrogenated-diamond surface, and their interface. The physical parameters such as the insulator capacitance are obtained, circumventing the series resistance and inductance effect. By comparing the IS and capacitancevoltage measurements, the frequency dispersion of the capacitance-voltage characteristic is discussed. [ABSTRACT FROM AUTHOR]

The self-assembly of cobalt coordination frameworks (Co-CPs) with a two-dimensional morphology is demonstrated by a solvothermal method. The morphology of the Co-CPs has been controlled by various solvothermal conditions. The two-dimensional nanostructures agglomerated by Co3O4nanoparticles remained after the pyrolysis of the Co-CPs. The as-synthesized Co3O4 anode material is characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge measurements. The morphology of Co3O4plays a crucial role in the high performance anode materials for lithium batteries. The Co3O4 nanoparticles with opened-book morphology deliver a high capacity of 597 mA h g after 50 cycles at a current rate of 800 mA g-1. The opened-book morphology of Co3O4 provides efficient lithium ion diffusion tunnels and increases the electrolyte/ Co3O4 contact/ interfacial area. At a relatively high current rate of 1200 mA g-1, Co3O4 with opened-book morphology delivers an excellent rate capability of 574 mA h g-1. [ABSTRACT FROM AUTHOR]

Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser, even at room temperature. However, the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface. To address this issue, we fabricated arrays of diamond nanostructures, differing in both diameter and top end shape, with HSQ and Cr as the etching mask materials, aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy (NV) embedded diamond. With a mixture of O2 and CHF3 gas plasma, diamond pillars with diameters down to 45 nm were obtained. The top end shape evolution has been represented with a simple model. The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement, larger than tenfold, and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected. These results provide useful information for future applications of nanostructured diamond as a single-photon source. [ABSTRACT FROM AUTHOR]