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In slow wave structures (SWSs) for helix traveling-wave tubes, both thermal conductivities (TCs) of materials and thermal contact resistances (TCRs) are temperature-dependent, which have a great influence on the heat dissipation of helix SWSs. This article presents an accurate and efficient thermal analysis method of helix SWSs by finite-element method (FEM). In this method, a novel contact boundary condition (CBC) approach is proposed. This CBC approach can easily integrate various TCR models to simulate temperature-dependent TCRs accurately and conveniently. Specially for double nonlinearities arising from temperature-dependent TCs and TCRs within helix SWSs, a fast nonlinear solver named FMONS is also proposed to significantly improve the efficiency of the thermal simulation for helix SWSs. Based on this method, we further developed a 3-D thermal design tool for helix SWSs called TS2. Different from all the present FEM codes, for example, ANSYS, our TS2 can directly model temperature-dependent TCRs. By simulating various helix SWSs including a global model of the entire helix SWS, it is found that our TS2 has very high accuracy and efficiency in the thermal analysis of helix SWSs, which would be very useful for the design of high-power helix traveling-wave tubes.

Considering the typical climatic environment and geological characteristics of Xinjiang, China, this study systematically investigated the influence of different factors on the arch expansion characteristics of cement-stabilized macadam base materials through a low-temperature salt expansion test, penetration test, thermal conductivity test, strength test, freeze–thaw cycle test and microscopic test, and proposed a reasonable range of design indicators. The mechanism of arch expansion was further elucidated. The results showed that the sensitive temperature range for cement-stabilized macadam materials is −12.5 to −5 °C. Reasonable salt content, water content, cement content, compaction or the rate of temperature decrease can slow the deformation due to arch expansion. The total salt content of cement-stabilized macadam should not exceed 0.2%, and the water content should not exceed 4.0%. It is suggested that the skeleton compact structure should be used to reduce the stress effect of salt expansion on the material.

The pharmaceutical wastewater (PW) produced during the production of antibiotics has a huge impact on the ecological environment. The efficient removal of residual antibiotics from PW has become a great challenge. Here, a ZIF-8/GO composite film, a new material, was prepared by loading ZIF-8/GO nanosheets onto the surface of a polyethyleneimine- (PEI-) modified nylon microporous support. This new material can effectively remove tetracycline (TC) from PW with a removal rate of 99%. In addition, the layer of ZIF-8/GO nanosheets on the surface of the carrier had certain defect sites. This feature not only made the film have a relatively high flux (502 L·m−2·h−1·bar−1) but also overcame the disadvantages of the traditional membrane separation technology, such as the high operation pressure required by the easy plugging of micropores. More importantly, the abovementioned advantages enable the novel material to be applied on a larger scale. A probable adsorption mechanism was investigated and suggested.

The object of this study was to remove the tetracycline (TC) residue in pharmaceutical wastewater after flocculation treatment. MnO2/graphene nanocomposite was synthesized by an in situ hydrothermal method and its TC removal rate was up to 99.4%. This nanocomposite had excellent water solubility. More importantly, the introduction of MnO2 nanorods allowed the avoidance of excessive stacking of treated graphene sheets during the adsorption process, which made the TC molecules to have more opportunities to make contact with the adsorbents. In order to eliminate the interference factors, the adsorption isotherm, kinetics, thermodynamics and mechanism were all studied in TC aqueous solution. The influence of solution pH, contact time, MnO2 loading amount, temperature and solution concentration on the adsorption process were also assessed. The main adsorption mechanism contributed to the complexation of Mn(IV) and π-π interactions of the benzene ring structure on treated graphene sheets with TC molecules.

The exploration and research of pavement piezoelectric energy harvesting technology provides new ideas for the collection and application of road green energy. To improve the applicability of the piezoelectric energy-harvesting units in road environment effectively, based on technical requirements of energy-harvesting units for pavements, this paper compares two processes for preparing stacked piezoelectric energy-harvesting units and evaluates their application performance in terms of electromechanical conversion performance and structural strength; and the optimal preparation process for the units is determined as well. Two detailed structure optimization schemes of U-shaped interlayer copper foil electrode structure and lateral lead electrode structure are designed, which are tested and evaluated from the three perspectives of energy output performance, working durability and material properties, and the optimal electrode structure is determined. The results indicate that at 0.7 MPa–10 Hz, the parallel connected units prepared based on the multilayer adhesive process can increase the terminal voltage by 28.0 V and the output power by 22.80 mW, which are superior than units prepared by the monolithic co-firing process. In addition, the multilayer units exhibit good structural stability and weatherability. Under the same load condition, the optimal load resistances of the units with the U-shaped interlayer copper foil electrode and the lateral lead electrode can reach 20 kΩ with comparable energy outputs. Subsequently, mechanical testing is conducted after 50,000 simulation (MTS) cyclic loading, the structural performance of the U-shaped interlayer copper foil units is relatively durable and stable: the open-circuit voltage is attenuated by 4.4 V, the output power is attenuated by 3.30 mW, and the average capacitance of a single unit is only attenuated by 3.4 nF. Finally, future research plan is discussed.

The widely utilization of pharmaceutical and personal care products in the pharmaceutical therapies and agricultural husbandry has led to the worldwide pollution in the environment. However, effective purification of water contaminated by tetracycline (TC) remains a great challenge. Here, 2-dimensional (2D) zeolitic imidazolate framework-L (ZIF-L) nanoflakes with a leaf-like morphology, which could selectively adsorb TC, was successfully synthesized in aqueous media at room temperature. The removal efficiency of ZIF-L powder for TC from pharmaceutical wastewaters was greatly influenced by the solution pH, contact time, temperature and solution concentration. In order to solve these problems, ZIF-L nanoflakes were fabricated on the surface of polyethyleneimine (PEI) modified nylon microporous filter to form a 3-dimensional (3D) composite film by vacuum filtration. The result showed that this novel material could effectively remove about 99.0% of TC from pharmaceutical wastewater. Furthermore, ZIF-L film not only excluded the effects of solution pH, contact time, temperature and solution concentration on the adsorption capacity for TC, but also had a high flux (1639 L m−2 h−1 bar−1), making it suitable for a large-scale application. The probable adsorption mechanism was investigated and suggested.

With the ever-increasing laser power and repetition rate, thermal control of laser media is becoming increasingly important. Except for widely used air cooling or a bonded heat sink, water cooling of a laser medium is more effective in removing waste heat. However, how to protect deliquescent laser media from water erosion is a challenging issue. Here, novel waterproof coatings were proposed to shield Nd:Glass from water erosion. After clarifying the dependence of the waterproof property of single layers on their microstructures and pore characteristics, nanocomposites that dope SiO2 in HfO2 were synthesized using an ion-assisted co-evaporation process to solve the issue of a lack of a high-index material that simultaneously has a dense amorphous microstructure and wide bandgap. Hf0.7Si0.3O2/SiO2 multifunctional coatings were finally shown to possess an excellent waterproof property, high laser-induced damage threshold (LIDT) and good spectral performance, which can be used as the enabling components for thermal control in high-power laser cavities.

Sn15Sb85 thin films with different thickness are prepared by magnetron sputtering. The evolution of Sn15Sb85 thin film from the amorphous state to the crystalline state is studied by an in-situ resistance temperature measurement system. The crystallization temperature, electrical resistance, crystallization activation energy, and data retention capacity of Sn15Sb85 thin film increase significantly with film thickness decreasing. The near infrared spectrophotometer is used to record the diffuse reflectance spectra of amorphous Sn15Sb85 film. The results show that the band gap energy increases with film thickness decreasing. The surface morphology of Sn15Sb85 film after being crystalized is observed by atomic force microscope, which shows that the thinner film has lower roughness. The analysis of X-ray diffraction indicates that the grain size becomes smaller and the crystallization may be inhibited by reducing the film thickness. T-type phase change memory cells based on Sn15Sb85 thin films with different thickness are fabricated by the CMOS technology. The electrical performances of phase change memory show that the thinner Sn15Sb85 film has a larger threshold switching voltage and smaller RESET operation voltage, which means the better thermal stability and lower power consumption. The outcomes of this work provide the guidance for designing the high-density phase change memory by reducing the size of Sn15Sb85 thin film.

The influence of coating thickness on laser-induced damage (LID) characteristics of anti-reflection (AR) coatings irradiated by 1064 nm nanosecond laser pulses was investigated. Two HfOsub2/sub/SiOsub2/subAR coatings with different physical thicknesses, 0.7 and 2.7 μm, were prepared and tested. To study the effect of coating thickness on a laser-induced damage threshold (LIDT) in isolation, electric field intensities (EFIs) at the substrate-coating interface were kept the same by using proper AR designs. Moreover, 2 nm artificial gold particles with a density of 10 mmsup-2/supwere implanted into the substrate-coating interface to achieve reliable experimental results. An optical microscope (OM) and a scanning electron microscope (SEM) were used for an online LIDT test and offline LID morphology observation, respectively. The typical LID morphology of thicker AR coatings was flat bottom craters with diameters of 20-50 μm, which can be easily observed by an online OM. For thinner AR coatings, hemispherical craters with diameters down to 1 μm were found as typical LID morphology by a SEM. However, these tiny craters could not be observed by an online OM. Moreover, such tiny craters did not grow with subsequent pulses, so they did not degrade the functional laser damage resistance of the thin AR coatings. When identified with an online OM, the LIDT of thinner AR coatings is found to be about two times higher than the thicker ones, and large delamination was mainly found as the LID morphology of AR coatings with high fluence. When observed with a SEM, the LIDT of thin AR coatings with tiny craters was over 60% lower than the LIDT of thick AR coatings, which agrees with the model that less energy is required to form smaller LID craters of thinner coatings.

To study the effects of tourmaline type and content on the road performance of rubber powder modified asphalt mixture, different types of tourmaline rubber powder modified asphalt mixtures were prepared by adding tourmaline powder instead of equal weight mineral filler into the mixtures. Based on indoor simulation test, the high temperature stability, low temperature crack resistance and water stability of rubber powder modified asphalt mixture under different tourmaline type and content were systematically analyzed. The results show that with the increase of tourmaline powder content, the road performance of asphalt mixtures show an overall growth trend. The 60 °C of rutting test dynamic stability, the -10 °C of bending test flexural-tensile strain, immersion residual Marshall stability and freeze-thaw splitting tensile strength ratio of rubber powder modified asphalt mixtures with tourmaline powder increase by 12.5-19.6%, 7.5-12%, 1.8-4.7% and 1.7-4.3%, respectively.

The dry etching characteristic of new Ti0.5Sb2Te3(TST) phase change material was investigated by using the CF4 and Ar gas mixture. The research mainly focuses on how to optimize the experimental parameters such as gas flow rate within the chamber, CF4 /Ar flow ratio, the chamber background pressure and the incident RF power applied to the lower electrode. The results show that CF4 mainly plays a role of chemical etching and Ar plays a role of physical bombardment. The etching rate of TST films increases with the increasing concentration of CF4 in the gas mixture. The etching chamber pressure has less effect on the TST film etching speed, while the etching power has larger effect. The etch rate is up to 126 nm/min with the smooth etched surface(RMS=0.82 nm) and TST film profile is almost vertical(approaching 90°) using optimized etching parameters, including the total flow rate of 50 sccm, CF4 concentration of 26%, power of 400 W and pressure of 13.3 Pa.

We introduce artificial periodic defects with required size in colloidal photonic crystals by a simple and inexpensive photolithography. The morphology of colloidal photonic crystals with defects is observed by field emission scanning electron microscope (SEM) and optical properties by UV-VIS spectra. We find that the periodic photoresist strips will cause a blue shift and the shift value depends on the the size of periodic photoresist strips.

The influence of coating thickness on laser damage characteristics of HfO2/SiO2 anti-reflection coatings was investigated. Thinner coatings had higher laser-induced damage threshold, because their damage craters were too small to be online detected.

Recently, nanocrystal nonvolatile memory (NVM) devices using nanocrystals (NCs) have attracted great research interest. In this work, we investigated the feasibility of Ni nanocrystals embedded in metal oxide semiconductor (MOS) capacitor structure for NV

In order to investigate transportation of sulfate solution in concrete and its influence factors, transportation velocity and crystallization areas of sulfate solution in concrete, porosity and pore structure of concrete were tested by methods of transportation crystallization test and evaporable water test. Results show that under temperature (20±2)°C and relative humidity (60±5)％ environment, sulfate solution permeate concrete wall and get to concrete surface in very short time. The decrease of water to binder ratio and addition of mineral mixture to concrete can decrease transportation velocity and crystallization areas of sulfate solution in concrete. The transportation velocity and crystallization areas have great correlation with concrete porosity with pore dia. > 30nm.

In order to reduce the RESET current of phase change memory (PCM), which is fabricated using standard 0.13-μm CMOS technology, we have investigated various process factors that might affect the phase transition process, including doping concentration, diameter of bottom electrode contact (BEC) and different chalcogenide materials. Test results suggest that the PCM memory cell, utilizing Si2Sb2Te5 (SST) material as storage element with 80 nm BEC, can be operated using a 40 ns electrical pulse with current amplitude as small as 0.5 mA. This is mainly resulted from the high electrical resistances of the novel chalcogenide both in amorphous and crystalline state, which contribute greatly to the improved efficiency of heating process.

Sn-doped Ge2Sb2Te5 thin films deposited on Si(100)/SiO2 substrates by rf magnetron sputtering are investigated by a differential scanning calorimeter, x-ray diffraction and sheet resistance measurement. The crystallization temperatures of the 3.58 at.%, 6.92 at.% and 10.04 at.% Sn-doped Ge2Sb2Te5 thin films have decreases of 5.3, 6.1 and 0.9°C, respectively, which is beneficial to reduce the switching current for the amorphous-to-crystalline phase transition. Due to Sn-doping, the sheet resistance of crystalline Ge2Sb2Te5 thin films increases about 2–10 times, which may be useful to reduce the switching current for the amorphous-to-crystalline phase change. In addition, an obvious decreasing dispersibility for the sheet resistance of Sn-doped Ge2Sb2Te5 thin films in the crystalline state has been observed, which can play an important role in minimizing resistance difference for the phase-change memory cell element arrays.

Ag-doped Ge2Sb2Te5 films were deposited by rf magnetron sputtering on SiO2/Si substrates. The content of Ag ranging from 4.5 to 11.3 at.% is determined by inductively coupled plasma atomic emission spectrometry. The crystallization temperature of Ag-doped Ge2Sb2Te5 increases with the increasing Ag content and the stability of phase change film is improved greatly. Structures were measured by x-ray diffraction and the face-centered-cubic structure was more stable after Ag doping. Four-point probe was used to measure the sheet resistance of Ag-doped Ge2Sb2Te5 films annealed at different temperatures and it is indicated that Ag atoms increase the sheet resistance of Ge2Sb2Te5 thin film when the annealing temperature is higher than about 360 degrees C, which is beneficial for reducing the reset current. Current-voltage curves were tested and it is demonstrated that 4.5 at.% Ag doping into the Ge2Sb2Te5 film can reduce the threshold current from 1.46 mA to 0.25 mA and can only increase the threshold voltage slightly, which is very useful for low energy consumption.

A single nano-cell-element of chalcogenide-random access memory was fabricated by using the focused ion beam method. The minimum contact size between the Ge2Sb2Te5 phase change film and the top electrode film for the cell element is with diameter of 60 nm. The reversible phase transition between the RESET state and the SET state was successively realized. The minimum SET current is obtained to be about 0.28 mA.

Ge2Sb2Te5 film was deposited by RF magnetron sputtering on Si (100) substrate. The structure of amorphous and crystalline Ge2Sb2Te5 thin films was investigated using XRD, Raman spectra and XPS. XRD measurements revealed the existence of two different crystalline phases, which has a FCC structure and a hexagonal structure, respectively. The broad peak in the Raman spectra of amorphous Ge2Sb2Te5 film is due to the amorphous –Te–Te– stretching. As the annealing temperature increases, the broad peak separates into two peaks, which indicates that the heteropolar bond in GeTe4 and the Sb–Sb bond are connected with four Te atoms and other units such as (TeSb) Sb–Sb (Te2) and (Sb2) Sb–Sb (Te2), where some of the four Te atoms in the above formula are replaced by Sb atoms, remain in crystalline Ge2Sb2Te5 thin film. And from the results of Raman spectra and XPS, higher the annealing temperature, more Te atoms bond to Ge atoms and more Sb atoms substitute Te in (Te2) Sb–Sb (Te2).

In this paper, Ag11In12Te26Sb51 phase change semiconductor films have been prepared by dc sputtering. The crystallization behaviour of amorphous Ag11In12Te26Sb51 thin films was investigated by using differential scanning calorimetry and x-ray diffraction. It was found that the crystallization temperature is about 483K and the melting temperature is 754.8K and the activation energy for crystallization, Ea, is 2.07eV. The crystalline Ag11In12Te26Sb51 films were obtained using initializer. The initialization conditions have a great effect on the sheet resistance of Ag11In12Te26Sb51 films. We found that the effect of the initialization condition on the sheet resistance can be ascribed to the crystallinity of Ag11In12Te26Sb51 films. The sheet resistance of the amorphous (Ramo) film is found to be larger than 1×106Ω and that of the crystalline (Rcry) film lies in the range from about 103 to 104Ω. So we have the ratio Ramo/Rcry=102~103, which is sufficiently large for application in memory devices.

The effect of annealing temperature on crystallization of amorphous Ge2Sb2Te5 films with thickness of 40 nm is studied by TEM and AFM methods. The relationship between microstructure and resistivity of the Ge2Sb2Te5 film is investigated. From the TEM measurements, the grain size of crystallites increases gradually as the annealing temperature increases. When the annealing temperature is too high, voids are formed, which may originate from evaporation of the Ge2Sb2Te5 film at the elevated temperatures, formation of sink, being nucleated by residual vacancies, and surface roughness. The resistivity of the Ge2Sb2Te5 film decreases with the increasing annealing temperature and has slight changes when the temperature is higher than 400 degrees C. Phase transitions and scattering of crystallite boundaries may be the major factors affecting the resistivity of the Ge2Sb2Te5 film.

Amorphous zirconia thin films were deposited directly on silicon-on-insulator (SOI) substrates with thin top silicon by ultra-high vacuum electron beam evaporation. Spreading resistance profile and scanning transmission-electron microscopy (TEM) were used to detect the interface quality and microstructure, revealing that the interface between the zirconium oxide films and top silicon was abrupt and clear. The films kept to be amorphous up to the rapid thermal temperature of 700°C for 300 s, but arriving at 700°C an unknown interfacial product appeared, which was probably ZrSixOy. High frequency capacitance-voltage (C-V) characteristics at 1 MHz performed on metal-oxide-SOI structure revealed that this interfacial product exhibited good electrical properties of zirconia thin films. When the annealing temperature increased from 600°C to 700°C, flat voltage VFB changed from -2.451 to -1.741 eV, showing the improvement in the quality of the films. The cumulative region capacitance decreased from 3.058×10-11F to 3.012×10-11F, indicating increasing equivalent oxide thickness, which is in agreement with the result of high-resolution cross-sectional TEM.

In a compact Nd:Glass resonator, the laser that enters the gain medium at Brewster angle can work either for P-polarization or S-polarization, in which polarization the optical coatings possess higher laser-induced damage threshold (LIDT) was investigated. For the P-polarized configuration, only one high reflection (HR) coating on the rear surface of the Nd:Glass substrate is needed, and the laser-induced damage occurred near the substrate-coating interface at a fluence of 10 ± 2 J/cmsup2/sup(1064nm 10ns). Although S-polarized configuration needs two coatings, one HR coating and one anti-reflection (AR) coating on the rear and front surface of the Nd:Glass substrate respectively, its overall LIDT was about 1.8 times higher than that of the P-polarized configuration. The laser-induced damage occurred at the interface between the S-polarized AR coating and the Nd:Glass substrate. The observed interfacial damage behaviors were interpreted using a phenomenological model that took the nano-sized absorbers, electric-field intensity (EFI) distribution and coating thickness into consideration.

Si16Sb84-based line cell phase change random access memory (PCRAM), in which the Si16Sb84 phase change line is contacted by TiN electrodes with a nanoscale gap, is fabricated by electron beam lithography The lowest current and measured pulse width for RESET operation are 115 μA and 18 ns, respectively The measured shortest pulse width for recrystallization is 110ns, with applied pulse amplitude of 1.5 V. SET and RESET currents for line cells with different line lengths are determined. Endurance of 106 cycles with a resistance ratio of above 800 has been achieved.

In order to improve the reliability of C-RAM devices, a seamless sub-micro W heating electrode in diameter 260 nm is fabricated with standard 0.18 μm CMOS processing line. Then we successfully manufacture a chalcogenide random access memory device using this seamless sub-micro W heating electrode. The results show good electrical performance, e.g. the reset current of 1.3 mA and the set/reset cycle up to 109 have been achieved.

In order to improve nano-scale phase change memory performance, a super-clean interface should be obtained after chemical mechanical polishing (CMP) of Ge2Sb2Te5 phase change films. We use reactive ion etching (RIE) as the cleaning method. The cleaning effect is analysed by scanning electron microscopy and an energy dispersive spectrometer. The results show that particle residue on the surface has been removed. Meanwhile, Ge2Sb2Te5 material stoichiometric content ratios are unchanged. After the top electrode is deposited, current-voltage characteristics test demonstrates that the set threshold voltage is reduced from 13 V to 2.7V and the threshold current from 0.1mA to 0.025mA. Furthermore, we analyse the RIE cleaning principle and compare it with the ultrasonic method.

Highly arsenic-doped Si-on-insulator (SOI) substrate incorporated with buried MoSi2 layers is fabricated aiming at decreasing the collector series resistance of SiGe heterojunction bipolar transistors (HBTs) on SOI, thereby enhancing cutoff frequency (fT) performance and increasing the maximum value of fT (fTMAX). The fT performance at medium current is enhanced and current required for fT = 15 GHz is reduced by half. The value of fTMAX is improved by 30%.

We report the experimental phenomenon of large resistance change in plasma oxidized TiOx/TiNx film fabricated on W bottom-electrode-contact (W-BEC) array. The W-BEC in diameter 260?nm is fabricated by a 0.18??m CMOS technology, and the TiOx/TiNx cell array is formed by rf magnetron sputtering and reactive ion etching. In current?voltage (I?V) measurement for current-sweeping mode, large snap-back of voltage is observed, which indicates that the sample changes from high-resistance state (HRS) to low-resistance state (LRS). In the I?V measurement for voltage-sweeping mode, large current collapse is observed, which indicates that the sample changes from LRS to HRS. The current difference between HRS and LRS is about two orders. The threshold current and voltage for the resistance change is about 5.0?10?5?A and 2.5?V, respectively. The pulse voltage can also change the resistance and the pulse time is as shorter as 30?ns for the resistance change. These properties of TiOx/TiNx film are comparable to that of conventional phase-change material, which makes it possible for RRAM application.

Ge1Sb2Te4-based chalcogenide random access memory array, with a tungsten heating electrode of 260 nm in diameter, is fabricated by 0.18-μm CMOS technology. Electrical performance of the device, as well as physical and electrical properties of Ge1Sb2Te4 thin film, is characterized. SET and RESET programming currents are 1.6 and 4.1 mA, respectively, when pulse width is 100 ns. Both the values are larger than those of the Ge2Sb2Te5-based ones with the same structure and contact size. Endurance up to 106 cycles with a resistance ratio of about 100 has been achieved.

In order to reduce the reset current of chalcogenide random access memory, a W sub-microtube heater electrode with outer/inner diameter of 260/100 nm, which was fabricated with standard 0.18-μm technology, is proposed for the first time to achieve a reset current of about 0.5 mA. The reasons may be that sub-microtube increases the number of electrode edge and thermal efficiency is improved greatly because the thermal density on the edge of sub-microtube electrode is generally the highest.

We investigate the effect of chemicals on chemical mechanical polishing (CMP) of glass substrates. Ceria slurry in an ultra-low concentration of 0.25 wt.% is used and characterized by scanning electron microscopy. Three typical molecules, i.e. acetic acid, citric acid and sodium acrylic polymer, are adopted to investigate the effect on CMP performance in terms of material removal rate (MRR) and surface quality. The addition of sodium acrylic polymer shows the highest MRR as well as the best surface by atomic force microscopy after CMP, while the addition of citric acid shows the worst performance. These results reveal a mechanism that a long-chain molecule without any branches rather than small molecules and common molecules with ramose abundant-electron groups is better for the dispersion of the slurry and thus better for the CMP process.

Phase change memory (PCM) cell array is fabricated by a standard complementary metal–oxide–semiconductor process and the subsequent special fabrication technique. A chalcogenide Ge2Sb2Te5 film in thickness 50 nm deposited by rf magnetron sputtering is used as storage medium for the PCM cell. Large snap-back effect is observed in current–voltage characteristics, indicating the phase transition from an amorphous state (higher resistance state) to the crystalline state (lower resistance state). The resistance of amorphous state is two orders of magnitude larger than that of the crystalline state from the resistance measurement, and the threshold current needed for phase transition of our fabricated PCM cell array is very low (only several μA). An x-ray total dose radiation test is carried out on the PCM cell array and the results show that this kind of PCM cell has excellent total dose radiation tolerance with total dose up to 2×106 rad(Si), which makes it attractive for space-based applications.

A damascene structure of phase change memory (PCM) is fabricated successfully with the chemical mechanical polishing (CMP) method, and the CMP of Ge2Sb2Te5 (GST) and Ti films is investigated. The polished surface of wafer is analysed by scanning electron microscopy (SEM) and an energy dispersive spectrometer (EDS). The measurements show that the damascene device structure of phase change memory is achieved by the CMP process. After the top electrode is deposited, dc sweeping test on PCM reveals that the phase change can be observed. The threshold current of array cells varies between 0.90 mA and 1.15 mA.

We observe reversible phase transition phenomena in proto-type chalcogenide random access memory (C-RAM) devices adopting ultra-thin (12 nm) Ge2Sb2Te5 thin film. In this kind of proto-type device, the ultra-thin amorphous Ge2Sb2Te5 thin film undergoes a crystallization process when a voltage is applied. The polycrystalline Ge2Sb2Te5 remain unchanged when the voltage is below 0.6 V. A higher power is needed if the transition from polycrystalline to amorphous is expected. The re-amorphization process can be realized by applying a voltage higher than 0.7 V. The threshold voltage Vth and threshold electric field Eth of the transition from the polycrystalline state to the amorphous state in this proto-type device are ~0.7 V and ~5×105 V/cm, respectively. The programming voltage is significantly reduced compared to the values of C-RAM devices adopting a 200-nm-thick Ge2Sb2Te5 inset.

We report on the fabrication and characterization of a ZnO-based film-bulk acoustic-resonance device utilized as biosensor. The device has a multilayer structure which consists of piezoelectric element (Au/ZnO/Pt) and a Bragg-reflection-layer acoustic isolation consisting of multilayers of ZnO/Pt. Dielectric measurements have revealed that the device has a very high working frequency (up to ~3.1 GHz), meaning that the device may have a higher sensitivity than the devices reported in the literature.

Preferentially oriented cubic boron nitride films on nickel substrates have been grown using hot-filament-assisted rf plasma chemical vapor deposition method. X-ray photoelectron spectroscopy shows that the cubic boron nitride films are stoichiometric. Scanning electron microscopy and x-ray diffraction show that the films are of high quality with well-faceted and (220) preferentially oriented grains, without x-ray diffraction detectable hexagonal boron nitride phase. The nucleation and growth process has been investigated. After 40 min deposition, well aligned, well faceted cubic boron nitride nuclei can be seen on the substrates, and after 2 h deposition, the rectangular grains can be seen on the substrate with their corresponding edges parallel to each other in scanning electron microscopic images. The ratio of the diffraction peak height of (220) face to that of (111) face is about 5.2 in the x-ray diffraction pattern, but the corresponding value of the random cubic boron nitride crystallites is only 0.06.