Preparation of AIN thin films for film bulk acoustic resonator application by radio frequency sputtering

Aluminum nitride (AIN) thin films with high c-axis orientation have been prepared on a glass substrate with an A1bottom electrode by radio frequency (RF) reactive magnetron sputtering. Based on the analysis of Berg's hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AIN thin films is proposed. The N2 concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 ℃, a target-substrate distance of 60 mm and a N2 concentration of 25%, AIN thin film with prefer-ential (002) orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction (XRD) analysis, the full width at half maximum (FWHM) of AIN (002) was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AIN thin film. With other parameters held constant, any increase or decrease in N2 con-centration results in an increase in the FWHM of AIN.     

Characterization of DC magnetron sputtering deposited thin films of TiN for SBN/MgO/TiN/Si structural waveguide

INTRODUCTION Monocrystalline SBN (Strontium barium nio-bium, SrxBa1?xNb2O6, denoted SBNx?100, where 0.25≤x≤0.75) solid solution, is currently being inves-tigated as potential material for many micro-device applications, such as piezoelectric infrared detectors, piezoelectric, electro-optic modulators, and holo-graphic storage (Koch et al., 1998), because SBN has one of the largest known linear electro-optic coeffi-cients (r33=1300 pm/V for SBN75), two orders of magnitude larger th…     

Polycrystalline ZnS<Subscript>x</Subscript>Se<Subscript>1−x</Subscript> thin films deposited on ITO glass by MBE

MBE growth of ZnS_xSe_1−x thin films on ITO coated glass substrates were carried out using ZnS and Se sources with the substrate temperature ranging from 270°C to 330°C. The XRD σ/2σ spectra resulted from these films indicated that the as-grown polycrystalline ZnS_xSe_1−x thin films had a preferred orientation along the (111) planes. The evaluated crystal sizes as deduced from the FWHM of the XRD layer peaks showed strong growth temperature dependence, with the optimized temperature being about 290 °C. Both AFM and TEM measurements of these thin films also indicated a similar growth temperature dependence. High quality ZnS_xSe_1−x thin film grown at the optimized temperature had the smoothest surface with lowest RMS value of 1.2 nm and TEM cross-sectional micrograph showing a well defined columnar structure. Project supported by the National Science Council of PRC (No. 59910161981) and RGC grant from the Hong Kong Government under Grant (No. NS-FC/HKUST 35)     

Two-parameter characterization of low cycle, hysteretic fatigue data

The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis. Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel. Results demonstrate that the mechanical hysteresis loop areas, when plotted as a function of the number of loading cycles, show significant variations and demonstrate the three principal stages concerning the progress of the fatigue failure--initial accommodation, accretion of damage and terminal failure. These three stages of fatigue are marked by the transitions at cycles N2 and N3. Experimental results show that although fatigue life Nf ranges from 2644 cycles to 108 992 cycles, the ratios of N2/Nf and N3/Nf tend to be stable： N2/Nf=I 0.7%, N3/Nf=91.3%.     

Studies on characteristics of nanostructure of N-TiO2 thin films and photo-bactericidal action

Pseudomonas aeruginosa strain （AS 1.50） and Bacillus subtilis strain （AS 1.439） from Ming lake were decomposed by photocatalytic nanostructure N-TiO2 thin films in a photo-reactor under UV irradiation. The different thickness nanostructure N-TiO2 thin films coated on mesh grid were prepared by sol-gel method and immobilized at 500 ℃ （films A） or 350 ℃ （films B） for 1 h in a muffle furnace. The results showed that N-TiO2 thin film B （8.18 nm thickness, 2.760 nm height and 25.15 nm diameter） has more uniform granular nanostructure and thinner flat texture than N-TiO2 thin film A （12.17 nm thickness, 3.578 nm height and 27.50 nm diameter）. The bactericidal action of N-TiO2 thin film A and film B for Pseudomonas aeruginosa strain （AS 1.50） and Bacillus subtilis varniger strain （AS1.439） were investigated in this work. More than 95% of photocatalytic bactericidal efficiency for Pseudomonas aeruginosa strain （AS 1.50） and 75% for Bacillus subtilis strain （AS 1.439） were achieved by using N-TiO2 thin films-B for 70-80 rain of irradiation during the photo-bactericidal experimental process. The results indicated that the photo-induced bactericidal efficiency of N-TiO2 thin films probably depended on the characteristics of the films.     

Dependence of electrical and optical properties of IGZO films on oxygen flow

Amorphous InGaZnO (a-IGZO) films were deposited on the corning eagle XG (EXG) glass substrates using magnetron sputtering method. The structure, surface morphology, electrical and optical properties of these films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), semiconductor parameter analyzer and spectrophotometry, respectively. The influence of oxygen flow on the electrical properties of IGZO thin films was studied, showing that increasing oxygen flow changes the resistivity with six orders of magnitude. The contact resistance of ITO/IGZO is 7.35×10⁻² Ω·cm², which suggests that a good ohmic contact exists between In₂O₃: Sn (ITO) and IGZO film.     

Electrochemical study on semiconductive properties of the passive film on rebar in concrete

INTRODUCTION Steel rebar embedded in concrete is protectedagainst corrosion by the thin passive film on its sur-face and the physical protection from concrete. Thealkaline environment (pH≥12.5) of the concrete poresolution triggers passivation on the rebar surface andformation of the protective oxide film. The physicaprotection of concrete coverage hinders the invasionof aggressive agents. However, this passivity can bebroken down by local pH loss as a result of concretecracking or the…     

ZnS<Subscript>0.8</Subscript>Se<Subscript>0.2</Subscript> film for high resolution liquid crystal light valve

The structural characteristics and optical and electrical properties of molecular-beam-epitaxy (MBE) grown ZnS_0.8Se_0.2 thin films on indium-tin-oxide(ITO) glas substrates were investigated in this work. TheX-ray diffraction (XRD) results indicated that high quality polycrystalline ZnS_0.8Se_0.2 thin film grown at the optimized temperature had a prefered orientation along the (111) planes. The transmission electron microscopy (TEM) cross-sectional micrograph of the sample showed a well defined columnar structure with lateral crystal dimension in the order of a few hundred angstroms. Ultraviolet (UV) photoresponsivity as high as 0.01 A/W had been demonstrated and for wavelengths longer than 450 nm, the response was down from the peak response by more than 3 orders of magnitude. The thin ZnS_0.8Se_0.2 photosensor layer, with a wide energy gap and anisotropic electrical property, makes a transmission UV liquid crystal light valve (LCLV) with high resolution feasible. Project supported by the National Natural Science Foundation of China (No. 59910161981) and RGC grant from the Hong Kong Government Grant (No. NSFC/HKUST 35), China     

Left-handed materials in magnetized metallic magnetic thin films

INTRODUCTION Veselago (1968) showed that if both the permit- tivity ε and the magnetic permeability μ of a material are negative, the propagation direction of an elec- tromagnetic (EM) wave will be opposite to its energy flow direction. Such media are called left-handed materials (LHMs) since the electric field E, magnetic field H, and wave vector k in these media form a left-hand triplet of vectors, instead of a right-hand triplet observed in conventional materials. For a long time, …     

Thin film chip resistors with high resistance and low temperature coefficient of resistance

High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 type thin film chip resistors when the deposition time was about 11 min and deposition films were annealed at 500 ℃ for 120 min.The morphologies of Cr-Si-TaAl film surfaces were examined by scanning electron microscopy(SEM).The analysis suggests that Ta and Al may be distributed in CrSi2 film with mixed form of several structures(e.g.,bridge-like,capillary-like or island-like structures),and such a structure distribution is responsible for high film resistance and low TCR of Cr-Si-Ta-Al film.     

Characteristics of bottom gate a-Si TFT array for AM-OLEDs

The authors have fabricated bottom gate amorphous silicon thin film transistor (a-Si TFT) array using five-step lithography process.The device shows a field effect mobility of 0.43 cm 2 /(V·s),on/off ratio of 7.5×10 6 and threshold voltage of 0.87 V.The instability of a-Si TFT is ascribed to the defect state in the a-Si channel and SiNx/a-Si interface.The present a-Si TFT array with SiN x insulator could be a significant step towards the commercialization of active matrix organic lighting diode (AM-OLED) te...     

脉冲激光沉积法在多孔硅衬底上制备ZnS薄膜

用电化学阳极氧化法制备了一定孔隙率的多孔硅样品,然后用脉冲激光沉积法以PS为衬底生长一层ZnS薄膜.用X射线衍射仪、扫描电子显微镜和荧光分光光度计分别表征了ZnS薄膜的结构、形貌和ZnS/PS复合膜的光致发光性质.XRD结果表明,制备的ZnS薄膜沿β-ZnS(111)方向择优生长,结晶质量良好,但衍射峰的半峰全宽较大;SEM图像显示,ZnS薄膜表面出现一些凹坑,这是衬底PS的表面粗糙所致.室温下的光致发光谱表明,沉积ZnS薄膜后,PS的发光峰蓝移.把ZnS的蓝绿光与PS的橙红光叠加,在可见光区450~700 nm形成了一个较宽的光致发光谱带,ZnS/PS复合膜呈现较强的白光发射.     

Preparation and Characterization of Nano-Particles PZT Ferroelectric Thin Films by RF-Magnetron Sputtering

Pt/Ti bottom electrodes were fabricated on SiO2/Si substrates by magnetron dual-facing-target sputtering system. Lead zirconate titanate(PZT) thin films were deposited on Pt/Ti/ SiO2/Si substrates by radio frequency (RF) magnetron sputtering system. The thickness of PZT thin films which were deposited for 5 h was about 800 nm. XRD spectra show that PZT thin films deposited in Ar ambience and rapid-thermal-annealed for 20 min at 700 ℃ have good crystallization behavior and perovskite structure. AFM micrographs show that mean diameter of crystallites is 70 nm and surface structures of PZT thin films are uniform and dense. Raw mean, root mean square roughness and mean roughness of PZT thin films are 34.357 nm, 2.479 nm and 1.954 nm respectively. As test frequency is 1 kHz, dielectric constant of PZT thin films is 327.6. Electric hysteresis loop shows that coercive field strength, residual polarization strength and spontaneous polarization strength of PZT thin films are 50 kV/cm, 10 μC/cm2 and 13 μC/cm2 respectively.     

Polycrystalline ZnSxSe1-x thin films deposited on ITO glass by MBE

MBE growth of ZnSxSe1-x thin films on ITO coated glass substrates were carried out using ZnS and Se sources with the substrate temperature ranging from 270℃ to 330℃. The XRD θ/2θ spectra resulted from these films indicated that the as-grown polycrystalline ZnSxSe1-x thin films had a preferred orientation along the (111) planes. The evaluated crystal sizes as deduced from the FWHM of the XRD layer peaks showed strong growth temperature dependence, with the optimized temperature being about 290℃. Both AFM and TEM measurements of these thin films also indicated a similar growth temperature dependence. High quality ZnSxSe1-x thin film grown at the optimized temperature had the smoothest surface with lowest RMS value of 1.2 nm and TEM cross-sectional micrograph showing a well defined columnar structure.     

铝掺杂氧化锌薄膜的制备及其特性

采用直流反应磁控溅射法,制备了铝掺杂的氧化锌薄膜.结果显示：薄膜在500℃退火后透光率高,光敏特性良好,并且有明显的紫外光响应.其XRD衍射谱表明随着O2与Ar流量比的增加,对应于（002）晶面的衍射峰趋于尖锐,c轴取向突出明显.     

Experimental study on the inhibition of biological reduction of Fe(III)EDTA in NO x absorption solution

Scrubbing of NO _x from the gas phase with Fe(II)EDTA has been shown to be highly effective. A new biological method can be used to convert NO to N₂ and regenerate the chelating agent Fe(II)EDTA for continuous NO absorption. The core of this biological regeneration is how to effectively simultaneous reduce Fe(III)EDTA and Fe(II)EDTA-NO, two mainly products in the ferrous chelate absorption solution. The biological reduction rate of Fe(III)EDTA plays a main role for the NO _x removal efficiency. In this paper, a bacterial strain identified asKlebsiella Trevisan sp. was used to demonstrate an inhibition of Fe(III)EDTA reduction in the presence of Fe(II)EDTA-NO. The competitive inhibition experiments indicted that Fe(II)EDTA-NO inhibited not only the growth rate of the iron-reduction bacterial strain but also the Fe(III)EDTA reduction rate. Cell growth rate and Fe(III)EDTA reduction rate decreased with increasing Fe(II)EDTA-NO concentration in the solution. Project (No. 20176052) supported by the National Natural Science Foundation of China and the Scientific Research Foundation for Returned Overseas Chinese Scholars, Ministry of Education     

Application of near-infrared spectroscopy to predict sweetpotato starch thermal properties and noodle quality

Sweetpotato starch thermal properties and its noodle quality were analyzed using a rapid predictive method based on near-infrared spectroscopy （NIRS）. This method was established based on a total of 93 sweetpotato genotypes with diverse genetic background. Starch samples were scanned by NIRS and analyzed for quality properties by reference methods. Results of statistical modelling indicated that NIRS was reasonably accurate in predicting gelatinization onset temperature （To） （standard error of prediction SEP=2.014 ℃, coefficient of determination RSQ=0.85）, gelatinization peak temperature （Tp） （SEP=-1.371 ℃, RSQ=0.89）, gelatinization temperature range （Tr） （SEP=2.234 ℃, RSQ=0.86）, and cooling resistance （CR） （SEP=0.528, RSQ=0.89）. Gelatinization completion temperature （To）, enthalpy of gelatinization （△H）, cooling loss （CL） and swelling degree （SWD）, were modelled less well with RSQ between 0.63 and 0.84. The present results suggested that the NIRS based method was sufficiently accurate and practical for routine analysis of sweetpotato starch and its noodle quality.     

An analog front-end circuit for ISO/IEC 15693-compatible RFID transponder IC

INTRODUCTION The rapidly increasing application of radio fre- quency identification (RFID) includes supply chain management, access control to buildings, public transportation, airport baggage, and express parcel logistics (Karthaus and Fischer, 2003; Feldhofer, 2004; Glidden et al., 2004). Using an RFID system is a good approach for automated identification of products. RFID system consists of two major components, an interrogator (reader) and a transponder (tag), composed of an ant…     

Multiple pathways of integration: Acculturative change and associations with school adjustment in immigrant-origin adolescents

Tracing developmental pathways of immigrant-origin adolescents, this 3-year longitudinal study (2012–2015) examined within-person changes in cultural orientations and their consequences for school adjustment. Multivariate latent growth mixture modeling confirmed multiple pathways of integration, revealing variable acculturative changes along dual trajectories of heritage and mainstream orientations among European-origin (N = 592, M_age = 14.45, 55.1% boys) and Turkish- and Moroccan-origin adolescents (N = 1269, M_age = 14.70, 53.1% boys). Two trajectories for European-origin adolescents differed in heritage orientations (high decreasing and low increasing); for Turkish- and Moroccan-origin adolescents, three trajectories differed in mainstream orientations (high stable, low increasing, and high decreasing). Acculturative change affected aspects of later school adjustment: European-origin adolescents in high heritage orientation trajectories reported more belonging and emotional engagement; Turkish- and Moroccan-origin adolescents in high mainstream orientation trajectories reported more behavioral engagement.     

磁控溅射TiN薄膜及其性能研究

以直流反应磁控溅射方法在Si（111）基底上制备薄膜TiN.研究发现：在保持其他工艺参数不变的条件下,溅射气压在0.3～1.3 Pa范围内,薄膜的主要成分是（111）择优取向的立方相TiN.当溅射气压为0.5 Pa时,沉积的薄膜膜层致密均匀,色泽金黄,膜厚为115.8 nm,结晶性能好.在可见光区半透明而在红外光区呈高反射,红外反射率为90%,具有良好的太阳光谱选择性.