Carbon concentration dependent grain growth of Cu2ZnSnS4thin films

Organic solvents are commonly used in ink precursors of Cu2ZnSnS4 (CZTS) nanocrystals to make thin films for applications such as solar cells. However, the traces of carbon residual left behind by the organic solvents after high-temperature annealing is generally considered to restrict the growth of nanocrystals to form large grains. This work reported the first systematic study on the influence of carbon content of organic solvents on the grain growth of CZTS nanomaterial during high temperature sulfurization annealing. Solvents with carbon atom per molecule varying from 3 to 10 were used to made ink of CZTS nanocrystals for thin film deposition. It has been found that, after high temperature sulfurization annealing, a bilayer structure was formed in the CZTS film using organic solvent containing 3 carbon atoms per solvent molecule based on glycerol and 1,3-propanediol. The top layer consisted of closelypacked large grains and the bottom layer was made of as-synthesized nanoparticles. In contrast, the CZTS film made with the solvent molecule with more carbon atoms including 1,5-pentanediol (5 carbon atoms) and 1,7-heptanediol (7 carbon atoms) consisted of nanoparticles embedded with large crystals. It is believed that the carbon residues left behind by the organic solvents affected the necking of CZTS nanocrystals to form large grains through influencing the surface property of nanocrystals. Furthermore, it has also been observed that the solvent affected the thickness of MoS2 layer which was formed between CZTS and Mo substrate. A thinner MoS2 film (50 nm) was obtained with the slurry using carbon-rich terpineol as solvent whereas the thickest MoS2 (350 nm) was obtained with the film made from 1,3-propanediol based solvent. The evaluation of the photoactivity of the CZTS thin films has demonstrated that a higher photocurrent was generated with the film containing more large grains.

Effect of Thickness on The Optical Properties Change in Bi/As2S3 Bilayer Thin Films

Bilayer thin films of Bi/As2S3 were prepared from Bi and As2S3 by thermal evaporation technique under high vacuum. We have prepared three bilayer films of 905nm, 910nm and 915nm thickness with with As2S3 as bottom layer (900nm) and Bi as top layer (5,10,15 nm). We have compared the optical changes due to the thickness variation of Bi layer on As2S3 film. The changes were characterized by FTIR and XPS techniques.

Miniaturized Defected Ground High Isolation Crossovers

This letter relates to the design of crossovers for carrying criss crossing signals. Two types of crossovers are proposed in this letter. Both the crossovers are designed using a two layer printed circuit board. An unbroken continuous transmission line is routed in the top layer for carrying signal 1 from one node to another node. Transmission line used for carrying a signal 2 consists of three physically discontinuous, but electrically connected segments. Two end segments of these are located in the top layer while the middle segment is placed in the bottom layer. While Type I crossover offers an isolation of 25 dB, Type II crossover offers isolation better than 35 dB from dc to 10 GHz. These crossovers are compact and measure an actual size of 10 x 10 x 0.78 mm(3).

Enhancing the photocatalytic efficiency of sprayed ZnO thin films through double doping (Sn plus F) and annealing under different ambiences

Doubly (Sn + F) doped zinc oxide (ZnO:Sn:F) thin films were deposited onto glass substrates using a simplified spray pyrolysis technique. The deposited films were annealed at 400 degrees C under two different ambiences (air and vacuum) for 2 h. The photocatalytic activity of these films was assessed through photocatalytic decolorization kinetics of Methylene Blue (MB) dye and the decolorization efficiency of the annealed films was compared with that of their as-deposited counterpart. The photocatalytic studies reveal that the ZnO:Sn:F films annealed under vacuum environment exhibits better photocatalytic efficiency when compared with both air annealed and as-deposited films. The SEM and TEM images depict that the surface of each of the films has an overlayer comprising of nanobars formed on a bottom layer, having spherical grains. The studies show that the diameter of the nanobars plays crucial role in enhancing the photocatalytic activity of the ZnO:Sn:F films. The structural, optical and electrical studies substantiate the discussions on the photocatalytic ability of the deposited films. (C) 2014 Elsevier B.V. All rights reserved.

Fabrication of back contacts using laser writer and photolithography for inscribing textured solar cells

Semiconductor fabrication process begins with photolithography. Preparing a photo mask is the key process step in photolithography. The photo mask was fabricated by inscribing patterns directly onto a soda lime glass with the help of a laser beam, as it is easily controllable. Laser writer LW405-A was used for preparing the mask in this study. Exposure wavelength of 405 nm was used, with which 1.2 mu m feature size can be written in direct write-mode over the soda lime glass plate. The advantage of using the fabricated mask is that it can be used to design back contacts for thin film Photovoltaic (PV) solar cells. To investigate the process capability of LW405-A, same pattern with different line widths was written on soda lime glass samples at different writing speeds. The pattern was inscribed without proximity effect and stitching errors, which was characterized using optical microscope and field emission scanning electron microscope (FE-SEM). It was proven that writing speed of a mask-writer is decided according to the intended feature size and line width. As the writing speed increases, the edges of the patterns become rougher due to uneven scattering of the laser beam. From the fabricated mask, the solar cell can be developed embedding both the contacts at the bottom layer, to increase the absorption of solar radiation on the top surface effectively by increasing light absorption area.

Nutrient distributions for Georges Bank and adjacent waters in 1979

In this report we describe the temporal and spatial distributions of inorganic nutrients over Georges Bank and in adjacent waters and discuss major features with respect to tbe nutrient environments of pbytoplankton. Nitrate and orthophosphorus were rapidly depleted from the surface layer of much of the study area in spring, but major differences were found between the shallow areas on Georges Bank and the surrounding stratified waters. In the "well-mixed" area of Georges Bank, the depletion encompassed the entire water column and ammonium became the dominant form of inorganic nitrogen throughout. Dissolved silicon was depleted slowly over central Georges Bank, reaching a minimum concentration in September while orthophosphorus gradually increased during the summer. The nutrient environment of phytoplankton over central Georges Bank may be described as vertically uniform but temporally changing in the relative availability of the various nutrients. In areas that undergo stratification (e.g., the central Gulf of Maine), a quasi-steady state was established as the surface water layer formed, consisting of declining nutrient gradients from below the euphotic layer to the top of the water column. These intergrading nutrient environments are relatively stable through time. Destratification reintroduced nutrients to depleted areas beginning in October; however, dissolved silicon was again depleted over shallow Georges Bank in late autumn though nitrate remained abundant. Slope water has been found to enter the bottom layer of the Gulf of Maine via the Northeast Channel. High nutrient concentrations observed in the bottom water of the Northeast Channel are consistent with this mechanism being the nutrient source for the Gulf of Maine. (PDF file contains 40 pages.)

Jungfischsituation in der Nordsee wenig ermutigend

In order to investigate the abundanceand strength of most recent year classes of cod,haddock, whiting, Norway pout, herring, sprat, and mackerel seven researchvessels of ICES member states carried out a bottom trawl survey in the North Sea in January/February 1996. Germany took part in these investigations by R.V. "Walther Herwig III" from January 19 to February 9 covering 62 out of 332 international stations. No substantial positive or negative results concerning the incoming year classes were obtained. As expected, the hydrographc situation of the area under investigation was strongly influenced by the actual weather: On the one hand, the continuous cooling of the surface layer by cold air caused vertical mixing down into the bottom layer in larger areas, and led to decreasing water temperatures which were below the long term values in nearly all the North Sea at the end of the investigation period. On the other hand, the continuous southern to eastern winds over the North Sea led to horizontal water mass transports renewing vertical salinity differences and inducing regionally positive as weH as negative salinity anomalies of up to 0.6· 10-3. ,

Quantum Mechanics Studies of Fuel Cell Catalysts and Proton Conducting Ceramics with Validation by Experiment

We carried out quantum mechanics (QM) studies aimed at improving the performance of hydrogen fuel cells. This led to predictions of improved materials, some of which were subsequently validated with experiments by our collaborators.

In part I, the challenge was to find a replacement for the Pt cathode that would lead to improved performance for the Oxygen Reduction Reaction (ORR) while remaining stable under operational conditions and decreasing cost. Our design strategy was to find an alloy with composition Pt3M that would lead to surface segregation such that the top layer would be pure Pt, with the second and subsequent layers richer in M. Under operating conditions we expect the surface to have significant O and/or OH chemisorbed on the surface, and hence we searched for M that would remain segregated under these conditions. Using QM we examined surface segregation for 28 Pt₃M alloys, where M is a transition metal. We found that only Pt₃Os and Pt₃Ir showed significant surface segregation when O and OH are chemisorbed on the catalyst surfaces. This result indicates that Pt₃Os and Pt3Ir favor formation of a Pt-skin surface layer structure that would resist the acidic electrolyte corrosion during fuel cell operation environments. We chose to focus on Os because the phase diagram for Pt-Ir indicated that Pt-Ir could not form a homogeneous alloy at lower temperature. To determine the performance for ORR, we used QM to examine all intermediates, reaction pathways, and reaction barriers involved in the processes for which protons from the anode reactions react with O₂ to form H₂O. These QM calculations used our Poisson-Boltzmann implicit solvation model include the effects of the solvent (water with dielectric constant 78 with pH 7 at 298K). We found that the rate determination step (RDS) was the O_ad hydration reaction (O_ad + H₂O_ad -> OH_ad + OH_ad) in both cases, but that the barrier for pure Pt of 0.50 eV is reduced to 0.48 eV for Pt₃Os, which at 80 degrees C would increase the rate by 218%. We collaborated with the Pu-Wei Wu’s group to carry out experiments, where we found that the dealloying process-treated Pt2Os catalyst showed two-fold higher activity at 25 degrees C than pure Pt and that the alloy had 272% improved stability, validating our theoretical predictions.

We also carried out similar QM studies followed by experimental validation for the Os/Pt core-shell catalyst fabricated by the underpotential deposition (UPD) method. The QM results indicated that the RDS for ORR is a compromise between the OOH formation step (0.37 eV for Pt, 0.23 eV for Pt_2ML/Os core-shell) and H₂O formation steps (0.32 eV for Pt, 0.22 eV for Pt_2ML/Os core-shell). We found that Pt_2ML/Os has the highest activity (compared to pure Pt and to the Pt₃Os alloy) because the 0.37 eV barrier decreases to 0.23 eV. To understand what aspects of the core shell structure lead to this improved performance, we considered the effect on ORR of compressing the alloy slab to the dimensions of pure Pt. However this had little effect, with the same RDS barrier 0.37 eV. This shows that the ligand effect (the electronic structure modification resulting from the Os substrate) plays a more important role than the strain effect, and is responsible for the improved activity of the core- shell catalyst. Experimental materials characterization proves the core-shell feature of our catalyst. The electrochemical experiment for Pt_2ML/Os/C showed 3.5 to 5 times better ORR activity at 0.9V (vs. NHE) in 0.1M HClO₄ solution at 25 degrees C as compared to those of commercially available Pt/C. The excellent correlation between experimental half potential and the OH binding energies and RDS barriers validate the feasibility of predicting catalyst activity using QM calculation and a simple Langmuir–Hinshelwood model.

In part II, we used QM calculations to study methane stream reforming on a Ni-alloy catalyst surfaces for solid oxide fuel cell (SOFC) application. SOFC has wide fuel adaptability but the coking and sulfur poisoning will reduce its stability. Experimental results suggested that the Ni4Fe alloy improves both its activity and stability compared to pure Ni. To understand the atomistic origin of this, we carried out QM calculations on surface segregation and found that the most stable configuration for Ni₄Fe has a Fe atom distribution of (0%, 50%, 25%, 25%, 0%) starting at the bottom layer. We calculated that the binding of C atoms on the Ni4Fe surface is 142.9 Kcal/mol, which is about 10 Kcal/mol weaker compared to the pure Ni surface. This weaker C binding energy is expected to make coke formation less favorable, explaining why Ni₄Fe has better coking resistance. This result confirms the experimental observation. The reaction energy barriers for CHx decomposition and C binding on various alloy surface, Ni₄X (X=Fe, Co, Mn, and Mo), showed Ni₄Fe, Ni₄Co, and Fe₄Mn all have better coking resistance than pure Ni, but that only Ni₄Fe and Fe₄Mn have (slightly) improved activity compared to pure Ni.

In part III, we used QM to examine the proton transport in doped perovskite-ceramics. Here we used a 2x2x2 supercell of perovskite with composition Ba₈X₇M₁(OH)₁O₂₃ where X=Ce or Zr and M=Y, Gd, or Dy. Thus in each case a 4⁺ X is replace by a 3⁺ M plus a proton on one O. Here we predicted the barriers for proton diffusion allowing both includes intra-octahedron and inter-octahedra proton transfer. Without any restriction, we only observed the inter-octahedra proton transfer with similar energy barrier as previous computational work but 0.2 eV higher than experimental result for Y doped zirconate. For one restriction in our calculations is that the O_donor-O_acceptor atoms were kept at fixed distances, we found that the barrier difference between cerates/zirconates with various dopants are only 0.02~0.03 eV. To fully address performance one would need to examine proton transfer at grain boundaries, which will require larger scale ReaxFF reactive dynamics for systems with millions of atoms. The QM calculations used here will be used to train the ReaxFF force field.

Hydroacoustic study of spatial and temporal distribution of Gymnocypris przewalskii (Kessler, 1876) in Qinghai Lake, China

Gymnocypris przewalskii (Kessler 1876) is an endangered and state-protected rare fish species in Qinghai Lake, China. To further understand the life history and distribution of this fish, five surveys were carried out in Qinghai Lake between 2002-2006. Results of these surveys indicate that fishes were predominantly distributed about 2 m under the surface. In July, significant differences in fish density were found between surface and bottom layers (P = 0.001), and/or between middle and bottom layers (P = 0.025). Fish density was the greatest in the surface layer. In August and October, no significant differences were found between the different layers, but the bottom layer had a greater fish density. Furthermore, there were very large differences among different zones in fish distribution density. Differences in horizontal distribution were not significantly correlated to factors such as water depth and inshore distance, possibly because of very low and uniform fish density. Feeding, changes in water temperature, over-wintering and spawning appeared to influence fish distribution. Hydroacoustic estimates of G. przewalskii biomass in Qinghai Lake increased significantly between 2002 and 2006. We attribute this increase to the management measures put in place to protect this species.

Enhanced photocatalytic activity of TiO2 nano-structured thin film with a silver hierarchical configuration

TiO2 sol-gels with various Ag/TiO2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO2 sol-gel, four types of the TiO2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO,), TA (bottom layer was pure TiO,, surface layer was Ag modified), TT (pure TiO, thin film) and AA (TiO, thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (I-ph). LSV confirmed the existence of Ago state in the TiO, thin film. SEM and XRD experiments indicated that the sizes of the TiO,, nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film.

岷江上游高山林线附近优势树种土壤种子库和幼苗更新特征的研究

岷江上游地区高山/亚高山植被分布的坡向性分异显著，阴阳坡高山林线不仅物种组成差异明显，并且分布海拔呈现出阴坡高阳坡低的格局．阳坡林线树种主要是圆柏属乔木，林线类型多为渐变型，海拔高度大约在3 400m~3 800m；阴坡林线树种主要是冷杉，林线类型多为骤变型，海拔高度约在3 800m~4 400m．本研究采用土壤种子库物理筛选、室内萌发实验及野外群落调查等方法，对岷江上游地区阴坡岷江冷杉和阳坡祁连圆柏两类林线树种不同海拔梯度上土壤种子库以及幼苗库特征进行了调查，从土壤种子库和幼苗更新特征的角度对林线乔木树种种群更新特征进行了分析，进而对该地区高山林线在阴阳坡分布差异的原因进行了探讨，结果显示： 1．土壤种子库 阴坡：阴坡高山林线附近岷江冷杉土壤种子的平均密度大约为50.96粒/m2，其中树线以上10m处土壤种子密度为1.00粒/m2，树线处大约19.33粒/m2，林线交错带内土壤种子密度最高为136.83粒/m2，郁闭林内种子密度小于林线交错带，只有30.50粒/m2，种子平均空壳率为52％，霉变率达34%，完好种子只有6%．土壤种子库垂直分布特征为地被物层含种子比重最大，大约在67.50%左右；其次为0~2cm层，约18.84%左右；2~5cm层所占种子比例最小，约13.66%左右．霉变种子数量与土壤深度呈负相关． 阳坡：阳坡祁连圆柏土壤种子的平均密度为60.16粒/m2．树线以上10m处密度为1.92粒/m2，树线位置大约108.16粒/m2，林线交错带内平均为75.80粒/m2，郁闭林内种子密度小于林线交错带，只有20.00粒/m2．种子平均空壳率为36％，完好种子占49%，霉变率较低，大约为10%．阴阳坡林线树种土壤种子库垂直分布特征为：地被物层含种子最多，其次为0~4cm层，4~10cm层所占种子比例最小，霉变种子数量与土壤深度也呈负相关． 2． 幼苗库调查 阳坡：在树线以上区域没有发现幼苗，林线交错带内幼苗密度平均达3 250株/hm2，郁闭林内仅2 750株/ hm2．整个样地内1～2a幼苗很少甚至没有出现，3～10a的幼苗相对较多．空间分布上，祁连圆柏幼苗在林线交错带内接近随机分布，郁闭林内则介于随机分布和均匀分布之间． 阴坡：在树线以上幼苗密度为1 250株/ hm2，全部为1~2a幼苗，林线交错带内幼苗密度平均达7 000株/ hm2，郁闭林内达6 250株/ hm2．林线附近岷江冷杉幼苗丰富度以及幼苗的出现频率明显高于祁连圆柏，年龄结构也较祁连圆柏完整．岷江冷杉幼苗空间分布除了树线处幼苗的分布为随机分布，其他海拔则为集群分布． 3．从不同土壤深度的种子总量和幼苗数量的相关性检验发现，当年生幼苗数量跟表层种子总量相关性极显著, 但是两年生幼苗的数量与底层种子数量相关性显著．土壤种子在土壤中的垂直分布格局从一定程度上可以反映种子库的年际特征．岷江冷杉土壤种子库较丰富，种子散布后的存活力随着时间的变化逐渐下降，属于季节性瞬时种子库；祁连圆柏土壤种子散布格局为集群型分布，成熟种子大部分散布在母株冠幅内，属于永久性土壤种子库． 4．在阴坡林线交错带及以上区域还存在较为丰富的乔木土壤种子，并且在树线以上区域还发现了少量的岷江冷杉幼苗．从样地乔木的年龄结构发现，在林线交错带内上部到树线位置主要以幼龄林为主，且年龄结构完整，基本符合入侵性林线特征；阳坡林线交错带内幼苗出现频率很低，树线以上区域虽然存在种子库，但是没有幼苗出现，在林线交错带内乔木径级差距很大，年龄结构异常不完整，这种特征的林线将会面临两个可能结果：一种是维持现有状态，保持平衡；另外一种就是退化，但阳坡林线的实际动态趋势还有待长期定点研究． Treelines on the upper region of Minjiang River differ between the north aspect and the south aspect in their appearances, altitudes and tree species. On the north aspect, trees of Abies form a sharp and abrupt treeline ranging from 3800m to 4400m, while on the south the treeline is generally lower(3 400~3 800m), more open and gradual and mostly composed of Sabina. In this study, we examined the altitudinal gradients of soil seed banks and seedling recruitments at the treeline ecotones of a N-aspect and a S-aspect by using soil sieving, germination experiment and field investigations, analyzed the characteristics of population regeneration of tree species at the transitional zone and presented a analysis of the causes to the aspect-related difference in treeline patterns in the study area. Major results of our study include: 1． Soil seed bank N-aspect: Of the 50 plots investigated, the average density of soil seeds is 50.96/m2, in which well-formed seeds account for 6%, empty seeds 52%, parasitized seeds34%, and seeds damaged by animals 8%. The size of soil seed bank varies along altitude, being 1.00 seeds /m2 at the 10m above the treeline and ca.19.33 seeds/m2 at the upper limit of treeline. The highest density (136.83 seeds/m2) occurs at the treeline ecotone. By contrast, the density of soil seed for the closed forest is only 30.50 seeds/m2. In terms of vertical strata, 67.50% of the total seeds are at the surface layer, 18.84% at the middle layer (0~2cm) and 13.66% at deeper layer (2~5cm). The number of parasitized seeds is negatively correlated to soil depth. S-aspect: Of the 50 plots investigated, the average density of soil seeds is 60.16 seeds/m2, and the well-formed seeds account for 49%, empty seeds 36%, parasitized seeds10%, and seeds damaged by animals 1%. The size of soil seed bank varies along altitude, with 1.92 seeds/m2 recorded at the10m above the treeline，108.16 seeds/m2 at the upper limit of treeline, and 75.80 seeds/m2 at the treeline ecotone, while that for the closed forest is 20.00 seeds/m2. The number of seeds decreases with the depth of soil. As is on the N-aspect, the size of soil bank, from large to small, follows the order of the surface layer, the middle layer (0~4cm) and the bottom layer (4~10cm). The number of parasitized seeds is also negatively correlated to the depth of the soil. 2． Seedling bank N-aspect: A mean maximum seedling abundance of 31 000 seedlings/hm2 was recorded near alpine treeline at growing season. The density of seedlings is 1 250 seedlings/ha (all being 1 or 2 years old) at the alpine meadow 10m away above treeline, 7 000 seedlings/ha at treeline ecotone and 6 250 seedlings/ha for closed forest．The spatial distribution of Abies faxoniana seedlings is random at the upper limit of the treeline but clumped at other altitudes． S-aspect: No seedlings were found at the alpine meadow 10m away from the treeline. The density of seedlings was 3 250 seedlings/ha at treeline ecotone and 2 750 seedlings/ha for the closed forest．Hardly any 1 year current and 2 year-old seedlings appeared at the plots. The spatial distribution of Sabina przewalskii seedlings is random at treeline ecotone and between “random” and “even” forest closed forest． 3．Correlation tests of seedling population and seed bank at different soil layers indicated that the emergents were strongly correlated to seed bank at surface layer while the number of two-year seedlings was significantly correlated to the seed bank at the bottom of soil layer, indicating that germination mainly occurs at the soil surface while the middle or bottom layer was the reserve for non-germination or dead seeds. It can thus be postulated that Abies faxoniana soil seed bank is of seasonal transient type. By contrast, the soil seed bank of Sabina przewalskii is of persistent type and the soil seeds and seedlings of this species occurred more frequently near the islands of adult trees. 4．A good many soil seeds of both tree species were found near the treeline ecotone and above at N- and S-aspects. A few young seedlings were found above the Abies treeline. Investigation of five altitudinal transects respectively on N- and S-aspects indicated that Abies faxoniana has a more complete age structure than the stands of Sabina przewalskii. The age of firs decreased from closed forest to the upper limit of treeline, which suggests that the Abies treeline is advancing to higher altitude. While on the south aspect, only few Sabina przewalskii soil seeds and nearly no seedlings were found above the treeline ecotone. The stands exhibit extremely great difference in diameter classes with significantly incomplete age structure. This would lead to two possible results for the treelines: maintaining an equilibrium state at the current position or degenerating. But more studies should be carried out at longer time scales or larger spatial scales to understand whether the Sabina treeline is degenerating.

n-channel, ambipolar, and p-channel organic heterojunction transistors fabricated with various film morphologies

The relationship between the performance characteristics of organic field-effect transistors (OFETs) with 2,5-bis(4-biphenylyl)-bithiophene/copper hexadecafluorophthalocyanine (BP2T/F16CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n-channel, ambipolar, and p-channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the hetero-junction effect, which also leads to an evolution of the field-effect mobility with increasing film thickness. In BP2T/F16CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field-effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.

Surface and interface morphology of polystyrene/poly(methyl methacrylate) thin-film blends and bilayers

The surface and interface morphologies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) thin-film blends and bilayers were investigated by means of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. Spin-coating a drop of a PS solution directly onto a PMMA bottom layer from a common solvent for both polymers yielded lateral domains that exhibited a well-defined topographical structure. Two common solvents were used in this study. The structure of the films changed progressively as the concentration of the PS solution was varied. The formation of the blend morphology could be explained by the difference in the solubility of the two polymers in the solvent and the dewetting of PS-rich domains from the PMMA-rich phase. Films of the PS/PMMA blend and bilayer were annealed at temperatures above their glass-transition temperatures for up to 70 h. All samples investigated with AFM were covered with PS droplets of various size distributions. Moreover, we investigated the evolution of the annealed PS/PMMA thin-film blend and bilayer and gave a proper explanation for the formation of a relatively complicated interface inside a larger PS droplet.

Characteristics and flux of settling particulate matter in neritic waters: The southern Yellow Sea and the East China Sea

The typology and flux of settling particulate matter (SPM) were investigated based on sediment trap sampling at six typical stations in the Yellow Sea and the East China Sea. The settling particulate matter in the neritic seas was sorted into three categories, lithogenic particles, living organisms, and particle aggregates. The mass of individual organisms is an important portion of particulate matter in the neritic waters. The aggregates contain six types, mucus aggregates, fecal pellets, diatom aggregates, silicoflagellate aggregates, tintinnids, and miscellaneous aggregates, of which the silicoflagellate aggregates and tintinnids are the most abundant in the Yellow Sea and the East China Sea. High particle fluxes, such as 215 to 874 g m(-2). day(-1) SPM in the bottom layer, were found at three stations where the water was well mixed, and the maximum flux was detected in the boundary area between the Yellow Sea and the East China Sea, where a wide nepheloid layer was present. Hence, particle flux in neritic waters can be easily shifted by water turbulence. The net vertical flux (123 to 961 mg C day(-1)), the contribution of lateral advection to resuspension flux (5 to 76%), and the particulate organic carbon export ratio (18 to 60%) were estimated for the other three stations where the water was stratified. The highest values were all found in the upwelling area off the Zhejiang coast, suggesting that the area of high productivity provides a high net vertical flux of SPM. (C) 2010 Elsevier Ltd. All rights reserved.

Observational evidence of the Yellow Sea warm current

The Yellow Sea Warm Current (YSWC) is one of the principal currents in the Yellow Sea in winter. Former examinations on current activity in the Yellow Sea have not observed a stable YSWC because of the positioning of current meters. To further understand the YSWC, a research cruise in the southern Yellow Sea was carried out in the winter of 2006/2007. Five moorings with bottom-mounted acoustic Doppler current profilers (ADCP) were deployed on the western side of the central trough of the Yellow Sea. The existence and distributional features of the YSWC were studied by analyzing three ADCP moorings in the path of the YSWC in conjunction with conductivity-temperature-depth (CTD) data over the observed area in the southern Yellow Sea. The results show the following. (1) The upper layer of the YSWC is strongly influenced by winter cold surge; its direction and speed often vary along a south-north axis when strong cold surges arrive from the north. (2) The YSWC near the bottom layer is a stable northwest flowing current with a speed of 4 to 10 cm/s. By combining the analyses of the CTD data, we speculate that the core of the YSWC may lie near the bottom. (3) On a monthly average timescale, the YSWC is stably oriented with northward flow from the sea surface to the sea floor.