Quantitative determination of element distributions in silicon based thin film solar cells using SNMS

The determination of elemental distributions in thin film solar cells based on amorphous silicon using electron beam SNMS is possible by quantifying the measured ion intensities. The relative sensitivity factors (RSFs) for all elements measured have to be known. The RSFs have been determined experimentally using implantation and bulk standards with known concentrations of the interesting elements. The measured RSFs have been compared with calculated RSFs. The model used for the calculation of the RSFs takes into account the probability for electron impact ionization and the dwell time of the neutrals inside the postionization region. The comparison between measured and calculated RSF shows, that this model is capable to explain the RSFs for most elements. Differences between calculated and measured values can be explained by the formation of hydride and fluoride molecules (in case of H and F) and influences of the angular distribution of the sputtered neutrals in case of Al. The experimentally determined RSFs have been used for a quantification of depth profiles of the i-, buffer-, p- and front contact layers of a-Si solar cells.     

Quantitative determination of element distributions in silicon based thin film solar cells using SNMS

The determination of elemental distributions in thin film solar cells based on amorphous silicon using electron beam SNMS is possible by quantifying the measured ion intensities. The relative sensitivity factors (RSFs) for all elements measured have to be known. The RSFs have been determined experimentally using implantation and bulk standards with known concentrations of the interesting elements. The measured RSFs have been compared with calculated RSFs. The model used for the calculation of the RSFs takes into account the probability for electron impact ionization and the dwell time of the neutrals inside the postionization region. The comparison between measured and calculated RSF shows, that this model is capable to explain the RSFs for most elements. Differences between calculated and measured values can be explained by the formation of hydride and fluoride molecules (in case of H and F) and influences of the angular distribution of the sputtered neutrals in case of Al. The experimentally determined RSFs have been used for a quantification of depth profiles of the i-, buffer-, p- and front contact layers of a-Si solar cells.     

Studies of polarized ethylenes—VIII: Conformational analysis of twisted ethylenes

Push-pull ethylenes have been prepared, which in the ground state are twisted around the double bond, and the barriers for passage through a planar transition state have been measured with DNMR. The influence of steric and electronic factors on the rotational barriers has been investigated. Compounds have also been prepared where two barriers could be measured, one for passage through the planar state, and the other for passage through a 90° twisted state.     

Experimental lifetimes of some levels belonging to the 4p5nd (n = 4, 5, 6) configuration of Kr I

The radiative lifetimes of some levels belonging to the 4d, 5d and 6d configurations of Kr I have been measured using high frequency deflection technique with a delayed coincidence single-photon counting arrangement. The measurements have been performed under conditions where pressure dependent effects are negligible. Lifetimes of some of the levels have been measured for the first time. A comparison with other results is presented.     

Recombination of simple molecular ions studied in storage ring: dissociative recombination of H2O+

Dissociative recombination of vibrationally relaxed H2O+ ions with electrons has been studied in the heavy-ion storage ring CRYRING. Absolute cross-sections have been measured for collision energies between 0 eV and 30 eV. The energy dependence of the cross-section below 0.1 eV is found to be much steeper than the E-1 behaviour associated with the dominance of the direct recombination mechanism. Resonant structures found at 4 eV and 11 eV have been attributed to the electron capture to Rydberg states converging to electronically excited ionic states. Complete branching fractions for all dissociation channels have been measured at a collision energy of 0 eV. The dissociation process is dominated by three-body H + H + O breakup that occurs with a branching ratio of 0.71.     

Liquid crystal behaviour of linear copolymers—I

The molar volumes of some mesophasic linear homo- and copolymers have been measured as a function of temperature. Both the liquid crystal phase (nematic) and the isotropic liquid have been examined. The polymer chain is characterized by an alternating sequence of rigid groups and flexible spacers. The molar volumes measured for the liquid crystal phase give evidence for a substantially disordered conformation taken by the flexible spacers in the nematic phase. Analogies between homo- and copolymers are discussed.     

Construction of spectral sensitivity function using polychromatic UV sources.

A procedure is presented for constructing the spectral sensitivity functions of biological dosimeters, using five polychromatic UV sources possessing different emission spectra. Phage T7 and uracil biological dosimeters have been used for measuring the dose rates of the lamps. Their spectral sensitivity functions consisting of two exponential terms have been constructed. The parameters of the spectral sensitivity functions have been determined by comparing the directly measured and calculated dose-rate values. The parameters of the sensitivity function are accepted as correct values when the deviation of the measured and calculated values is a minimum. Based on the deviations between the constructed and the experimentally determined spectral sensitivities with monochromatic sources, the differences between the measured and calculated results are interpreted. The importance of the correct spectral sensitivity data is demonstrated through the effectiveness spectra of a TL 01 lamp for phage T7 killing, uracil dimerization and erythema induction.     

A positron lifetime study of the electron-beam-induced polymerization of 1,6-hexanediol diacrylate

Positron lifetime measurements have been used to characterize the electron-beam-induced polymerization of 1,6-hexanediol diacrylate (HDODA). Lifetimes were measured as a function of radiation dose over a range of 0.5–7.0 Mrad and analyzed into three components. All three components exhibited some variation with radiation dose. Variations in the longest lifetime component have been interpreted in terms of changes in free volume. These data have been compared with polymer fraction data for electron-irradiated HDODA obtained by gel extraction and by NMR measurements. The positron lifetime parameter that correlates most closely with polymerization as measured by those techniques is the intensity of the longest lived component.     

Experimental evidence for a low-lying torsional mode in polymers

Longitudinal and transverse sound velocities have been measured in several samples of polystyrene crosslinked with various weight percentages of divinylbenzene. Specific heats of these same samples have been measured previously. These data obtained calorimetrically, together with similar data obtained by others for some other polymers, can be accounted for by postulating the existence of a fourth mode of vibration with a velocity close to that measured for the two transverse modes. It is suggested that this fourth mode is one arising from the torsional coupling of the side groups along the backbone chain of the polymer molecule.     

The enthalpy of fusion and degree of crystallinity of polymers as measured by DSC

Crystalline polymers are not in thermal equilibrium and thermodynamic parameters such as enthalpy of fusion as determined by differential scanning calorimetry from the area under the melting endotherm over a wide temperature range have not been measured under equilibrium conditions. Accordingly measurements of the degree of crystallinity based on the enthalpy of fusion reflect experimental conditions, are incorrect in that they do not usually agree with those determined by other analytical procedures, such as density and WAX scattering, particularly when measured at ambient temperatures. While this has been repeatedly pointed out procedures used to determine the fractional crystallinity of polymers based on the enthalpy of fusion continue to be widely used.Using the First Law method, the enthalpy of fusion and fractional crystallinity have been measured as a function of temperature for metallocene polyethylene and polyethylene terephthalate during heating. The crystallinity measured on the sample prior to heating is in good agreement with that determined by density and wide angle X-ray diffraction.     

Correlation between excess adsorption data measured for solvent mixture/adsorbent systems and RM values obtained for different solutes chromatographed in binary mobile phases

This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity R_M is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases.     

Kinetic and thermodynamic considerations of the bracketing method: Entropy-driven proton-transfer reactions in a Fourier transform mass spectrometer

Several reports of experimentally derived proton affinity values and gas-phase basicity values for amino acids and peptides have recently appeared in the literature. Here, we show that the thermodynamic quantity that is measured by the Fourier transform mass spectrometry proton transfer bracketing of amino acids and peptides is gas-phase basicity and not proton affinity. Both experimental and theoretical evidence supports this conclusion. The difference between the values determined by proton transfer bracketing measurements for lysine versus leucine is consistent with a difference in gas-phase basicity rather than proton affinity. The rate of proton transfer from protonated lysine to a series of reference compounds have been measured. Entropy-driven, endothermic proton transfer is found to occur at the collision rate. Recent ab initio and semi-empirical calculations of the proton affinity of lysine are found to agree with the value that is derived from bracketing studies when one assumes that gas-phase basicity is measured. While entropy-driven reactions have been observed previously in high-pressure mass spectrometers, this is the first evidence for such reactions at low pressure in a Fourier transform mass spectrometer.     

Chemical corrosion on gamma-ray attenuation properties of barite concrete

The variation of photon attenuation coefficient on the chemical media has been investigated. For this purposes the linear attenuations of barite concrete have been measured at 662, 1773 and 1332 keV before leaving the chemical media and following a 6 month period. The linear attenuation coefficients have been measured using gamma spectrometer that contains a NaI(Tl) detector and 16k channel MCA. It was found from this measurement that the chemical media decreased the linear attenuation coefficients of the barite concrete and the barite rate is important for concrete production.     

A study of the alkene-ozone reactions, 2,3-dimethyl 2-butene + O3 and 2-methyl propene + O3, with photoelectron spectroscopy: measurement of product branching ratios and atmospheric implications

The reactions of ozone with the alkenes 2,3-dimethyl 2-butene (DMB) and 2-methyl propene (2MP) have been investigated using a flow-tube interfaced to a u.v. photoelectron spectrometer. These reactions were studied at low pressure at different reagent partial pressures, both with the alkene in excess and ozone in excess. In each case, photoelectron spectra recorded as a function of time have been used to estimate partial pressures of the reagents and products as a function of time using photoionization cross-sections of selected photoelectron bands of the reagents and products, which were measured separately. The yields of all the main products have been determined, some of which have been measured in previous studies. For each reaction, oxygen was observed as a product for the first time and its yield was measured. Kinetics simulations were performed using reaction schemes which were developed for these reactions, which are consistent with that used earlier for the ozone-ethene reaction, in order to determine the main reactions for production of the products. The experimental product yields have been used in a global model to estimate their global annual emissions in the atmosphere. For example, for the reaction of O(3) with 2MP the formaldehyde, formic acid and acetone global annual emissions are calculated as 0.4 Tg, 25.0 Gg and 0.16 Tg respectively, which are estimated as 0.02, 0.3 and 0.2% of the total annual emission respectively. For the reaction of O(3) with DMB, the acetone yield is higher at 0.9 Tg which is approximately 1% of the total annual estimated emission.     

Photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one in different solutions

A number of photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one have been measured for the first time including the prompt and P-type delayed fluorescence, and triplet-triplet absorption. Decay parameters, for the triplet-state of this molecule, have also been measured in different quenching conditions. The results are discussed and compared for those of similar molecules.     

Equilibrium solubility of alcohols in polystyrene attained by controlled diffusion

The solubility of alcohols in a polystyrene matrix during the diffusion process was measured by a gravimetric technique. It is shown that the amount of solvent swelling the polymer reaches an equilibrium saturation, which is dependent on the system and temperature, but independent on the sample preparation. Phase diagrams, similar to those measured by TM-DSC and cloud points of known mixtures, can therefore be constructed. These measurements provide accurate and reliable data for a theoretical treatment. The results have been interpreted by Flory-Huggins theory. Interaction parameters as well as their entropic and enthalpic components have been calculated. An analysis based on Hansen solubility parameters has also been performed.     

Impact of extended pi conjugation on methyl rotor-induced IVR in aromatic molecules

Laser-induced fluorescence excitation and resolved fluorescence spectra following excitations of the single vibronic levels (SVL) of p-vinyltoluene (p-VT) and p-vinylfluorobenzene (p-VFB) have been measured in a seeded supersonic free-jet expansion. A complete vibronic assignment of the fluorescence spectrum measured following excitation of the 0(0)0-band of p-VT has been presented. Normal vibrational modes in the S0 and S1 states of the molecule have been calculated by CASSCF method, and the correlation between the two set of modes is made by expressing the excited-state normal modes in terms of those of the ground state. The calculations predict that in the excited state methyl and vinyl torsional motions of p-VT are extensively mixed with many of the out-of-plane modes of the aromatic ring. Our resolved fluorescence spectral data measured following SVL excitations essentially agree with such predictions. In the excited state, the molecule exhibits a dramatically low threshold for the rotor-induced IVR in a supersonic jet expansion. Several mechanisms have been discussed to explain the phenomenon.     

特征参量法1: 简单级数反应的热动力学研究法

建立了测定热动力学体系冷却常数的线性拟合法和简单级数反应通用的热动力学研究法---特征参量法。导出了简单级数反应的动力学参数Kn和速率常数kn的通用计算式。应用冷却常数的线性拟合法在不同温度下测定了两个反应体系的冷却常数, 探讨了温度、浓度、介质及装样方式对冷却常数的影响。应用简单级数反应的特征参量法研究了一级、二级、三级和分数级反应的热动力学, 结果文献值吻合。讨论了热动力学体系的冷却常数对速率常数计算结果的影响。     

Imaging surface spectroscopy for two- and three-dimensional characterization of materials

Secondary ion mass spectrometry (SIMS) exhibits a unique potential for the measurement of two-and three-dimensional distributions of trace elements in advanced materials, which is demonstrated on relevant technological problems. One example is the characterization of high purity iron. With this material segregation experiments have been performed and the initial and final distribution of the trace elements have been measured. Another example is the investigation of the corrosion behaviour of high purity chromium. Samples oxidized with (16)O and (18)O have been measured to explain the growing and adhesion of the oxide layer. All imaging techniques generate a vast quantitiy of data. In order to extract the important information the assistance of chemometric tools is essential. Detection of chemical phases by classification using neural networks or de-noising of scanning-SIMS images by wavelet-filtering demonstrates the increase of the performance of analytical imaging techniques.     

Transport of gaseous mixtures through membranes

Thermoosmosis of ternary mixtures of oxygen, nitrogen, and carbon dioxide across a porous unglazed membrane has been studied, The thermoosmotic pressure difference, ΔP, created by a temperature difference, ΔT, has been measured at various mean temperatures and pressures. Experimental data have been interpreted in the light of non-equilibrium thermodynamics of irreversible processes and the dusty gas model of Mason. Heats of transport for the mixtures, Q^★, have been estimated from the measured values of pressure difference and temperature difference. It is found that the heat of transport of mixtures is independent of the mean temperature and temperature difference as was found in earlier studies on multicomponent mixtures.