PCD Method Research Articles

Improved accuracy of eddy-current sensor based carrier lifetime measurement using laser excitation

In the manufacturing of modern solar cells, the early-phase quality inspection is crucial to detect harmful impurities and to reduce production waste. Thus, the charge-carrier lifetime measurement is beneficial before slicing the silicon ingot into wafers. Optimization of the widely used eddy-current detected photoconductance decay (e-PCD) technique for lifetime measurements is necessary to keep the pace with the new challenges appearing in photovoltaics. We investigated the dependence of the accuracy of the measurable carrier lifetime on the excitation laser parameters in the entire relevant carrier lifetime range. The complex behaviour of surface-recombination phenomena and its time evolution is studied by computer simulation. We optimized the components and parameters of the measurement setup and found that a 1064 nm laser is rather optimal compared to the 980 nm laser used previously. Using a longer wavelength laser source with elevated photon flux results in an improved accuracy of carrier lifetime recorded at Δn = 1015 cm−3 excess carrier concentration. A convincing similarity is found by comparing results from as-sliced and passivated surfaces. The optimized laser e-PCD method was compared to the flash-lamp based PCD method (known as QSSPC). Results agree very well for longer carrier lifetimes for which both systems evaluates the PCD curves in transient mode. However, for lower carrier lifetimes the universal transient mode operation of the e-PCD method is advantageous in terms of consistency.

A multilevel local mesh refinement with the PCD Method

We propose in this contribution a successive local mesh refinement with the PCD method. The multilevel local refinement improves the accuracy and gives a better precision, locally and globally, with a lower computational costs particularly if the considered problem has an anomaly. Here we present how a successive local mesh refinement can be handled. We conclude by presenting numerical experiments to show the interest of a multilevel local mesh refinement for the 2D diffusion equation.

Use of ammonium sulfite as a post-column derivatization reagent for rapid detection and quantification of aldehydes by LC-MS

Derivatization is frequently used in liquid chromatography–mass spectrometry (LC-MS) to improve the ionization characteristics of analytes, and facilitate their structural elucidation and quantification. However, the off-line derivatization process usually requires more analysis time. Therefore, the present work develops a novel LC/post-column derivatization (PCD)/MS (LC-PCD-MS) method for rapid detection of aldehydes in complex samples. The PCD method is based on a bisulfite addition reaction with aldehydes that can be easily conducted by mixing the LC elute with an (NH4)2SO3 solution via a tee. The resulting derivatives readily produce diagnostic HSO3− ions under collision induced dissociation (CID) in the negative ion mode of MS, even at an extremely low CID energy such as 1 eV, which can significantly improve the detection selectivity of aldehydes and reduce the occurrence of false positives. The limits of detection (LODs) of hexanal and heptanal were 3 nM and 2 nM, respectively. Moreover, good linearity in the concentration range of 0.01–1 μM for hexanal and heptanal was obtained with the determination coefficient (R2) being greater than 0.996 and the intra- and inter-day relative standard deviations (RSDs) were lower than 13.5% and 17.9%, respectively, indicating the acceptable reproducibility of the method. The LC-PCD-MS method was successfully applied for the rapid quantification of aldehydes in human urine and solvent extracts of traditional Chinese medicines (TCMs). Furthermore, a precursor ion scan strategy based on the diagnostic HSO3− ion was also developed and applied for the preliminary screening of aldehydes in complex samples of cinnamon and lemongrass.

The best strategy for local mesh refinement with the PCD method

We propose in this contribution numerical tests for local mesh refinement with the PCD method. We investigate two rates of local mesh refinement: the ratio 2 and the ratio 3. First we introduce a local mesh refinement by subdividing the elements of the zone to be refined by the ratio 2 in each direction, i. e. each coarse element is subdivided by 4 fine elements. Second, we subdivide the elements of the zone to be refined by the ratio 3 in each direction, i. e. each coarse element is subdivided by 9 fine elements. Here we investigate some numerical experiments to show that the optimal local refinement rate is 2. This is in agreement with the regularity assumptions required for the proposed discretisation.

The best strategy for local mesh refinement with the PCD method

The best strategy for local mesh refinement with the PCD method

The PCD Method on Composite Grid

We introduce a discretization method of boundary value problems(BVP) in the case of the two dimensional diffusion equation on arectangular mesh with refined zones. The method consists inrepresenting the unknown distribution and its derivatives bypiecewise constant distributions (PCD) on distinct meshes togetherwith an appropriate approximate variational formulation of the exactBVP on this piecewise constant distributions space. This method,named the PCD method, has the advantage of producing the mostcompact possible discrete stencil. Here, we analyze and prove theconvergence of the PCD method and determine upper bounds on itsconvergence rate.

Identifying irrigation zones across a 7.5-ha ‘Pinot noir’ vineyard based on the variability of vine water status and multispectral images

Vine water status, yield and berry composition are variables within a vineyard. There is current interest in defining zones of similar yield and berry composition. The aim of this study was to compare two methods for identifying zones of similar yield within a 7.5-ha ‘Pinot noir’ vineyard. The two methods were based on: spatial distribution of average midday leaf water potential (ΨL) and plant cell density (PCD = near-infrared/red) which is a vegetation index. A proposal for splitting the vineyard into eight new irrigation zones was assessed. A ‘blind’ zonation based on regular polygons of equal sizes was also established as a standard for comparison. Coefficients of variation (C v) in yield for both methods were compared with that of the blind zonation. In 2006 and 2007, a k-means cluster analysis indicated that variability in ΨL was mainly effected by soil properties. In both years, the vineyard was fully irrigated (100 % ETc). The two methods did not improve yield C v for full irrigation in 2006 and 2007 compared to blind zonation. In 2009, regulated deficit irrigation (RDI) was applied resulting in higher variability in ΨL and yield. The ΨL method of zonation significantly reduced coefficient of variation under RDI but PCD method did not despite the reduction in C v by 16.7 %. We recommend irrigation zonation based on ΨL when RDI is applied.

Protection and Deprotection Approach for the Introduction of Functional Groups into Metal−Organic Frameworks

A noncoordinating hydroxyl group was introduced into a metal-organic framework (MOF) by a procedure involving a protection, complexation, and deprotection (PCD) reaction sequence, and the crystal structure of a novel MOF, [Zn(dhybdc)(bpy)] x 4 DMF (1), was determined. 1 did not have an interpenetrated structure. The three-dimensional pores had large apertures. Results showed that the PCD method is a novel synthetic method for the introduction of various functional groups into MOFs.

PCR-mediated one-step deletion of targeted chromosomal regions in haploid Saccharomyces cerevisiae

Chromosome rearrangements, especially chromosomal deletions, have been exploited as important resources for functional analysis of genomes. To facilitate this analysis, we applied a previously developed method for chromosome splitting for the direct deletion of a designed internal or terminal chromosomal region carrying many nonessential genes in haploid Saccharomyces cerevisiae. The method, polymerase chain reaction (PCR)-mediated chromosomal deletion (PCD), consists of a two-step PCR and one transformation per deletion event. In this paper, we show that the PCD method efficiently deletes internal regions in a single transformation. Of the six chromosomal regions targeted for deletion by this method, five regions (16 to 38 kb in length) containing 10 to 19 nonessential genes were successfully eliminated at high efficiency. The one targeted region on chromosome XIII that was not deleted was subsequently found to contain sequences essential for yeast growth. While 14 individual genes in this region have been reported to be nonessential, synthetic lethal interactions may occur among these nonessential genes. Phenotypic analysis showed that four deletion strains still exhibited normal growth while possible synthetic growth defects were observed in another strain harboring a 19-gene deletion on chromosome XV. These results demonstrate that the PCD method is a useful tool for deleting genes and for analyzing their functions in defined chromosomal regions.

侵入深さ一定法による残留応力分布の放射光非破壊測定(S06-2 材料内部の非破壊応力評価,S06 放射光による応力測定と残留応力評価)

The X-ray method is known as the most powerful method to measure the subsurface distribution of residual stresses. To obtain the precise stress distribution, the constant penetration depth (PCD) method by proposed Akiniwa et al was extended to be applicable for non-equi-biaxial state of stresses. The PCD method is only applicable to polycrystals without strong texture. For the thin films with fiber texture, the scattering vector constant (SVC) method was proposed. The CPD method was applied to measure the residuals tress distribution of silicon nitride bombarded with steel fine particles, and the SVC method was applied to TiN thin films carted on steel substrate by the ion beam mixing method.

A simple procedure based on the PCD method for determination of recombination lifetime and surface recombination velocity in silicon

A two-step method based on measurement of the decay of photoconductivity and use of chemical surface passivation has been developed to determine both recombination lifetime and surface recombination velocity of carriers in high-resistivity silicon. Lifetime up to 3-4 ms and surface recombination velocity down to 2-5 cm s-1 can be measured on samples no more than 300 mu m thick. The method can be used in a wide field of applications, especially for material characterization and process control.

Silver as a Lifetime Killer in p-Ge, and a Hole Trap in Ge(Li) Detectors

The temperature dependence of the lifetime in silver doped p-Ge, as measured by the PCD method, is shown to be in agreement with a model for recombination through multivalent flaws. New values of capture cross section are determined (σ o/n = 1.5×10-14 cm2, σn- = 0.75×10-16 cm2). Lifetimes of electrons and holes are also measured on a silver doped Ge(Li) detector, by means of two techniques, using a collimated beam of ∂-rays (137Cs). Silver causes preferential hole tarpping and therefore cannot be responsible for the preferential electron trapping usually observed.

Leakage current of lithium-diffused germanium diodes as a tool for lifetime measurement

Li-diffused diodes are prepared from germanium material for use in lithium drifted gamma-spectrometers. At room temperature and above, the measured leakage current of these diodes is shown to be in close agreement with the theoretical diffusion current of an idealized N +P junction. This diffusion current is numerically calculated and plotted, taking into account the temperature dependence of all parameters involved, except for the minority carrier lifetime. To compare theory with experiment, use is made of the room temperature resistivity and lifetime (as measured by the PCD method). Different assumptions of the theoretical model are tested.