EXAFS as Powerful Analytical Tool for the Investigation of Organic–Inorganic Hybrid Materials

The potential and application of X‐ray absorption spectroscopy (XAS) for structural investigations of organic–inorganic hybrid materials, with a special emphasis on systems consisting of inorganic building blocks (clusters) embedded into polymer backbones, is extensively reviewed. In the first part of the paper, the main features of organic–inorganic hybrid materials, their classification, the synthetic approaches for their preparation, and their applications are concisely presented, whereas the particular issues related to their characterization are discussed in more detail. In the second section of the paper, the principles and the theoretical background of the XAS method, including experimental design, data reduction, evaluation, analysis, and interpretation are described and discussed. Examples of potentialities of the method for the short‐range structural investigation of inorganic nanostructures in hybrids are provided, and the state‐of‐the‐art in the field of hybrid materials is reviewed. In the third part, six different case studies belonging to our past and present experience in this field are presented and discussed, with a particular focus on their XAS investigation.     

Quantitative oxide charge determination by photocurrent analysis

A new method is presented for the quantitative determination of insulator charges Q_Is from photo induced diffusion currents. Q_Is is determined by analyzing the interface recombination of charge carriers in illuminated electrolyte/insulator/semiconductor structures. Measured characteristics are explained theoretically and an evaluation procedure is developed for the determination of Q_Is which is based on the comparison of the simulated with the experimental data. Q_Is values obtained from the proposed method are compared with those from capacitance voltage measurements. A very good agreement can be observed between the results of both methods.     

Electrical impedance spectroscopy of the human prostate

Tissue electrical impedance is a function of its architecture and has been used to differentiate normal and cancer tissues in a variety of organs including breast, cervix, skin, and bladder. This paper investigates the possibility of differentiating normal and malignant prostate tissue using bioimpedance spectra. A probe was designed to measure impedance spectra over the range of 10 kHz to 1 MHz. The probe was fully characterized using discrete loads and saline solutions of different concentrations. Impedance spectra of five ex vivo prostates were measured in the operating room immediately following radical prostatectomy. Wilcoxon signed-rank tests were used to compare the normal and malignant findings. The impedance probe had a signal-to-noise ratio (SNR) > 84 dB across the entire spectrum and measured a tissue volume of approximately 46 mm(3). At 10 kHz, prostate conductivity (or) ranged from 0.232 S/m to 0.310 S/m for tumor and from 0.238 S/m to 0.901 S/m for normal tissue. At 1 MHz the ranges were 0.301 S/m to 0.488 S/m for tumor and 0.337 S/m to 1.149 S/m for normal. Prostate permittivity (epsilonr) ranged from 6.64 x10(4) to 1.25 x 10(5) for tumor and from 9.08 x 10(4) to 4.49 x 10(5) for normal tissues at 10 kHz. And, at 1 MHz the er ranges were 9.23 x 10(2) to 1.88 x 10(3) for tumor and 1.16 x 10(3) to 2.18 x 10(3) for normal tissue. Both sigma and epsilonr of tumor tissue were found to be significantly lower than that of normal tissue (P < 0.0001). Conductivity and permittivity are both higher in normal prostate tissues than they are in malignant tissue making them suitable parameters for tissue differentiation. This is in agreement with trends observed in other tissues reported in much of the literature. Expanded studies are needed to further validate this finding and to explore the biological mechanism responsible for generating the results.     

Calculation of cosmic ray limited maximum DC blocking voltages of high voltage silicon PIN diodes

A power law approach as used by Fulop for the treatment of impact ionization and breakdown in abrupt silicon P–N junctions [Fulop W. Calculation of avalanche breakdown voltages of silicon P–N junctions. Solid-State Electron. 1967;10:39–43] is developed in this paper to provide simple-to-use equations for the quantitative evaluation of cosmic ray related phenomena in high voltage power devices. Being empirical in nature, such approaches have no physical background and only serve the purpose of generating a simple and compact mathematical framework. The resulting compact model allows for a quick and straightforward computation of DC blocking voltages as a function of FIT rate, n-base doping and temperature. The determination of model parameters is based on the theory and data given in [Zeller HR. Cosmic ray induced failures in high power semiconductor devices. Solid-State Electron. 1995;38(12):2041–6]. With the new approach, calculating first-hand maximum DC blocking voltages for high voltage power semiconductor devices becomes as effortless as the calculation of the breakdown voltage.     

Giant Thermopower at Low Temperatures in Novel Clathrates Ba<Subscript>8</Subscript>{Cu,Zn}<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>46−<Emphasis Type="Italic">x</Emphasis></Subscript>

In the present work we focus on cubic type I Ba-Ge-based clathrates, where Ge in Ba₈Ge₄₃ \square₃\rm Ba_8Ge_{43} \square_3 (where □ is a vacancy) is substituted by Cu, Zn, Pd, and Si. Structural investigations in all cases confirm cubic primitive symmetry consistent with the space group type Pm[`3]nPm\bar{3}n of a typical type I clathrate structure with lattice parameter a ≈ 1.06 nm. Electronic transport has been studied in a broad temperature range from 4.2 K to about 800 K, demonstrating that substitution allows fine-tuning of the charge carrier density, shifting the materials into the proximity of a metal-to-insulator transition. This is evidenced from giant thermopower reaching values of 400 μV/K in the case of Ba₈Cu_5.2Zn_0.8Ge_40.0 at temperatures well below room temperature (T _max ^S  ≈ 150 K).     

Anode Interfacial Tuning via Electron‐Blocking/Hole‐Transport Layers and Indium Tin Oxide Surface Treatment in Bulk‐Heterojunction Organic Photovoltaic Cells

The effects of anode/active layer interface modification in bulk‐heterojunction organic photovoltaic (OPV) cells is investigated using poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and/or a hole‐transporting/electron‐blocking blend of 4,4′‐bis[(p‐trichlorosilylpropylphenyl)‐phenylamino]biphenyl (TPDSi₂) and poly[9,9‐dioctylfluorene‐co‐N‐[4‐(3‐methylpropyl)]‐diphenylamine] (TFB) as interfacial layers (IFLs). Current–voltage data in the dark and AM1.5G light show that the TPDSi₂:TFB IFL yields MDMO‐PPV:PCBM OPVs with substantially increased open‐circuit voltage (V_oc), power conversion efficiency, and thermal stability versus devices having no IFL or PEDOT:PSS. Using PEDOT:PSS and TPDSi₂:TFB together in the same cell greatly reduces dark current and produces the highest V_oc (0.91 V) by combining the electron‐blocking effects of both layers. ITO anode pre‐treatment was investigated by X‐ray photoelectron spectroscopy to understand why oxygen plasma, UV ozone, and solvent cleaning markedly affect cell response in combination with each IFL. O₂ plasma and UV ozone treatment most effectively clean the ITO surface and are found most effective in preparing the surface for PEDOT:PSS deposition; UV ozone produces optimum solar cells with the TPDSi₂:TFB IFL. Solvent cleaning leaves significant residual carbon contamination on the ITO and is best followed by O₂ plasma or UV ozone treatment.     

EXIF-white balance recognition for image forensic analysis

Due to the lack of post-processing resistance, traditional forensic methods are vulnerable to cascade image manipulations, e.g. copy-and-paste operation followed by high compression. Different from these traditional methods, a new forensic method that has the ability to resist multiple types of post-processing, is proposed by using white balance from the EXchangeable Image File format (EXIF) header. We first extract image quality metrics between each two combination of one original image and twelve re-balanced images. By regularizing the eigen spectrum of image quality metrics, the compact set of image eigen features is then selected for recognizing different EXIF-white balance modes via the SVM classifier. The experimental results show that the proposed method has the ability to resist the influence of high compression or heavy downsampling in both theoretical and realistic scenarios. Furthermore, thanks to image eigen features affected by cascade image operations, it is possible to lead to a wrong white balance mode. Thus, we use the EXIF-white balance parameter as a manipulator indicator for forgery detection. Based on the forgery photos in practice, the proposed evidence can detect cascade manipulated images which are subject to copy-and-paste followed by different white balance post-processing operations, high compression or heavy downsampling.     

Indium tin oxide-free semi-transparent inverted polymer solar cells using conducting polymer as both bottom and top electrodes

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated as a transparent cathode to replace indium tin oxide (ITO) in inverted polymer solar cells. Increasing the thickness of the PEDOT:PSS electrode leads to a reduction in transparency and sheet resistance which lowers the photocurrent but increases the fill factor of the solar cells. The offset of photocurrent and fill factor as the thickness is increased leads to a saturation of the power conversion efficiency to 3%. These electrodes were applied to flexible substrates showing similar device performance to glass based devices. Cyclic bending test of these flexible polymer electrodes show improved conversion efficiency retention (92%) when compared to flexible ITO based electrodes (50%) after 300 bend cycles. In addition to using PEDOT:PSS as a cathode replacement for ITO in inverted solar cells, its use as a semi-transparent anode replacement to Ag is also examined. Semi-transparent inverted solar cells fabricated with ITO as the cathode and PEDOT:PSS as the top anode electrode were demonstrated showing efficiencies of 2.51% while replacement of both ITO and Ag with PEDOT:PSS as both the cathode and anode show efficiencies of 0.47%.     

Metastable Copper‐Phthalocyanine Single‐Crystal Nanowires and Their Use in Fabricating High‐Performance Field‐Effect Transistors

This paper describes a simple, vapor‐phase route for the synthesis of metastable α‐phase copper‐phthalocyanine (CuPc) single‐crystal nanowires through control of the growth temperature. The influence of the growth temperature on the crystal structures, morphology, and size of the CuPc nanostructures is explored using X‐ray diffraction (XRD), optical absorption, and transmission electron microscopy (TEM). α‐CuPc nanowires are successfully incorporated as active semiconductors in field‐effect transistors (FETs). Single nanowire devices exhibit carrier mobilities and current on/off ratios as high as 0.4 cm² V^?1 s^?1 and >10⁴, respectively.     

UV nanoimprint lithography process optimization for electron device manufacturing on nanosized scale

Imprint specific process parameters like the residual layer thickness and the etch resistance of the UV polymers for the substrate etch process have to be optimized to introduce UV nanoimprint lithography (UV NIL) as a high-resolution, low-cost patterning technique for research and industry into electron device manufacturing. Additionally, UV NIL processes have to be compatible with conventional silicon (Si) semiconductor processing. Within this work, the minimization of the residual layer thickness by using a multi-drop ink-jet system, which was integrated into the imprint stepper NPS300 from S-E-T-(formerly SUSS MicroTec), in combination with a low viscous UV polymer from Asahi Glass Company is shown. The etch resistance of different UV polymers against the poly-Si etch process was increased by 50% with an appropriate post-exposure bake. A poly-Si dry etch process was used to pattern the gates of short channel MOSFETs. After optimizing the poly-Si etch, properly working short channel MOSFETs with a minimum gate length of about 90 nm were fabricated demonstrating successfully the compatibility of UV NIL with conventional Si semiconductor processing on nanosized scale.