bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduced structural defect densities in a‐plane GaN layers on r‐plane sapphire through buffer layer engineering
Authors: Armitage R. , Hirayama H. , Kondo Y. 
Published: June 2007

AbstractNonpolar a‐plane GaN epilayers were grown by metalorganic vapour phase epitaxy on r‐plane sapphire substrates using three different buffer layer structures. The investigated structures consisted of GaN grown on: (A) AlN nucleation layer; (B) AlN plus Al0.25Ga0.75N intermediate layer; (C) AlN, Al0.25Ga0.75N, and GaN/Al0.25Ga0.75N superlattice. The samples were characterized by X‐ray diffraction, transmission electron microscopy, and atomic force microscopy. Structure (B) exhibited much lower overall structural defect densities than structure (A), with narrower X‐ray rocking curves by a factor of 1.5‐2. Compared to structure (B), structure (C) showed a factor of 2 lower density of screw dislocations in TEM although the densities of other types of defects were not significantly reduced. Type (B) and (C) structures also exhibited smoother surface morphologies than Type (A). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructure of a‐plane AlN grown on r‐plane sapphire and on patterned AlN templates by metalorganic vapor phase epitaxy
Authors: Okada N. , Imura M. , Nagai T. , Balakrishnan K. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. , Maruyama H. , Noro T. , Takagi T. , Bandoh A. 
Published: June 2007

AbstractThe growth of a‐plane AlN (a‐AlN) on r‐plane sapphire substrate and the epitaxial lateral overgrowth (ELO) of a‐AlN on patterned a‐AlN has been performed by high‐temperature metalorganic vapor phase epitaxy. The ELO a‐AlN layers coalesced well on the a‐AlN template with trenches formed along 〈10$ \bar 1 $0〉. A detailed study of the microstructure by transmission electron microscopy revealed that the stacking faults due to facet slip are completely annihilated above the trenches of the patterned AlN. Furthermore, a dislocation density as low as 9.1×107 cm–2 was achieved by ELO. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterisation of multiple carrier transport in indium nitride grown by molecular beam epitaxy
Authors: Fehlberg Tamara B. , Umana‐Membreno Gilberto A. , Gallinat Chad S. , Koblmüller Gregor , Bernardis Sarah , Nener Brett D. , Parish Giacinta , Speck James S. 
Published: June 2007

AbstractQuantitative mobility spectrum analysis (QMSA) was performed on multiple magnetic field Hall effect measurements of indium nitride grown by molecular beam epitaxy. This enables two clearly distinct electron species to be identified, which are attributed to the bulk and a surface accumulation layer. In this material, single magnetic field data corresponds to neither electron species, as both contribute significantly to the total conduction. The bulk electron distribution has an extracted average Hall mobility of 3570 cm2/(Vs) at 300 K with a concentration of 1.5 × 1017 cm–3, while the surface electrons have sheet charge density that is an order of magnitude higher than previously reported surface concentrations. The high quality bulk characteristics revealed emphasise the importance of using multi‐carrier analysis when performing transport measurements on InN.
Characterization of free‐standing GaN substrates prepared by self lift‐off
Authors: Lee S. W. , Goto H. , Minegishi T. , Lee W. H. , Ha J. S. , Lee H. J. , Lee Hyo‐jong , Lee S. H. , Goto T. , Hanada T. , Cho M. W. , Yao T. 
Published: June 2007

AbstractFree‐standing GaN layers were successfully prepared by self lift‐off process. Single crystalline ZnO buffer layer and GaN layer were successively grown on sapphire substrate by plasma assisted molecular beam epitaxy. Thick GaN film was grown on this template substrate for the realization of stress‐free free‐standing substrate by hydride vapor phase epitaxy. The a‐axis and c‐axis lattice constants of free‐standing GaN were 3.189Å and 5.185Å, respectively. Peak positions of photoluminescence spectrum were D0X of 3.4715 eV and FXA of 3.4791 eV. These results suggest that the stress‐free GaN layers were successfully prepared by self lift‐off process. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular dynamics simulation of thermal conductivity of GaN/AlN quantum dot superlattices
Authors: Kawamura Takahiro , Kangawa Yoshihiro , Kakimoto Koichi 
Published: June 2007

AbstractWe calculated thermal conductivity of GaN/AlN quantum dot superlattices by molecular dynamics simulation. The results of investigation of the effect of quantum dots on thermal conductivity as a function of superlattice period are presented in this paper. An empirical potential function of Stillinger‐Weber potential was used for simulations. Thermal conductivity was obtained by Green‐Kubo's equation. The results show that the values of thermal conductivity parallel to the wetting layers decreased due to the effect of quantum dots. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of local tunneling phenomena in green InGaN‐based LEDs
Authors: Onushkin Grigory , Lee Jinhyun , Yang Jung‐Ja , Park Seong‐Eun , Kim Min‐Ho , Koike Masayoshi 
Published: June 2007

AbstractThe tunneling radiative recombination in green InGaN based Light Emitting Diodes (LEDs) has been studied by micro‐Electroluminescence measurements. It was found that this recombination was very local, which has lateral size less than 1 μm and spectral peak position around 600 nm. Changes of growth conditions led to a reduction in the concentration of these defects, improving the current‐voltage characteristics and slightly enhancing the optical efficiency of green LEDs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation process of sharp‐pointed structures on GaN nanorods during RF‐MBE growth and their field emission characteristics
Authors: Terayama M. , Hasegawa S. , Uchida K. , Ishimaru M. , Hirotsu Y. , Asahi H. 
Published: June 2007

AbstractWe have investigated layer structures of an AlN/GaN superlattice (SL) in nanorods by cross‐sectional transmission electron microscopy to clarify the formation process of sharp‐pointed structures on GaN nanorods during plasma assisted molecular beam epitaxial (PA‐MBE) growth. It is found that during 75‐160 nm MBE growth, flat interfaces of the AlN/GaN SL in nanorods develop into chevron‐shaped interfaces. Beyond a thickness of 165 nm, AlN/GaN SL nanorods continue to grow with nearly the same chevron‐shaped interfaces, and finally these interfaces appear as the sharp‐pointed structures on the top of nanorods. In contrast to GaN and AlN/GaN SL nanorods, no formation of the sharp‐pointed structures is observed for AlN nanorods. This indicates that the formation of the sharp‐pointed structures is ascribed to GaN growth. We will discuss thickness dependence of FE characteristics of GaN nanorods in relation with the formation of the sharp‐pointed structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of enhancement‐mode AlxGa1–xN/GaN junction heterostructure field‐effect transistors with p‐type GaN gate contact
Authors: Fujii T. , Tsuyukuchi N. , Hirose Y. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. 
Published: June 2007

AbstractWe have investigated the device performance, such as the breakdown voltages between gate‐source contacts and drain‐source contacts, threshold voltage (Vth) and on resistance (RON), of enhancement‐mode AlxGa1–xN/GaN junction heterostructure field‐effect transistors (JHFET) with a p‐type GaN gate. Fabricating an Al0.15Ga0.85N/GaN JHFET with a gate length of 2 μm without surface passivation, we have achieved a completely enhancement‐mode JHFET with a threshold voltage of +0.55 V, and breakdown voltages between gate‐source and drain‐source were over 100 V and 250 V, respectively. RON is as low as 4.5 mΩ · cm2 at VG = 3.0 V. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvements of quantum efficiency and thermal stability by using Si delta doping in blue InGaN/GaN multiple quantum well light‐emitting diodes
Authors: Wu Gwo‐Mei , Chung Ta‐Jen , Nee Tzer‐En , Kuo Da‐Chuan , Chen Wei‐Jen , Ke Chih‐Chun , Hung Cheng‐Wei , Wang Jen‐Cheng , Chen Nei‐Chuan 
Published: June 2007

AbstractThe improvements of quantum efficiency and thermal stability by using Si delta doping in blue InGaN/GaN multiple quantum well (MQW) structures have been investigated. The high‐resolution X‐ray diffraction (HR‐XRD) indicated better interface properties in the MQWs for Si delta doping structures. The Arrhenius plots of the temperature‐dependent photoluminescence (PL) spectra were used to reveal the enhancements of the radiative recombination. The activation energy was increased from 115 to 140 meV for the InGaN/GaN MQW sample with Si delta doping. The improvements of the thermal stability and activation energy were attributed to the supply of electrons from the Si delta doping barrier region into the InGaN well layer and the increase in hole capturing by the higher energy barrier in the valence band. Si delta doping process plays a crucial role in carrier recombination to significantly suppress carrier leakage, which not only increases the exciton confinement, but also improves the quantum efficiency. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Leak current in high resistive GaN buffer layer and its light responsiveness
Authors: Tanaka T. , Moriya Y. , Sahara M. , Yukimoto T. , Kamogawa H. , Otoki Y. , Mishima T. 
Published: June 2007

AbstractWe observed unique light responsiveness in HR GaN leak current, in which the current was drastically reduced under LED illumination of 2.65 eV or lower photon energy. Free carrier excitation by the illumination and consequential electron capture into the electron traps would rationalize the phenomenon. The threshold energy in our measurement was well associated with the carbon related very deep electron trap reported elsewhere (P. B. Klein et al., Appl. Phys. Lett. 79, 3527 (2001) [3]). Observation of this phenomenon provides us a very simple way to characterize both the HR GaN resistivity and the concentration of electron traps in the GaN buffer simultaneously. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of electrical properties of insulators (Si3N4, SiO2, AlN, and Al2O3)/0.5 nm Si3N4/AlGaN/GaN heterostructures
Authors: Maeda Narihiko , Hiroki Masanobu , Watanabe Noriyuki , Oda Yasuhiro , Yokoyama Haruki , Yagi Takuma , Makimoto Toshiki , Enoki Takatomo , Kobayashi Takashi 
Published: June 2007

AbstractThe electrical properties in AlGaN/GaN heterostructures with Si‐ and Al‐based insulators (Si3N4, SiO2, AlN, and Al2O3) have been examined and analyzed. By insulators deposition, significant increase in the two‐dimensional electron gas (2DEG) density (Ns) was observed with the order of Ns(Al2O3) > Ns(AlN) ∼ Ns(SiO2) > Ns(Si3N4) > N0 (N0: Ns without insulators). As the result, the decrease in the sheet resistance (R) was observed; the smallest order of R was R(Al2O3) < R(AlN) < R(Si3N4) < R0 ∼ R(SiO2) (R0: R without insulator). The insulators deposition effect has thus been shown to be significant and different among insulators. The increase in Ns was analyzed in terms of the change in the potential profile, and the observed differences in Ns among insulators have been interpreted. The band engineering including insulators is indispensable in understanding and designing AlGaN/GaN HFETs, since insulators are commonly used for the surface passivation as well as for the gate insulators, and the insulators deposition is to alter the essential device parameters such as the source resistance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Incorporation of self assembled In‐rich InGaN nanostructure to achieve redshift in InGaN/GaN heterostructures
Authors: Soh C. B. , Hartono H. , Chen P. , Chua S. J. 
Published: June 2007

AbstractThe epitaxy growth of InGaN/GaN MQWs posed a great challenge, especially when high In content have to be incorporated for long wavelength applications such as the cyan and green LEDs. To realize devices with superior characteristic, In‐rich InGaN nanostrucutres (QDs) have been fabricated using InGaN wetting layer and trimethylIndium treatment in InGaN well. In InGaN QWs, nanometer scale fluctuation of the indium nanostructures can lead to “QD‐like” states which act as nucleation site to enhance In incorporation. This leads to red‐shift in PL dominant peak emission and a broadening of PL spectrum at its higher wavelength. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principle study on crystal growth of Ga and N layers on GaN substrate
Authors: Doi K. , Maida N. , Kimura K. , Tachibana A. 
Published: June 2007

AbstractGaN surfaces show several types of the surface growth depending on the surface structures. In this study, we have simulated some kind of initial states of GaN surface growth from the viewpoint of metal‐organic chemical‐vapor deposition (MOCVD). It is clarified that NH3 molecules and N radicals can not fully terminate the (0001) Ga surface, and that chemical reactions between trimethylgallium and NH3 in gas‐phase is desirable to some extent because the products which contain GaN cores are immediately stabilized on the GaN(0001) surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Depth distribution of strain in GaN/AlN/SiC heterostructures by DUV micro‐Raman spectroscopy
Authors: Kitamura T. , Nakashima S. , Mitani T. , Nakamura N. , Furuta K. , Okumura H. 
Published: June 2007

AbstractWe measured the depth distribution of strain in GaN/AlN/SiC heterostructures by using deep ultraviolet (DUV) micro‐Raman and photoluminescence spectroscopies with bevel shaped specimens. Raman signal of AlN were detectable for the layers thicker than 15 nm. AlN and GaN layers had compressive strain in the whole region and the strain relaxation along the growth direction was observed. In this study, the variation of the Raman shift was well explained by a strain relaxation model that the misfit dislocations are distributed not only at the interface, but also throughout the film. The relaxation rate related to the generation rate of misfit dislocations was different for the AlN and GaN layers grown by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical characterization of high In content cubic InGaN on GaAs(001) substrates by RF‐MBE
Authors: Nakamura Teruyuki , Endo Yuta , Katayama Ryuji , Yaguchi Hiroyuki , Onabe Kentaro 
Published: June 2007

AbstractHigh In content cubic InGaN films have been successfully grown on GaAs(001) substrates by rf‐plasma assisted molecular beam epitaxy (RF‐MBE). The X‐ray diffraction analysis has confirmed the Ga content of the cubic InGaN films increases with increasing the group‐III flux ratio (Ga/(Ga+In)). The maximum Ga content of the c‐InGaN film is about 29% based on an analysis of the X‐ray diffraction 2θ/ω scan. By 2θ/ω and ω X‐ray reciprocal space mapping measurements, hexagonal‐phase and twin‐phase InGaN are found to be generated from c‐InGaN{111} facets. By low temperature PL measurement, the c‐In1–xGaxN peak shifts from 0.41 eV (x = 0) to 0.72 eV (x = 0.09) with increasing Ga content, showing that the bandgap of c‐InGaN is ∼300meV smaller than that of h‐InGaN with the same alloy composition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of strain in GaN/AlN quantum dots by means of resonant Raman scattering: the effect of capping
Authors: Cros A. , Budagosky J. A. , Garro N. , Cantarero A. , Coraux J. , Renevier H. , Proietti M. G. , Favre‐Nicolin V. , Daudin B. 
Published: June 2007

AbstractWe have studied in detail changes in the strain state of GaN/AlN quantum dots during the capping process. μ‐Raman scattering experiments allowed the detection of a resonant mode which provided information on the evolution of strain with capping. Simultaneously, Multiwavelength Anomalous Diffraction (MAD) and Diffraction Anomalous Fine Structure (DAFS) experiments were performed on the same samples, providing the independent determination of the wurtzite lattice parameters a and c. The remarkable agreement between Raman and X‐ray data stands out the suitability of polar vibrational modes for the determination of strain in nanostructures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of reflective GaN mesa sidewalls for the application to high extraction efficiency LEDs
Authors: Lee Jae‐Soong , Lee Joonhee , Kim Sunghwan , Jeon Heonsu 
Published: June 2007

AbstractWe proposed and demonstrated a modified GaN light‐emitting diode (LED) structure. The structure was made by integrating angled sidewalls to an otherwise conventional LED structure. Various GaN sidewall angles were obtained by adjusting etch conditions and the etched surface roughness was ∼2 nm. Near‐field emission patterns indicated that the angled sidewalls efficiently deflect photons that are initially guided laterally within the GaN epilayer into the off‐surface direction. For sidewall angle of 30°, total surface emission strength was improved by a factor exceeding 3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High temperature growth of AlN film by LP‐HVPE
Authors: Tsujisawa K. , Kishino S. , Liu Y. H. , Miyake H. , Hiramatsu K. , Shibata T. , Tanaka M. 
Published: June 2007

AbstractAlN films were grown on AlN/sapphire templates at 1400–1500 °C using low‐pressure hydride vapor phase epitaxy (LP‐HVPE). Compared to the step‐flow growth of AlN film at 1200 °C with growth rate of 2.1 μm/h, AlN films with atomic steps were obtained at 1400–1500 °C even with high growth rate. For the AlN film grown at 1450 °C with growth rate of 14.3 μm/h, the RMS value is 0.75 nm and the FWHM values of (0002) and (10‐12) X‐ray rocking curve (XRC) are 351 and 781 arcsec, respectively. Since the FWHM value of (10‐12) XRC for the AlN/sapphire template is 1492 arcsec, the crystal quality of HVPE‐grown AlN is greatly improved compared with the AlN/sapphire template, which is also confirmed by TEM observation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In situ gravimetric monitoring of decomposition rate on the surface of (0001) c‐plane sapphire for the high temperature growth of AlN
Authors: Akiyama K. , Araki T. , Murakami H. , Kumagai Y. , Koukitu A. 
Published: June 2007

AbstractThe thermal stability of (0001) sapphire was investigated at atmospheric pressure using the in situ gravimetric monitoring (GM) method. The weight change of a sapphire substrate was monitored at various hydrogen partial pressures in carrier gas (P) at temperatures over 1200 °C. Although the sapphire substrate was stable up to 1450 °C in an inert carrier gas (P = 0.0 atm), sapphire decomposition started to occur at 1200 °C in H2 carrier gas (P = 1.0 atm). Moreover the activation energy and order of reaction for sapphire surface decomposition changed at approximately 1300 °C. These results indicate that the rate‐limiting reaction for sapphire decomposition shifts near 1300 °C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAsN quantum dots grown on GaAs(001) substrates by MOVPE
Authors: Kuboya S. , Thieu Q. T. , Nakajima F. , Katayama R. , Onabe K. 
Published: June 2007

AbstractThe self‐assembled InAsN quantum dots (QDs) were grown on the GaAs (001) substrates by MOVPE using 1,1‐dimethlhydrazine (DMHy) and tertiarybutylarsine (TBAs) as the N and As precursors, respectively. The size distribution of the InAs(N) QDs grown at 450 °C and 420 °C is found bimodal. The InAsN QDs are typically 4‐11 nm in height and 30‐41 nm in width. The N incorporation into InAs induces the decrease of the QDs size, due to the increase of the wetting layer thickness. The density of the InAsN QDs with a nominal source supply of 2.6‐3.0 ML, increases from 1.1‐1.3×1010 cm–2 for the 450 °C growth to 2.1‐2.3×1010 cm–2 for the 420 °C growth. The photoluminescence peaks (at 300 K) of the InAs(N) QDs grown at both temperatures clearly show a red‐shift to 1200 nm by N incorporation. This red‐shift is in contrast with the blue‐shift expected from the decrease in the dot sizes (quantum size effect), indicating the huge bandgap bowing induced by N incorporation is dominant over the quantum size effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extraction‐efficiency enhancement of InGaN‐based vertical LEDs on hemispherically patterned sapphire
Authors: Lee Jae‐Hoon , Oh Jeong‐Tak , Choi Seok‐Boem , Woo Jong‐Gun , Lee Su‐Yeol , Lee Myoung‐Bok 
Published: June 2007

AbstractTo improve the external quantum efficiency, a vertical type InGaN LED (VT‐LED) is fabricated on a sapphire substrate with a surface hemispherically‐patterned by laser lift‐off (LLO) technique. As a result, the VT‐LEDs with a concavely patterned surface revealed an enhanced luminous intensity by four times compared to the device with a planar surface. This improvement in the VT‐LED performances is explained to be attributed mainly to the increase in the escaping probability of photons due to the corrugated LED surface. The use of metallic substrate prepared by nickel electroplating seems the other factor for the increase of luminous intensity by considering reduced current crowding and better thermal conductivity. These devices are advantageous for high power operation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue light emitting diode fabricated on a‐plane GaN film over r‐sapphire substrate and on a‐plane bulk GaN substrate
Authors: Naoi Y. , Ikeda K. , Hama T. , Ono K. , Choi R. , Fukumoto T. , Nishino K. , Sakai S. , Lee S. M. , Koike M. 
Published: June 2007

AbstractWe studied the growth technique for the dislocation reduction in a‐plane GaN grown by metal organic chemical vapour deposition (MOCVD) using AlInN buffer layer, high temperature atomic layer epitaxy, and trenched r‐sapphire technique. By using these techniques, the crystal quality was much improved. We also fabricated blue light emitting diodes (LEDs) on a‐plane GaN film over r‐sapphire substrate and on a‐plane bulk GaN substrate. The electroluminescence (EL) characteristics of the LED samples were examined, and we found that the EL near field pattern from homo‐epitaxially grown a‐GaN based LED was spatially uniform, although the pattern from the LED on r‐sapphire substrate was not uniform. The output power at the wavelength of 430nm was 0.72mW at the 20mA injection current for the sample on a‐plane bulk GaN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cathodoluminescence characterization of [11$ \bar 2 $0]‐oriented InGaN/GaN thin films grown on r‐plane sapphire substrates by metalorganic vapor‐phase epitaxy
Authors: Kusakabe K. , Furuzuki T. , Ohkawa K. 
Published: June 2007

AbstractWe report the cathodoluminescence (CL) characterization of nonpolar [11$ \bar 2 $0]‐oriented InGaN/GaN thin films grown on r‐plane sapphire substrates by atmospheric metalorganic vapor‐phase epitaxy. The epitaxial GaN films grown on r‐plane sapphire substrates frequently show facet surface morphology. The CL peak wavelength and local indium composition of InGaN grown on them were gradually varied with the probed position from the facet summit to valley. In a‐plane InGaN, the facet summit was In‐rich area while the valley was In‐poor area. This is due to the material transport issue during epitaxial growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel HVPE technology to grow nanometer thick GaN, AlN, AlGaN layers and multi‐layered structures
Authors: Usikov Alexander , Shapovalova Lisa , Kovalenkov Oleg , Sukhoveev Vitali , Volkova Anna , Ivantsov Vladimir , Dmitriev Vladimir , Meng Fanyu , Datta Ranjan , Mahajan Subhash , Readinger Eric , Garrett Gregory , Wraback Michael , Reshchikov Michael 
Published: June 2007

AbstractIn this paper, we demonstrate new results on controllable HVPE growth of nitride materials with a deposition rate below 0.02 microns per minute and the first quantum size structures fabricated by HVPE. The nm‐scale layer thicknesses were verified by transmision electron microscopy (TEM) and photoluminescence (PL). Quantum well (QW) GaN/AlGaN and AlN/AlGaN structures have been grown by HVPE for the first time. Properties of the HVPE grown QWs are reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)