Abstract The complex formation between l‐histidine (HHis) and aluminum(III) ion in water solutions was studied by UV spectrophotometric and 27‐Al NMR measurements at 298 K. UV spectra were measured on solutions in which the total concentration of histidine was from 15.0 to 50.0 mmol/dm3 and the concentration ratio of histidine to aluminum was varied from 3∶1 to 10∶1 in the pH range between 4.2 and 6.0. The spectra were taken in the wavelength interval 240–340 nm. Nonlinear least‐squares treatment of the spectrophotometric data indicates the formation of the complexes Al(HHis)3+, Al(His)2+, Al(HHis)His2+, and Al2(OH)His4+ with the overall formation constants βp,q,r: log β1,1,1=11.90±0.04, log β1,1,0=7.25±0.08, log β1,2,1=20.1±0.1, and log β2,1,1=5.92±0.12 (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively). 27Al‐NMR spectra were taken on solutions with the concentration of aluminum 50 mmol/dm3 and that of histidine 250 mmol/dm3. In the pH interval 5.0–6.1, two resonances at 9.5 ppm and 12.0 ppm were assigned to Al(HHis)2+ and Al(HHis)(His)2+ (or Al(OH)(HHis)22+), respectively. 相似文献
Polycrystalline silicon (poly‐Si) films were fabricated by aluminum (Al)‐induced crystallization of Si‐rich oxide (SiOx) films. The fabrication was achieved by thermal annealing of SiOx /Al bilayers below the eutectic temperature of the Al–Si alloy. The poly‐Si film resulting from SiO1.45 exhibited good crystallinity with highly preferential (111) orientation, as deduced from Raman scattering, X‐ray diffraction, and transmission electron microscopy measurements. The poly‐Si film is probably formed by the Al‐induced layer exchange mechanism, which is mediated by Al oxide. 相似文献
A series of Cs 4d and Al 2p spectra associated with valence‐band and cut‐off spectra have been used to characterize the interaction between caesium and tris(8‐hydroxyquinoline) aluminium (Alq3) molecules in a Cs‐doped Alq3 layer. The Cs 4d and Al 2p spectra were tuned to be very surface sensitive by selecting a photon energy of 120 eV at the National Synchrotron Radiation Research Center, Taiwan. A critical Cs concentration exists, above which a new Al 2p signal appears next to the Al 2p peak of Alq3 in the lower binding‐energy side. The Al 2p signal was analyzed and assigned as being contributed from a mixture of Alq2, Alq and Al. Experimental data supported the observation that bond cutting of Alq3 by the doped Cs atoms occurred at high Cs doping concentration. 相似文献
A series of Al 2p, K 2p, O 1s and N 1s core‐level spectra have been used to characterize the interaction between potassium (K) and tris(8‐hydroxyquinoline) aluminium (Alq3) molecules in the K‐doped Alq3 layer. All core‐level spectra were tuned to be very surface sensitive in selecting various photon energies provided by the wide‐range beamline at the National Synchrotron Radiation Research Center, Taiwan. A critical K concentration (x = 2.4) exists in the K‐doped Alq3 layer, below which the K‐doped atoms generate a strained environment near the O and N atoms within 8‐quinolinoline ligands. This creates new O 1s and N 1s components on the lower binding‐energy side. Above the critical K coverage, the K‐doped atoms attach the O atoms in the Al—O—C bonds next to the phenoxide ring and replace Al—O—C bonds by forming K—O—C bonds. An Alq3 molecule is disassembled into Alq2 and Kq by bond cutting and bond formation. The Alq2 molecule can be further dissociated into Alq, or even Al, through subsequent formations of Kq. 相似文献
In this study, metal‐assisted etching (MAE) with nitric acid (HNO3) as a hole injecting agent has been employed to texture multi‐crystalline silicon wafers. It was previously proven that addition of HNO3 enabled control of surface texturing so as to form nano‐cone shaped structures rather than nanowires. The process parameters optimized for optically efficient texturing have been applied to multi‐crystalline wafers. Fabrication of p‐type Al:BSF cells have been carried out on textured samples with thermal SiO2/PECVD‐SiNx stack passivation and screen printed metallization. Firing process has been optimized in order to obtain the best contact formation. Finally, jsc enhancement of 0.9 mA/cm2 and 0.6% absolute increase in the efficiency have been achieved. This proves that the optimized MAE texture process can be successfully used in multi‐crystalline wafer texturing with standard passivation methods.
J –V curves and SEM images of the nano and iso‐textured samples. jsc enhancement of 0.9 mA/cm2 together with 0.6% absolute efficiency gain was observed on nano‐textured samples. 相似文献
The presence of native oxide on the surface of silicon nanoparticles is known to inhibit charge transport on the surfaces. Scanning electron microscopy (SEM) studies reveal that the particles in the printed silicon network have a wide range of sizes and shapes. High‐resolution transmission electron microscopy reveals that the particle surfaces have mainly the (111)‐ and (100)‐oriented planes which stabilizes against further oxidation of the particles. X‐ray absorption spectroscopy (XANES) and X‐ray photoelectron spectroscopy (XPS) measurements at the O 1s‐edge have been utilized to study the oxidation and local atomic structure of printed layers of silicon nanoparticles which were milled for different times. XANES results reveal the presence of the +4 (SiO2) oxidation state which tends towards the +2 (SiO) state for higher milling times. Si 2p XPS results indicate that the surfaces of the silicon nanoparticles in the printed layers are only partially oxidized and that all three sub‐oxide, +1 (Si2O), +2 (SiO) and +3 (Si2O3), states are present. The analysis of the change in the sub‐oxide peaks of the silicon nanoparticles shows the dominance of the +4 state only for lower milling times. 相似文献
CdWO4 crystals grown by the Czochralski method at the low-temperature gradient were investigated with electron spin resonance (ESR) spectroscopy. ESR spectra did not contain the spectra of impurity ions typical for the CdWO4 structure, i.e., Fe3+, Mn2+, and Cr3+. At the same time, in the studied crystals a complex ESR spectrum having the hyperfine structure due to two nonequivalent tungsten atoms was observed (W183;I=1/2; natural abundance, 14.28%). Angular dependence analysis and simulation of ESR spectra have shown that this novel spectrum is described by a spin-Hamiltonian with the following parameters:D=839 G,E=80 G,gxx=2.01,gyy=1.97,gzz=1.987 and electron spinS=7/2. There is one magnetically nonequivalent position of the center in the crystal structure and the direction ofDzz andgzz corresponds to the direction of Wn-Wn+2 (or Cdn-Cdn+2) in the crystal structure. Because of the fact that it is in principle impossible to achieve the electron stateS=7/2 for the d-shell of one transition metal ion and taking into account the fact that such electron state is realized for two nonequivalent tungsten atoms, we suppose the defect structure to be the chain W2+-M+-W3+. In the structure of this defect the ion M+ is diamagnetic, the ions W2+ and W3+ have electron spinS=2 andS=3/2, respectively. The necessary condition for such defect to exist is to place this chain of ions in cadmium positions for the charge compensation. the reason for such defects to form is supposed to be the incorporation of M+ ions into the CdWO4 lattice. The presence of W2+ and W3+ in Cd positions in the defect structure provides the charge compensation and the lowering of the lattice stress. 相似文献
Aluminum-doped p-type polycrystalline silicon thin films have been synthesized on glass substrates using an aluminum target
in a reactive SiH4+Ar+H2 gas mixture at a low substrate temperature of 300 °C through inductively coupled plasma-assisted RF magnetron sputtering.
In this process, it is possible to simultaneously co-deposit Si–Al in one layer for crystallization of amorphous silicon,
in contrast to the conventional techniques where alternating metal and amorphous Si layers are deposited. The effect of aluminum
target power on the structural and electrical properties of polycrystalline Si films is analyzed by X-ray diffraction, Raman
spectroscopy, scanning electron microscopy and Hall-effect analysis. It is shown that at an aluminum target power of 100 W,
the polycrystalline Si film features a high crystalline fraction of 91%, a vertically aligned columnar structure, a sheet
resistance of 20.2 kΩ/□ and a hole concentration of 6.3×1018 cm−3. The underlying mechanism for achieving the semiconductor-quality polycrystalline silicon thin films at a low substrate temperature
of 300 °C is proposed. 相似文献