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Differences in the local structure and composition of anodic TiO2 nanotubes annealed in vacuum and air
摘要： This work is dedicated to the influence of thermal treatment procedures in vacuum and air atmosphere on the structural features of multiwalled TiO2 anodic nanotubes (NTs) formed in fluorine-containing ethylene glycol (EG) based electrolyte investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with EDX and electronic nanodiffraction (STEM nanodiffraction), IR and Raman spectroscopy, XPS and ToF SIMS. Using electron nanodiffraction technique, there were estimated TiO2 nanocrystallite sizes for the inner layer of the NTs after annealing in air and vacuum for the first time. The differences in carbon distribution profiles in TiO2 nanotube crosscut after thermal treatments in air and vacuum were discussed. It was found that thermal treatment in vacuum leads to different phase composition of TiO2 NTs IL comparing to annealing in air. A sequential thermal treatment (firstly in vacuum and then in air) enables to remove carbon from TiO2 NTs surface and partly from TiO2 NTs IL and prevent detachment of IL from OL at the same time. The obtained data will be useful for understanding the mechanisms of structural modifications during thermal treatments as well as for functional properties optimization of such nanostructures.
关键词： Anodizing,TiO2 nanotubes,Thermal treatment,Electron nanodiffraction,HAADF-STEM
更新于2025-09-23 15:19:57
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Strain Mapping of CdTe Grains in Photovoltaic Devices
摘要： Strain within grains and at grain boundaries (GBs) in polycrystalline thin-film absorber layers limits the overall performance because of higher defect concentrations and band fluctuations. However, the nanoscale strain distribution in operational devices is not easily accessible using standard methods. X-ray nanodiffraction offers the unique possibility to evaluate the strain or lattice spacing at nanoscale resolution. Furthermore, the combination of nanodiffraction with additional techniques in the framework of multimodal scanning X-ray microscopy enables the direct correlation of the strain with material and device parameters such as the elemental distribution or local performance. This approach is applied for the investigation of the strain distribution in CdTe grains in fully operational photovoltaic solar cells. It is found that the lattice spacing in the (111) direction remains fairly constant in the grain cores but systematically decreases at the GBs. The lower strain at GBs is accompanied by an increase of the total tilt. These observations are both compatible with the inhomogeneous incorporation of smaller atoms into the lattice, and local stress induced by neighboring grains.
关键词： X-ray microscopy,nanodiffraction,X-ray diffraction (XRD),solar cells,multimodal,CdTe,X-ray,strain,X-ray fluorescence (XRF),photovoltaic,X-ray beam induced current (XBIC)
更新于2025-09-19 17:13:59
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Evolution of microstructure and mechanical properties of a graded TiAlON thin film investigated by cross-sectional characterization techniques
摘要： In the last years, quaternary oxynitrides have emerged as a new class of materials due to their tunable properties. Within the present work, a graded TiAl(O)N film was grown by magnetron sputter deposition, using TiAl targets with a Ti/Al atomic ratio of 40/60, constant nitrogen and stepwise increasing oxygen partial pressure over the film thickness. The microstructural evolution of the film was investigated by transmission electron microscopy and synchrotron X-ray nanodiffraction. Complementary, cross-sectional μ-Raman spectroscopy was performed to further validate the phase evolution. The first layer, grown without the addition of oxygen, showed a prevalent wurtzite (w) structure and a subordinate face centered cubic (fcc) phase fraction. The addition of small amounts of oxygen resulted in the stabilization of the fcc-phase and the w-phase vanished. With increasing film thickness and thus, increasing oxygen content, increasing amounts of an additional amorphous phase fraction were observed. In the first layers, tensile in-plain strain was determined, which turns to compressive towards the film surface. Cross-sectional nanonindentation revealed increasing hardness and elastic modulus with increasing oxygen content in the first layers as a result of the w to fcc transition; however, towards the film surface the hardness decreases, which can be related to the increasing amorphous phase fraction.
关键词： sputtering,TiAlON,graded film,cross-sectional nanoindentation,synchrotron X-ray nanodiffraction,TEM
更新于2025-09-04 15:30:14