A typical body-centered cubic (BCC) CoFe(110) peak was discovered at approximately 2θ = 44.7°. At 2θ = 46°, 46.3°, 47.7°, 55.4°, 54.6°, and 56.4°, the Ybsub.2Osub.3 and Cosub.2Osub.3 oxide peaks were ...visible in all samples. However, with a heat treatment temperature of 300 °C, there was no typical peak of CoFe(110). Electrical characteristics demonstrated that resistivity and sheet resistance reduced dramatically as film thickness and annealing temperatures increased. At various heat treatments, the maximum hardness was 10 nm. The average hardness decreased as the thickness increased, and the hardness trend decreased slightly as the annealing temperature was higher. The highest low-frequency alternative-current magnetic susceptibility (χsub.ac) value was discovered after being annealed at 200 °C with 50 nm, and the optimal resonance frequency (fsub.res) was discovered to be within the low-frequency range, indicating that the Cosub.40Fesub.40Ybsub.20 film can be used in low-frequency applications. The maximum saturation magnetization (Ms) was annealed at 200 °C for 50 nm. Thermal disturbance caused the Ms to decrease as the temperature reached to 300 °C. The results show that when the oxidation influence of as-deposited and thinner films is stronger than annealing treatments and thicker thickness, the magnetic and electrical properties can be enhanced by the weakening peak of the oxide, which can also reduce interference.
The aim of this work is to investigate the effect of annealing and thickness on various physical properties in Co
Fe
Yb
thin films. X-ray diffraction (XRD) was used to determine the amorphous ...structure of Co
Fe
Yb
films. The maximum surface energy of 40 nm thin films at 300 °C is 34.54 mJ/mm
. The transmittance and resistivity decreased significantly as annealing temperatures and thickness increased. At all conditions, the 10 nm film had the highest hardness. The average hardness decreased as thickness increased, as predicted by the Hall-Petch effect. The highest low-frequency alternative-current magnetic susceptibility (χ
) value was discovered when the film was annealed at 200 °C with 50 nm, and the optimal resonance frequency (ƒ
) was in the low frequency range, indicating that the film has good applicability in the low frequency range. At annealed 200 °C and 50 nm, the maximum saturation magnetization (Ms) was discovered. Thermal disturbance caused the Ms to decrease when the temperature was raised to 300 °C. The optimum process conditions determined in this study are 200 °C and 50 nm, with the highest Ms, χ
, strong adhesion, and low resistivity, which are suitable for magnetic applications, based on magnetic properties and surface energy.
The aim of this work is to investigate the effect of annealing and thickness on various physical properties in Cosub.40Fesub.40Ybsub.20 thin films. X-ray diffraction (XRD) was used to determine the ...amorphous structure of Cosub.40Fesub.40Ybsub.20 films. The maximum surface energy of 40 nm thin films at 300 °C is 34.54 mJ/mmsup.2. The transmittance and resistivity decreased significantly as annealing temperatures and thickness increased. At all conditions, the 10 nm film had the highest hardness. The average hardness decreased as thickness increased, as predicted by the Hall-Petch effect. The highest low-frequency alternative-current magnetic susceptibility (χsub.ac) value was discovered when the film was annealed at 200 °C with 50 nm, and the optimal resonance frequency (ƒsub.res) was in the low frequency range, indicating that the film has good applicability in the low frequency range. At annealed 200 °C and 50 nm, the maximum saturation magnetization (Ms) was discovered. Thermal disturbance caused the Ms to decrease when the temperature was raised to 300 °C. The optimum process conditions determined in this study are 200 °C and 50 nm, with the highest Ms, χsub.ac, strong adhesion, and low resistivity, which are suitable for magnetic applications, based on magnetic properties and surface energy.
MoO
/V
O
hybrid nanobilayers are successfully prepared by the sol-gel method with a spin- coating technique followed by heat -treatment at 350 °C in order to achieve a good crystallinity. The ...composition, morphology, and microstructure of the nanobilayers are characterized by a scanning electron microscope (SEM) and X-ray diffractometer (XRD) that revealed the a grain size of around 20-30 nm, and belonging to the monoclinic phase. The samples show good reversibility in the cyclic voltammetry studies and exhibit an excellent response to the visible transmittance. The electrochromic (EC) window displayed an optical transmittance changes (Δ
) of 22.65% and 31.4% at 550 and 700 nm, respectively, with the rapid response time of about 8.2 s for coloration and 6.3 s for bleaching. The advantages, such as large optical transmittance changes, rapid electrochromism control speed, and excellent cycle durability, demonstrated in the electrochromic cell proves the potential application of MoO
/V
O
hybrid nanobilayers in electrochromic devices.
In this study, X-ray diffraction (XRD) analysis showed the amorphous nature of the Cosub.60Fesub.20Ybsub.20 films deposited at room temperature (RT), 100 °C, and 200 °C. The body-centered cubic (BCC) ...CoFe (110) characteristic peak was visible at 44.7° after annealing films of 40 nm and 50 nm at 300 °C. The highest alternating current magnetic susceptibility (χsub.ac) value was 0.21 at 50 Hz in a 50 nm, and the lowest resistivity value was 1.02 (×10sup.−2 Ω·cm) in a 50 nm. In terms of nano-indication measurement, the highest value of hardness was 9.29 GPa at 300 °C in a 50 nm. When the thickness increased from 10 nm to 50 nm, the hardness and Young’s modulus of the Cosub.60Fesub.20Ybsub.20 film also showed a saturation trend. The Cosub.60Fesub.20Ybsub.20 film had the maximum surface energy at 50 nm after 300 °C annealing. The transmittance of Cosub.60Fesub.20Ybsub.20 films decreased when the thickness was increased because the thickness effect suppresses the photon signal. Due to high χsub.ac, low electrical performance, strong nano-mechanical properties, and high adhesion, it was discovered in this work that 50 nm with annealing at 300 °C was the ideal condition for the magnetic and adhesive capabilities of Cosub.60Fesub.20Ybsub.20 film. More importantly, replacing the CoFeB seed or buffer layer with a thin CoFeYb film improved the thermal stability, making CoFeYb films attractive for practical magnetic tunnel junction (MTJ) applications. Furthermore, the specific properties of Cosub.60Fesub.20Ybsub.20 films were compared to those of Cosub.60Fesub.20Ysub.20 films, demonstrating that the specific properties of these two materials may be compared.
Among many transition-metal oxides, Fe
O
anode based lithium ion batteries (LIBs) have been well-investigated because of their high energy and high capacity. Iron is known for elemental abundance and ...is relatively environmentally friendly as well contains with low toxicity. However, LIBs based on Fe
O
suffer from particle aggregation during charge-discharge processes that affects the cycling performance. This study conjectures that iron agglomeration and material performance could be affected by dopant choice, and improvements are sought with Fe
O
nanoparticles doped with 0.2% Ti. The electrochemical measurements show a stable specific capacity of 450 mAh g
at 0.1 C rate for at least 100 cycles in Ti doped Fe
O
. The stability in discharge capacity for Ti doped Fe
O
is achieved, arising from good electronic conductivity and stability in microstructure and crystal structure, which has been further confirmed by density functional theory (DFT) calculation. Detailed distribution function of relaxation times (DFRTs) analyses based on the impedance spectra reveal two different types of Li ion transport phenomena, which are closely related with the electron density difference near the two Fe-sites. Detailed analyses on EIS measurements using DFRTs for Ti doped Fe
O
indicate that improvement in interfacial charge transfer processes between electrode and Li metal along with an intermediate lithiated phase helps to enhance the electrochemical performance.
Pectin polymers are considered for lithium-ion battery electrodes. To understand the performance of pectin as an applied buffer layer, the electrical, magnetic, and optical properties of pectin films ...are investigated. This work describes a methodology for creating pectin films, including both pristine pectin and Fe-doped pectin, which are optically translucent, and explores their potential for lithium-ion battery application. The transmission response is found extended in optimally Fe-doped pectin, and prominent modes for cation bonding are identified. Fe doping enhances the conductivity observed in electrochemical impedance spectroscopy, and from the magnetic response of pectin evidence for Fe
is identified. The Li-ion half-cell prepared with pectin as binder for anode materials such as graphite shows stable charge capacity over long cycle life, and with slightly higher specific capacity compare with the cell prepared using polyvinylidene fluoride (PVDF) as binder. A novel enhanced charging specific capacity at a high C-rate is observed in cells with pectin binder, suggesting that within a certain rate (∼5 C), pectin has higher capacity at faster charge rates. The pectin system is found as a viable base material for organic-inorganic synthesis studies.
Stress variation induced bandgap tuning and surface wettability switching of spinel nickel ferrite (NiFe
O
, NFO) films were demonstrated and directly driven by phase transition via a post-annealing ...process. Firstly, the as-deposited NFO films showed hydrophilic surface with water contact angle (CA) value of 80 ± 1°. After post-annealing with designed temperatures ranged from 400 to 700 °C in air ambience for 1 hour, we observed that the crystal structure was clearly improved from amorphous-like/ nanocrystalline to polycrystalline with increasing post-annealing temperature and this phenomenon is attributed to the improved crystallinity combined with relaxation of internal stress. Moreover, super-hydrophilic surface (CA = 14 ± 1°) was occurred due to the remarkable grain structure transition. The surface wettability could be adjusted from hydrophilicity to super-hydrophilicity by controlling grain morphology of NFO films. Simultaneously, the saturation magnetization (M
) values of NFO films at room temperature increased up to 273 emu/cm
accompanied with transitions of the phase and grain structure. We also observed an exceptionally tunable bandgap of NFO in the range between 1.78 and 2.72 eV under phase transition driving. Meanwhile, our work demonstrates that direct grain morphology combined with the stress tuning can strongly modulate the optical, surface and magnetic characteristics in multifunctional NFO films.
博士
國立臺北科技大學
機電學院機電科技博士班
105
This work has focused on the study of structure, morphology, chemical adsorption, surface wettability, and optical properties of hydrophobic ZnO nanostructured films onto ...glass substrate by using magnetron sputtering technique. We systematically modulated grain structure from nano- to micro- types by controlling the various internal stress states of films to study the relationship between morphology and surface wettability. The evolution of surface wettability was found to change from hydrophobicity to hydrophilicity as transforming the internal stress states from compressive to nearly-free, meanwhile, the ability of surface chemical absorption is getting weak. Moreover, glancing angle deposition (GLAD) method was used to improve the surface wettability of ZnO nanostructured films. While the ZnO film sputtered at the glancing angle of 30◦, the numbers of smaller grains spread onto the film surface and stacked, then, begins to form many smaller size apertures that could provide much more opportunity for air storage and become air pocket to shore up the water droplet that leads to better surface wetting behavior. However, the surface morphology transition can be attributed to the shadow effect which is induced during GLAD process. In addition, we first found that the surface wettability and optical properties of ZnO nanostructured films can be improved and controlled by capping with various thicknesses of magnetic metal layer, besides, to the best of our knowledge, the thickness effect of magnetic metal capping layer atop textured ZnO related to the unique physical properties is seldom studied. Firstly, pure ZnO nanostructured film exhibits a remarkable near-band-edge emission peak located at around 370 nm with a bandgap of 3.35 eV. When a single magnetic metal layer ranged from 5 to 20 nm was capped onto ZnO film, the intensity of near-band-edge emission peak decreased and the emission band shifted. This phenomenon was due to the oxygen vacancy effect and could be attributed to rise concentration of structural defects in the bilayer films. Therefore, a simple tunable method is achieved and presented here that the surface wettability and optical property of ZnO phase can be effectively controlled by capping a single bimetallic magnetic layer. The magnetic metal/ZnO heterostructure bilayer films exhibited many novel and valuable magnetoelectric applications in future due to its multifunctional behaviors.
