Investigation of atomic mixing during adsorption of iron film on silver substrate

The results of calculations of the energy and magnetic characteristics of the activated adsorption of a monolayer ferromagnetic iron film on the silver surface are presented. The studies were carried out using two approaches: the variational method of the spin density functional taking into account temperature effects and inhomogeneous distribution of magnetization and the ab initio one, implemented using the VASP software package. Calculations were made of the total and interfacial energies, magnetic moment and adsorption energy of the Fe / Ag system, depending on the orientation of the substrate face, the coating parameter Θ and the fraction of adatoms in the film. The strong influence of mixing and the energetic advantage of the formation of a "sandwich" system have been revealed. A continuous Fe film will not form on the close-packed Ag face, which is confirmed by experimental studies.

Effect of the Sputtering Power on the Structure, Morphology and Magnetic Properties of Fe Films

In this paper, the radio frequency (RF) magnetron sputtering (MS) method was utilized to fabricate multiple sets of the iron film samples under different sputtering powers. With the help of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM), how the sputtering power affected the structure, morphology and magnetic properties of the iron film was studied. XRD results showed that all Fe films have a polycrystalline bcc structure and (110) preferred orientation. According to the Bragg equation calculation, the larger the sputtering power, the larger the average grain size, which is consistent with the results of AFM particle size analysis. The main reason is that the sputtering power affects the grain growth mode. As the sputtering power increases, it gradually changes from a small island-like growth to a thick columnar growth. However, from the surface morphology and height profile, we saw that the iron film deposited under 230 W had the most uniform grain size distribution and the grain size was relatively small. This is why thin films deposited under this condition have the best soft magnetic properties. The saturation magnetization (Ms) reaches 1566 emu/cm3, coercivity (Hc) is 112 Oe, and squareness ratio (Mr/Ms) is 0.40. Therefore, iron film prepared under 230 W has good comprehensive properties (highest Ms, lower Hc and Mr/Ms) that provide an experimental basis for further thin film research work.

Fe2O3 Blocking Layer Produced by Cyclic Voltammetry Leads to Improved Photoelectrochemical Performance of Hematite Nanorods

Hematite is a low band gap, earth abundant semiconductor and it is considered to be a promising choice for photoelectrochemical water splitting. However, as a bulk material its efficiency is low because of excessive bulk, surface, and interface recombination. In the present work, we propose a strategy to prepare a hematite (α-Fe2O3) photoanode consisting of hematite nanorods grown onto an iron oxide blocking layer. This blocking layer is formed from a sputter deposited thin metallic iron film on fluorine doped tin oxide (FTO) by using cyclic voltammetry to fully convert the film into an anodic oxide. In a second step, hematite nanorods (NR) are grown onto the layer using a hydrothermal approach. In this geometry, the hematite sub-layer works as a barrier for electron back diffusion (a blocking layer). This suppresses recombination, and the maximum of the incident photon to current efficiency is increased from 12% to 17%. Under AM 1.5 conditions, the photocurrent density reaches approximately 1.2 mA/cm2 at 1.5 V vs. RHE and the onset potential changes to 0.8 V vs. RHE (using a Zn-Co co-catalyst).

Fabrication and performance test of biodegradable supercapacitor

ABSTRACTPower source plays an important role in keeping normal functions of biodegradable electronic devices. In this paper, we proposed a fabrication method of biodegradable supercapacitor (BSC), which can provide energy for portable and implantable medical electronics. The BSC has a sandwich-like symmetric structure, which was assembled layer by layer. The electrochemical performances of BSC were measured, including the cyclic voltammetry test, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Titanium foil was used as a template to generate microstructure for polylactic acid (PLA) supporting substrate. The microstructure provided strong adhesion force for iron film in sputtering process. The nanoporous zinc oxide layer was prepared by evaporation-driven self-assembly technology on iron film. The nanoporous structure was in favour of ionic storage in charging-discharging process. About 60% of capacitance retention was achieved after 3000 times of cycling test. After connecting three BSC in series, a green LED pattern was lighted up immediately, indicating that the energy was stored in BSC device successfully. After immersing the BSC in DMEM, the BSC can be totally degraded gradually. This work provided a feasible scheme for developing biodegradable energy storage device, it also gave a possible avenue for powering biodegradable electronic devices.