Magnetoelastic constant of thin films determined by a four-point bending apparatus

We have developed a method to variably induce lattice strains and to quantitatively evaluate the induced magnetic anisotropy. Both tensile and compressive strains were introduced into epitaxial films of cobalt ferrite (CFO) grown on a single crystal MgO(001) substrate using a four-point bending apparatus made of a plastic material fabricated by a 3D printer. The change in magnetic anisotropy due to bending strain can be measured quantitatively by using the conventional magneto-torque meter. The strain-induced magnetic anisotropy increased with the tensile strain and decreased with the compressive strain as expected from a phenomenological magnetoelastic theory. The magnetoelastic constant obtained from the changes in bending strains shows quantitatively good agreement with that of the CFO films with a uniaxial epitaxial strain. This signifies that the magnetoelastic constant can be evaluated by measuring only one film sample with strains applied by using the bending apparatus.

Bandgap engineering of α-Ga2O3 by hydrostatic, uniaxial, and equibiaxial strain

Ga2O3 is a wide bandgap semiconductor and an understanding of its bandgap tunability is required to broaden the potential range of Ga2O3 applications. In this study, the different bandgaps of α-Ga2O3 were calculated by performing first-principles calculations using the pseudopotential self-interaction correction method. The relationships between these bandgaps and the material's hydrostatic, uniaxial, and equibiaxial lattice strains were investigated. The direct and indirect bandgaps of strain-free α-Ga2O3 were 4.89 eV and 4.68 eV, respectively. These bandgap values changed linearly and negatively as a function of the hydrostatic strain. Under the uniaxial and equibiaxial strain conditions, the maximum bandgap appeared under application of a small compressive strain, and the bandgaps decreased symmetrically with increasing compressive and tensile strain around the maximum value.

Revealing nano-scale lattice distortions in implanted material with 3D Bragg ptychography

Small ion-irradiation-induced defects can dramatically alter material properties and speed up degradation. Unfortunately, most of the defects irradiation creates are below the visibility limit of state-of-the-art microscopy. As such, our understanding of their impact is largely based on simulations with major unknowns. Here we present an x-ray crystalline microscopy approach, able to image with high sensitivity, nano-scale 3D resolution and extended field of view, the lattice strains and tilts in crystalline materials. Using this enhanced Bragg ptychography tool, we study the damage helium-ion-irradiation produces in tungsten, revealing a series of crystalline details in the 3D sample. Our results lead to the conclusions that few-atom-large ‘invisible’ defects are likely isotropic in orientation and homogeneously distributed. A partially defect-denuded region is observed close to a grain boundary. These findings open up exciting perspectives for the modelling of irradiation damage and the detailed analysis of crystalline properties in complex materials.

Effect of the annealing temperature on the structural properties of hafnium nanofilms by magnetron sputtering

In this work investigated the effect of the annealing temperature on hafnium nanofilms obtained by DC magnetron sputtering on Si substrates. The nanofilms annealed through 100°C to 700°C by a High-Temperature Strip Heater Chambers (HTK-16N) on an X-ray Diffractometer (XRD). The microstructure and morphology of the films at different temperatures were investigated by XRD, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman Microspectrometer (RS). It was found that annealing affects changes in the lattice strains, texture, grain size, and roughness of Hf nanofilms. According to XRD data, the structure of the thin films showed amorphous from room temperature to 100°C and starting from a temperature of 200°C were changed crystallization. At 500°C a monoclinic structure corresponding to hafnium dioxide HfO2was formed in hafnium nanofilms.

Controlling of Lattice Strains for Crack-Free and Strong Ferroelectric Barium Titanate Films by Post-Thermal Treatment

In this study, we experimentally demonstrate the fabrication of ultra-smooth and crystalline barium titanate (BTO) films on magnesium oxide (MgO) substrates by engineering the lattice strain and the crystal structure via thermal treatment. We first grow crack-free BTO thin films at oxygen-depleted condition, and enhance the ferroelectric characteristics by post-annealing at high temperature. The roughened surface due to recrystallization during post-annealing is controlled by chemical-mechanical polishing (CMP) to retain the ultra-smooth surface morphology. Oxygen-depleted deposition allows a highly strained BTO film to grow on a MgO substrate with an ultra-smooth surface, and post-annealing relaxes the strain, resulting in the enhancement of the ferroelectricity. From Raman spectroscopy, reciprocal space map (RSM), and capacitance–voltage (C–V) curve measurements, we observe that the ferroelectricity of the BTO film strongly depends on the lattice strain relaxation and the phase transition from a-axis to c-axis oriented crystal structure.

Analysis the effect of cutting speed on wear and crystal structure on CVD and PVD layer carbide insert materials

It has been done analysis effect of cutting speed on wear and crystal structure on CVD and PVD layer carbide inserts has been performed. The purpose of the study was to determine the effect of cutting speed on wear, crystal size, dislocation density and micro lattice strain on CVD and PVD layer carbide insert materials to cut the AMS5643 stainless steel material. CVD and PVD layer carbide insert cutting process with cutting speed variation 113; 126; 140; 175 m/min with cutting motion of 0.38 mm/round and depth of cut 1.5 mm fixed. Wear test results showed that CVD layer carbide insert wear was 15% higher than PVD layer carbide inserts. The results showed that the size of CVD layer carbide insert crystals was smaller than PVD layer carbide inserts by 42% and the dislocation density of CVD layer carbide inserts made no significant difference to PVD layer carbide inserts, as well as micro lattice strains for CVD layer carbide inserts greater than PVD layer carbide inserts.