Transmission Electron Microscopy Investigations of unstable InGaAsP epitaxial layers and calculation of image contrast

In last years interest to unstable semi-conductor alloys as to one of possibilities of nanoscale heterostructure production has renewed. In 80th years the direct evidence of homogeneous film dissociation to domains of various structure was shown by TEM. Before our work starts the images of InGaAsP layers that were grown in unstable region of phase diagram has been obtained by several research groups [1-3]. It was informed that TEM plane view images of such layers contain fine-scale structure (with period about 10 nm) and coarse-scale structure (with period about 100 nm) of intensity modulation along [100] and [010] directions. In the literature there are two opinions about these images. A number of authors suppose that coarse-scale modulation structure corresponds to solution modulation of unstable InGaAsP layer. Origin of fine-scale structure either are not explained or it is considered, that fine-scale modulation structure is inherent in all solid layers with three or more components. Another authors consider that only fine-scale structure correspond to solution modulation. And coarse-scale structure is consequence of layer dissolving and it can arise due to redistribution of strain fields in sample or curvature of samples surface. Our goal is to study influence of growth conditions on InGaAsP laye

Comparative Energy Modeling of Multiwalled Mg₃Si₂O₅(OH)₄ and Ni₃Si₂O₅(OH)₄ Nanoscroll Growth

Spontaneously scrolling hydrosilicate nanotubes raise additional attention due to their sorption, catalytic, and other functional properties. Layered hydrosilicates like chrysotile and pecoraite form primarily multiwalled nanotubes and nanoscrolls with relatively wide diameter and length distributions. To understand the reasons behind these issues we propose here an energy model of multiwalled nanoscroll formation and growth that accounts for strain, surface, and adhesion energy changes. Objects of comparison are chrysotile and pecoraite nanoscrolls, obtained by hydrothermal synthesis and characterized by X-ray diffraction and microscopic techniques. Energy modeling reveals a preferable nanoscroll cross-section consisting of 12 to 13 chrysotile layers or 25 to 26 pecoraite layers. The energy effect of scrolling is relatively low (3–5 kJ/mol), and the energy minimum becomes broader during growth

Magnetic properties of synthetic Ni

The present study focuses on the magnetic properties of the nanotubular Ni3Si2O5(OH)4 pecoraite, the structural analogue of chrysotile, obtained by hydrothermal synthesis. The cell parameters of the material, determined by X-ray diffraction, are $a=0.528(1)\ \text{nm}$ , $b=0.917(0)\ \text{nm}$ , $c=1.460(1)\ \text{nm}$ and $\beta=92.4(7)^{\circ}$ . The element analysis revealed the decrease of the Ni:Si ratio after hydrothermal treatment. The synthesized nanotubes have bigger outer and inner diameters in comparison to chrysotile. Using a vibration sample magnetometer, we determined the temperature of the ferromagnetic transition (23.7 K), $\mu_{\mathrm{eff}}$ of the $\text{Ni}^{2+}$ ion in pecoraite $(3.48\ \mu \text{B})$ and the blocking temperature (18 K)