Increasing the quantum efficiency of InAs/GaAs QD arrays for solar cells grown by MOVPE without using strain-balance technology

Research into the formation of InAs quantum dots (QDs) in GaAs using the metalorganic vapor phase epitaxy technique ispresented. This technique is deemed to be cheaper than the more often used and studied molecular beam epitaxy. The bestconditions for obtaining a high photoluminescence response, indicating a good material quality, have been found among awide range of possibilities. Solar cells with an excellent quantum ef?ciency have been obtained, with a sub-bandgapphoto-response of 0.07 mA/cm2per QD layer, the highest achieved so far with the InAs/GaAs system, proving the potentialof this technology to be able to increase the ef?ciency of lattice-matched multi-junction solar cells and contributing to abetter understanding of QD technology toward the achievement of practical intermediate-band solar cells

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)