The fabrication of one-dimensional nanostructures such as nanowhiskers attracts more and more attention due to their versatile device application. Contrary to the routine vapour-liquid-solid (VLS) method of the nanowhiskers growth which relies on the use of metal catalyst nanoparticles, so called catalyst-free (or self-catalytic) method allows to avoid any contaminations of nanowhiskers from a metal catalyst and therefore is of importance for the creation of the new devices.
MnP and Mn2P nanowhiskers have been grown by molecular-beam epitaxy (MBE) technique without any preliminary deposited metal catalyst on InP(100) and GaAs(111)B substrates. Mn was supplied using conventional Knudsen cell, whereas P2 was obtained by decomposition of tertiarybutylphosphine (TBP) inside the cracking cell.
The morphology measurements performed using SEM have shown that most of nanowhiskers obtained orient along crystallographic directions equivalent to <111>. STEM investigations have revealed that the growth of nanowhiskers is apt to be caused by the formation of Mn-based nanoclucters on the substrate surface. The self-catalytic growth of MnxP nanowhiskers has been found to be depended on the type of the substrates. The chemical composition of elements of nanowhiskers grown on GaAs(111)B substrate was detected to be close to Mn2P phase, while in case of InP(100) substrate the composition seemed to be correspond to MnP phase. Some of the nanowhiskers obtained on InP(100) substrate have more complicated structure containing InP part despite of the fact, that our MBE apparatus does not contain any In supply source, during which their amount has been increased with increase of the time of growth. It seems to be caused by the excess evaporation from InP substrate as well as diffusion of In atoms and their following absorption by MnP nanowhiskers. In this case, MnP nanowhiskers supposedly acted as a catalyst for the growth of InP nanowhiskers.
The measurements of temperature and field dependences of magnetization which have been carried out using vibration sample magnetometer (VSM) have shown that samples with nanowhiskers obtained on InP(100) substrate exhibit ferromagnetic properties up to room temperatures.
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