Ferromagnetic nanoclusters hybridized in Mn-incorporated GaInAs layers during metal–organic vapour phase epitaxial growth on InP layers under low growth temperature conditions

We demonstrate the successful formation of ferromagnetic nanoclusters in Mn-incorporated GaInAs layers grown by metal–organic vapour phase epitaxy on InP(100) substrates under low growth temperature conditions below 450 °C. We find that MnAs nanoclusters with NiAs-type hexagonal crystallographic structures, which show ferromagnetic characteristics up to a relatively high temperature of about 305 K, are formed near the layer surfaces of Mn-incorporated GaInAs layers grown at 440 °C. After deposition of undoped InP layers on Mn-incorporated GaInAs layers, MnP nanoclusters with orthorhombic cubic crystallographic structures, in which 7% arsenic is incorporated, are formed in InP layers. The samples with MnP nanoclusters show strong ferromagnetic coupling up to about 305 K, although the Curie temperature of MnP bulk compounds is 291 K. Energy dispersive x-ray spectroscopy (EDS) indicates that Mn concentrations in InP and GaInAs layers surrounding MnP nanoclusters are almost negligible. MnAs nanoclusters are also formed in Mn-incorporated GaAs layers grown under low growth temperature conditions of 450 °C on GaAs(100) substrates. From the results of magnetic characterizations with respect to growth temperatures of the samples, we found that all the Mn-incorporated GaAs layers grown at temperatures below 450 °C showed ferromagnetic behaviour.http://www.iop.org

Hexagonal ferromagnetic MnAs nanocluster formation on GaInAs∕InP (111)B layers by metal-organic vapor phase epitaxy

The authors report the self-assembly of hexagonal MnAs nanoclusters on GaInAs (111)B surfaces by metal-organic vapor phase epitaxy. The ferromagnetic behavior of the nanoclusters dominates the magnetic response of the samples when magnetic fields are applied in a direction parallel to the wafer plane. For the magnetic fields applied in a direction perpendicular to the plane, diamagnetic characteristics are dominant. The results indicate that the c axis of the nanoclusters is perpendicular to the plane, and that their a axis is in plane. They are consistent with the results of crystallographic analysis, where the nanoclusters' c axis is shown to be along a GaInAs [–1–1–1] direction

Knowledge exploratory project for nanodevice design and manufacturing

We are developing a framework for knowledge creation in nanodevice development, based on collaboration between nanodevice engineers and computer science researchers. Development of nanodevices requires a variety of knowledge; some of this knowledge is tacit, based on the user's experience. Therefore, it is difficult to become a good engineer in this development process. We propose the concept of "Evidence-based experiment planning" and develop a process for supporting experiment planning in nanodevice development. This system applies knowledge discovery techniques to records of previous experiments to extract experienced engineers' tacit knowledge

Magnetic Sensor Devices Based on Ordered Planar Arrangements of MnAs Nanocluster

We propose planar magneto-electronic devices based on accurately positioned and shaped ferromagnetic MnAs nanoclusters in NiAs structure. The prototype discussed consists of a small hexagon-shaped cluster sandwiched between two elongated clusters with fixed magnetic orientations. The magnetization of the center cluster is free and can be rotated by an external magnetic field. Our ab initio calculations yield a strong dependence of the conductance as a function of the direction of the external magnetic field which exhibits an in-plane symmetry of 360 degrees

Magnetic domain characterizations of anisotropic-shaped MnAs nanoclusters position-controlled by selective-area metal-organic vapor phase epitaxy

The authors report the buildup fabrication and magnetic domain characterizations of anisotropic-shaped MnAs nanoclusters position-controlled on partially SiO2-masked GaAs (111)B substrates by selective-area metal-organic vapor phase epitaxy. Magnetic force microscopy reveals that both the symmetric- and anisotropic-shaped nanoclusters show spontaneous magnetization at room temperature. Some of the nanoclusters show a single magnetic domain, in which magnetized directions are along one of the a-axes of NiAs-type MnAs, after the external magnetic fields up to 3500 Gauss are applied in-plane. The magnetic domains are well controlled by introducing both magnetocrystalline and shape magnetic anisotropies in the anisotropic-shaped nanoclusters