Magnetic properties of GaMnAs nanodot arrays fabricated using porous alumina templates

Abstract

CdSe quantum dots-poly(3-hexylthiophene) nanocomposite sensors for selective chloroform vapor detection at room temperature Appl. Phys. Lett. 101, 173108 (2012) An "edge to edge" jigsaw-puzzle two-dimensional vapor-phase transport growth of high-quality large-area wurtzite-type ZnO (0001) nanohexagons Appl. Phys. Lett. 101, 173105 (2012) Ti-doped hematite nanostructures for solar water splitting with high efficiency J. Appl. Phys. 112, 084312 (2012) Near-infrared enhanced carbon nanodots by thermally assisted growth Appl. Phys. Lett. 101, 163107 (2012) Additional information on J. Appl. Phys. Ordered arrays of GaMnAs magnetic semiconductor nanodots have been fabricated using anodic porous alumina templates as etch masks. The magnetic behavior is studied for prepared arrays with 40 nm dot diameter, 15 nm dot thickness, and 80 nm periodicity. The disklike nanodots exhibit an easy axis for fields applied in the radial direction and a hard axis in the smaller direction. In the radial direction superparamagnetism is observed with a blocking temperature of 30 K. The fabrication technique is convenient for preparing nanodot arrays of compound semiconductors that cannot be formed by self-assembly techniques. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2955450͔ INTRODUCTIONAs research in nanoscale electronics and magnetics is flourishing, so is the demand for nanostructures of unique materials. Following the progress of growing twodimensional ͑2D͒ epitaxial structures, there has been significant advancement in fabricating lower-dimensional structures, namely, nanodots, nanowires, and nanotubes. Fabrication of highly ordered nanodot arrays composed of quantum dot semiconductors 1 and ferromagnetic nanoparticles 2,3 is drawing increased interest as advanced devices call for smaller nanostructured systems.1,4 Current research on the preparation of semiconducting nanodot arrays relies mainly on self-assembly during growth, such as InAs quantum dots in GaAs or postgrowth fabrication using photo lithography or electron beam lithography and etching. Another promising technique for fabricating nanodot arrays is the use of porous templates, such as anodic porous alumina. These can be used as shadow masks for direct deposition, [5][6][7] selective etching, 7-9 and preparation of imprint molds. 10,11 There are several advantages of using these mask techniques: ͑1͒ the fabrication of smaller dot sizes Ͻ10 nm, ͑2͒ the rapid manufacture of large-size arrays, and ͑3͒ the possibility of fabricating nanodot arrays made from a larger class of materials, including metals, compound semiconductors, and insulators. This report describes the fabrication and magnetic properties of GaMnAs magnetic semiconductor nanodot arrays. The fabrication process uses anodic porous alumina as deposition masks followed by plasma etching. A thin film of the ferromagnetic semiconductor GaMnAs is first deposited on a GaAs substrate. This is followed by the deposition of metal nanodots on the film surface using porous alumina as a mask. A ke...

Fast fabrication of self-ordered anodic porous alumina on oriented aluminum grains by high acid concentration and high temperature anodization

“…Self-ordered anodic porous alumina, which is fabricated by anodization of aluminum with nanopores arranged in a quasi-periodic hexagonal pattern [1][2][3][4][5], has been widely used as a template for the synthesis of various nano-structured materials, such as nano-dots [6], nano-wires [7,8], nanotubes [9,10], and especially for arrays of nano-elements whose collective behavior may not be realized by individual nano-elements [11,12], such as phonic band gap crystals [13], nano-magnetic arrays [14,15], nano-electronics [16], and so on.…”

InGaAs Quantum Dots on Cross‐Hatch Patterns as a Host for Diluted Magnetic Semiconductor Medium

“…MBE is typically used to grow III-V compounds such as GaAs (the host for GaMnAs), InAs (host for InMnAs), and InGaAs (host for GaInMnAs); all are potential hosts for room-temperature DMS materials. Recently, it has been shown that GaMnAs nanodot arrays are a DMS with = 140 K [9]. The synthesis of such GaMnAs quantum dot arrays, however, requires top-down masking technique which creates structural defects and is thus inferior to self-assembled techniques that can grow defects-free QDs, particularly if the technique can grow self-assembled and self-aligned QDs.…”

Macrospin behavior and superparamagnetism in (Ga,Mn)As nanodots

“…The onset of superparamagnetism of nanosized flat ͑Ga,Mn͒As nanodots with in-plane anisotropy has been recently proved. 16 However, the results did not allow testing the validity of the Néel-Brown model as the size distribution was large and the inplane anisotropy rather complicated. In this paper, we focus on a very well-defined system ͑narrow size distribution, outof-plane anisotropy͒ which simplifies interpretations and allows proving that the Néel-Brown model can really be applied to this material.…”