Ion beam sputtered nanostructured semiconductor surfaces as templates for nanomagnet arrays

Abstract

The ongoing tendency for increasing the storage densities in magnetic recording techniques requires a search for efficient routes to fabricate and characterize nanomagnet arrays on solid supports. Spontaneous pattern formation in semiconductor heteroepitaxy or under ion erosion of semiconductor surfaces yields nanostructured substrates that can serve as templates for subsequent deposition of magnetic material. The nanostructured morphology of the template can easily be replicated into the magnetic coating by means of the shadow deposition technique which allows one to selectively cover specific areas of the template with magnetic material. Here, we demonstrate that ion bombardment induced hexagonally arranged GaSb dots are suitable templates for fabricating by shadow deposition close-packed nanomagnets with a lateral extension of ≤50 nm, i.e. with a resulting storage density of up to 0.2 Tbit in(-2). Magnetic-force microscopy (MFM) measurements revealed that the individual nanomagnets-which are located on the tops of the semiconductor hillocks-are single domain and show mainly independent magnetization. The coupling behaviour was estimated from correlation function analysis of the MFM data. In addition, magneto-optical Kerr effect measurements demonstrate that the nanomagnets can be magnetized either out-of-plane or in-plane and show remanence at room temperature, with a coercive field of 120 mT.

Thin Film Deposition Using Energetic Ions

“…Shadow deposition at moderate angles between 20 and 45° allows the formation of nanomagnet sizes below 20 nm and storage densities of at least 0.2 Tbit in -2 . [ 165 ]. Alternatively, deposition of homogeneous thin films, covered by an overlayer susceptible to pattern formation and subsequent ion erosion of this top-layer, leading to a structured surface topography with local variations in the effective sputter yield, will lead to ordered arrays of magnetic nanoparticles [ 166 , 167 ].…”

Ion-Induced Nanoscale Ripple Patterns on Si Surfaces: Theory and Experiment

“…It was shown that the morphology of the nanorippled substrates modifies the magnetic properties of ultrathin single-crystalline [19] and poly-crystalline [20,21,22] metal films. In a similar manner, arrays of close-packed nanomagnets could recently be obtained by shadow deposition on hexagonally ordered dot patterns [23]. Moreover, the self-organized alignment of physical-vapor deposited metal nanoparticles on nanorippled substrates was recently observed, leading to large arrays of nanoparticle chains exhibiting polarization-dependent plasmon absorption [24,25].…”

“…With the same technique, also arrays of metallic nanowires could be produced [26,27,28]. Most of these applications crucially depend on certain properties of the template patterns such as a high degree of order in the case of storage media [17,23] or a well defined ripple wavelength that fits to the growth conditions of the nanoparticles [24]. A precise control of the pattern properties in turn requires detailed knowledge of the pattern formation process and the contributing mechanisms.…”

On the magnetic nanostructure of a Co-Cu alloy processed by high-pressure torsion

“…The domain sizes are in the range of 100 nm corresponding to the grain size in the as-deformed state [12], indicating single-domain behavior. To qualitatively characterize the morphology and magnetic domain sizes for each annealing temperature, we employ the following procedure which has been introduced for a comprehensive surface roughness characterization [26,27] but can also be applied to the MFM signal [28]. This procedure considers so-called auto-correlation and height-height correlation functions [26].…”