Study of focused-ion-beam–induced structural and compositional modifications in nanoscale bilayer systems by combined grazing incidence x ray reflectivity and fluorescence

Abstract

2012) 'Study of focused-ion-beaminduced structural and compositional modications in nanoscale bilayer systems by combined grazing incidence x ray reectivity and uorescence.', Journal of applied physics., 111 (4). 044324.Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A detailed analysis of the structural and compositional changes in NiFe=Au bilayers induced by a focused ion beam (FIB) is presented. NiFe=Au bilayers with different thickness were irradiated with a focused 30 keV Ga þ ion beam, and the evaluation of the individual layers and interfaces were investigated systematically as a function of a broad range of irradiation fluence using grazing incidence x ray reflectivity (GIXRR) and angular dependent x ray fluorescence (ADXRF) techniques carried out at synchrotron radiation sources. Experimental data were collected from 1.3 mm  4.5 mm structures, and irradiation of such a broad areas with a 100-nm-wide focused ion beam is a challenging task. Two irradiation regimes were identified: For Ga þ fluences < 15.6  10 14 ion=cm 2 (low dose regime), the main influence of the focused ion beam is on the interface and, beyond this dose (high dose regime), sputtering effects and ion implantation becomes significant, eventually causing amorphization of the bilayer system. The broadening of the NiFe=Au interface occurs even at the lowest dose, and above a critical fluence (U ¼ 1.56  10 14 ion=cm 2 ) can be represented by an interfacial-intermixed layer (Ni x Fe y Au (1-x-y) ; x ¼ 0.5-0.6, y ¼ 0.1-0.15) formed between the NiFe and Au layers. The thickness of this layer increases with irradiation fluence in the low dose regime. A linear relationship is found between the squared intermixing length and irradiation fluence, indicating that FIB-induced mixing is diffusion controlled. The ballistic model fails to describe FIB-induced intermixing, indicating that thermodynamical factors, which might be originated from FIB specific features, should be taken into account. Despite the complexity of the chemical and structural formation, good agreement between the experiment and theory highlights the functionality of the combined GIXRR and ADXRF techniques for studying intermixing in high resolution. V C 2012 American Institute of Physics. [http://dx

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties

“…The structure of the interface was also investigated through grazing incidence x-ray reflectivity (GIXR) measurements at the XMaS beamline at the ESRF, Grenoble, France. Full details of the experimental procedure and analysis of the interface width as a function of irradiation dose can be found in our previous work [25]. In this paper, we extend the structural analysis to elucidate the nature of the interfaces in terms of the contributions from chemical intermixing and topological roughness.…”

Local control of magnetic damping in ferromagnetic/non-magnetic bilayers by interfacial intermixing induced by focused ion-beam irradiation

“…In contrast, intermixing at the FM/NM interface was significant, leading to a compositionally graded alloy extending over several nanometers at the interface. 28 Furthermore, quasi-static MOKE, SQUID, and x-ray magnetic circular dichroism (XMCD) measurements of FIB irradiated NiFe/Au bilayers revealed complex changes in the magnetization as a function of the ion beam dose. 24 For a 2.5 nm Au cap, the saturation magnetization falls rapidly in the low dose regime to a minimum around 1.3-2.0 pC/lm 2 and recovers to a small peak before falling further with increasing irradiation.…”

“…Detailed analysis of the structural changes induced by low-dose FIB irradiation in NiFe/Au bilayers, undertaken using grazing incidence x-ray reflectivity, x-ray fluorescence, and Monte Carlo simulations, 28 showed that sputtering of material was very limited at these doses and restricted to the non-magnetic capping layer. Also, Ga þ implantation was a very small dopant fraction (up to the order of 1%) over the relevant dose range.…”

“…24 The precessional frequency falls with ion beam dose, but displays a small peak that is correlated in dose with a feature in the dose dependent magnetic moment. 28 The origin of this behavior is not currently understood.…”

Improving metal/semiconductor conductivity using AlOx interlayers on n-type and p-type Si

“…This kind of intermixing is possible at the very early stage of metal deposition on ultra-thin interfacial layers. 25 Several models have been proposed to explain the origin of this dipole effect, such as oxygen vacancies caused by substitution of dopant metal atoms in high-j dielectrics, 26 average dipole moment of bonds at the interface, 27 and group electronegativity of dopant parent metals in the dipole layer. 28 The dipole sets up a large electric field close to the Si interface causing a sharp increase in the band bending of the Si majority carrier band.…”