Focused electron beam induced deposition: A perspective

Abstract

Summary Background: Focused electron beam induced deposition (FEBID) is a direct-writing technique with nanometer resolution, which has received strongly increasing attention within the last decade. In FEBID a precursor previously adsorbed on a substrate surface is dissociated in the focus of an electron beam. After 20 years of continuous development FEBID has reached a stage at which this technique is now particularly attractive for several areas in both, basic and applied research. The present topical review addresses selected examples that highlight this development in the areas of charge-transport regimes in nanogranular metals close to an insulator-to-metal transition, the use of these materials for strain- and magnetic-field sensing, and the prospect of extending FEBID to multicomponent systems, such as binary alloys and intermetallic compounds with cooperative ground states. Results: After a brief introduction to the technique, recent work concerning FEBID of Pt–Si alloys and (hard-magnetic) Co–Pt intermetallic compounds on the nanometer scale is reviewed. The growth process in the presence of two precursors, whose flux is independently controlled, is analyzed within a continuum model of FEBID that employs rate equations. Predictions are made for the tunability of the composition of the Co–Pt system by simply changing the dwell time of the electron beam during the writing process. The charge-transport regimes of nanogranular metals are reviewed next with a focus on recent theoretical advancements in the field. As a case study the transport properties of Pt–C nanogranular FEBID structures are discussed. It is shown that by means of a post-growth electron-irradiation treatment the electronic intergrain-coupling strength can be continuously tuned over a wide range. This provides unique access to the transport properties of this material close to the insulator-to-metal transition. In the last part of the review, recent developments in mechanical strain-sensing and the detection of small, inhomogeneous magnetic fields by employing nanogranular FEBID structures are highlighted. Conclusion: FEBID has now reached a state of maturity that allows a shift of the focus towards the development of new application fields, be it in basic research or applied. This is shown for selected examples in the present review. At the same time, when seen from a broader perspective, FEBID still has to live up to the original idea of providing a tool for electron-controlled chemistry on the nanometer scale. This has to be understood in the sense that, by providing a suitable environment during the FEBID process, the outcome of the electron-induced reactions can be steered in a controlled way towards yielding the desired composition of the products. The development of a FEBID-specialized surface chemistry is mostly still in its infancy. Next to application development, it is this aspect that will likely be a guiding light for the future development of the field of focused electron beam induced deposition.

Fabrication of FeSi and Fe3Si compounds by electron beam induced mixing of [Fe/Si]2 and [Fe3/Si]2 multilayers grown by focused electron beam induced deposition

“…Here we notice that understanding the reason for the sharp transition of Fig. 1 involves the solution of a system of Langmuir differential adsorption rate equations and the knowledge of the related adsorption, diffusion, desorption and decomposition parameters [19,23,24], which is beyond the aim of the present work. However, as an hint for future investigations, we observe that the residence time of Si 5 H 12 in the SEM was rather long, since it was possible to grow Si-based deposits for some hours after having close the relative Si 5 H 12 dosimeter.…”

“…This picture is maintained until the flux of F e(CO) 5 Electron irradiation has been used to induce phase transformations in bulk and low dimensional systems [27,28], and to tune the physical properties of graphene and carbon nanotubes [29]. In a series of recent papers we have started to investigate the effects of electron beam irradiation on the microstructure of FEBID samples [19]. For example, it was shown that during electron-beam irradiation the carbon-like matrix of Pt-C nanocomposites tends to graphitize, while the intergrain distance of the P t nanograins is reduced, which is due to carbon removal and to an increase of the diameter of the grains [30].…”

“…The deposits fabricated by means of these precursors are either amorphous or granular metals made of metallic nanoparticles embedded in a carbonaceous matrix. Depending on the metal atomic species and the atomic concentrations, either insulating, semiconducting, metallic or superconducting samples can be prepared [18,19,22].…”

“…In FEBID the adsorbed molecules of a precursor gas injected in a scanning electron microscope (SEM) dissociate by the interaction with the electron beam depositing the sample during the rastering process [18,19].…”

Dielectric sensing by charging energy modulation in a nano-granular metal

“…Sensitive Hall sensor devices have been developed employing Cobased structures obtained with the precursor CO 2 (CO) 8 with excellent sensitivity for local magnetic stray field detection [1,2]. The development of miniaturized strain and force sensors followed next which took advantage of the nano-granularity of Pt(C)-based FEBID structures obtained from the precursor CH 3 CpCH 3 Pt (Cp: cyclopentadienyl) [3] and proved to be highly interesting for atomic force microscopy sensors [4]. The working principle for the exploited strain-resistance effect was found to be rooted in the sensitive dependence of the hopping transport between the metallic Pt nano-grains of about 3 nm diameter through a carbonaceous matrix [5].…”