An effective postgrowth electrical tuning, via an oxygen releasing method, to enhance the content of non-noble metals in deposits directly written with gas-assisted focused-electron-beam-induced deposition (FEBID) is presented. It represents a novel and reproducible method for improving the electrical transport properties of Co-C deposits. The metal content and electrical properties of Co-C-O nanodeposits obtained by electron-induced dissociation of volatile Co(CO) precursor adsorbate molecules were reproducibly tuned by applying postgrowth annealing processes at 100 °C, 200 °C, and 300 °C under high-vacuum for 10 min. Advanced thin film EDX analysis showed that during the annealing process predominantly oxygen is released from the Co-C-O deposits, yielding an atomic ratio of Co:C:O = 100:16:1 (85:14:1) with respect to the atomic composition of as-written Co:C:O = 100:21:28 (67:14:19). In-depth Raman analysis suggests that the amorphous carbon contained in the as-written deposit turns into graphite nanocrystals with size of about 22.4 nm with annealing temperature. Remarkably, these microstructural changes allow for tuning of the electrical resistivity of the deposits over 3 orders of magnitude from 26 mΩ cm down to 26 μΩ cm, achieving a residual resistivity of ρ/ρ = 0.56, close to the value of 0.53 for pure Co films with similar dimensions, making it especially interesting and advantageous over the numerous works already published for applications such as advanced scanning-probe systems, magnetic memory, storage, and ferroelectric tunnel junction memristors, as the graphitic matrix protects the cobalt from being oxidized under an ambient atmosphere.

The growing interest in magnetic nanowires (NWs) is connected to possibility of employing them for advanced applications in wide technological fields, such as data storage and biotechnology. In addition, NWs can be used as sensor devices for several applications, since they present high sensitivity to their environment. One of the major challenges when dealing with transport measurements in NWs is to trap them between electrodes, which allows electrical characterization and therefore fabrication of nanowire-based devices. Electrically neutral NWs can be deposited by dielectrophoresis (DEP) method, which requires the application of an alternating electric field between electrodes. In this work, Ni nanowires (NiNWs) fabricated by electrodeposition technique and properly dispersed in a dimethylformalmide (DMF) solution were deposited on top of Pt electrodes using the DEP method. The deposited NiNWs exhibit initially a Schottky-like current versus voltage behavior due to the high contact resistance between NiNW and electrode. Its reduction down to three orders of magnitude, reaching value less than the NiNW resistance, was achieved by depositing an ion beam-assisted 10 nm-thick Pt layer over the NWs extremities. Therefore, this method presents a suitable process of NWs deposition and electrical characterization. This can be used for investigation of electrical transport properties of individual NWs and fabrication of NWsbased devices, such as sensors and field-effect transistors. Especially for ferromagnetic NWs, one can use the present method for fabrication of magnetic field-effect transistors (MagFET).

Grande parte das pesquisas em materiais avançados esta vinculada a caracterizações elétricas, medidas de resistividade em função da temperatura, campo magnético e ângulo em relação ao campo magnético. Para a caracterização de materiais para aplicação em futuros dispositivos ou para melhor entendimento das propriedades de elétrica e magnéticas desses materiais. Essa área dentro da matéria condensada tem uma grande gama de aplicações. O desenvolvimento de novos dispositivos como MRAM, MagFET e SpinFET dependem desta caracterização inicial.

No abstract

The growing interest in magnetic nanowires (NW) is connected to possibility of employing them for advanced applications in wide technological fields, such as data storage and biotechnology. In addition, NW can be used as sensor devices for several applications, since they present high sensitivity to the environment. One of the major challenges when dealing with transport measurements in NW is to trap them between electrodes, which allows electrical characterization and therefore fabrication of nanowire-based devices. This can be used for investigation of electrical transport properties of individual NW and fabrication of NW-based devices, such as sensors and field effect transistors. Especially for ferromagnetic NW, one can use the present method for fabrication of magnetic field-effect transistors (MagFET).