R. Che

Fabrication and electron holography characterization of FePt alloy nanorods

Well-aligned, ferromagnetic FePt nanorods have been fabricated by electron beam-induced deposition using an ultrahigh-vacuum scanning electron microscope. A mixture gas of iron pentacarbonyl and cyclopentadienylplatinum (IV) trimethyl was used as a precursor and post-annealing at 600 °C for 2 h was performed to accomplish the crystallization process. Each nanorod was composed of a chain of crystalline Fe-Pt alloy nanoparticles encapsulated within a carbon-containing sheath. The nanoparticles were identified to be face centered tetragonal (fct) FePt phase (L10,P4∕mmm) by electron diffraction and high-resolution transmission electron microscopy (HRTEM). The residual magnetic flux density Br of the nanorods was evaluated to be about 1.53 T via off-axis electron holography, showing a strong ferromagnetic character.

Field electron emission from single carbon nanorod fabricated by electron beam induced deposition

Individual carbon nanorod was fabricated on a tungsten needle tip by electron beam induced deposition. Precursor was phenanthrene (C4H10) and deposition experiment was done using a scanning electron microscope at room temperature. Tungsten needle tip together with the as-deposited nanorod was mounted inside a specially designed transmission electron microscope (TEM) specimen holder and its field electron emission properties were investigated in situ. Relationship between micro-structure and emission property of the nanorod was established. It was found that the surface structure at the top of nanorod, such as a small protrusion within only several nanometers scale, has significant influence on the field emission property. An emission current of several tens of nano-ampere flowing through this nanorod could induce resistance heating. In several minutes, this thermal energy could transform the original amorphous carbon into a graphite-like structure embedded with fullerenes. The turn-on voltage of the graphite-like nanorod was about 11 V less than that of the original amorphous case.

Effects of heat treatment on electric properties of nanorods formed by electron beam-induced deposition

Nanometer-sized rods were fabricated by an electron beam-induced deposition technique with iron pentacarbonyl. The electric properties of the as-deposited and heat-treated nanorods were measured in situ using a transmission electron microscope. The obtained current?voltage curve showed a nonlinear characteristic, and the resistivity was in the order of 10-2 ? m in the case of the as-deposited nanorods. After a heat treatment at 600 ?C in vacuum, the nanorods transformed to ?-Fe, and a resistivity of approximately 10-6 ? m and a metallic characteristic were obtained. This suggests that position- and shape-controlled metallic nanowires can be formed by electron beam-induced deposition combined with heat treatment.

Carbon nanostructure on a tungsten needle tip formed by electron beam induced deposition and its graphitization through resistive heating

Using ferrocene as a precursor, an amorphous carbon nanorod was fabricated on a tungsten needle tip by electron beam induced deposition inside an ultrahigh-vacuum scanning electron microscope at room temperature. This needle tip was driven by a stepping motor and pizeo-driving device to make contact with a molybdenum substrate inside a specially designed transmission electron microscope (TEM) specimen holder. A 100 µA current flowed through this nanorod and resistance heating was induced. Within 120 s, the original amorphous carbon nanorod was transformed into graphite nanostructures by this thermal energy. This phase transformation process was confirmed by high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). After applying a current of 120 s, graphite sheets with 0.34 nm lattice spacing in HRTEM image and π* bonding peak in EELS spectra were detected from the nanorod, which were not detected before that treatment.

Low Energy Ga Ion Beams Bombardment onside Insulating Materials and X-ray Emission

X-ray spectra from the surface of insulating samples were measured using a 30 kV Ga+ focused ion beam instrument equipped with an energy dispersive X-ray spectrometer, showing an intense emission of low energy X-rays from insulating materials such as Al-K and O-K of Al2O3. This low energy ion induced X-ray emissions (LIIXE) from insulating materials is expected as a new analytical technique for light elements in insulating samples. It was found that X-ray yield induced by Ga+ ion beam irradiation depends on the incident beam energy. It was also found that high voltage of a secondary electron detector located near the sample strongly influences the intensity of X-ray emission, implying that bombardment of electrons, which may come from the chamber wall, onside the sample surface is a key phenomenon for the X-ray emissions.

Resistivity measurements of nanorods formed by electron beam-induced deposition

Insulators and conductors as well as semiconductors are necessary to make an electronic device. The electric properties of nanometer-sized structures or wires produced by EBID are, therefore, of importance for the application to nanodevices. In this paper, the resisitivity of nanorods produced by electron beam-induced deposition was measured.

In situ generation and growth behavior of alpha-Fe nanocrystals by electron beam induced deposition using iron pentacarbonyl

In this work, it was found that alpha-Fe nanocrystals were generated and grew around the focused electron beam irradiation points (deposited nanodots) on the substrate at room temperature during the EBID process in an ultrahigh-vacuum field emission gun scanning electron microscope (UHV-FEG-SEM), operated at 30 kV with a precursor of Fe(CO)/sub 5/.

Carbon nanostructures formation by electron beam induced deposition at the apex of tungsten needle tip

In this investigation, individual carbon nanostructures were fabricated by EBID and subsequent current flowing at the apex of tungsten needle tip. This flowing current generates certain thermal energy induced by the resistance itself. Driven by the applied electric current and the associated ohm thermal energy, the as-deposited nanorod was transformed from the original amorphous phase into crystalline graphite structures. Hence, the in situ phase transformation process was successfully observed inside transmission electron microscope (TEM).

Potential distribution in resistivity measurement for nanorods formed by electron beam induced deposition

In the present work, EBID nanorods formed on a metal substrate and on tungsten tip were made contact in a transmission electron microscope (TEM) and its current vs. potential characteristics were measured in-situ. Electron holography was attempted to observe a local potential distribution (e.g., local resistance distribution) during the current-potential measurement.