Focused Electron and Ion Beam Induced Deposition on Flexible and Transparent Polycarbonate Substrates (original) (raw)
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Metal-insulator transition in Pt-C nanowires grown by focused-ion-beam-induced deposition
Physical Review B, 2009
We present a study of the transport properties of Pt-C nanowires created by focused-ion-beam ͑FIB͒-induced deposition. By means of the measurement of the resistance while the deposit is being performed, we observe a progressive decrease in the nanowire resistivity with thickness, changing from 10 8 ⍀ cm for thickness ϳ20 nm to a lowest saturated value of 700 ⍀ cm for thickness Ͼ150 nm. Spectroscopy analysis indicates that this dependence on thickness is caused by a gradient in the metal-carbon ratio as the deposit is grown. We have fabricated nanowires in different ranges of resistivity and studied their conduction mechanism as a function of temperature. A metal-insulator transition as a function of the nanowire thickness is observed. The results will be discussed in terms of the Mott-Anderson theory for noncrystalline materials. An exponential decrease in the conductance with the electric field is found for the most resistive samples, a phenomenon understood by the theory of hopping in lightly doped semiconductors under strong electric fields. This work explains the important discrepancies found in the literature for Pt-C nanostructures grown by FIB and opens the possibility to tune the transport properties of this material by an appropriate selection of the growth parameters.
Materials Research …, 2005
A Dual Beam Focused Ion Beam (FIB) machine has been used to deposit platinum contacts on different nanostructured materials using both electron-and ion-assisted deposition. The electrical quality of the deposited platinum has been studied, and the feasibility of using this nanofabrication method to extract electrical parameters of nanomaterials demonstrated. The advantage of combining electron-and ion-assisted deposition instead of using only ion-assisted deposition is discussed. The possibility of applying this method in the fabrication of future nanodevices is demonstrated in a gas nanosensor prototype.
2014
Platinum nanowires with controlled texture and crystallite size were fabricated in nanoporous ion-track etched polycarbonate membranes by electrochemical deposition with different potential pulse sequences. The application of specific potential pulses ranging from À0.5 V to À1.3 V and reverse pulses with +0.2 V allows switching between a light h111i texture and a pronounced h100i texture along the nanowire axis. At the same time, the crystallite size determined by XRD was significantly increased from approx. 20 nm to 45 nm, yielding oligocrystalline wires, which are very difficult to obtain with Pt electrodeposition due to its pronounced tendency towards instantaneous nucleation. TEM verified the increase of the calculated average crystallite size of the Pt nanowires. We have been able to prove the necessity of each potential pulse and pulse duration by changing them in a systematical way. Key strategy to achieve large crystallite sizes and a pronounced texture was to reduce oversaturation of Pt adatoms during the reduction step and to preferentially dissolve lattice defects and nucleation sites by anodic removal. Additionally, the homogeneity of the Pt nanowire growth was evaluated for the applied pulse sequences by SEM. The results show that by reducing the deposition current density, the uniformity of the Pt nanowires was strongly enhanced. The proposed rational synthetic strategy allows to optimize the crystallinity, texture and monodispersity of Pt nanowires and is thus of considerable relevance for tailoring the functional properties of these structures.
Microelectronic Engineering, 2011
Experimental studies of the temperature dependent resistivity of platinum nanowires grown on an oxidised silicon wafer by using focused ion beam (FIB) have been made. A series of 4-terminal resistivity measurements were carried out in the temperature range 50-300 K on single nanowires of width and thickness $100 nm grown by decomposition of an organometallic precursor using Ga + ions of different accelerating voltages from 10 keV to 30 keV. Energy dispersive X-ray spectroscopy showed the nanowires to be composed of more than 60% by volume of carbon, the remainder being principally platinum and gallium. The exact composition depends on the accelerating voltage of the ions used. There is clear evidence from cross-sectional microscopy that the material is a composite consisting of a metallic phase present in the form of nanoscale clusters, randomly distributed in a matrix of carbon. Electrical measurements are consistent with this, showing a critical volume concentration for conduction, which is typical of electron transport in composites with percolating metal phase. Results show an unexpectedly high sensitivity of the temperature dependence of resistivity near the critical volume concentration, which has been explained to arise from thermal strain effects. The anomalous temperature/strain effects observed in this investigation might be exploited in temperature measurement and strain sensor applications.
Platinum thin films deposited on silicon oxide by focused ion beam: characterization and application
Journal of Materials Science, 2008
Focused ion beam system was used for deposition of platinum (Pt) thin films on thermally oxidized silicon (Si). Various test patterns (squares and lines) were deposited for electrical characterization of the films, using 2-and 4terminal measurements. Tests with parallel Pt lines were also carried out, and considerable leakage was detected for the interline distances in the sub-micron range. We investigated two ways to decrease the leakage current: inducing surfaces roughness and using an oxygen plasma after patterns deposition. A method of dielectrophoresis with an AC electric field was applied to align and deposit metallic multi-wall carbon nanotubes (CNT) between pre-fabricated metal, gold, and palladium electrodes with a micron-scale separation. Further, using focused electron and ion beam-deposited Pt contacts in two different configurations (''Pt-on-CNT'' and ''CNT-on-Pt''), 4-terminal measurements have been performed to evaluate intrinsic nanotube resistances.
Etched heavy ion tracks in polycarbonate as template for copper nanowires
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2001
30 and 40 lm thick polycarbonate foils were irradiated with Au 197 and Pb 208 ions of kinetic energy 1±2 GeV with uences between 10 6 and 10 9 ions/cm 2 . The latent tracks generated by the heavy ions were chemically etched providing membranes with cylindrical pores of diameters between 30 and 200 nm. These membranes have been used as templates for the creation of metallic nanowires of very high aspect ratio. A thin metal ®lm deposited on one side of the membrane acted as cathode in the two-electrode electrochemical cell, while a copper cone served as anode. The wires were grown potentiostatically. The electrochemical process was monitored by registering chronoamperometric curves for dierent cathode overvoltages, temperatures and concentrations of the electrolyte. Under suitable conditions, single-crystalline needles were produced. The morphology and crystallinity of the copper nanowires were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diraction. Ó
Nano Letters, 2014
We report an electron-beam based method for the nanoscale patterning of the poly(ethylene oxide)/LiClO 4 polymer electrolyte. We use the patterned polymer electrolyte as a high capacitance gate dielectric in single nanowire transistors and obtain subthreshold swings comparable to conventional metal/oxide wrap-gated nanowire transistors. Patterning eliminates gate/contact overlap which reduces parasitic effects and enables multiple, independently controllable gates. The method's simplicity broadens the scope for using polymer electrolyte gating in studies of nanowires and other nanoscale devices. 1 Keywords: III-V nanowires, polymer electrolytes, electron beam lithography, nanoelectronics.
Journal of Nanomaterials, 2009
We study the origin of the strong difference in the resistivity of focused-electron-and focused-Ga-ion-beam-induced deposition (FEBID and FIBID, resp.) of Pt performed in a dual beam equipment using (CH 3 ) 3 Pt(CpCH 3 ) as the precursor gas. We have performed in-situ and ex-situ resistance measurements in both types of nanodeposits, finding that the resistivity of Pt by FEBID is typically four orders of magnitude higher than Pt by FIBID. In the case of Pt by FEBID, the current-versus-voltage dependence is nonlinear and the resistance-versus-temperature behavior is strongly semiconducting, whereas Pt by FIBID shows linear currentversus-voltage dependence and only slight temperature dependence. The microstructure, as investigated by high-resolution transmission electron microscopy, consists in all cases of Pt single crystals with size about 3 nm embedded in an amorphous carbonaceous matrix. Due to the semiconducting character of the carbon matrix, which is the main component of the deposit, we propose that the transport results can be mapped onto those obtained in semiconducting materials with different degrees of doping. The different transport properties of Pt by FEBID and FIBID are attributed to the higher doping level in the case of FIBID, as given by composition measurements obtained with energy-dispersive X-ray microanalysis.