Nano-sized Devices Research Articles

Origins of magnetic damping measurement variations using ferromagnetic resonance for nano-sized devices

It is shown that ferromagnetic resonance measured in larger thin films yield varying results for damping in nanosized devices. Results are shown to critically depend on magnetic parameters, scalar and vector. Results here also explain why different experiments have concluded different size-dependent trends measuring damping with in-plane devices. The observed variation is due, in part, to a crossover in the dominant eigen-mode and unique eigen-mode evolution. However, antithesizing in-plane devices, we find that for out-of-plane magnetization, distinct symmetric eigen-modes demonstrates ideal stability, leading to no variation in apparent damping, suggesting a better measurement configuration using larger samples.

Thermal Stress Induced Thin Film Transfer from Single-crystal Silicon Layer on Sapphire Substrate

Silicon-on-sapphire (SOS) is a member of the silicon-on-insulator (SOI) family which uses a hetero-epitaxial process to generate thin films of semiconductor materials. SOS has become an attractive technology for low-power and radio-frequency integrated circuits. This study tends to apply SOS to thin film solar cell by thin film transfer technique. The nano-scale silicon thin film can be generated on the high quality sapphire substrate to form SOS. SOS is soaked in the special H+-chemical solution at first. The aluminum layer is bonded by thermal annealing treatment and the silicon thin film will transfer to the aluminum layer with cooling slowly due to the thermal stress induced. Through the special H+ chemical treatment and the annealing process, the SOS can be transferred to Si/Al layer and sapphire layer successfully. The Si/Al layer can be applied to thin film solar cell or other nano-size devices. The sapphire layer can be recycle for the SOS use.

The Stripping Behavior of High-Dose Ion-Implanted Photoresists in Supercritical CO2 Formulations

A new type of high-dose ion-implanted photoresist (HDI PR) stripping method was reported based on supercritical CO2 (scCO2) microemulsions consisting of branched hydrocarbon surfactant 2-ethyl hexanol polyoxyethylene-polyoxypropylene (EH-3) and co-solvent dimethylsulfoxide (DMSO). The optimized concentration of EH-3 and DMSO in scCO2 were 3 wt% and 2 vol.%, respectively, and the ratio of H2O and EH-3 is 1:1. The post-etch HDI PRs containing crust polymer were removed in the scCO2 microemulsions under the pressure of 10–25 MPa at 40–80°C for 10 min. The results revealed that the stripping efficiency increased with the pressure and temperature when the temperature is lower than 60°C. The 94% removal efficiency was achieved at 60°C and 20 MPa and then it gradually decreased as the temperature is higher than 60°C due to the lower scCO2 density at higher temperature. The magnetic agitation and pressure pulsation were favorable to HDI PR removal. The optimum stripping parameters were determined to be 60°C and 25 MPa for 20 min at which 100% photoresist removal efficiency was achieved in EH-3/DMSO/scCO2 microemulsions. This environmentally benign method provides a promising alternative to effectively strip the HDI PR for nano-sized devices in microelectronics processing.

Hybrid polymer-metal nanospheres based on highly branched gold nanoparticles for potential medical applications

Hybrid polymer-metal nanospheres are potential nano-sized medical devices that can provide multi-functions such as medical imaging and drug/biomolecule delivery. Gold nanoparticle-based hybrid nanospheres are particularly attractive owing to the unique optical and electronic properties that they possess. The polymer in hybrid nanospheres can be tasked for cancer cell targeting, DNA delivering etc. In the current investigation, a simple one-pot synthesis method was developed for producing folic acid-chitosan-capped gold (Au@CS-FA) nanospheres. These nanospheres consisted of a flower-like gold nanoparticle core and a cross-linked folic acid (FA)-conjugated chitosan shell. During the synthesis of Au@CS-FA nanospheres, FA-conjugated chitosan molecules acted as a reductant for gold and also as a structure-directing agent for the formation of highly branched gold nanoparticles. The evolution of Au@CS-FA nanospheres during their manufacture was studied using various analytical techniques and the mechanism of formation and growth was proposed. The Au@CS-FA nanospheres exhibited high-surface-enhanced Raman scattering which could be utilised for imaging at the single molecule level. The biopolymer shell was functionalised with -NH(2) and -COOH groups, which could be readily conjugated with macromolecules, peptides, nucleotides etc. for potentially wide applications of Au@CS-FA nanospheres in the medical field.

QUANTUM CAPACITANCE EFFECT ON ZIG-ZAG GRAPHENE NANOSCROLLS (ZGNS) (16, 0)

Miniaturization of electronic devices carries them to the quantum limits which mean quantum effect will be dominant in nano-size device characterization. A first band analytical model of the quantum capacitance for (16, 0) zig-zag graphene nanoscroll (ZGNS) is presented. The behavior of the quantum capacitance within the degeneracy limits is approximated using the Maxwell–Boltzmann approximation within a range of E - EF > 3KBT. The quantum capacitance is subsequently derived from the carrier density of the ZGNS due to its significance within one-dimensional (1D) devices by employing the Taylor's series expansion for parabolic energy band structure approximation. Additionally, the quantum capacitance analytical derivation in term of ZGNS physical form considering the Archimedean spiral-type structure is modeled. Because of its unique geometry structure which provides high area for intercalation, it is expected that ZGNS structure (length and interlayer distances) will alter the quantum capacitance. We also report that at first sub-band of (16, 0) ZGNS the quantum capacitance reach degenerate limit at approximately of ≅ 0.49 × 10-10 F/m @ 49 pF/m .

Non-equilibrium spatial distribution of Rashba spin torque in ferromagnetic metal layer

We study the spatial distribution of spin torque induced by a strong Rashba spin-orbit coupling (RSOC) in a ferromagnetic (FM) metal layer, using the Keldysh non-equilibrium Green's function method. In the presence of the s-d interaction between the non-equilibrium conduction electrons and the local magnetic moments, the RSOC effect induces a torque on the moments, which we term the Rashba spin torque. A correlation between the Rashba spin torque and the spatial spin current is presented in this work, clearly mapping the spatial distribution of Rashba spin torque in a nano-sized ferromagnetic device. When local magnetism is turned on, the out-of-plane (Sz) Spin Hall effect (SHE) is disrupted, but rather unexpectedly an in-plane (Sy) SHE is detected. We also study the effect of Rashba strength (αR) and splitting exchange (Δ) on the non-equilibrium Rashba spin torque averaged over the device. Rashba spin torque allows an efficient transfer of spin momentum such that a typical switching field of 20 mT can be attained with a low current density of less than 107A/cm2.

Molecular Communication Using Brownian Motion With Drift

Inspired by biological communication systems, molecular communication has been proposed as a viable scheme to communicate between nano-sized devices separated by a very short distance. Here, molecules are released by the transmitter into the medium, which are then sensed by the receiver. This paper develops a preliminary version of such a communication system focusing on the release of either one or two molecules into a fluid medium with drift. We analyze the mutual information between transmitter and the receiver when information is encoded in the time of release of the molecule. Simplifying assumptions are required in order to calculate the mutual information, and theoretical results are provided to show that these calculations are upper bounds on the true mutual information. Furthermore, optimized degree distributions are provided, which suggest transmission strategies for a variety of drift velocities.

Nonlinear resonant control of cross-cut photonic flows

We introduce the concept of a resonant tunneling photonic nanotriode that makes possible the mutual control of cross-cut light flows. The idea of this concept is based on the strong resonant interaction between the nearly phase-matched quasi-localized eigenmode of nonlinear planar dielectric waveguides and incident beams. We demonstrate that by means of variation of input guided wave intensities even small nonlinear phase mismatches may switch the bistable system from one equilibrium state to another and back, resulting in deep modulation of beam reflection and transmission coefficients due to the exchange between trapped and free photons. The suggested nanosize device can also serve as light amplifier, light modulator, controlled coupler, light flows divider, etc.

Anti-CEA loaded maghemite nanoparticles as a theragnostic device for colorectal cancer

Nanosized maghemite particles were synthesized, precoated (with dimercaptosuccinic acid) and surface-functionalized with anticarcinoembryonic antigen (anti-CEA) and successfully used to target cell lines expressing the CEA, characteristic of colorectal cancer (CRC) cells. The as-developed nanosized material device, consisting of surface decorated maghemite nanoparticles suspended as a biocompatible magnetic fluid (MF) sample, labeled MF-anti-CEA, was characterized and tested against two cell lines: a high-CEA expressing cell line (LS174T) and a low-CEA expressing cell line (HCT116). Whereas X-ray diffraction was used to assess the average core size of the as-synthesized maghemite particles (average 8.3 nm in diameter), dynamic light scattering and electrophoretic mobility measurements were used to obtain the average hydrodynamic diameter (550 nm) and the zeta-potential (−38 mV) of the as-prepared and maghemite-based nanosized device, respectively. Additionally, surface-enhanced Raman spectroscopy (SERS) was used to track the surface decoration of the nanosized maghemite particles from the very first precoating up to the attachment of the anti-CEA moiety. The Raman peak at 1655 cm−1, absent in the free anti-CEA spectrum, is the signature of the anti-CEA binding onto the precoated magnetic nanoparticles. Whereas MTT assay was used to confirm the low cell toxicity of the MF-anti-CEA device, ELISA and Prussian blue iron staining tests performed with both cell lines (LS174T and HCT116) confirm that the as-prepared MF-anti- CEA is highly specific for CEA-expressing cells. Finally, transmission electron microscopy analyses show that the association with anti-CEA seems to increase the number of LS174T cells with internalized maghemite nanoparticles, whereas no such increase seems to occur in the HCT116 cell line. In conclusion, the MF-anti-CEA sample is a biocompatible device that can specifically target CEA, suggesting its potential use as a theragnostic tool for CEA-expressing tumors, micrometastasis, and cancer-circulating cells.

Slot Optical Waveguide Usage in Forming Passive Optical Devices

We have reviewed the work on SOI slot optical waveguides followed by our work. In a slot waveguide structure, light can be confined in a low index slot guarded by high index slabs. Slot structures are being used in forming complex structures; such as ring resonator circuits. The increased round trip in ring resonator circuits signifies the importance of dispersion calculations. We did analytical and numerical investigations of slot structures' dispersion characteristics. Our dispersion tuned slot structures can help in reducing the dispersion effects on optical signal, which will in turn improve the efficiency of light-on-chip circuits. Since the advent of slot optical waveguides, SOI based slot optical waveguides have been under consideration. It has been found that glass based slot optical waveguide structures with relatively low refractive index contrast ratio can also play an important role in forming complex nano-size optical devices. We made use of power confined inside low index slot regions for a double slot structure. Opto-mechanical sensors have been proposed based upon: (a) variation in power confined inside low index slot region due to the movement of central high index slab under the action of external force (temperature, pressure, humidity, etc). vide Chinese Patent No. ZL 200710176770.1, 2007 (b) variation in power confined inside low refractive index slot regions due to movement of both slots under the action of external force (temperature, pressure, humidity, etc).

Size Evolution of the Surface Plasmon Resonance Damping in Silver Nanoparticles: Confinement and Dielectric Effects

A key parameter for optimizing nanosized optical devices involving small metal particles is the spectral width of their localized surface plasmon resonances (LSPR), which is intrinsically limited by the confinement-induced broadening (quantum finite size effects). I have investigated the size evolution of the LSPR width induced by quantum confinement in silver nanoparticles isolated in vacuum or embedded in transparent matrixes. Calculations have been performed within the time-dependent local density approximation in an extended size range, up to 40000 conduction electrons (diameter D ≈ 11 nm). The slope characterizing the 1/D linear evolution predicted by the simple classical “limited mean free path” model is found to depend noticeably on the surrounding matrix. The confinement-induced damping of the collective LSPR excitation is shown to be intimately related to the departure of the electron-background interaction from a pure harmonic law. In jellium-type models the damping is governed by the electronic...

Novel SOI Structures and Characterization Strategy

Innovative SOI materials and devices are reviewed with special attention to their electrical characterization. Appropriate measure-ment techniques and accurate interpretation of the experimental data are necessary steps for evaluating nanosize devices. Informative examples are selected from various structures including ultrathin SOI and GeOI, strained MOSFETs, multiple-gate transistors, nanowires, tunneling and memory devices.

Organic Nano-Sized Pigment Based on Bis(4-(N-(9,9-Diethyl-2- Fluorenyl)Phenylamino)Phenyl)Fumaronitrile as Highly Efficient Red Fluorescence

Red fluorescence was widely applied in full color organic light-emitting display and anti- counterfeit technology. Due to concentration quenching red fluorescence was weak and even no luminescence in a solution or solid state. Therefore, novel red fluorescent pigment bis(4-(N-(9, 9- diethyl-2-fluorenyl)phenylamino)phenyl)fumaronitrile (EFPAFN) with non-planar fluorenylamino group and fumaronitrile core was prepared. The compound existed a pair of antiparallel dipole limiting molecular interaction, showed strong red photoluminescence which centralized at 657 nm in solid film. The decomposition temperature of EFPAFN was observed at around 422 °C. In different polarity of solvents the absorption and emission peaks of EFPAFN showed positive and then negative solvatochromic shifts. EFPAFN in water/tetrahydrofuran (v/v, 9:1) mixture was adjusted and aggregated into small size particles in the range of 141-531 nm or big size particles of 255-825 nm as fluorescent organic nanoparticles (FONs). FONs of EFPAFN with donor-acceptor group showed strong emission at 653 nm and had potential applications in nano-sized fluorescence and optoelectronic device.

The influences of technological conditions and Au cluster islands on morphology of Ga2O3 nanowires grown by VLS method on GaAs substrate

The synthesis of semiconductor nanowires is more and more interested to the applications for building blocks of the innovative nano-sized devices and circuits, but the research and fabrication of these nanowires are also holding a number of difficulties and challenges. Among many different kinds of semiconductor nanowires, Ga2O3 is increasingly grown for many promising applications in nano-device production, namely nanowire LED and Laser. So far there are many synthesizing methods of semiconductor nanowires, among them the vapor–liquid–solid (VLS) method is simple, cheap and popular. However, when we use the VLS method for nanowire growth, various technological problems exist. This paper aims at investigating some influences of the growth technological conditions and Au metal catalyst on the morphology of Ga2O3 nanowire grown by VLS on GaAs substrate. The main considering factors include the different growing temperatures and times, the effects of Au diffusion, Au droplets formation, Au cluster islands formation, and gas volume of the growing tube/ampoule at the 10−1 torr low air pressure. The obtained experimental results regarding the structural properties of nanowires under these effects investigated by scanning electron microscopy, field emission scanning electron microscopy, high angle annular dark field and bright field, scanning transmission electron microscopy, energy-dispersive X-ray techniques, and focus ion beam are presented and discussed.

Robust Noise Modulation of Nonlinearity in Carbon Nanotube Field-Effect Transistors

Carbon nanotubes (CNTs) are one of the candidates for nanosize devices such as field-effect transistors. CNT field-effect transistors (CNTFETs) have very special properties sometimes caused by surface states. For example, they are also well known as noisy devices caused by the molecule adhesion on the surface. Nonlinear systems, however, have some advantages such as weak signal detection or enhancement in working with noise. The small signal enhancement was conventionally studied as stochastic resonance. Therefore, we study the modification of nonlinearity of the systems under noise. For actual applications, the noise is also generated from the devices. Thus, we combined the noise CNTFET and another CNT transistor for the trial nonlinear system. Then, the sine wave amplification in the transistor with 1/ f noise of CNTFETs was measured. We used two different combinations of CNTFETs for noise and nonlinear CNTFETs, and observed the robustness of the noise modification on the nonlinearity.

Cobalt Nano Particle Size Dependence of Noise Modulations in Relation to Nonlinearity

Carbon nanotubes (CNTs) are low-dimensional materials, and their surface therefore affects several properties of CNTs. For example, CNT field effect transistors (CNTFETs) are well known as noisy devices caused by the adhesion of molecules on the surface. However, nonlinear systems sometimes have advantages in working with noise. Therefore, we combined the noise CNTFET and another transistor of CNT for a trial nonlinear system. The sine wave amplification in the transistor with noise was then measured. In this system, the control of noise is required for operation of the device and this might be common for nano-sized devices. We can control the noise properties of CNTFET through the control of the Co nano particles catalyst. Depending on fabrication conditions, the noise of a CNTFET has different noise intensity and gate voltage (Vg) dependence with 1/f type noise. Noise in CNTFETs grown on small Co particles can be controlled within the small |Vg|, and the control range for noise is wide. We studied the modification of nonlinearity using our trial nonlinear system. It was governed by the ratio of the signals and the noise, and shows the robustness of modification. [DOI: 10.1380/ejssnt.2010.115]

Nano-scale modification and doping of diamond: interesting science and promising technology

Diamond is a unique material with outstanding physical and chemical properties. Among these are very unusual properties of the diamond surface; i.e., its negative electron affinity when hydrogen terminated (i.e., 'negative work-function') and the p-type 2D electrical conductivity it shows (when exposed to different atmospheres). These make diamond a material of choice for the fundamental study of a variety of electron-emission processes as well as for their application, on the nano-scale, as point cold electron-emission devices and various nano-size electronic devices. The uniqueness of the diamond surface, when hydrogen terminated are discussed. Results on the emission of electrons from diamond induced by an external electric field (field emission) by electron-impact (secondary electron emission) and by ion-impact (ion-induced electron-emission) are reviewed. Modifications of these properties on the nano-scale by single ion-impacts and by localised electric fields (from a STM tip) are demonstrated. Stunning results on huge ion-induced electron emission and their rapid degradation are presented and explained. The possible application of the electron-emission from diamond utilising its 2D surface conductivity and the resulting quantisation are discussed enabling the realisation of low dimensional (line and point) devices including point sources of cold electrons and for nano scale electronic devices.

A Novel Bottom-Up Fabrication Process for Controllable Sub-100 nm Magnetic Multilayer Devices

We present a fabrication process for controllable sub-100 nm magnetic multilayer devices, pseudo spin valve, using a novel bottom-up technique. Stack of multilayer devices with diameter in nanometer scales were successfully made through a template of Ge/SiO2 stencil mask with very well undercutting profile of SiO2 insulating layer. The niche of using this method is that a device with diameter below 100 nm can be made through a twice larger Ge hole of stencil mask. The desired dimension of the active device layers was achieved with a thick buffer metal layer deposited first, giving rise to a narrower neck for later active layers deposition. Moreover, this stencil mask technique can be utilized as device templates of not only magnetic multilayer devices but also other nano-sized devices such as phase changed memory devices.

Investigation diffusion mechanism of β-lactam conjugated telechelic polymers of PEG and β-cyclodextrin as the new nanosized drug carrier devices

Six new prodrugs including conjugated telechelic polymer of β-cyclodextrin-poly (ethylene glycol)- β-cyclodextrin ( β-CD-PEG- β-CD) and or parent β-cyclodextrin ( β-CD) were designated as the new drug carrier agents containing β-lactam antibiotics such as ampicillin (AMP), amoxicillin (AMO) and cephalexin (CEP) prodrugs for potentially local administration pharmaceutical applications. Investigation of the drug release dynamics in buffered media with pH 7.4 showed that the drug released through the prodrug matrix with slightly deviation, follows Fickian diffusion mechanism. Using equation “log (M t/M ∞) = log k + n log t” it has revealed that the synthesized prodrugs 5a–c, 6a–c have the “ n” values 0.333, 0.334, 0.390, 0.540, 0.514 and 0.473, respectively. In fact, the prodrug 6c showed the least deviation from Fickian diffusion mechanism.

Bacteriophage M13 as a scaffold for preparing conductive polymeric composite fibers

Using biological templates to build one-dimensional functional materials holds great pr omise in developing nanosized electrical devices, sensors, catalysts, and energy storage units. In this communication, we report a versatile assembly process for the preparation of water-soluble conductive polyaniline (PANi)/M13 composite nanowires by employing the bacteriophage M13 as a template. The surface lysine residues of M13 can be derivatized with carboxylic groups to improve its binding ability to the aniline; the resulting modifi ed M13 is denoted as m-M13. Highly negatively-charged poly(sulfonated styrene) was used both as a dopant acid and a stabilizing agent to enhance the stability of the composite fi bers in aqueous solution. A transparent solution of the conductive PANi/m-M13 composite fi bers can be readily obtained without any further purifi cation step. The fi bers can be easily fabricated into thin conductive fi lms due to their high aspect ratio and good solubility in aqueous solution. This synthesis discloses a unique and versatile way of using bionanorods to produce composite fi brillar materials with narrow dispersity, high aspect ratio, and high processibility, which may have many potential applications in electronics, optics, sensing, and biomedical engineering.