Nano Fabrication

Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source, lenses and a four quadrant photodetector to amplify and measure the deflection of the cantilever probe. This optical method for deflection sensing limits the capability of AFM to obtaining images in transparent environments only. In addition, tapping mode imaging in liquid environments with transparent sample chamber can be difficult for laser-probe alignment due to multiple different refraction indices of materials. Spurious structure resonance can be excited from piezo actuator excitation. Photothermal actuation resolves the resonance confusion but makes optical setup more complicated. In this paper, we present the design and fabrication method of coated active scanning probes with piezoresistive deflection sensing, thermomechanical actuation and thin ...

The etching profile of silicon micro-scale Fresnel rings (MSFR) array using 〖SF〗_6 based Reactive ion etching (RIE) is reported in this paper. This micro-scale Fresnel rings array was created on a Silicon substrate with poly methyl methacrylate (PMMA) mask during the RIE process. Effects of oxygen〖 (O〗_2) addition and the process pressure decreasing were described by chemical reactions of plasma etching as well as the experimental results. The atomic force microscopy (AFM) was utilized to investigate the etching profile of these micro-scale Fresnel rings arrays. Etching of micro-scale Fresnel rings with 〖 O〗_2 addition results in vertical sidewall profile with the approximate surface roughness of 3 nm in the inter-ring spacing, while V-groove shaped in sidewall was obtained in absence of 〖  O〗_2. These Fresnel rings have a good potential to be used in various optical systems and electronics applications.

In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness.

The effect of gold attachment on the physical characteristics, cellular uptake, gene expression efficiency, and biocompatibility of magnetic iron oxide (MNP) vector was investigated in vitro in BHK21 cells. The surface modification of magnetite with gold was shown to alter the morphology and surface charge of the vector. Nonetheless, despite the differences in the surface charge with and without gold attachment, the surface charge of all vectors were positive when conjugated with PEI/DNA complex, and switched from positive to negative when suspended in cell media containing serum, indicating the adsorption of serum components onto the composite. The cellular uptake of all MNP vectors under the influence of a magnetic field increased when the composite loadings increased, and was higher for the MNP vector that was modified with gold. Both bare magnetite and gold-coated magnetite vectors gave similar optimal gene expression efficiency, however, the gold-coated magnetite vector required a 25-fold higher overall loading to achieve a comparable efficiency as the attachment of gold increased the particle size, thus reducing the surface area for PEI/DNA complex conjugation. The MNP vector without gold showed optimal gene expression efficiency at a specific magnetite loading, however further increases beyond the optimum loading decreased the efficiency of gene expression. The drop in efficiency at high magnetite loadings was attributed to the significant reduction in cellular viability, indicating the bare magnetite became toxic at high intracellular levels. The gene expression efficiency of the gold-modified vector, on the other hand, did not diminish with increasing magnetite loadings. Intracellular examination of both bare magnetite and gold-coated magnetite vectors at 48 h post-magnetofection using transmission electron microscopy provided evidence of the localization of both vectors in the cell nucleus for gene expression and elucidated the nuclear uptake mechanism of both vectors. The results of this work demonstrate the efficacy of gold-modified vectors to be used in cellular therapy research that can function both as a magnetically-driven gene delivery vehicle and an intracellular imaging agent with negligible impact on cell viability.TEM micrographs of ultra-thin section of BHK21 cells at 48 h post-magnetofection with gold coated and bare MNP vectors. The figures show the nuclear membrane bulging inwards for vectors uptake and final localization of vectors in the cell nucleus for gene expression.► Efficacy of gold-modified magnetic gene delivery vector in cellular therapy research. ► Magnetically-driven gene delivery vehicle and as an intracellular imaging agent.► Bare and gold-coated magnetite vectors under TEM showed localization in cell nucleus for gene expression and elucidated nuclear uptake mechanism.

3D Simulation was carried out and compared with fabricated ZnO NWFET. The device had the following electrical output characteristics: mobility value of 10.0 cm2/Vs at a drain voltage of 1.0 V, threshold voltage of 24 V, and subthreshold slope (SS) of 1500 mV/decade. The simulation showed that the device output results are influenced by two main issues: (i) contact resistance (Rcon ≈ 11.3 MΩ) and (ii) interface state trapped charge number density (QIT = 3.79 x 1015 cm-2). The QIT was derived from the Gaussian distribution that depends on two parameters added together. These parameters are: an acceptor-like exponential band tail function gGA(E) and an acceptor-like Gaussian deep state function gTA(E). By de-embedding the contact resistance, the simulation is able to improve the device by producing excellent field effect mobility of 126.9 cm2/Vs.

This paper summarizes a TEDx Talk that the European physics professor Ille C. Gebeshuber, who has been living in South East Asia for nearly five years now, gave to a live audience of 800 in Kuala Lumpur, Malaysia, in July 2012. A similar talk is also given as an invited lecture at the 4th International Conference of Bionic Engineering in China in August 2013. The talk highlights the importance of news ways of doing science and of doing engineering that are needed to successfully address the major challenges humankind is currently facing, and how a generalistic approach synergistically combining Eastern and Western thinking might help in this respect. Biomimetics is stressed as an integrated, generalist way of learning from living nature, and as best practice example for developing new approaches that are based on understanding rather than learning by heart, with memory, reason and imagination as pillars, bridging fields of specialization and of education and thereby blending the kno...

We present a novel post-release stress-engineering process that can provide out-of-plane curvature to initially planar MEMS structures. This process uses a layer of evaporated Chromium (Cr) with intrinsic compressive stress to provide the required curvature. The stressor layer is applied post-release, and is patterned using shadow masks fabricated in-situ as part of the surface micromachining fabrication process. The masks can be reconfigured to provide variable stressor layer coverage of the underlying structures without the use of photolithography. A model is presented that encompasses the increase in deflection, and thus non-uniform chromium coverage, during the stress-engineering of released structures.

ABSTRACT In this contribution, vertically aligned carbon nanotubes (VACNTs) were synthesized by chemical vapor deposition (CVD). The effects of intrinsic disorders constructed by mobile surface contaminants on the structural perfection of carbon nanotubes (CNTs) were investigated. The results indicated a complete picture on the effect of the involved parameters on the lattice defects of modulated CNTs based on the cooling step. Raman scattering showed that the different cooling methods of the CVD preforms altered the bound complex defects of the structure of the CNTs. Moreover, an array of CNTs was removed from the silicon substrate by applying the neutralized cooling method on the CVD, while the vertical and parallel orientations were retained. The FESEM images, coupled with Raman spectroscopy results, confirm the morphological improvements of the growth CNTs based on the neutralized cooling method.

The presence of hazardous gases in environment above a certain limit causes toxic effects, which is harmful for human being and other creatures. In addition to the toxic gases, some volatile organic compounds like are also dangerous for lives when inhaled in substantial quantities. Therefore it is important to detect these harmful gases and compounds properly to save our lives. For this purpose we had carried out our experiments to check the sensitivity of our prepared SnO 2-CNT based gas sensor towards the volatile organic compound (Acetone) and toxic gases (Carbon Monoxide). Cross sensitivity of the sensors were also observed when they were subjected to the presence of combustible gases like Methane and volatile organic compound like Ethyl Alcohol. Keywords-SnO 2-CNT sensor, Thermo gravimetric analysis, X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM)

In this work, we demonstrate a wafer-level zinc oxide (ZnO) nanowire fabrication process using ion beam etching and a spacer etch technique. The proposed process can accurately define nanowires without an advanced photolithography and provide a high yield over a 6-inch wafer. The fabricated nanowires are 36 nm wide and 86 nm thick and present excellent transistor characteristics. The pH sensitivity using a liquid gate was found to be 46.5 mV/pH, while the pH sensitivity using a bottom gate showed a sensitivity of 366 mV/pH, which is attributed to the capacitance coupling between the top-and bottom-gates. The maximum process temperature used in the fabrication of the nanowire sensors is optimized to be 200 °C (after wet oxidation) which makes it applicable to low-cost substrates such as glass and plastic. The Ion Beam Etching (IBE) process in this work is shown to be highly transferable and can therefore be directly used to form nanowires of different materials, such as polysilicon and molybdenum disulfide, by only an adjustment of the etch time.

Carbon nanotubes (CNTs) exhibit extraordinary physical and electronic properties because of their
intermolecular structure. In this proposed researched paper we introduced a novel technique for the preparation of
Carbon nanotubes using Allium cepa extract. Collagen thin film sheet is having a resistance of more than 10Mohms and
it acts an insulator. Hence we want to prepare as a semiconducting collagen thin film, first, we incorporated a
conducting ink to reduce the resistance to semiconducting range, less than 2M ohms. Therefore, a conducting ink was
prepared by mixing carbon nanotubes, collagen and hydroxylethyl cellulose. Secondly, Collagen thin films were
prepared using fish scales; it is an insulator thin film sheet which has flexibility and more physico-chemical strength.
Keywords: Thin film, Fish scales, Collagen, Semiconductor.

In this paper we overview recent attempts at
co-integrating silicon nano-electro-mechanical systems
(NEMS) with nanoelectronic devices aiming to add more
functionalities to conventional electronic devices in
‘More-than-Moore’ domain and also explore novel
operating principles in ‘Beyond CMOS’ domain.

Boron-doped strontium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by using a polymeric precursor technique. The powders were characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and physical properties measurement system (PPMS) techniques. The XRD results showed that these patterns have a two-phase mixture. The phases are face-centered cubic (fcc) and body-centered cubic (bcc). Values of the crystallite size, dislocation density, and microstrain were calculated by using the Scherrer equation. The lattice parameters were calculated for fcc and bcc phases. The SEM results showed that needle-like grains are formed in boron-undoped composite materials, but the needle-like grains changed to the plate-like grains with the addition of boron. The distribution of the nanofiber diameters was calculated and the average diameter of the boron-doped sample is smaller than the boron-undoped one. PPMS values showed that the electrical resistivity values decreased, but the thermal conductivity values, the Seebeck coefficients, and figure of merit (ZT) increased with increasing temperature for the two samples.

A suspended double-clamped beam for a NV-Memory is fabricated and characterised.The recipe developed to suspend the beam structure shows a high selectivity rate.Once biased, the beam pulls-in but due to the short-range forces pull-out was missing.Short-range forces such as the van der Waals are stronger when in contact (Al/SiO2Al/SiO2).A relationship to overcome such forces is obtained through 2D-FEM analysis.We report the fabrication and characterisation of a suspended double-clamped beam structure that is implemented as a movable control gate within a hybrid high-speed non-volatile memory device. This structure features a foundation of SiO2/Si layers over which a poly-Si layer (sacrificial) is deposited by using a low-pressure chemical vapour deposition (LPCVD) and as a movable control gate, an aluminium (Al) layer is deposited by using an e-beam evaporator. The Al layer is patterned with double-clamped beam structures by using photolithography and through a combination of wet and dry etching processes, the structures are successfully suspended and characterised by using a C–V meter. From the structure characterisation, the pull-in curve is successfully obtained and due to unexpected large short-range forces such as the van der Waals forces, the pull-out curve is not observed. In order to clarify this issue, a numerical analysis is performed in which the structural materials under test shown the influence of such short-range forces on the structure and a solution to override them is proposed.

Injectable hydrogels with biodegradability have in situ formability which in vitro/in vivo allows an effective and homogeneous encapsulation of drugs/cells, and convenient in vivo surgical operation in a minimally invasive way, causing smaller scar size and less pain for patients. Therefore, they have found a variety of biomedical applications, such as drug delivery, cell encapsulation, and tissue engineering. This critical review systematically summarizes the recent progresses on biodegradable and injectable hydrogels fabricated from natural polymers (chitosan, hyaluronic acid, alginates, gelatin, heparin, chondroitin sulfate, etc.) and biodegradable synthetic polymers (polypeptides, polyesters, polyphosphazenes, etc.). The review includes the novel naturally based hydrogels with high potential for biomedical applications developed in the past five years which integrate the excellent biocompatibility of natural polymers/synthetic polypeptides with structural controllability via chemical modification. The gelation and biodegradation which are two key factors to affect the cell fate or drug delivery are highlighted. A brief outlook on the future of injectable and biodegradable hydrogels is also presented (326 references).

The helix angle, chirality, and radius of helical ribbons are predicted with a comprehensive, three-dimensional analysis that incorporates elasticity, differential geometry, and variational principles. In many biological and engineered systems, ribbon helicity is commonplace and may be driven by surface stress, residual strain, and geometric or elastic mismatch between layers of a laminated composite. Unless coincident with the principle geometric axes of the ribbon, these anisotropies will lead to spontaneous, three-dimensional helical deformations. Analytical, closed-form ribbon shape predictions are validated with table-top experiments. More generally, our approach can be applied to develop materials and systems with tunable helical geometries.