Self-aligned Nanostructures Research Articles

Self-Aligned Plasmonic Lithography for Maskless Fabrication of Large-Area Long-Range Ordered 2D Nanostructures.

This paper proposes a one-step maskless 2D nanopatterning approach named self-aligned plasmonic lithography (SPL) by line-shaped ultrafast laser ablation under atmospheric conditions for the first time. Through a theoretical calculation of electric field and experimental verification, we proved that homogeneous interference of laser-excited surface plasmon polaritons (SPPs) can be achieved and used to generate long-range ordered 2D nanostructures in a self-aligned way over a wafer-sized area within several minutes. Moreover, the self-aligned nanostructures can be freely transferred between embossed nanopillars and engraved nanoholes by modulating the excitation intensity of SPPs interference through altering the incident laser energy. The SPL technique exhibits further controllability in the shape, orientation, and period of achievable nanopatterns on a wide range of semiconductors and metals by tuning processing parameters. Nanopatterned films can further act as masks to transfer structures into other bulk materials, as demonstrated in silica.

Formation of silicon nanostructures with a combination of spacer technology and deep reactive ion etching

A new method of fabricating high aspect ratio nanostructures in silicon without the use of sub-micron lithographic technique is reported. The proposed method comprises two important steps including the use of CMOS spacer technique to form silicon nitride nanostructure masking followed by deep reactive ion etching (DRIE) of the silicon substrate to form the final silicon nanostructures. Silicon dioxide is used as the sacrificial layer to form the silicon nitride nanostructures. With DRIE a high etch selectivity of 50:1 between silicon and silicon nitride was achieved. The use of the spacer technique is particularly advantageous where self-aligned nanostructures with potentially unlimited lengths are formed without the need of submicron lithographic tools and resist materials. With this method, uniform arrays of 100 nm silicon nanostructures which are at least 4 μm tall with aspect ratio higher than 40 were successfully fabricated.

Self-aligned nanostructures created by swift heavy ion irradiation

In tetrahedral amorphous carbon (ta-C) swift heavy ions create conducting tracks of about 8 nm in diameter. To apply these nanowires and implement them into nanodevices, they have to be contacted and gated. In the present work, we demonstrate the fabrication of conducting vertical nanostructures in ta-C together with self-aligned gate electrodes. A multilayer assembly is irradiated with GeV heavy ions and subsequently exposed to several selective etching processes. The samples consist of a Si wafer as substrate covered by a thin ta-C layer. On top is deposited a SiNx film for insulation, a Cr layer as electrode, and finally a polycarbonate film as ion track template. Chemical track etching opens nanochannels in the polymer which are self-aligned with the conducting tracks in ta-C because they are produced by the same ions. Through the pores in the polymer template, the Cr and SiNx layers are opened by ion beam sputtering and plasma etching, respectively. The resulting structure consists of nanowires embedded in the insulating carbon matrix with a built in gate electrode and has potential application as gated field emission cathode.

A Semiconductor-based Field-effect Platform for (Bio-)Chemical and Physical sensors: From Capacitive EIS Sensors and LAPS over ISFETs to Nano-scale Devices

ABSTRACTThe coupling of semiconductor field-effect devices (FED) together with chemical and biological recognition elements, like functional intelligent materials, biomolecules and living cells, represents an attractive platform for the creation of different (bio-)chemical sensors, multi-parameter analysis systems and bio-chips. This paper summarises recent developments and current research activities in the field of (bio-)chemically modified FEDs, scaling down from capacitive EIS (electrolyte-insulator-semiconductor) sensors and LAPS (light-addressable potentiometric sensor) to ISFETs (ion-sensitive field-effect transistor) that have been realised in our laboratory. Selected examples of application of ISFETs for the detection of physical parameters in liquids are presented, too. With the aim of future development of nano-devices for the detection of single biomolecules, the possibility of a simple preparation of different self-aligned nano-structures by using conventional photolithography and pattern-size reduction technique has been experimentally demonstrated.

Towards self-aligned nanostructures by means of layer-expansion technique

A new and simple nanostructuring method that combines the conventional photolithography and layer expansion or pattern-size reduction technique is presented. The method is based on a complete conversion of a photolithographically patterned metal layer to a metal-oxide mask with improved pattern-size resolution using the thermal oxidation process. The mask can be further applied for the fabrication of different nanostructures and nano-devices.

Determination of CoSi2 Self-Aligned Nanostructures with Grazing Incidence X-ray Absorption Spectroscopy

Self-aligned nanostructures (SAN) made by reacting Co nanoparticles with crystalline Si substrates at high temperatures were studied with grazing incidence X-ray absorption spectroscopy (GI-XAS). The results from extended X-ray absorption fine structure (EXAFS) analysis and X-ray absorption near-edge spectroscopy (XANES) were used to identify SAN as crystalline CoSi2. Theoretical calculations of EXAFS and XANES spectra of several crystalline cobalt silicides were performed with the FEFF8 package. On the basis of these studies, the SAN samples were determined to contain nearly pure CoSi2.

Growth of Self‐Aligned Crystalline Cobalt Silicide Nanostructures from Co Nanoparticles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Growth of Self-Aligned Crystalline Cobalt Silicide Nanostructures from Co Nanoparticles

We have developed a new method with which we can for the first time produce self-aligned cobalt silicide (CoSi2) nanostructures from Co nanoparticles. These nanostructures are formed by reacting Co nanoparticles with Si substrates at 900 °C. Their dimensions are normally 3 to 10 nm wide and up to a few micrometers long. The orientations of these nanostructures are controlled by the crystalline substrate, as they are orthogonally and hexagonally aligned on Si(100) and Si(111), respectively. Because these self-aligned nanostructures (SAN) are thermally stable up to 1000 °C in air and chemically inert to prolonged treatment with strong acids, and because their sizes are uniform and much smaller than those made from lithography, they can be ideal materials for making components such as electric contacts, interconnects, and gates for future nanoelectronics.