100-nm Width Research Articles

Fracture Toughness Evaluation of a Cracked Au Thin Film by Applying a Finite Element Analysis and Bulge Test

This paper presents a finite element analysis of a pre-cracked freestanding gold thin film subjected to bulge test. These tests were conducted in order to determine the elasto-plastic properties and fracture toughness of the gold films. For the experimental tests, a pre-crack was introduced in the center of the film by focused ion beam (FIB) milling with a length of 10 and a width of 100nm. For the numerical fracture analysis, the problem was divided into two stages; the first stage was the development of the numerical model on the whole film without pre-crack (elasto-plastic analysis) and the second one was performed on a film portion that included the pre-crack (sub-modeling stage). Three different notches (rounded, sharp and V-sharp) were applied to calculate the stress intensity factor around the crack tip using path independent J-integral. The obtained results show that the load-deflection curves for non-cracked and pre-cracked film reproduced the experiments using the calculated elasto-plastic properties. This indicates that the proposed models presented a good correlation and robustness. Additionally, fracture toughness values were calculated between 0.288 and 0.303with J-integral values 1.037 J/m2 (elastic) and 1.136 J/m2 (elasto-plastic) which correspond with other calculations available in the literature.

Carrier density distribution in silicon nanowires investigated by scanning thermal microscopy and Kelvin probe force microscopy

The use of scanning thermal microscopy (SThM) and Kelvin probe force microscopy (KPFM) to investigate silicon nanowires (SiNWs) is presented. SThM allows imaging of temperature distribution at the nanoscale, while KPFM images the potential distribution with AFM-related ultra-high spatial resolution. Both techniques are therefore suitable for imaging the resistance distribution. We show results of experimental examination of dual channel n-type SiNWs with channel width of 100nm, while the channel was open and current was flowing through the SiNW. To investigate the carrier distribution in the SiNWs we performed SThM and KPFM scans. The SThM results showed non-symmetrical temperature distribution along the SiNWs with temperature maximum shifted towards the contact of higher potential. These results corresponded to those expressed by the distribution of potential gradient along the SiNWs, obtained using the KPFM method. Consequently, non-uniform distribution of resistance was shown, being a result of non-uniform carrier density distribution in the structure and showing the pinch-off effect. Last but not least, the results were also compared with results of finite-element method modeling.

Biomimetic hierarchical growth and self-assembly of hydroxyapatite/titania nanocomposite coatings and their biomedical applications

This article describes a systematic study of the biomimetic hierarchical growth of hydroxyapatite (HA)/titania (TiO2) nanocomposite layered coatings applied by a simple sol–gel dip coating method. Highly stable HA and TiO2 sols were prepared prior to inducing biomimetic hierarchical growth. Initially, the samples formed a small leaf like structure; however, increasing the dipping cycle resulted in formation of an elongated seed-like structure. Increasing the number of dipping cycles further resulted in a ‘bowtie’ or straw-bale like nanowire structure with a length of 500nm and a width of 100nm. Each nanowire like structure had a width of very few nanometers. The crystalline structures, micro/nano structures and surface properties of the coatings were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy respectively. In vitro cellular assays revealed that the growth of the cells in the ‘bowtie’ like structure improved over other samples.

Experimental demonstration of silicon slot waveguide with low transmission loss at 1064 nm

Silicon slot waveguides that can operate at the wavelength of high silicon absorption are experimentally demonstrated on SOI wafer. The measured transmission loss coefficient could be as low as 2.28±0.03dB/mm at the wavelength of 1064nm (the slot width of 100nm), which is much lower than the absorption loss of silicon (5dB/mm at 1064nm). According to the simulation, such value is dominated by the surface roughness of sidewalls. The transmission loss is potentially to be reduced to <1dB/mm if the sidewall roughness could be reduced to ~5nm. We believe that this work could pave the way to achieving all silicon photonic integrated circuits, which are attractive for future optical interconnect and chemical/biological analysis.

Selective electroless plating of silver nanograting patterns with no lateral growth for the fabrication of polarizers

Metal patterning has been useful for fabricating many optical and electronic devices. Among all the patterning methods, selective electroless plating in combination with micro-contact printing (μCP) is a simple process compatible with roll-to-roll processing. However, this process suffers from the difficulty to avoid lateral growth during the electroless plating of metal. That will place a limitation on the fabrication of nanoscale patterns, such as the metal wire grid polarizer. In this study, we launch a new approach to restrict the lateral growth of metal by depositing metal selectively in the grooves of a three-dimensional template. The template was first treated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) only on the protrusion surface using μCP, and then treated in SnCl2 solution to activate the surface of the trenches for the selective electroless plating (ELP) of silver inside the trenches. A wire-grid polarizer was thus fabricated by selectively depositing 70nm-thick silver in the trenches of a nanograting template with a trench width of 100nm and a pitch of 180nm. The maximum extinction ratio of the polarizer thus obtained was about 130 in the wavelength range of 635–650nm.

Nanogratings containing sub-10-nm wide trenches by dimension reduction from sloped polymer profile

Large area nanograting patterns are useful in many applications but difficult to fabricate. The authors demonstrate a low temperature dimension reduction method, as a cost-effective alternative to high resolution lithography, to define nanogratings as narrow as 8–10nm. In this process, the slope of prepatterned polymer gratings, with pitch of 200nm or larger and width of 100nm or larger, is contrillably changed from the original straight to curved or sloped. Then, shadow metal evaporation is used to coat the sloped polymer profile to define a much narrower opening. This opening is then transferred to underlying material by plasma etching to form sub-10-nm trenches. The width of trenches can be well controlled by both slope of the profile and angle of metal evaporation. Low processing temperature (as low as 55–85°C—depending on polymer) allows this method to be used with a wide variety of materials.

Device operation of InGaN heterojunction bipolar transistors with a graded emitter-base design

The device operation of InGaN heterojunction bipolar transistors with a graded InGaN emitter-base design grown by metal organic chemical vapor deposition on sapphire substrates is demonstrated. The Gummel plot, current gain, and common-emitter current-voltage characteristics of the device are presented. The dc common-emitter current gain of a 25×25μm2 (emitter size) device increases with collector current and the current gain reaches a high value of 13 at IC=10mA with a base width of 100nm and a hole concentration of p=2×1018cm−3. The improved device performance is attributed to the graded emitter-base design as well as the high quality of the material made possible by the indium composition grading that enables the epitaxial growth of InGaN layers with a low density of pits or defects. The results demonstrate the potential of the graded InGaN emitter-base junction design in nitride heterojunction bipolar transistors.

Magnetic domain configurations in spark-eroded ferromagnetic shape memory Ni-Mn-Ga particles

Spherical particles of the ferromagnetic shape memory material Ni51Mn29Ga20 obtained by spark erosion transform during cooling from the high-temperature Heusler L21 cubic phase into tetragonal martensite. Using the Fresnel (i.e., Lorentz) imaging mode, magnetic domains with an average width of 100nm are observed in the modulated martensitic phase in the absence of a magnetic field. The magnetization distribution within individual particles is determined using electron holography. The magnetic flux lines change direction when crossing boundaries between crystallographic twin variants. These boundaries, where the easy c-axis of the crystallographic variants rotate by 86.5°, coincide with quasi-90° magnetic domain walls, with thickness of approximately 17nm. The magnetization saturation determined by electron holography is about 0.57T.

Nanoscale deposition of solid inks via thermal dip pen nanolithography

We demonstrate that nanolithography can be performed using a heated atomic force microscope (AFM) cantilever tip to control the deposition of a solid organic “ink.” The ink, octadecylphosphonic acid (OPA), has a melting temperature near 100°C and can self-assemble on mica. Postdeposition analysis shows that deposition occurs only when the cantilever tip is heated above OPA’s melting temperature, that the deposited structure does not spread significantly while cooling, and that a cool tip coated with OPA does not contaminate the substrate during subsequent imaging. Single lines were written with a width of 100nm. This approach greatly expands the potential of dip pen nanolithography, allowing local control of deposition and deposition of materials typically immobile at room temperature, while avoiding potential problems arising from inadvertent deposition and postdeposition diffusion.

Plasmons in the modulated and confined 2DEG: A Raman scattering study

Lateral wire arrays have been fabricated from a single modulation-doped GaAs quantum well employing reactive ion etching. Depending on the etch depth, the two-dimensional electron gas (2DEG) in the well acquires different degrees of modulation up to complete confinement. The different regimes are identified by their unique photoluminescence and Raman spectra. Deep-etched wires show plasmon resonances down to a width of 100nm.