Search

Quantum Nanoscience, Applied Sciences

The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valuable signal for high-resolution imaging as well as a mechanism for very precise nanofabrication [3]. The low proximity effects, due to the low yield of backscattered ions and the confinement of the forward scattered ions into a narrow cone, enable patterning of ultra-dense sub-10 nm structures. This paper presents various nanofabrication results obtained with direct-write, with scanning helium ion beam lithography, and with helium ion beam induced deposition., Kavli Institute of Nanoscience, Applied Sciences

The photonic properties of two classes of wavelength-sized cavities are reported for deeply etched InP/InGaAsP/InP planar photonic crystals. The high aspect, deeply etched structures are studied as potential building blocks for nonmembrane type photonic devices in standard InP photonic integrated circuits. The first class consists of cavities of one unit cell in one direction and varying size in the other planar direction. The studied class includes a Fabry–Perot type cavity with one row of missing holes, a simple single missing hole defect cavity, and a cavity consisting of two holes which have been slightly shifted and reduced in hole radius. The best observed quality factor of 65 in this class is obtained for a single hole defect cavity. The second class is comprised of cavities which are derived from a three missing row defect in one direction and varying size in the other direction. This includes a Fabry–Perot type cavity with three rows of missing holes, a point defect cavity consisting of seven unetched holes and a six hole ring cavity. The best observed quality factor of 300 is obtained for the ring cavity in this second class of structures, which is adequate for applications., Kavli Institute of Nanoscience, Applied Sciences

This letter presents the application of electrostatic pull-in instability to study the size-dependent effective Young’s Modulus ? ( ~170–70?GPa) of [110] silicon nanocantilevers (thickness ~1019–40?nm). The presented approach shows substantial advantages over the previous methods used for characterization of nanoelectromechanical systems behaviors. The ? is retrieved from the pull-in voltage of the structure via the electromechanical coupled equation, with a typical error of ? 12%, much less than previous work in the field. Measurement results show a strong size-dependence of ?. The approach is simple and reproducible for various dimensions and can be extended to the characterization of nanobeams and nanowires., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

Photonic crystal (PC) devices in the InP/InGaAsP/InP planar waveguide system exhibiting narrow bandwidth features were investigated for use as ultrasmall and tunable building blocks for photonic integrated circuits at the telecom wavelength of 1.55 ?m. The H1 cavity, consisting of a single PC-hole left unetched, represents the smallest possible cavity in a dielectric material. The tuning of this cavity by temperature was investigated under the conditions as etched and after the holes were infiltrated with liquid crystal (LC), thus separating the contributions of host semiconductor and LC-infill. The shift and tuning by temperature of the MiniStopBand (MSB) in a W3 waveguide, consisting of three rows of holes left unetched, was observed after infiltrating the PC with LC. The samples finally underwent a third processing step of local wet underetching the PC to leave an InGaAsP membrane structure, which was optically assessed through the ridge waveguides that remained after the under etch and by SNOM-probing., Kavli Institute of Nanoscience, Applied Sciences

The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valuable signal for high-resolution imaging as well as a mechanism for very precise nanofabrication [3]. The low proximity effects, due to the low yield of backscattered ions and the confinement of the forward scattered ions into a narrow cone, enable patterning of ultra-dense sub-10 nm structures. This paper presents various nanofabrication results obtained with direct-write, with scanning helium ion beam lithography, and with helium ion beam induced deposition., Kavli Institute of Nanoscience, Applied Sciences

Tuning of the resonant wavelength of a single hole defect cavity in planar photonic crystals was demonstrated using transmission spectroscopy. Local post-production processing of single holes in a planar photonic crystal is carried out after selectively opening a masking layer by focused ion beam milling. The resonance was blue-shifted by enlargement of selected holes using local wet chemical etching and red-shifted by infiltration with liquid crystals. This method can be applied to precisely control the resonant frequency, and can also be used for mode selective tuning.

Wavelength-sized point defect cavities coupled to access waveguides are reported for deeply etched InP⁄InGaAsP⁄InP two-dimensional photonic crystals. The observed quality factor of 60 is comparable to those found for one-row defect Fabry–Perot cavities and for simple point defect cavities in membranes. The quality factor was changed by varying the number of rows of holes. Upon infiltration of the holes with liquid crystal, frequency tuning was demonstrated.

Local post-production processing of single holes in a planar photonic crystal is demonstrated by selectively opening a masking layer by focused ion beam milling. Local tuning was optically demonstrated by both blueshifting and subsequent red-shifting the

A method for improving the aspect ratio of ultrahigh-resolution structures in negative electron-beam resist is provided for enhanced pattern-transfer capabilities. The essence of the proposed method is to form a protective “cap” on top of the resist structure by means of electron-beam-induced deposition (EBID) in a self-aligned approach. This is implemented by a combination of electron-beam lithography and EBID during exposure of the resist material in the presence of a precursor gas. The results of the proposed method using hydrogen silsesquioxane resist material are presented and discussed, including various attempts to further optimize this method., QN/Quantum Nanoscience, Applied Sciences

A high-contrast-ratio (30 dB) photonic band gap in the near-infrared transmission of hole-type GaN two-dimensional photonic crystals(PhCs) is reported. These crystals are deeply etched in a 650 nm thick GaN layer grown on sapphire. A comparison of the measured spectrum with finite difference time domain simulations gives quantitative agreement for the dielectric band and qualitative agreement for the air band. The particular behavior of the air band arises from the relatively low index contrast between the GaN layer and the sapphire substrate. Our results call for extension of the operation of GaNPhCs to the visible range.

An extensive investigation has been performed on inductively coupled plasmaetching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Cl₂ with the addition of N₂ or O₂ for sidewall passivation. The influence of different process parameters such as gas flows, temperature,pressure, ion energy, and inductively coupled plasma power on the hole geometry is presented. It is concluded that photonic crystals can be etched with Cl₂ only; however, temperature and pressure control is critical. Adding passivation gases largely broadens the window in the parameter space for hole etching. Most importantly, etching of narrow holes can be carried out at higher temperatures where the etching is mass limited and spontaneous etching of InP by Cl₂ occurs.