Electrically conducting, ultra-sharp, high aspect-ratio probes for AFM fabricated by electron-beam-induced deposition of platinum.
Ultramicroscopy 133 (2013) 62-66
Abstract:
We report on the fabrication of electrically conducting, ultra-sharp, high-aspect ratio probes for atomic force microscopy by electron-beam-induced deposition of platinum. Probes of 4.0 ±1.0 nm radius-of-curvature are routinely produced with high repeatability and near-100% yield. Contact-mode topographical imaging of the granular nature of a sputtered gold surface is used to assess the imaging performance of the probes, and the derived power spectral density plots are used to quantify the enhanced sensitivity as a function of spatial frequency. The ability of the probes to reproduce high aspect-ratio features is illustrated by imaging a close-packed array of nanospheres. The electrical resistance of the probes is measured to be of order 100 kΩ.The control of shrinkage and thermal instability in SU-8 photoresists for holographic lithography
Advanced Functional Materials 21:9 (2011) 1593-1601
Abstract:
The negative-tone epoxy photoresist, SU-8, expands ≈1% by volume after postexposure baking. However, if the maximum optical fl uence is comparable to that at the insolubility threshold, as in a holographic exposure, the developed resist shrinks ( ≈35% by volume) due to the removal of light oligomers not incorporated into the polymeric network. IR spectroscopy shows that, at this level of exposure, only 15% of the epoxy groups in the insoluble polymer have reacted; consequently microstructural elements soften and collapse at > 100 °C. When the light oligomers are removed, the sensitivity of the resist is unchanged, provided that 5% (w/w) of a high-molecular-weight reactive plasticizer (glycidoxy-terminated polyethylene glycol) is added, but it shrinks less on development and, when used as a photonic crystal template, shows improved uniformity with less cracking and buckling. Reinforcing the polymer network by reaction with the polyfunctional amine (bis- N , N′ -(3-aminopropyl) ethylenediamine) increases the extent of cross-linking and the thermal stability, allowing inverse replicas of photonic crystal templates to be fabricated from both Al:ZnO and Zr3N4 using atomic layer deposition at temperatures up to 200 °C. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.Replicated photonic crystals by atomic layer deposition within holographically defined polymer templates
Applied Physics Letters 94:26 (2009)
Abstract:
We report the replication of holographically defined photonic crystals using multistage atomic layer deposition. Low- and high-temperature atomic layer depositions were combined with selective etching to deposit and remove multiple conformal thin films within three-dimensional polymer templates. Using intermediate Al 2 O 3 inverse replicas, temperature- sensitive SU-8 photonic crystal templates were faithfully replicated with TiO 2 and GaP, greatly increasing the dielectric contrasts of the photonic crystals. Optical measurements are in good agreement with the calculated band structures. © 2009 American Institute of Physics.Towards registered single quantum dot photonic devices.
Nanotechnology 19:45 (2008) 455307
Abstract:
We have registered the position and wavelength of a single InGaAs quantum dot using an innovative cryogenic laser lithography technique. This approach provides accurate marking of the location of self-organized dots and is particularly important for realizing any solid-state cavity quantum electrodynamics scheme where the overlap of the spectral and spatial characteristics of an emitter and a cavity is essential. We demonstrate progress in two key areas towards efficient single quantum dot photonic device implementation. Firstly, we show the registration and reacquisition of a single quantum dot with 50 and 150 nm accuracy, respectively. Secondly, we present data on the successful fabrication of a photonic crystal L3 cavity following the registration process.Study of two-photon laser photolithography with SU-8 at cryogenic temperatures
Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006 (2006)