Micron Feature Research Articles

ASPITZERSTUDY OF 21 AND 30 μm EMISSION IN SEVERAL GALACTIC CARBON-RICH PROTOPLANETARY NEBULAE

We have carried out mid-infrared spectroscopy of seven Galactic proto-planetary nebulae (PPNs) using the Spitzer Space Telescope. They were observed from 10-36 microns at relatively high spectral resolution, R~600. The sample was chosen because they all gave some evidence in the visible of a carbon-rich chemistry. All seven of the sources show the broad, unidentified 21 micron emission feature; three of them are new detections (IRAS 06530-0213, 07430+1115, and 19477+2401) and the others are observed at higher S/N than in previous spectra. These have the same shape and central wavelength (20.1 microns) as found in the ISO spectra of the brighter PPNs. The 30 micron feature was seen in all seven objects. However, it is not resolved into two separate features (26 and 33 microns) as was claimed on the basis of ISO spectra, which presumably suffered from the noisy detector bands in this region. All showed the infrared aromatic bands (AIB) at 11.3, 12.4, and 13.3 microns. Five of these also appear to have the C2H2 molecular band at 13.7 microns, one in absorption and four in emission. This is extremely rare, with only one other evolved star, IRC+10216, in which C2H2 emission has been observed. Four also possessed a broad, unidentified emission feature at 15.8 microns that may possibly be related to the 21 micron feature. Model fits were made to the spectral energy distributions for these PPNs to determine properties of the detached circumstellar envelopes. The 21 micron feature has been seen in all Galactic carbon-rich PPNs observed, and thus its carrier appears to be a common component of the outflow around these objects.

SPITZERINFRARED SPECTROGRAPH OBSERVATIONS OF CLASS I/II OBJECTS IN TAURUS: COMPOSITION AND THERMAL HISTORY OF THE CIRCUMSTELLAR ICES

We present observations of Taurus-Auriga Class I/II protostars obtained with the Spitzer InfraRed Spectrograph. Detailed spectral fits to the 6 and 15 micron features are made, using publicly-available laboratory data, to constrain the molecular composition, abundances, and levels of thermal processing along the lines of sight. We provide an inventory of the molecular environments observed, which have an average composition dominated by water ice with ~12% CO_2 (abundance relative to H_2O), >~2-9% CH_3OH, <~14% NH_3, ~4% CH_4, ~2% H_2CO, ~0.6% HCOOH, and ~0.5% SO_2. We find CO_2/H_2O ratios nearly equivalent to those observed in cold clouds and lines of sight toward the galactic center. The unidentified 6.8 micron profiles vary from source to source, and it is shown to be likely that even combinations of the most common candidates (NH_4+ and CH_3OH) are inadequate to explain the feature fully. We discuss correlations among SED spectral indices, abundance ratios, and thermally-processed ice fractions and their implications for CO_2 formation and evolution. Comparison of our spectral fits with cold molecular cloud sight-lines indicates abundant prestellar ice environments made even richer by the radiative effects of protostars. Our results add additional constraints and a finer level of detail to current full-scale models of protostellar and protoplanetary systems.

The Next Generation of Drug-Delivery Microdevices

Advances in microelectromechanical systems (MEMS) and miniaturization technologies have enabled the creation of biomedical microdevices intended for use in the treatment of various chronic and acute illnesses. The ability to create very precisely defined micrometer and nanometer features allows for the production of a new generation of biomedical devices that can be implanted using minimally invasive procedures to provide controlled therapeutic drug delivery. We believe that there is a wide variety of pharmacological therapies in which these novel drug-delivery systems could be implemented, including treatments for cancer and trauma. Clinical Pharmacology & Therapeutics (2009); 85, 5, 544–547 doi:10.1038/clpt.2009.4

Site-isolated, intermolecularly photocrosslinkable and patternable dendritic quinacridones

Quinacridone-cored dendrimers with photocrosslinkable cinnamate moieties on the periphery can be patterned down to 5 micron features while retaining luminescence.

MID-INFRARED SPECTRA OF OPTICALLY-SELECTED TYPE 2 QUASARS

Type 2 quasars are luminous Active Galactic Nuclei whose central engines are seen through large amounts of gas and dust. We present Spitzer spectra of twelve type 2 quasars selected on the basis of their optical emission line properties. Within this sample, we find a surprising diversity of spectra, from those that are featureless to those showing strong PAH emission, deep silicate absorption at 10 micron, hydrocarbon absorption, high-ionization emission lines and H_2 rotational emission lines. About half of the objects in the sample are likely Compton-thick, including the two with the deepest Si absorption. The median star-formation luminosity of the objects in our sample measured from the strength of the PAH features is 5x10^11 L_sun, much higher than for field galaxies or for any other AGN sample, but similar to other samples of type 2 quasars. This suggests an evolutionary link between obscured quasars and peak star formation activity in the host galaxy. Despite the high level of star formation, the bolometric output is dominated by the quasar in all cases. For a given strength of 10 micron Si absorption, ULIRGs are significantly colder than are type 2 quasars (their F_nu[14.5 micron]/F_nu[27.5 micron] ratio is 0.5 dex lower), perhaps reflecting different obscuration geometries in these sources. We find that the appearance of the 10 micron feature (i.e., whether it shows in emission or in absorption) is well-correlated with the optical classification in type 1 and type 2 quasars, contrary to some models of clumpy obscuration. Furthermore, this correlation is significantly stronger in quasars (L_bol>10^45 erg/s) than it is in Seyfert galaxies (L_bol<<10^45 erg/s).

Increasing cell adhesion on plasma deposited fluorocarbon coatings by changing the surface topography

In designing new biomaterials, it is of outstanding importance to consider how cells respond to specific chemical and topographical features on the material surface. The behavior of most cell types in vivo is strictly related to specific chemical and topographical cues that characterize the extra cellular environment. In particular, during their lives cells react to topographical patterns such as those of the extracellular matrix (ECM), of micro and/or nanometric dimensions. The production of micrometric and/or nanometric features on artificial materials usually involves expensive and time-consuming methods of manufacturing, such as electron beam and colloidal lithography. In this article, different "Teflon-like" structured surfaces were deposited from tetrafluoroethylene (C(2)F(4))-fed plasmas, for the study of cell adhesion and growth. The reaction of different cell lines to different topographical features was evaluated and compared with cell behavior on flat samples with the same chemical composition. Cell adhesion was calculated from area covered by cells at different time of culture. Beside this, cell proliferation was determined with the MTT test. Cell morphology and filopodia interaction with the nanofeatures were also estimated by optical and scanning electron microscopy. A dramatic difference both in adhesion and growth was found between cells seeded on flat and rough surfaces with the density and spreading of adhered cells varying as a function of the roughness of coatings.

Polymeric barrier membranes for device packaging, diffusive control and biocompatibility

Current state-of-the-art implantable micron feature electronic devices are capable of monitoring and stimulating functions in vivo. Within an EU Framework VI project a further step was taken in developing key microsystem technologies and communication methods that could bring intelligence directly to the human interface, in the form of reactive medical implants and ambulatory measurement systems. Information from these devices is planned to be transmitted out into the wider environment for remote processing. However, the packaging of such state-of-the-art devices to enhance tissue biocompatibility, and to protect conducting elements from in vivo corrosion during extended use, along with protecting the body from toxins leaching from implant components, remains a concern. Candidate polymeric barriers as hydration resistant and solute impermeable interfaces to mitigate such major problems of chronic implantation were investigated. Materials studied included silicone rubber, PVC, polyurethane, and diamond-like carbon (DLC). Polymer permeability to water solutes was marginally improved through incorporation of lipid into these structures. Surface biocompatibility was assessed on the basis of protein film deposition in vitro and by cell viability studies in tissue culture. Short-term toxicity was not observed for any of the tested materials, though there were substantial differences in hydration. Additionally, polypyrrole over active electrodes shows feasibility for controlled tissue interfacing whilst retaining electrical conductivity.

Infrared Spectroscopy of the Diffuse Ionized Halo of NGC 891

We present infrared spectroscopy from the Spitzer Space Telescope at one disk position and two positions at a height of 1 kpc from the disk in the edge-on spiral NGC 891, with the primary goal of studying halo ionization. Our main result is that the [Ne III]/[Ne II] ratio, which provides a measure of the hardness of the ionizing spectrum free from the major problems plaguing optical line ratios, is enhanced in the extraplanar pointings relative to the disk pointing. Using a 2D Monte Carlo-based photo-ionization code which accounts for the effects of radiation field hardening, we find that this trend cannot be reproduced by any plausible photo-ionization model, and that a secondary source of ionization must therefore operate in gaseous halos. We also present the first spectroscopic detections of extraplanar PAH features in an external normal galaxy. If they are in an exponential layer, very rough emission scale-heights of 330-530 pc are implied for the various features. Extinction may be non-negligible in the midplane and reduce these scale-heights significantly. There is little significant variation in the relative emission from the various features between disk and extraplanar environment. Only the 17.4 micron feature is significantly enhanced in the extraplanar gas compared to the other features, possibly indicating a preference for larger PAHs in the halo.

Semi-crystalline poly(4-methyl-1-pentene) polymers for replication of high aspect ratio diffractive features

Two transparent semi-crystalline poly(4-methyl-1-pentene) copolymers (P4MP1) of different molar mass distributions were used for injection molding of high aspect ratio (height/width) diffractive gratings. High quality sub-micron and micron features with aspect ratios of 1.6:1 were obtained with low mold temperatures. According to SEM and AFM measurements, replication of the features depended on substrate thickness and polymer. The copolymer with lower Mn and Mw penetrated deeper into the feature cavities in thin substrates, but showed poorer thermal stability and replication fidelity.

Patterning Aluminum Thin Films by Water-Mediated Nano-Transfer Printing

We report a new nano-transfer printing (nTP) method that uses a water-mediated transfer process. Water-mediated nTP is based on the direct transfer of a metal thin lm from a stamp to a substrate via water-mediated surface bonding between the stamp and the substrate. This procedure can generate aluminum (Al) patterns with micrometer and nanometer-scale feature sizes. Furthermore, an array of Al nanochannels is fabricated by using this method. The transferred Al patterns chemically bound to the substrate surface and thus exhibit strong adhesion.

Improved cost-effective fabrication of arbitrarily shaped μIPMC transducers

Conventional ionic polymer–metal composite (IPMC) production cuts individual transducers from bulk IPMC sheets. This paper presents a novel photolithographic technique that grows a large array of identical devices on a thin (∼µm range) parylene diaphragm supported on a perforated substrate of material that is immune to the subsequent processing liquids. In particular, the new technique relies on a unique wax fill-up and removal concept that can produce arbitrarily shaped Nafion films with micron feature size. The developed process is cheap and results in devices of high uniformity and reliability, with greater design flexibility. Microtensile testing characterizes the fracture profiles of the non-electroded Nafion film and IPMC. Young's modulus is characterized, as well as maximum displacement and current consumption under various loading, driving voltages, waveforms and frequencies. High product quality and low process costs make this process of interest for mass production of micromachined IPMC transducers.

Injection Molding Nanoscale Features with the Aid of Induction Heating

During injection molding of micron or submicron scale features, incomplete filling frequently occurs, resulting from premature freezing of the polymer melt in contact with a cold mold. In order to overcome the filling difficulty without increasing the total cycle time, the mold surface temperature was raised rapidly by induction heating. A prototype mold insert with cooling channels was fabricated and integrated with a nickel stamp having nanoscale-grating structures. The nickel stamp surface was successfully heated from 25 to 258°C in 2.7 sec. Four different mold surface temperatures, 100, 150, 200 and 250°C, were tested to determine if the nanograting structures can be replicated with an optical quality cyclic olefin copolymer. Experimental results indicate that the nanocavities were successfully filled when the surface temperature reached 250°C, but mold release caused drag damages on the nanogratings. Further, coupled thermoelectromagnetic analyses were carried out to simulate the induction heating process of the nanostructured mold insert. The predicted surface temperature responses in general agree with the experimental ones and the simulation model can be used in the further development of process control and mold design in micro/nano molding.

Photolithographic synthesis of high-density DNA probe arrays: Challenges and opportunities

The continual need for increased manufacturing capacity in the production of GeneChip™ DNA probe arrays, and the expanding use of these arrays into new areas of application such as molecular medicine, has stimulated the development of new chemistries and production methods with higher efficiency and resolution. For current production methods based on contact photolithography, modifications in substrate materials and photoactivated synthesis reagents have provided significant improvements in array performance and information content (≥4×106 sequences∕cm2). An alternative next-generation manufacturing process is also in development, which utilizes photoacid generating polymer films, and automated projection lithography systems. This process has the ability to fabricate arrays with 1 micron feature pitch and smaller, providing an unprecedented sequence density of 108∕cm2 and greater.

Hybrid tooling by a combination of high speed cutting and electrochemical milling with ultrashort voltage pulses

Electrochemical machining with ultra short voltage pulses (ECF) is an innovative technique to machine electrochemically active materials at micrometer feature size, particularly hard materials like stainless steel. Because ECF is an electrochemical process the workpiece as well as the tool are submerged in an appropriate electrolyte. The workpiece is electrochemically etched by a galvanic current. Therefore no mechanical forces, no thermal load and no tool wear occurs. Due to the use of short voltage pulses in the range of 10-200 ns the electrochemical process is confined to a small area around the tool. The ability to manufacture microstructures even in stainless steel makes ECF the ideal technique for the processing of micro moulds. For a higher through-put and a reasonable size of the moulds it is useful to manufacture the micro moulds in two steps. First conventional high precision milling is used to manufacture the main structure. Afterwards the structure is finished by the ECF process. Since these two steps are carried out on two different machines, the workpiece has to be aligned in the ECF machine after the milling process. Using a matching strategy alignment errors like rotation to the xy-plane, errors in scaling of the length of the axis and translation in the xy-plane can be corrected automatically by transforming the CAD/CAM data in a way that they match the two co-ordinate systems. It is shown by test-pattern that this strategy works very accurately. There is almost no mismatch between the HSC pre-milled structure and the ECF added microstructure in the different examples shown here. This investigation shows that hybrid tooling with ECF is a time saving approach to add microstructures with the ECF-process into pre-milled moulds. Therefore hybrid tooling has a high potential to become one of the leading techniques to manufacture cavities, e.g. for micro moulds in stainless steel.

Abundant Crystalline Silicates in the Disk of a Very Low Mass Star

We announce the discovery of SST-Lup3-1, a very low mass star close to the brown dwarf boundary in Lupus III with a circum(sub)stellar disk, discovered by the `Cores to Disks' Spitzer Legacy Program from mid-, near-infrared and optical data, with very conspicuous crystalline silicate features in its spectrum. It is the first of such objects with a full 5 to 35 micron spectrum taken with the IRS and it shows strong 10 and 20 micron silicate features with high feature to continuum ratios and clear crystalline features out to 33 micron. The dust in the disk upper layer has a crystalline silicate grain fraction between 15% and 33%, depending on the assumed dust continuum. The availability of the full Spitzer infrared spectrum allows an analysis of the dust composition as a function of temperature and position in the disk. The hot (~ 300 K) dust responsible for the 10 micron feature consists of a roughly equal mix of small (~ 0.1 micron) and large (~ 1.5 micron) grains, whereas the cold (~ 70 K) dust responsible for the longer wavelength silicate features contains primarily large grains (> 1 micron). Since the cold dust emission arises from deeper layers in the inner (< 3 AU) disk as well as from the surface layers of the outer (3-5 AU) disk, this provides direct evidence for combined grain growth and settling in the disk. The inferred crystalline mass fractions in the two components are comparable. Since only the inner 0.02 AU of the disk is warm enough to anneal the amorphous silicate grains, even the lowest fraction of 15% of crystalline material requires either very efficient mixing or other formation mechanisms.

Infrared spectroscopy of HCOOH in interstellar ice analogues

Context: HCOOH is one of the more common species in interstellar ices with abundances of 1-5% with respect to solid H2O. Aims: This study aims at characterizing the HCOOH spectral features in astrophysically relevant ice mixtures in order to interpret astronomical data. Methods: The ices are grown under high vacuum conditions and spectra are recorded in transmission using a Fourier transform infrared spectrometer. Pure HCOOH ices deposited at 15 K and 145 K are studied, as well as binary and tertiary mixtures containing H2O, CO, CO2 and CH3OH. The mixture concentrations are varied from 50:50% to ~10:90% for HCOOH:H2O. Binary mixtures of HCOOH:X and tertiary mixtures of HCOOH:H2O:X with X = CO, CO2, and CH3OH, are studied for concentrations of ~10:90% and ~7:67:26%, respectively. Results: Pure HCOOH ice spectra show broad bands which split around 120 K due to the conversion of a dimer to a chain-structure. Broad single component bands are found for mixtures with H2O. Additional spectral components are present in mixtures with CO, CO2 and CH3OH. The resulting peak position, full width at half maximum and band strength depend strongly on ice structure, temperature, matrix constituents and the HCOOH concentration. Comparison of the solid HCOOH 5.9, 7.2, and 8.1 micron features with astronomical data toward the low mass source HH 46 and high mass source W 33A shows that spectra of binary mixtures do not reproduce the observed ice features. However, our tertiary mixtures especially with CH3OH match the astronomical data very well. Thus interstellar HCOOH is most likely present in tertiary or more complex mixtures with H2O, CH3OH and potentially also CO or CO2, providing constraints on its formation.

The 15–20 μmSpitzerSpectra of Interstellar Emission Features in NGC 7023

We present 15 - 20 micron long-slit spectra, from the Infrared Spectrograph (IRS) on Spitzer, of NGC 7023. We observe recently-discovered interstellar emission features, at 15.9, 16.4, 17.0, 17.4, 17.8, and 18.9 microns, throughout the reflection nebula. The 16.4 micron emission feature peaks near the photodissociation front northwest of the star, as do the aromatic emission features (AEFs) at 3.3, 6.2 and 11.3 microns. The 16.4 micron emission feature is thus likely related to the AEFs and radiates by non-equilibrium emission. The new 18.9 micron emission feature, by contrast, decreases monotonically with stellar distance. We consider candidate species for the 18.9 micron feature, including polycyclic aromatic hydrocarbons, fullerenes, and diamonds. We describe future laboratory and observational research needed to identify the 18.9 micron feature carrier.

Combined electron beam and UV lithography in SU-8

We present combined electron beam and UV lithography (CEUL) in SU-8 as a fast and flexible lithographic technique for prototyping of functional polymer devices and pattern transfer applications. CEUL is a lithographic technique suitable for defining both micrometer and nanometer scale features in a single polymer film on the wafer scale. The height of the micrometer and nanometer scale features is matched within 30 nm. As a pattern transfer application, we demonstrate stamp fabrication and thermal nanoimprint of a 2-dimensional array of 100 nm wide lines with a pitch of 380 nm in connection with micrometer scale features.

Photoresist Free Negative and Positive Photolithographic Deposition of Zirconium Oxide Films from Photosensitive Metal Organic Compounds

ABSTRACTPhotoresist free photolithographic deposition of zirconium oxide from photosensitive zirconium complexes has been achieved using photochemical metal organic deposition. In this contribution, the deposition of patterned zirconium oxide is used as an example to demonstrate both negative and positive photolithographic deposition. In the prototypical deposition of zirconium oxide by photochemical metal organic deposition, a solution containing zirconium (IV) di-n-butoxide bis(2, 4-pentanedionate) was used to spin coat a silicon substrate, resulting in an amorphous film. The film was then exposed to UV light leading to the formation of zirconium oxide and other volatile products. The resultant zirconium oxide film was investigated by X-ray diffraction and Auger Electron Spectroscopy. Irradiating the precursor film through a photo mask led to a latent image which yielded either a negative or a positive pattern dependent upon developer. Subject to further photochemical or thermal treatment, a zirconium oxide pattern can be obtained. Similar results were obtained using a series of zirconium (IV) complexes. Both positive and negative patterns of zirconium oxide with 2 micron feature sizes were obtained.

Compositional dependence of infrared absorption spectra of crystalline silicates

The infrared optical properties and absorption spectra of the melilite solid solution series are reported. Melilite is a high-temperature condensate, and is expected to condense during the early phase of the condensation sequence. In this study, samples of the melilite solid solution series were newly synthesized between the aluminium end member (gehlenite) and the magnesium end member (akermanite) at ∼10% intervals in chemical composition, and the infrared absorption spectra of their samples were measured. Variation in the absorption features were detected: such variations include changes in numbers of absorption peaks, peak intensity, peak position, and peak width. The prominent absorption peaks appeared at 10-13 micron, 14, 15, 17, 19, 21, 24, 30, 37 and in the 60 micron region. In particular, the 10 micron feature complex and the 60 micron broad features are very sensitive to chemical composition. For application to and implications for astronomical data, we focused on the 60 micron feature, and carried out a comparison with ISO data of NGC 6302. Our data set will supply the spectroscopic basis for the interpretation of astronomical data accumulated by space and ground based observatories such as ISO, the Spitzer Space Telescope, the AKARI (ASTRO-F) and the Subaru telescope.