Projects in Materials Analysis and
Characterization:
Project
1. Studies of Electrical Conductance
through Molecular Monolayers, Organic Thin Films and Semiconducting Particle
Assemblies
E. Allen (Emily.Allen@sjsu.edu); J. C. Scott (jcscott@almaden.ibm.com)
Charge transport across nanometer thick films of soft-matter requires the deposition of a top electrical contact that does not damage the fragile underlying structure. In previous work, following the method of Akkerman et al., we have developed a process for making arrays of such devices, and have demonstrated their application to determine the electrical conductance of self-assembled molecular monolayers (SAM). In the next stage of this project, we propose to employ the device structure to a wider variety of materials, including thin organic conducting films and assemblies of semiconducting particles stabilized by organic surfactants. The organic materials will include conjugated oligomers with end-group functionalization such that their attachment and electrical injection barrier to gold may be evaluated.
Project 2. AFM Studies of Chemically Modified Surfaces
J. Pesek (Joseph.Pesek@sjsu.edu); J. Frommer (frommer@almaden.ibm.com)
A
number of different techniques are amenable to studying the inner surface of
etched chromatographic capillaries and mcirofluidic
channels2-5. Scanning
electron microscopy provides a good visual indication of the topography of the
etched surface. By SEM it has been
determined that significant roughness is present with radial extensions of up
to 5 microns. Atomic force microscopy (AFM) provides a better
understanding of surface topography as a function of derivatizing conditions
and the nature of the bonded groups. While AFM images correlate well with the
SEM data, AFM can also be used to estimate roughness as well as to measure
surface forces. The intern will learn
these methods of characterization and techniques for attaching various
compounds to AFM tips for the measuring surface forces. Since the tips are made of silicon, bonding
reactions with the surface oxide (organosilanization
or silanization/hydrosilation) can be used to attach
the desired moieties, i.e., octyldimethylchlorosilane
for hydrophobic interactions or glycidylpropyltrimethoxy
silane for hydrophilic interactions. This approach has been tested and preliminary
images correlate well to the images produced by a conventional AFM tip. Force measurements have also been made
between these tips and the inner walls of etched chemically modified
capillaries. With the modified tips, the
intern will measure the specific forces that mimic the types of interactions
between solutes and the bonded moiety.
The intern's AFM measurements will determine the uniformity of surface
coverage as well as roughness which,
in the past, indicated surface area increases in the range of several hundred
to a thousand fold or more. These
experiments help identify potential applications for this unique capillary
configuration and a new polymer (polyhydridomethylsiloxane)
developed for microfluidic devices and are essential
to the fundamental understanding of chemically modified surfaces as an
electrophoretic separation medium.
Capillary and chip fabrication for this study as well as the
electrophoretic experiments to correlate separation capabilities with surface
characteristics determined by the AFM and SEM measurements will be done by the
intern at SJSU. The collaboration for
this project between SJSU and the
Project 3. Vibrational Spectroscopy for the Detection
and Analysis of Biomolecular Interactions
R. Terrill (rterrill@jupiter.sjsu.edu)
We are developing a novel biointeraction analysis (BIA) method that is similar to surface plasmon resonance (SPR) but harnesses the power of surface enhanced infrared (SEIR) spectroscopy as a spectral detection element – “SEIR-BIA” for short. Biointeraction analysis is crucial to understand how living systems function because to know how living systems function, and how to maintain and repair them requires that we know how biomolecules interact. The SPR method is very powerful and increasingly popular, but we intend to augment this power by using infrared spectral detection. The infrared spectrum will encode information regarding the identity and details of the molecules involved that is simply not available in the visible-wavelength interrogation.
The intern will be using our SPR and SEIR apparatus to explore model biomolecule interactions such as the surface binding and duplexation of single-stranded DNA (commercially available). This will involve skills in the preparation of noble metal films, pure and buffered biomolecule solutions, the collection and interpretation of spectral data and the manipulation of data using basic chemometric methods.
It is essential that experimental data be collected in order to address the following desired information:
a. What factors control the analytical availability of information?
a. How to maximize the signal to noise ratio in these settings?
b. What are the major noise sources?
c. How to analyze mathematically the responses that we do observe in order to discriminate between target and interferant and other noise sources?
b. What new kinds of information can we derive from these responses?
a. Can we detect and / or decipher structural and compositional changes occur during the binding events?
b. Are there slow molecular re-organizations or other subtle effects such as denaturation or decomposition that accompany binding that would not be evident in a less structurally sensitive detection method?
Project 4. Improving TEM Sample Preparation of Magnetic Multilayer Specimens
P. Rice (pmrice@almaden.ibm.com); L. E. Krupp (lkrupp@us.ibm.com)
Magnetic multilayers are important in research on magnetic random access memory and magnetic sensors and have many applications in other technologies. TEM is vital for characterization of these films. The effect of the sample preparation method on the structure or surface of a sample (usually less than 40 nm thick) is a perennial question. In this project the intern will conduct mechanical polishing and ion milling experiments to find the best conditions for consistently producing damage free TEM cross sections from magnetic multilayers on Si coupons. The intern will learn to use the state-of-the-art Multiprep TM polishing system, the precision ion polishing system (PIPSTM), and a "Gentle Mill" (200 volt) ion polisher at IBM. These sample preparation methods are essential for the subsequent use of Field Emission TEM studies on a JEOL 2010F. A comparison of the effect of the preparation methods will come from TEM and EELS results on the samples. If the modifications to the 'Gentle Mill' ion polisher are complete, the intern will help calibrate the instrument as well as develop and write a standard operating procedure (SOP) for the newly configured ion mill.
Projects in
Chemical Synthesis:
Project 5. Functionalized Star Polymers:
Synthesis, Characterization, Assembly and Applications
R. D. Miller (rdmiller@almaden.ibm.com); M. McNeil
(Melanie.McNeil@sjsu.edu); R.
Chung (W.Richard.Chung@sjsu.edu)
Star polymers offer many of the
characteristics of dendrimers e.g. core sections from
which branches emanate, polymer chains containing functionality from which
interstitial space is generated and peripheral functionality to interrogate the
environment or to provide a scaffold for subsequent chemical constructs.
Although star polymers are not new, modern synthetic methods have delivered
simplicity, versatility, and manufacturability along with similar potential
applications without the cost, synthetic difficulties and limited functionality
availability for dendrimers.
We have developed routes to star
polymers utilizing arm first routes employing controlled polymerization
techniques including anionic, controlled free radical and ring opening
polymerization techniques to produce particles ranging in size from 5-50nm and
containing an abundance of functionality. Depending on the synthetic route, the
core and arms can be hydrophilic or hydrophobic and peripheral substitutes such
as thiols, amines, carboxylic acids, esters, sugars,
zwitterions, azides, acetylenes, olefins, silanes, halogens, phorphyrins,
fullerenes, polymer initiators, polymers, peptides etc can be generated. These
materials can be used as porogens and pore size
scaffolds for the deposition of silica-like encapsulating shells, catalysts for
metallic nanoparticle deposition and growth,
encapsulating media for hydrophobic reagents with subsequent controlled
release, surface active reagents, constructs for layer-by-layer deposition in
the formation of controlled nanostructures and other applications. Recently, we
have developed synthetic routes to amphiphilic unimolecular micelles and star polymers containing
biodegradable cores composed of poly- lactones, lactides
and carbonates. Depending on the peripheral substituents, the star polymers can
be water soluble or not.
We will study the encapsulation of
various reagents within functionalized star polymers including environmentally
responsive markers, explore catalyzed reactions occurring within the particle
interior and study the kinetics of release as a function of solvent and polymer
structure. We will use fluorescence emission to probe the interior particle
environment and study energy and electron transfer reactions occurring by intra
and interparticle processes. In addition, we will
study the construction of nanostructures on patterned and unpatterned
surfaces using layer-by-layer self assembly
driven by acid-base interactions, metal coordination assembly and
hydrogen bonding assembly rather than by the more commonly utilized
electrostatic interactions. Using appropriate chromophores
we will study energy transfer cascades between spaced layers of different
energetically suitable dyes separated by ligand spacers. The use of multivalent star polymer ligands will be extended to the layer-by-layer assembly of
nanoparticles, magnetic and otherwise to produce ordered arrays on surfaces
where the particle-particle interactions are mediated by the size of the ligand
spacers. The kinetics and thermodynamics of the L-b-L assembly will be
monitored directly by surface plasmon resonance and
by quartz crystal microbalance which have been modified to accommodate solution
flow cells.
Project
6. The Design of Lanthanide-Based Luminescent Probes
G.
Muller (Gilles.Muller@sjsu.edu)
Crucial to modern drug
discovery is the recognition of chiral molecules. To fully understand the structure-activity
relationships and structure-property relationships that are often based on
“pharmaceutical profiling”, one needs to develop a reliable method
to measure the absolute stereochemistry of each analog prepared or separated. Researchers are beginning to look at single-enantiomer drugs as possible treatments for cancer,
cardiovascular disease, and central nervous system defects. Thus, the emergence of new techniques in chiral
separation and resolution must be found to meet this growing demand.
The ultimate goal of this
work is to demonstrate that the circularly polarized luminescence (CPL) spectroscopic
technique is an attractive complementary/alternative method to the presently
available methods (i.e. NMR, HPLC, Capillary Electrophoresis, optical rotation,
or circular dichroism) for projects aimed at probing specific chiral structural
changes and/or for recognition of chiral biological molecules. Thus, the
projects envisaged are aimed at (i) evaluating the
chiral recognition properties of promising functionalized luminescent chiral Ln(III) complexes used as probes for specific target
molecules (i.e. amino acids), and/or (ii) understanding the relationships
between the structures of proteins and their ability to bind metal ions where
the metal ions are substituted by Ln(III) ions. Of
special interest is the importance of the alkaline earth divalent cations Mg(II) and Ca(II) in many biological processes
including enzyme activation, nucleic acid stabilization, muscle contraction,
secretion, or synaptic transmission. Despite their important biological
functions, these ions do not exhibit useful spectroscopic/magnetic probe
properties due to their inert-gas electronic configuration and the absence of
unpaired electrons, and consequently preclude the use of conventional
spectroscopic techniques for structural and dynamics studies. On the other
hand, the study of enantiomeric recognition of
biologically substrates is an ongoing active research because it can provide
valuable information concerning molecular recognition mechanisms in biological
materials.
Project 7. Dye-Doped Nanoparticles from
Block Copolymer Micelles
H.-C. Kim (hckim@almaden.ibm.com)
Luminescent
nanomaterials such as quantum dots, metal (e.g. Ag) nanoparticles, and
dye-doped polymer particles and silica nanoparticles have attracted much
attention due to their superior optical properties. In particular, silica
nanoparticles doped with organic dye molecules provide high quality luminescent
signals with strong fluorescent intensity, excellent photostability,
easy surface modification, size uniformity and tunability.
Using appropriate synthetic methods, a variety of dye molecules can be
incorporated into a single silica particle.
This project is
for developing a method using block copolymer micelles to generate
nanoparticles containing organic dyes, organosilicate
precursor and metals. To minimize the leakage of the organic dye molecules from
confined micelles while retaining highly amplified optical signal, this
proposal will focus on (1) searching methods to obtain stable block copolymer
micelles in various solvent systems, (2) incorporation of organic dyes into
block copolymer micelles, (3) incorporation of organosilicate
precursor into micelles to provide structural stability and (4) developing
method to incorporate Ag into micelles to enhance fluorescence intensity.
Project 8. Organic Catalysis: A General Platform for Living Polymerization
Jim Hedrick (hedrick@almaden.ibm.com)
Technological advances continue to present many complex ecological issues. As a consequence, pollution prevention and waste management constitute two significant challenges of the 21st century. Since the recent establishment of a green program at the EPA, modern synthetic methodologies are encouraged to preserve efficacy of function while minimizing toxicity, use renewable feedstocks, and use catalytic and /or recyclable reagents to minimize waste. Growing trends in asymmetric synthesis for classic reactions that use organic molecules as promoters have provided an alternative to traditional organometallic reagents. We have developed a series of new organic catalyst platforms for living polymerization. The development of these new catalysts has led to novel patterns of reactivity for the enchainment of monomers to structurally well defined macromolecules. In this summer program, we will continue this general strategy to well-defined macromolecules by exploiting the unique mechanistic aspects of organic catalysis.
http://www.almaden.ibm.com/st/chemistry/ps/catalysts/
Projects in
lithography:
Project 9. Directed Polymer Self-assembly for Lithographic
Applications
J. Cheng (chengjo@us.ibm.com)
Miniaturization is the driving force to improve device performance and reduce the cost for chip manufacturing. In face of the increasing cost and difficulty of patterning ever-smaller features, material and process innovation are required to extend the feasibility and affordability of patterning options into the deep nanometer region. Directed self-assembly of block copolymers, which brings together the precise pattern placement of conventional “top-down” lithography methods with the well-defined nanostructures and self-healing properties of “bottom-up” block copolymer self-assembly, is one of the potential candidates to extend lithographic patterning beyond current resolution limits. In this decade, much work has been done to demonstrate the resolution enhancement and CD variation control based on directed self-assembly method. While significant progress in directed self-assembly of block copolymers has been achieved, the challenges of integrating polymer self-assembly into standard lithographical process remain one of the major hurdles to polymer self-assembly impacting the lithography roadmap. We propose a summer intern project to study the materials and processes for integration of directed self-assembly into optical lithography.
Two major directed self-assemblies are graphoepitaxy
and chemical epitaxy. In the graphoepitaxy method, self-assembly is guided by the topographical
features of lithographically prepatterned
substrates. Self-aligned polymer domains
form parallel line-space patterns in topographical prepatterns,
thereby increasing pattern resolution by subdividing the topographical
pattern. In the chemical epitaxy method, self-assembly is guided by
lithographically-determined dense chemical patterns with the same spatial
frequency as the block copolymer domains.
The affinity between the chemical patterns on the substrate and the
block copolymer domains results in the precise registration and CD variation
reduction of underlying chemical patterns. We recently demonstrated an
integrated directed self-assembly method combining the advantages of both graphoepitaxy and dense chemical epitaxy
using sparse chemical that dramatically
heals defects
and reduces feature size variation of the poorly-defined electron-bean resist
patterns. Even though a successful
integration of directed self-assembly with electron-beam lithography has been
achieved, issues remain in the integration directed self-assembly with optical
lithography.
This summer intern project will investigate the materials
for integration of directed self-assembly into optical lithography. The student
will learn to design and tailor the materials and processes to generate
lithographically defined prepatterns for directed
self-assembly. Hands-on experience will include patterning using interference
lithography, surface characterization and visualization of polymer
self-assembly through microscopic techniques. The goal of this project is to
gain in-depth understanding of surface properties and self-assembly behavior of
the guiding patterns and to integrate directed self-assembly into the standard
optical lithography process.
Projects in Biologically
Derived and Self Assembly Systems:
Project 10. Supramolecular
and Biomimetic Polymers
A. Nelson (alshak@us.ibm.com)
Many biological processes, such as DNA transcription
and protein-protein interactions are driven by self-assembly of smaller
components into larger assemblies by employing molecular recognition. As the current trend of creating smaller
electronic devices continues, there is an increasing need to develop the
materials and methods required to continue this trend. Emulating the assembly processes, as they
occur in Nature, is one route to generating new materials for devices and other
applications that require particular attention to events as they occur at the
nanoscale. Our group focuses upon using
and understanding molecular recognition to control the organization of polymers
in solution, in bulk, and as thin films.
This includes synthesizing molecular recognition elements, employing
controlled polymerization techniques, and investigating their self-assembly
behavior.
Project 11. Controlled Placement of Nanostructures
S.Swanson
(saswans@almaden.ibm.com) , G. Wallraff (wallraff@almaden.ibm.com)).
The synthetic formation of
nanostructures such as nanorods and nanospheres with monodisperse size has progressed but the
controlled placement of these structures to form useful nanodevices
is still a challenge. This study will
focus on using biomolecular recognition systems such
as biotin/streptavidin to assemble nanostructures
onto DNA origami tiles. For example,
semiconducting cadmium sulfide (CdS) nanorods have been grown with gold nanospheres
on each end. After ligand exchange, the
water-soluble nanorods can be decorated with thiol-terminated biotin for controlled placement on streptavidin-modified DNA origami.
Project in Materials
Modeling
Project 12. Modeling of Phase Change
Materials and Devices
G. Burr (burr@almaden.ibm.com)
Phase-change memory is a non-volatile memory technology
that is being widely pursued as a possible next-generation replacement for the semiconductor
Flash memory pervasively used in today’s cell phones, MP3 players, and
digital cameras. However, the improved
speed and endurance of such a phase-change memory opens the possibility of
“storage-class” memory – a single technology that combines
the low cost of a magnetic hard-disk, the high performance (fast data access)
of DRAM, and the robustness and non-volatility of Flash memory.
A summer internship in this topic
would be centered on the numerical modeling of phase-change materials and devices. The intern would use our unique custom-built
modeling software, which can model electrical operation of memory devices,
optical illumination of memory materials, and long-term thermal annealing of
devices and materials. We use this
simulator in order to further improve our understanding of the physical
mechanisms in this memory technology, by matching simulations against measured
(and published) experimental characterization data of phase-change and other
memory materials and devices. The
project would include materials characterization, deposition of phase-change or
other memory materials, electrical testing of phase-change or other memory
devices, and potentially even device fabrication as time permits.