Benzenesulfonates, para-substituted with amine, chloride and methyl groups were successfully incorporated into layered double hydroxides of two different compositions, 2:1 Mg-Al LDH and 2:1 Zn-Al LDH. These parent materials were also doped with small amounts of nickel and the differences in the two systems were studied. The hexamethylenetetramine route of layered double hydroxide synthesis was investigated to verify if the mechanism is indeed homogeneous. This included attempting preparation of 2:1 Mg-Al LDH, 2:1 Zn-Al LDH and 2:1 Zn-Cr LDH with two different concentrations of hexamethylenetetramine. The analytical data of the products suggest that the homogeneous precipitation may not be the true mechanism of reaction involved in LDH synthesis by this method.

Hydrogen terminated silicon surfaces have been utilized to develop sensors for semiconductor and environmental applications. The interaction of these surfaces with different environments has also been studied in detail. The sensor assembly relevant to the semiconductor industry utilizes a silicon-based sensor to detect trace levels of metallic contaminants in hydrofluoric acid. The sensor performance with respect to two non-contaminating reference electrode systems was evaluated. In the first case, conductive diamond was used as a reference electrode. In the second case, a dual silicon electrode system was used with one of the silicon-based electrodes protected with an anion permeable membrane behaving as the quasi reference electrode. Though both systems could function well as a suitable reference system, the dual silicon electrode design showed greater compatibility for the on-line detection of metallic impurities in HF etching baths. The silicon-based sensor assembly was able to detect parts- per-trillion to parts-per-billion levels of metal ion impurities in HF. The sensor assembly developed for the environmental application makes use of a novel method for the detection of Ni2+using attenuated total reflection (ATR) technique. The nickel infrared sensor was prepared on a silicon ATR crystal uniformly coated by a 1.5 micron Nafion film embedded with dimethylglyoxime …

Electrodeposition of diamond-like carbon (DLC) films was studied on different substrates using two different electrochemical methods. The first electrochemical method using a three-electrode system was studied to successfully deposit hydrogenated DLC films on Nickel, Copper and Brass substrates. The as-deposited films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV). A variety of experimental parameters were shown to affect the deposition process. The second electrochemical method was developed for the first time to deposit hydrogen free DLC films on Ni substrates through a two-electrode system. The as-deposited films were characterized by Raman spectroscopy and FTIR. According to Raman spectra, a high fraction of diamond nanocrystals were found to form in the films. Several possible mechanisms were discussed for each deposition method. An electrochemical method was proposed to deposit boron-doped diamond films for future work.

Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of …

The reactivity of oxide surfaces and metal-oxide interfaces play an important role in many technological applications such as corrosion, heterogeneous catalysis, and microelectronics. The focus of this research was (1) understanding the effects of water vapor exposure of ultrathin aluminum oxide films under non-ultrahigh vacuum conditions (>10-9 Torr) and (2) characterization of Pt growth modes on ultrathin Ta silicate and silicon dioxide films and the effects of growth modes on adhesion of a Cu overlayer. These studies were conducted with X-ray photoelectron spectroscopy (XPS). Ni3Al(110) was oxidized (10-6 Torr O2, 800K) followed by annealing (1100K). The data indicate that the annealed oxide film is composed of NiO, Al2O3 and an intermediate phase denoted here as "AlOx". Upon exposure of the oxide film at ambient temperature to increasing water vapor pressure (10-6 - 5 Torr), a shift in both the O(1s) and Al(2p)oxide peak maxima to lower binding energies is observed. In contrast, exposure of Al2O3/Al(polycrystalline) to water vapor under the same conditions results in a high binding energy shoulder in the O(1s) spectra which indicates hydroxylation. Spectral decomposition provides further insight into the difference in reactivity between the two oxide films. The corresponding trends of the O(1s)/Ni0(2p3/2) and Al(2p)/Ni0(2p3/2) spectral …

The TaSiO6 films, ~8Å thick, were formed by sputter deposition of Ta onto ultrathin SiO2 substrates at 300 K, followed by annealing to 600 K in 2 torr O2. X-ray photoelectron spectroscopy (XPS) measurements of the films yielded a Si(2p) binding energy at 102.1 eV and Ta(4f7/2) binding energy at 26.2 eV, indicative of Ta silicate formation. O(1s) spectra indicate that the film is substantially hydroxylated. Annealing the film to > 900 K in UHV resulted in silicate decomposition to SiO2 and Ta2O5. The Ta silicate film is stable in air at 300K. XPS data show that sputter-deposited Cu (300 K) displays conformal growth on Ta silicate surface (TaSiO6) but 3-D growth on the annealed and decomposed silicate surface. Initial Cu/silicate interaction involves Cu charge donation to Ta surface sites, with Cu(I) formation and Ta reduction. The results are similar to those previously reported for air-exposed TaSiN, and indicate that Si-modified Ta barriers should maintain Cu wettability under oxidizing conditions for Cu interconnect applications. XPS has been used to study the reaction of tert-butylimino tris(diethylamino) tantalum (TBTDET) with atomic hydrogen on SiO2 and organosilicate glass (OSG) substrates. The results on both substrates indicate that at 300K, TBTDET partially dissociates, forming …

Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid (AA) have been synthesized and used as building blocks for creating three-dimensional networks. The close-packed PNIPAM-co-allylamine and PNIPAM-co-AA nanoparticles were stabilized by covalently bonding neighboring particles at room temperature and at neutral pH; factors which make these networks amicable for drug loading and release. Controlled release studies have been performed on the networks using dextran markers of various molecular weights as model macromolecular drugs. Drug release was quantified under various physical conditions including a range of temperature and molecular weight. These nanoparticle networks have several advantages over the conventional bulk gels for controlling the release of biomolecules with large molecular weights. Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) can self-assemble into crystals with a lattice spacing on the order of the wavelength of visible light. By initiating the crystallization process near the colloidal crystal melting temperature, while subsequently bonding the PNIPAM-co-allylamine particles below the glass transition temperature, a nanostructured hydrogel has been created. The crystalline hydrogels exhibit iridescent patterns that are tunable by the change of temperature, pH value or even protein concentration. This kind of soft and wet hydrogel with periodic structures may lead to new sensors, devices, and displays operating in aqueous …

The electrochemical quartz crystal microbalance (EQCM) has been proven an effective mean of monitoring up to nano-scale mass changes related to electrode potential variations at its surface. The principles of operation are based on the converse piezoelectric response of quartz crystals to mass variations on the crystal surface. In this work, principles and operations of the EQCM and piezo-electrodes are discussed. A conductive oxide, ruthenium oxide (RuO2) is a promising material to be used as a diffusion barrier for metal interconnects. Characterization of copper underpotential deposition (UPD) on ruthenium and RuO2 electrodes by means of electrochemical methods and other spectroscopic methods is presented. Copper electrodeposition in platinum and ruthenium substrates is investigated at pH values higher than zero. In pH=5 solutions, the rise in local pH caused by the reduction of oxygen leads to the formation of a precipitate, characterized as posnjakite or basic copper sulfate by means of X-ray electron spectroscopy and X-ray diffraction. The mechanism of formation is studied by means of the EQCM, presenting this technique as a powerful in-situ sensing device.

This dissertation focuses on the chemistry, detection, and control of metals and metal contaminants during manufacturing of integrated circuits (ICs) on silicon wafers. Chapter 1 begins with an overview of IC manufacturing, including discussion of the common aqueous cleaning solutions, metallization processes, and analytical techniques that will be investigated in subsequent chapters. Chapter 2 covers initial investigations into the chemistry of the SC2 clean - a mixture of HCl, H2O2, and DI water - especially on the behavior of H2O2 in this solution and the impact of HCl concentration on metal removal from particle addition to silicon oxide surfaces. Chapter 3 includes a more generalized investigation of the chemistry of metal ions in solution and how they react with the silicon oxide surfaces they are brought into contact with, concluding with illumination of the fundamental chemical principles that govern their behavior. Chapter 4 shows how metal contaminants behave on silicon wafers when subjected to the high temperature (≥ 800 °C) thermal cycles that are encountered in IC manufacturing. It demonstrates that knowledge of some fundamental thermodynamic properties of the metals allow accurate prediction of what will happen to a metal during these processes. Chapter 5 covers a very different but …

Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3∙Cu(OH)2 in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH = 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V vs Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived a crude test called "the Scotch tape test", which stick the scotch tape on the sample, then peel off the tape and see if the copper film peels off or not. Characterization by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray photon spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicate that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics do not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO4/H2SO4 solution at pH > 1 at -0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small …

An extremely facile and novel method called spontaneous deposition, to deposit noble metal nanoparticles on a most stable form of carbon (C) i.e. diamond is presented. Nanometer sized particles of such metals as platinum (Pt), palladium (Pd), gold (Au), copper (Cu) and silver (Ag) could be deposited on boron-doped (B-doped) polycrystalline diamond films grown on silicon (Si) substrates, by simply immersing the diamond/Si sample in hydrofluoric acid (HF) solution containing ions of the corresponding metal. The electrons for the reduction of metal ions came from the Si back substrate. The diamond/Si interfacial ohmic contact was of paramount importance to the observation of the spontaneous deposition process. The metal/diamond (M/C) surfaces were investigated using Raman spectroscopy, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffractometry (XRD). The morphology (i.e. size and distribution) of metal nanoparticles deposits could be controlled by adjusting the metal ion concentration, HF concentration and deposition time. XRD data indicate the presence of textured and strained crystal lattices of Pd for different Pd/C morphologies, which seem to influence the electrocatalytic oxidation of formaldehyde (HCHO). The sensitivity of electrocatalytic reactions to surface crystal structure implies that M/C could be fabricated for specific electrocatalytic applications. The research also …

The dissertation consists of the following three sections: 1. Hydroxyapatite (HA) coatings. In this work, we deposited HA precursor films from weak basic electrolytic solution (pH= 8-9) via an electrochemical approach; the deposits were changed into crystallite coatings of hydroxyapatite by sintering at specific temperatures (600-800 ºC). The formed coatings were mainly characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD patterns show well-defined peaks of HA when sintered under vacuum conditions. FTIR measurements indicate the existence of hydroxyl groups, which were confirmed by the characteristic intensity of the stretching and bending bands at ~3575 and ~630 cm-1, respectively. The SEM shows an adhesive, crack free morphology for the double-layer coating surface of the samples sintered in a vacuum furnace. 2. Silver/polymer/clay nanocomposites. Silver nanoparticles were prepared in layered clay mineral (montmorillonite)/polymer (PVP: poly (vinyl pyrrolidone)) suspension by an electrochemical approach. The silver particles formed in the bulk suspension were stabilized by the PVP and partially exfoliated clay platelets, which acted as protective colloids to prevent coagulation of silver nanoparticles together. The synthesized silver nanoparticles/montmorillonite/PVP composite was characterized and identified by XRD, SEM, and TEM (transmission electron microscopy) measurements. 3. Ce-doped lead …

An iodine surface layer has been prepared on Ru(poly) and Ru(0001) electrodes by exposure to iodine vapor in UHV and polarizing in a 0.1 M HClO4/0.005 M KI solution, respectively. A saturation coverage of I on a Ru(poly) electrode passivates the Ru surface against significant hydroxide, chemisorbed oxygen or oxide formation during exposure to water vapor over an electrochemical cell in a UHV-electrochemistry transfer system. Immersion of I-Ru(poly) results in greater hydroxide and chemisorbed oxygen formation than water vapor exposure, but an inhibition of surface oxide formation relative that of the unmodified Ru(poly) surface is still observed. Studies with combined electrochemical and XPS techniques show that the iodine surface adlayer remained on top of the surface after cycles of overpotential electrodeposition/dissolution of copper on both Ru(poly) and Ru(0001) electrodes. These results indicate the potential bifunctionality of iodine layer to both passivate the Ru surface in the microelectronic processing and to act as a surfactant for copper electrodeposition. The electrodeposition of Cu on Ru(0001) or polycrystalline Ru was studied using XPS with combined ultrahigh vacuum/electrochemistry methodology (UHV-EC) in 0.1 M HClO4 with Cu(ClO4)2 concentrations ranging from 0.005 M to 0.0005 M, and on polycrystalline Ru in a 0.05M H2SO4/0.005 M CuSO4/0.001 …

Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3∙Cu(OH)2 in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH = 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V versus Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived a crude test called "the Scotch tape test", which involves sticking the scotch tape on the sample, then peeling off the tape and observing if the copper film peels off or not. Characterization by scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) and X-ray photon spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicated that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics does not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO4/H2SO4 solution at pH > 1 at -0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small …

The ability to passivate metallic surfaces under non-UHV conditions is not only of fundamental interests, but also of growing practical importance in catalysis and microelectronics. In this work, the passivation effect of a surface iodine layer on air-exposed Ta for the copper electroless deposition was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Although the passivation effect was seriously weakened by the prolonged air exposure, iodine passivates the Ta substrate under brief air exposure conditions so that enhanced copper wetting and adhesion are observed on I-passivated Ta relative to the untreated surface.

Experimental mole fraction solubilities of several carboxylic acids (2-methoxybenzoic acid, 4-methoxybenzoic acid, 4-nitrobenzoic acid, 4-chloro-3-nitrobenzoic acid, 2-chloro-5-nitrobenzoic acid,2-methylbenzoic acid and ibuprofen) and 9-fluorenone, thianthrene and xanthene were measured in a wide range of solvents of varying polarity and hydrogen-bonding characteristics. Results of these measurements were used to calculate gas-to-organic solvent and water-to-organic solvent solubility ratios, which were then substituted into known Abraham process partitioning correlations. The molecular solute descriptors that were obtained as the result of these computations described the measured solubility data to within an average absolute deviation of 0.2 log units. The calculated solute descriptors also enable one to estimate many chemically, biologically and pharmaceutically important properties for the ten solutes studied using published mathematical correlations.

Homogeneous hydrogels made of an interpenetrating network of poly(N-isopropylacrylamide) (PNIPAm) and poly(acrylic acid) (PAAc) are synthesized by a two-step process; first making PNIPAm hydrogels and then interpenetrating acrylic acid throughout the hydrogel through polymerization. The kinetic growth of the IPN is plotted and an equation is fitted to the data. When diluted to certain concentrations in water, the hydrogels show reversible, inverse thermal gelation at about 34°C. This shows unique application to the medical field, as the transition is just below body temperature. A drug release experiment is performed using high molecular weight dyes, and a phase diagram is created through observation of the purified, concentrated gel at varying concentrations and temperatures.

Plasma polymerization techniques were used to synthesize and deposit hydrogel on silicon (Si) substrate. Hydrogel is a network of polymer chains that are water-insoluble and has a high degree of flexibility. The various fields of applications of hydrogel include drug release, biosensors and tissue engineering etc. Hydrogel synthesized from different monomers possess a common property of moisture absorption. In this work two monomers were used namely 1-amino-2-propanol (1A2P) and 2(ethylamino)ethanol (2EAE) to produce polymer films deposited on Si ATR crystal. Their moisture uptake property was tested using FTIR-ATR technique. This was evident by the decrease in -OH band in increasing N2 purging time of the films. Secondly, two monomer compounds namely vinyl acetic acid and glycidyl methacrylate which have both amine and carboxylic groups are used as solid surface for the immobilization of bovine serum albumin (BSA). Pulsed plasma polymerization was used to polymerize these monomers with different duty cycles. Initial works in this field were all about protein surface adsorption. But more recently, the emphasis is on covalent bonding of protein on to the surface. This immobilization of protein on solid surface has a lot of applications in the field of biochemical studies. The polymerization of vinyl acetic acid …

Ruthenium, proposed as a new candidate of diffusion barrier, has three different kinds of oxides, which are native oxide, electrochemical reversible oxide and electrochemical irreversible oxide. Native oxide was formed by naturally exposed to air. Electrochemical reversible oxide was formed at lower anodic potential region, and irreversible oxides were formed at higher anodic potential region. In this study, we were focusing on the effect of copper electrodeposition on each type of oxides. From decreased charge of anodic stripping peaks and underpotential deposition (UPD) waves in cyclic voltammetry (CV), efficiency of Cu deposition dropped off indicating that interfacial binding strength between Cu and Ru oxides was weakened when the Ru surface was covered with irreversible oxide and native oxide. Also, Cu UPD was hindered by both O2 and H2 plasma modified Ru surfaces because the binding strength between Cu and Ru was weakened by O2 and H2 plasma treatment. Cu/Ru and Cu/Ta bimetallic corrosion was studied for understanding the corrosion behavior between diffusion barrier (Ta and Ru) and Cu interconnects under the post chemical mechanical planarization (CMP) process in semiconductor fabrication. Gallic acid is used in post CMP slurry solution and is known well as antioxidant which is supposed to oxidize …

Copper (Cu) electrodeposition on ruthenium (Ru) oxides was studied due to important implications in semiconductor industry. Ruthenium, proposed as the copper diffusion barrier/liner material, has higher oxygen affinity to form different oxides. Three different oxides (the native oxide, reversible oxide, and irreversible oxide) were studied. Native oxide can be formed on exposing Ru in atmosphere. The reversible and irreversible oxides can be formed by applying electrochemical potential. Investigation of Cu under potential deposition on these oxides indicates the similarity between native and reversible oxides by its nature of inhibiting Cu deposition. Irreversible oxide formed on Ru surface is rather conductive and interfacial binding between Cu and Ru is greatly enhanced. After deposition, bimetallic corrosion of Cu/Ru in different polyphenols was studied. Polyphenols are widely used as antioxidants in post chemical mechanical planarization (CMP). For this purpose, different trihydroxyl substituted benzenes were used as antioxidants. Ru, with its noble nature enhances bimetallic corrosion of Cu. Gallic acid (3,4,5 - trihydroxybenzoic acid) was chosen as model compound. A mechanism has been proposed and validity of the mechanism was checked with other antioxidants. Results show that understanding the chemical structure of antioxidants is necessary during its course of reaction with Cu.

The shift to the Cu/low-k interconnect scheme requires the development of diffusion barrier/adhesion promoter materials that provide excellent performance in preventing the diffusion and intermixing of Cu into the adjacent dielectrics. The integration of Cu with low-k materials may decrease RC delays in signal propagation but pose additional problems because such materials are often porous and contain significant amounts of carbon. Therefore barrier metal diffusion into the dielectric and the formation of interfacial carbides and oxides are of significant concern. The objective of the present research is to investigate the fundamental surface interactions between diffusion barriers and various low-k dielectric materials. Two major diffusion barriers¾ tatalum (Ta) and titanium nitride (TiN) are prepared by DC magnetron sputtering and metal-organic chemical vapor deposition (MOCVD), respectively. Surface analytical techniques, such as X-ray photoelectronic spectroscopy (XPS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) are employed. Ta sputter-deposited onto a Si-O-C low dielectric constant substrate forms a reaction layer composed of Ta oxide and TaC. The composition of the reaction layer varies with deposition rate (1 Å-min-1 vs. 2 Å-sec-1), but in both cases, the thickness of the TaC layer is found to be at least 30 Å on the basis of …

The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. …

Hydrogen terminated silicon surfaces play an important role in the integrated circuit (IC) industry. Ultra-pure water is extensively used for the cleaning and surface preparation of silicon surfaces. This work studies the effects of ultra-pure water on hydrogen passivated silicon surfaces in a short time frame of 120 minutes using fourier transform infrared spectroscopy – attenuated total reflection techniques. Varying conditions of ultra-pure water are used. This includes dissolved oxygen poor media after nitrogen bubbling and equilibration under nitrogen atmosphere, as well as metal contaminated solutions. Both microscopically rough and ideal monohydride terminated surfaces are examined. Hydrogen terminated silicon is also used as the sensing electrode for a potentiometric sensor for ultra-trace amounts of metal contaminants. Previous studies show the use of this potentiometric electrode sensor in hydrofluoric acid solution. This work is able to shows sensor function in ultra-pure water media without the need for further addition of hydrofluoric acid. This is considered a boon for the sensor due to the hazardous nature of hydrofluoric acid. Thin carbon films can be formed by spin coating photoresist onto silicon substrates and pyrolyzing at 1000 degrees C under reducing conditions. This work also shows that the electroless deposition of palladium and …

Monodispersed microgels composed of poly-acrylic acid (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating networks were synthesized by 2-step method with first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The semi-dilute aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermo-reversible gelation. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated to PAAc and PNIPAM, respectively. Three applications based on this novel hydrogel system are presented: a rich phase diagram that opens a door for fundamental study of phase behavior of colloidal systems, a thermally induced viscosity change, and in situ hydrogel formation for controlled drug release. Clay-polymer hydrogel composites have been synthesized based on PNIPAM gels containing 0.25 to 4 wt% of the expandable smectic clay Na-montmorillonite layered silicates (Na-MLS). For Na-MLS concentrations ranging from 2.0 to 3.2 wt%, the composite gels have larger swelling ratio and stronger mechanical strength than those for a pure PNIPAM. The presence of Na-MLS does not affect the value of the lower critical solution temperature (LCST) of the PNIPAM. Surfactant-free hydroxypropyl cellulose (HPC) microgels have been synthesized in salt solution. In a narrow sodium chloride concentration range from 1.3 …