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We have investigated the Chemisorption of halogens on semiconductor surfaces in order to develop a better understanding of passivation and etching of these surfaces. We have shown that halogen chemisorption occurs onto both Si(111) and GaAs(100) via both dissociative chemisorption and abstraction. In abstractive chemisorption of a diatomic molecular halogen, one halogen atoms sticks to the surface while the other is ejected back into the gas phase. The abstraction process can be chemically selectivity for one of the two atoms in an interhalogen such as ICl. Furthermore, both abstraction and dissociation can be chemically selective for the Ga atoms on the GaAs(100) surface. The chemisorption of halogens can passivate the surface both chemically and electronically. Passivation occurs when a stable homogeneous monolayer of surface monohalide is formed. For GaAs(100), passivation can unpin the Fermi level; this is a critical step in developing a CMOS technology of GaAs. We are now studying the deposition of insulators on GaAs for use in high speed low power wireless communication and satellite technology with support from DoD.

The interrelated effects of initial surface preparation and precursor predosing on defect passivation of atomic layer deposited (ALD) Al2O3/InGaAs(100) interfaces are investigated. Interface trap distributions are characterized by capacitance-voltage and conductance-voltage analysis of metal-oxide-semiconductor capacitors. Thermal desorption conditions for a protective As2 layer on the InGaAs surface and dosing conditions of trimethylaluminum prior to ALD-Al2O3 are varied to alter the interface trap densities. Experimental results are consistent with the predictions of ab initio electronic structure calculations showing that trimethylaluminum dosing of the As-rich In0.53Ga0.47As(100) surface suppresses interface traps by passivating As dangling bonds prior to the initiation of Al2O3 deposition.

Polarized ultraviolet light from an excimer laser (193 nm) was used to photodesorb and photodissociate N2O and NH3 adsorbed on a cold Pt(111) surface. The photodesorbed species and their time-of-flight (TOF) were monitored by Resonantly Enhanced Multiphoton Ionization spectroscopy. For N2O, we have observed both the ejection of ballistic O atoms and the release of slow thermalized N2 molecules. The ballistic oxygen atoms leave the surface either in the ground state O(3P) or in the first electronically excited state O(1D). A lobular angular distribution pointing away from the surface normal was measured for the ballistic O(3P) in agreement with a binding geometry where the linear N2O is tilted N-end down on the Pt(111) surface. Evidence for the production of N2 photofragments thermalized by the surface includes both low (approximately 90 K) rotational and translational temperatures of the N2 as well as a lack of correlation between rotational and translational energy. For NH3 the irradiation of a submonolayer coverage largely favors the desorption rather than the dissociation of NH3. For multilayer coverages however, a strong dissociation channel is activated and atomic H is seen to desorb from the surface. A bimodal distribution was found for the TOF of the H photofragments. The fastest channel (0.7 eV) corresponds to the ejection of undeflected ballistic H fragments produced near the surface. For bulk NH3 photodissociated deep within the multilayer, the TOF of the H radicals shows an unexpected thermalized distribution.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Junctions between metals and molecules play an important role in molecular electronics. Advances in this field are hampered by the lack of understanding of the electronic structure of organic-metal interfaces. In his Perspective, Kummel highlights the report by Nazin et al. (3), who have used scanning tunneling microscopy (STM) to assemble a metal-molecule-metal junction. Subsequently, they employed the STM tip to probe the atomic structure and local electronic properties of the metal-molecule interface in unprecedented detail. They find evidence for strong coupling between the molecular and metal states. Such coupling affects the conductivity of metal-molecule-metal junctions.

Using in situ atomic scale imaging with scanning tunneling microscopy/spectroscopy, a combination of atomic hydrogen dosing, annealing, and trimethyl aluminum dosing is observed to produce an ordered unpinned passivation layer on an air exposed InGaAs(001)-(4 × 2) surface with only monatomic steps. This shows that conventional gate-last semiconductor processing can be employed to fabricate a variety of electronic devices, even on air exposed compound semiconductors.

Background: Breast conservation therapy (BCT) has been shown to have equal survival efficacy to total mastectomy and provides improved cosmesis. This has resulted in BCT being the preferred treatment of choice for localized tumors. BCT, however, results in about 25-50% of procedures with positive margin status which most likely require a second surgery to remove the remaining tumor mass. These second surgeries inhibit the healing process, reduce cosmesis and increase the risk of complications. Intra-operative determination of margin status has been previously demonstrated using imprint cytology (IC) of tumor margin faces with 96% sensitivity and 100% specificity, but this method requires an experienced cytopathologist and is prone to error if not done meticulously due to the difficulty of searching for cancer cells on large slides. Therefore the requirement for an automated imprint cytology analysis system is acute. Methods: Hematoxylin and eosine (H&E) stained imprint cytology specimens were scanned at 40X on an iScan Coreo Au (BioImagene, Inc., Sunnyvale, CA). Resultant digital images were used to train a linear discriminant algorithm to classify between cancer cells, white blood cells, and debris/junk particles. A unique combination of shape, color and local area descriptors was applied to allow for automated discrimination in a fast parallelized fashion to facilitate intra-operative use. The 16 specimen training set as determined by permanent section consisted of 5 positive, 3 close and 8 negative margins. The resulting classifier was then used on a separate testing set of 8 positive cases (46 IC specimens) as previously determined by permanent section (6 cases) or manual imprint cytology (2 cases) evaluation. Results: Automated evaluation of 46 IC specimens yielded 9 positive specimens in 4 cases. Of the 6 positive permanent section specimens, 2 were confirmed by automated analysis. 2 cases that were deemed negative by permanent section but positive by manual permanent section had 100% agreement. On aggregate, a 50% positive margin identification rate was observed. Conclusion: Automated margin analysis has an enhanced ability to reduce the number of second surgeries by identifying positive margins during the initial surgery. The ability to quickly determine margin status is necessary for intra-operative use and we believe that by taking advantage of the iScan Coreo Au slide scanner's ability to change magnification while scanning will provide us with the necessary analysis times. In the future we will integrate this advanced analysis system into an automated intra-operative evaluation tool. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4887. doi:10.1158/1538-7445.AM2011-4887

The response rate of breast cancer to first line chemotherapies is encouraging, but 20-30% of patients develop chemoresistance to these drugs, and consequently, have a cancer reoccurrence 7-10 months after their last treatment. Chemoresistance is believed to be due to drug efflux proteins responsible for the removal of many commonly used anti-neoplastic agents. One possible way to overcome these drug efflux pumps is to give higher doses of chemotherapy, but high doses of such agents commonly lead to chemocytotoxicity. Targeted PLGA-Lipid hybrid nanoparticle (NP) drug delivery systems have been developed that can deliver high doses of chemotherapy agents specifically to breast cancer cells. A practical cancer targeting drug delivery system will reduce the overall amount of chemotherapy agents given to patients for a given amount of targeted NPs endocytosed by cancer cells. Biodegradable NPs were synthesized using a novel nano-precipitation lipid-polymer hybrid platform which also allows for the encapsulation of hydrophobic chemotherapy drugs within the NPs. Using this method, drug free NPs have been shown to have an average diameter size of 81.78 nm (PDI: 0.25), while single loaded NPs, with Paclitaxel or Doxorubicin, show an average size between 72.33 to 89.64 nm (PDI: 0.242 to 0.339), signifying that the synthesis technique creates consistent sub 100nm particles. The majority of all NPs show a zeta-potential value of > -30 mV consistent with the NPs having sufficient repulsive interaction to be mono-dispersed in solution under physiological conditions. Folate receptors are often over expressed on the surfaces of cancer cells; therefore, folic acid was incorporated to the surface of these NPs as a cancer targeting ligand. Previous studies have shown that HeLa cells, a cervical cancer cell line, over expresses folate receptors. Immunofluorescence studies show that folic acid coated PLGA-Lipid hybrid NPs are readily endocytosed by HeLa cells compared to non-targeted NPs. Cytoxicity studies will determine the increased effectiveness of drug delivery with targeted PLGA-Lipid hybrid NPs vs. untargeted PLGA-Lipid hybrid NP in cell lines and in animal models. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2308. doi:10.1158/1538-7445.AM2011-2308

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Interfacial bonding geometry and electronic structures of In(2)O on InAs and In(0.53)Ga(0.47)As(001)-(4×2) have been investigated by scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS). STM images show that the In(2)O forms an ordered monolayer on both InAs and InGaAs surfaces. In(2)O deposition on the InAs(001)-(4×2) surface does not displace any surface atoms during both room temperature deposition and postdeposition annealing. Oxygen atoms from In(2)O molecules bond with trough In/Ga atoms on the surface to form a new layer of O-In/Ga bonds, which restore many of the strained trough In/Ga atoms into more bulklike tetrahedral sp(3) bonding environments. STS reveals that for both p-type and n-type clean In(0.53)Ga(0.47)As(001)-(4×2) surfaces, the Fermi level resides near the valence band maximum (VBM); however, after In(2)O deposition and postdeposition annealings, the Fermi level position is close to the VBM for p-type samples and close to the conduction band minimum for n-type samples. This result indicates that In(2)O bonding eliminates surface states within the bandgap and forms an unpinned interface when bonding with In(0.53)Ga(0.47)As/InP(001)-(4×2). Density function theory is used to confirm the experimental finding.

The reaction of trimethyl aluminum on the group III rich reconstructions of InAs(0 0 1) and In(0.53)Ga(0.47)As(0 0 1) is observed with scanning tunneling microscopy/spectroscopy. At high coverage, a self-terminated ordered overlayer is observed that provides the monolayer nucleation density required for subnanometer thick transistor gate oxide scaling and removes the surface Fermi level pinning that is present on the clean InGaAs surface. Density functional theory simulations confirm that an adsorbate-induced reconstruction is the basis of the monolayer nucleation density and passivation.

A comparison is made between the electronic structures determined in ultrahigh vacuum of three surfaces using scanning tunneling spectroscopy (STS) and Kelvin probe force microscopy (KPFM). STS and KPFM illustrates Fermi level pinning of clean InAs(001)-(4×2) and InGaAs(001)-(4×2) surfaces and near flat band conditions for InAs(110) cleaved surfaces. However, for InAs(001)-(4×2) and InGaAs(001)-(4×2), STS and KPFM data show very different positions for the surface Fermi level on identical samples; it is hypothesized that the difference is due to the Fermi level measured by KPFM being shifted by a static charge dipole to which STS is much less sensitive.

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Copper phthalocyanine (CuPc) thin film transistors were fabricated using a tapered edge bottom contact device geometry, and mobility saturation was observed for devices with CuPc thicknesses of 12 monolayers (MLs) and greater. The mobility saturation is attributed to a significantly decreased contact resistance resulting from a bilayer resist lift-off method, as compared with a single layer resist lift-off method. Threshold voltages are also found to saturate above 12 ML CuPc thicknesses.

Hafnium oxide interfaces were studied on two related group III rich semiconductor surfaces, InAs(0 0 1)-(4x2) and In(0.53)Ga(0.47)As(0 0 1)-(4x2), via two different methods: reactive oxidation of deposited Hf metal and electron beam deposition of HfO(2). The interfaces were investigated with scanning tunneling microscopy and spectroscopy (STS). Single Hf atom chemisorption sites were identified that are resistant to oxidation by O(2), but Hf islands are reactive to O(2). After e(-) beam deposition of1 ML of HfO(2), single chemisorption sites were identified. At low coverage (1 ML), the n-type and p-type HfO(2)/InGaAs(0 0 1)-(4x2) interfaces show p-type character in STS, which is typical of clean InGaAs(0 0 1)-(4x2). After annealing below 200 degrees C, full coverage HfO(2)/InGaAs(0 0 1)-(4x2) (1-3 ML) has the surface Fermi level shifted toward the conduction band minimum for n-type InGaAs, but near the valence band maximum for p-type InGaAs. This is consistent with the HfO(2)/InGaAs(0 0 1)-(4x2) interface being at least partially unpinned, i.e., a low density of states in the band gap. The partially unpinned interface results from the modest strength of the bonding between HfO(2) and InGaAs(0 0 1)-(4x2) that prevents substrate atom disruption. The fortuitous structure of HfO(2) on InAs(0 0 1)-(4x2) and InGaAs(0 0 1)-(4x2) allows for the elimination of the partially filled dangling bonds on the surface, which are usually responsible for Fermi level pinning.

In situ x-ray photoelectron spectroscopy was performed during thermal desorption of a protective As layer and subsequent atomic layer deposition (ALD) of Al2O3 on In0.53Ga0.47As(001). H2O dosing on the As-decapped surface caused formation of As oxides and As hydroxides, which were reduced by a subsequent trimethylaluminum (TMA) pulse. However, when a TMA pulse was performed first, the In0.53Ga0.47As(001) surface did not oxidize during subsequent ALD cycles, suggesting passivation by TMA adsorption at water-reactive sites. Scanning tunneling microscopy performed on a structurally-similar InAs(001) surface after H2O dosing revealed that surface defects are created by displacement of surface As atoms during oxidation. These surface defects act as interface states, consistent with the inferior capacitance-voltage characteristics of H2O-first ALD-Al2O3 capacitors compared to TMA-first samples.

Folate conjugated poly(lactic-co-glycolic acid) (PLGA) silica nanoparticles (NP) are being synthesized as drug carriers to cancer cells. The PLGA nanoparticles are synthesized by first combining PLGA and dye in acetonitrile. This mixture is then dropped into an aqueous solution containing lecithin (a lipid) and poly(ethylene glycol) (PEG) to form an emulsion. The acetonitrile is evaporated leaving the nanoparticles in a water suspension. Silicic acid is used to coat the PLGA NP through the sol-gel process assisted by poly-L-lysine to template the growth of the silica shell. This makes a more hydrophilic and easily modified surface. 3-aminopropyltriethoxysilane is used to coat the silica surface with amine groups. Then folic acid is coupled to the amine modified silica surface. The folic acid acts as a targeting agent which recognizes folate receptors on the membrane surface of cancer cells. A fluorescent dye is loaded into the PLGA core to mimic a hydrophobic drug in these initial studies. Then the ability of PLGA silica NP with folate are allowed to undergo endocytosis into the HeLa cells, and the degree of uptake is assessed by fluorescence microscopy. The results are compared to folate PLGA NP as a control. Detailed synthesis of these silica PLGA nanoparticles, their characterization, surface functionalization, and their applications will be presented. This presentation was made possible by NIH grants:5P30CA23100; and 1U54CA132379/1U54CA132384. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2660.

Oxide monolayers and submonolayers formed by vapor deposition of In2O and SiO oxides on InAs001-4 2 were studied by scanning tunneling microscopy. At low coverage, In2O molecules bond to the edges of the rows and most likely form new In–As bonds to the surface without any disruption of the clean surface structure. Annealing the In2O/InAs001-4 2 surface to 380°C results in the formation of flat ordered monolayer rectangular islands. The annealed In2O no longer bonds with just the As atoms at the edge of row but also forms new O–In bonds in the trough. SiO chemisorption on InAs001-4 2 is completely different than In2O chemisorption. At room temperature, even at low coverage SiO adsorbates bond to themselves and form nanoclusters. For SiO/InA001-4 2 postdeposition annealing does not disperse the nanoclusters into flat islands. Both In2O and SiO depositions on the InAs001-4 2 surface do not displace surface atoms during both room temperature deposition and postdeposition annealing.

III-V semiconductor field effect transistors require an insulator/channel interface with a low density of electrically active defects and a minimal interface dipole to avoid Fermi level pinning. We demonstrate that an atomically abrupt and unpinned interface can be formed between an In0.53Ga0.47As (100) channel and an Al2O3 dielectric layer grown by atomic layer deposition (ALD) when oxidation of the substrate surface is prevented before and during oxide deposition. X-ray photoelectron spectra and electron microscopy indicate that in situ desorption of a protective As2 layer on the In0.53Ga0.47As (100)−4×2 surface followed by ALD of Al2O3 produced an atomically abrupt interface without Fermi level pinning. Temperature-dependent and frequency-dependent capacitance-voltage and conductance-voltage analysis of the resulting Pt/Al2O3/InGaAs capacitors are consistent with movement of the Fermi level through the InGaAs band gap. Moreover, the nearly ideal flat band voltages observed for gate metals of widely var...

Background: Multiple operations are a major problem for breast conservation therapy. Accurate interpretation of intra-operative tumor margins can limit multiple re-excision procedures in order to obtain negative margins while maintaining a good cosmetic result from BCT. Intra-operative touch preparations have been used in the past but can be difficult to interpret without an experienced cytopathologist.Objective: To examine the reliability of fluorescently labeled intra-operative touch preps in conjunction with automated analysis in correctly identifying cancer cells compared to final pathologic diagnosis.Methods: Touch preps were propctively performed on 38 consecutive cases of patients undergoing breast surgery. The surgical cases included 15 invasive tumors, 9 ductal carcinoma in situ, 5 prophylactic mastectomies, and 9 normal tissues from breast reduction operations. Tumors were grossly located by a surgical pathologist and a cross sectional cut was made at the suspected tumor center. Touch preps with poly-l-lysine coated slides were then taken on the tissue surfaces exposed from the cross sectional cut. Additionally, the location where the touch preps were performed was isolated in a cassette and separated for later comparison. In cases of benign disease, touch preps were performed at the center of the excised tissue. The slides were fixed in 95% ethanol and stained with a Cytokeratin, an epithelial cell marker, and Hoechst, a nuclear stain. The prepared slides were then imaged with an automated fluorescent microscope, and suspected cancer cells were detected through standard image processing and statistical techniques.Results: The overall accuracy of our automated fluorescence analysis was 95% for identifying invasive or pre-invasive cancer compared final pathologic diagnosis. The overall specificity was 100% (there were no false positives). The sensitivity for ductal carcinoma in situ was 75% and invasive cancer was 90%. Overall sensitivity was 87% which is comparable to the best reported results from manual examination of touch preparations.Conclusion: Automated analysis of fluorescently stained touch prep slides is highly accurate in identifying cancer with no false positives. The immunofluorescence stains and automated microscopy may help the pathologist to quickly identify cancer cells in fresh breast tissue during BCT operations, and, thus, limit breast re-excisions in the future. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6016.

The electrical degradation (aging) of copper phthalocyanine (CuPc) organic thin film transistors (OTFTs) was investigated. Thick (1000 ML) and ultrathin (4 ML) channel thicknesses were used in bottom contact OTFTs to correlate the electrical effects of aging with film microstructure. Proper TFT saturation behavior was unattainable in thick devices subject to ambient aging; however ultrathin devices were significantly less susceptible and maintained good saturation and subthreshold behavior. Therefore 1000 monolayer (ML) CuPc OTFTs were characterized in ambient air, clean dry air, clean humidified air, and NOx environments to isolate the ambient components that induce aging. Thick channel devices which had been aged in ambient air to the point of losing all saturation behavior could be restored to proper saturation behavior by exposure to clean humidified air. The data are consistent with aging resulting primarily from adsorption of strong oxidants from ambient air within the grain boundaries of the CuPc f...

The NO chemisorption dynamics on ordered multilayer iron phthalocyanine (FePc) and quasiamorphous multilayer tetra-t-butyl FePc (ttbu-FePc) films on a Au(111) substrate was investigated using the King and Wells reflection technique. The NO zero coverage or initial sticking probabilities (S(0)) were measured as a function of sample temperature (T(s)) and beam energy (E(i)). The experimental results for both films show a monotonic decrease in S(0) with increasing T(s) and E(i) consistent with NO adsorption occurring via a multiple pathway precursor-mediated mechanism in which the adsorbate initially physisorbs to the FePc organics, diffuses, and chemisorbs to the Fe metal center. The saturation coverage is 3% for the multilayer FePc surface and only 2% for the multilayer ttbu-FePc surface consistent with NO chemisorption occurring only on the Fe metal, where NO chemisorbs to 100% of the surface Fe metal centers. The reduced saturation coverage in the ttbu-FePc film is attributed to fewer Fe metal centers in the less dense ttbu-FePc films. A comparison of NO sticking on a multilayer FePc/Au(111) film with NO sticking on a monolayer FePc/Au(111) film shows that S(0) is greater on the multilayer FePc film for all T(s) and E(i), consistent with an increase in collision inelasticity for NO/multilayer FePc/Au(111).

Chemical sensing properties of phthalocyanine thin-film transistors have been investigated using nearly identical n- and p-channel devices. P-type copper phthalocyanine (CuPc) has been modified with fluorine groups to convert the charge carriers from holes to electrons. The sensor responses to the tight binding analyte dimethyl methylphosphonate (DMMP) and weak binding analyte methanol (MeOH) were compared in air and N(2). The results suggest that the sensor response involves counterdoping of pre-adsorbed oxygen (O(2)). A linear dependence of chemical response to DMMP concentration was observed in both n- and p- type devices. For DMMP, there is a factor of 2.5 difference in the chemical sensitivity between n- and p-channel CuPc thin-film transistors, even though it has similar binding strength to n- and p-type CuPc molecules as indicated by the desorption times. The effect is attributed to the difference in the analyte perturbation of electron and hole trap energies in n- and p-type materials.

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A bilayer lift-off process has been employed to fabricate optimal electrode contact geometry for statistical characterization of ultrathin organic thin-film transistors (OTFTs). For over 100 p-channel ultrathin (12 ML) copper phthalocyanine (CuPc) OTFTs, the bilayer photoresist lift-off process increased the field effect mobility by two orders of magnitude, decreased the contact resistance by three orders of magnitude, increased the on/off ratio by one order of magnitude, and the threshold voltage was decreased by a factor of three compared to conventionally processed devices. The generality of the method was validated by fabricating OTFTs in four different phthalocynaines and CuPc OTFTs with eight different channel thicknesses.

To develop an atomistic understanding of the binding of NO with iron phthalocyanine (FePc), the interaction between NO (an electron withdrawing gas) and NH3 (an electron donating gas) with an isolated FePc molecule (monomer) was compared with density functional theory. The simulations show that NO strongly chemisorbs to the Fe metal and physisorbs to all the nonmetal sites. Additionally, when NO physisorbs to the inner ring nitrogens, NO subsequently undergoes a barrierless migration to the deep chemisorption well on the Fe metal. Conversely, NH3 only weakly chemisorbs to the Fe metal and does not bind to any other sites. Projected density of states simulations and analysis of the atomic charges show that the binding of NO to the FePc metal results in a charge transfer from the Fe metal to the NO chemisorbate; the opposite effect is observed for the binding of NH3 to the Fe metal. Simulations of NO binding to the Fe metal of a monolayer FePc film and FePc trimer were also performed to show that intermolecular FePc-FePc interactions have a negligible effect on the FePc electronic structure and NO binding.

The gas-surface reaction dynamics of NO impinging on an iron(II) phthalocyanine (FePc) monolayer were investigated using King and Wells sticking measurements. The initial sticking probability was measured as a function of both incident molecular beam energy (0.09–0.4eV) and surface temperature (100–300K). NO adsorption onto FePc saturates at 3% of a monolayer for all incident beam energies and surface temperatures, suggesting that the final chemisorption site is confined to the Fe metal centers. At low surface temperature and low incident beam energy, the initial sticking probability is 40% and decreases linearly with increasing beam energy and surface temperature. The results are consistent with the NO molecule sticking onto the FePc molecules via physisorption to the aromatics followed by diffusion to the Fe metal center, or precursor-mediated chemisorption. The adsorption mechanism of NO onto FePc was confirmed by control studies of NO sticking onto metal-free H2Pc, inert Au(111), and reactive Al(111).

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A pulsed gating method has been developed to enhance the baseline stability of organic thin-film transistor (OTFT) chemical sensors. Trap states in the organic films are the major source of the OTFTs baseline drift under static gate bias, which is identified as the bias stress effect (BSE). BSE typically reduces the baseline current by 60% over 20h in phthalocyanine based OTFT sensors. The baseline drift has been reduced below 1% over 20h in the absence of the analyte using the pulsed gating method. With pulsed gating, the baseline drift on exposure to 15 methanol pulses is less than 0.09%∕h, and the response to this analyte is fully recoverable. Similar ultralow drift results were obtained for methanol sensing on three different phthalocyanine OTFTs. Combining the pulsed gating with low duty cycle analyte pulses, this method is also applicable to obtain ultralow drift (0.04%∕h) even for low vapor pressure analytes such as organophosphonate nerve agent simulants.

Ultrathin cobalt phthalocyanine transistors of 4 ML have been fabricated for chemical sensing. Compared to 50 ML devices, the ultrathin transistors show faster response times, higher base line stabilities, and sensitivity enhancements of 1.5–20 for the five analytes tested. The enhanced response for the ultrathin transistors provides insight into the device physics. The absorption of analytes changes the surface doping level and trap energies. The changes in surface trap energies perturb the charge transport properties of the ultrathin devices, thereby, making these devices more sensitive.

Impedance spectroscopy has been used to identify analytes in semiconducting metallophthalocyanine thin films. Above a critical concentration, the magnitudes of the high frequency conductivity changes are invariant with concentration but distinct for different analytes and can be used for analyte identification. The analyte-induced ac conductivity changes above 5kHz have been converted to frequency shifts in a circuit resonance and used to differentiate methanol, ethanol, and isopropanol vapors in a nitrogen carrier gas. The analyte-induced changes in the conductivity are consistent with analyte-induced changes in the charge relaxation times.

The comparison of density functional theory cluster and slab approaches is presented for modeling the formation of electrically pinned and unpinned metal oxide-III/V semiconductor interfaces. Thermodynamic stability, interfacial electrical properties, interfacial charge trap formation and bonding structures are examined critically in the case of gallium oxide formation on the GaAs(001)-β2(2×4) surface via direct oxidation of the surface with thermal O2(g) and by vapor deposition of Ga2O(g). It is seen in both cluster and slab models that the direct oxidation with thermal O2 will lead to an electrically pinned surface, while vapor deposition of Ga2O will electrically passivate the surface, effectively unpinning the interface. Fermi-level pinning and unpinning is observed in the local density of states (DOS) in the band-gap region, in the charge distribution per surface atom, and in the geometric structures. It is seen that the DOS can be accurately predicted using either cluster or slab DOS. When cluster D...

We have measured the rotational state distribution and the angular momentum alignment and orientation of N2 scattered from Ag(111) at 540 K. Using resonance enhanced multiphoton ionization (REMPI), we are able to probe the scattered flux as a function of the exit angle θexit. For a modestly glancing incident beam (θi =30°) and incident translational energy, Ei =0.3 eV, the angular momentum alignment (tumbling vs helicoptering) at both quasispecular detection (θexit=35°) and superspecular detection (θexit=50°) is only weakly dependent upon the surface temperature. However, the angular momentum orientation (clockwise vs counterclockwise rotation) is strongly affected by the surface temperature. Raising the surface temperature from Ts =90 K to Ts =540 K causes the orientation to decrease substantially. Stochastic trajectory calculations were carried out in conjunction with the experiments. They reveal that at low temperature there is an averaging over two important initial conditions: the two‐dimensional imp...

The rotational state populations and the quadrupole and hexadecapole alignment moments of N2 scattered off clean Ag(111) are determined by resonance enhanced multiphoton ionization (REMPI). The scattered N2 is found to be highly aligned with its rotational angular momentum vector J parallel to the surface. The degree of alignment is found to increase with increasing rotational excitation. We see less than perfect alignment at intermediate J values indicating that the surface is not completely flat. The alignment is relatively insensitive to incident energy, incident angle, or surface temperature Ts. However, the rotational state population distributions show pronounced rainbows for higher incident energy and/or more grazing exit angle. The rotational state distributions are found to depend strongly on the final scattering angle at low Ts; this effect is markedly reduced at higher Ts. Time‐of‐flight measurements are used to determine the average velocity of the scattered N2 as a function of rotational leve...

A well‐characterized Ag(111) surface in an ultrahigh vacuum system is bombarded with supersonically cooled N2 and the scattered molecules are detected near the specular angle using 2+2 resonance enhanced multiphoton ionization. The first three even spatial moments of the angular momentum distribution have been measured. The zeroth moment is the population of a given rotational level, while the second and fourth moments describe the quadrupole and hexadecapole alignment of the J vector with respect to the surface normal. The relative population distribution shows an excess at high J characteristic of rotational rainbow scattering. For J>7, the second and fourth moments closely approach their limiting values expected when the J vector lies in the plane of the surface. It is concluded that the N2/Ag(111) system closely approaches the ideal of a rigid rotor colliding with a flat surface.

A method is presented for determining the population A(0)0, the quadrupole alignment factors A(2)0, A(2)1, A(2)2, and the hexadecapole alignment factors A(4)0, A(4)1, A(4)2, A(4)3, A(4)4 for a (v,J) ground state distribution of a diatomic molecule probed by linearly polarized two‐photon nonresonant excitation. General expressions are developed for the O, P, Q, R, and S branch transitions as a function of the rotational quantum number J. This treatment assumes that the resonant state reached by the two‐photon transition is subsequently detected independent of its alignment. This can be achieved by 2+n multiphoton ionization in which the ionization steps are saturated, or by 2+1 laser induced fluorescence in which the fluorescence is collected independent of its polarization and spatial anisotropy. To extract the population and the eight alignment parameters the line intensities must be measured for several polarization settings of the laser beam. However, when the ground state distribution has cylindrical ...

We have probed the angular momentum orientation of N2 scattered from cold Ag(111) when the N2 approaches the surface along the surface normal. Using resonance enhanced multiphoton ionization (REMPI) and pulsed molecular beam techniques, we are able to probe the flux backscattered along the surface normal. In accordance with the restrictions on cylindrically symmetric systems, the molecules backscattered along the surface normal have no angular momentum orientation nor does the entire scattered flux integrated over all exit angles. However, for detection away from the surface normal, we observe substantial angular momentum orientation; the degree and direction of orientation depends upon the rotational state being probed. Molecular dynamics calculations reproduce the experimental results semiquantitatively. The calculations show that for N2 incident along the surface normal, the exit angle is largely determined by the two‐dimensional impact parameter of the molecule within the crystal unit mesh. However, t...

The orientation of the angular momentum of N2 scattered from clean Ag(111) is determined by resonance‐enhanced multiphoton ionization. The orientation is the net helicity or handedness of the sense of rotation, i.e., clockwise vs counterclockwise. The orientation of the scattered N2 is measured along a direction perpendicular to the scattering plane. The degree and sign of the orientation is found to depend strongly on the final rotational quantum number J and on the final scattering angle. The results require that there are forces acting in the plane of the surface during the scattering. The observed behavior can be reproduced qualitatively by a conventional hard‐cube, hard‐ellipsoid model to which a tangential friction has been introduced to account for the in‐plane forces. This produces a splitting of the rotational rainbow peak which leads to changes of sign of the orientation as a function of rotational quantum number. Thus, orientation measurements provide a unique probe of in‐plane gas–surface forces.

Purpose Monoclonal antibodies (mAb) are an important and growing class of cancer therapeutics, but pharmacokinetic analyses have in many cases been constrained by the lack of standard and robust pharmacologic assays. The goal of this project was to develop a general method for the production of immunoassays that can measure the levels of therapeutic monoclonal antibodies in biologic samples at relevant concentrations. Methods Alemtuzumab and rituximab are monoclonal approved for the treatment of B-cell malignancies and were used as a model system. Phage-displayed peptide libraries were screened for peptide sequences recognized by alemtuzumab (anti-CD52) or rituximab (anti-CD20). Synthetic biotinylated peptides were used in enzyme-linked immunosorbent assays (ELISA). Peptides directly synthesized on polymer resin beads were used in an immunofluorescent-based assay. Results Peptide mimetope sequences were recovered for both mAb and confirmed by competitive staining and kinetic measurements. A peptide-based ELISA method was developed for each. The assay for rituximab had a limit of detection of 4 μg/ml, and the assay for alemtuzumab had a limit of detection of 1 μg/ml. Antibody-specific staining of peptide conjugated beads could be seen in a dose-dependent manner. Conclusion Phage-displayed peptide libraries can be a source of highly specific mimetopes for therapeutic mAb. The biotinylated forms of those peptides are compatible with conventional ELISA methods with sensitivities comparable to other assay methods and sufficient for pharmacological studies of those mAb given at high dose. The process outlined here can be applied to any mAb to enable improved pharmacokinetic analysis during the development and clinical use of this class of therapies. Electronic supplementary material The online version of this article (doi:10.1007/s00280-009-1240-1) contains supplementary material, which is available to authorized users.

When an anisotropic ensemble of isolated atoms or molecules absorbs radiation from a polarized laser beam and the resulting fluorescence is collected independent of wavelength (1+1 unresolved LIF) with optional polarization analysis, the moments of the spatial distribution of the angular momentum J of the initial state in the ensemble may be determined. Previously, work by A. C. Kummel, G. O. Sitz, and R. N. Zare [J. Chem. Phys. 88, 7357 (1988)] correctly derived what possible moments can be found when cylindrical symmetry is present. This work shows that several additional alignment moments, not mentioned in KSZ, can be found in ensembles having noncylindrical symmetry.

The measurement of the alignment and orientation of nitrogen scattered from Ag(111) is reported. Pulsed supersonic beam of nitrogen is scattered off a clean Ag(111) crystal and the scattered nitrogen is detected by two−photon resonant four−photon ionization.(AIP)

Positive margins and the resulting multiple operations are a major problem for breast conservation therapy. Accurate assessment of intraoperative tumor margins can limit multiple re-excision procedures. Intraoperative touch preparations have been used in the past but can be difficult to interpret without an experienced cytopathologist. The objective of this study is to examine the reliability of enhanced intraoperative touch preps (EIOTP) compared with final pathologic margins. We prospectively performed EIOTP on 20 tumors in women undergoing breast conservation therapy. Six margins and the main tumor were touched onto poly-L-lysine coated slides. The slides were stained with anti MUC1 and anti-E-cadherin antibodies, and Hoechst nuclear stain. A parallel set of slides were stained with hematoxylin and eosin for comparison. The EIOTP results were compared with pathologic interpretation of paraffin embedded permanent sections. A total of 120 margins underwent EIOTP in 20 patients. We found a sensitivity equal to 80 per cent, specificity 100 per cent, positive predictive value 100 per cent, and negative predictive value 99 per cent. EIOTP in conjunction with MUC-1 and E-cadherin by immunofluorescence is a sensitive and highly specific mechanism to identify cancer cells at breast tissue margins. The immunofluorescence stains may help the pathologist to identify cancer cells in fresh breast tissue and limit breast re-excisions in the future.