Top PDF Self-Assembled Monolayers for Phosphorus Doping of Silicon for Field Effect Devices

Self-Assembled Monolayers for Phosphorus Doping of Silicon for Field Effect Devices

Self-Assembled Monolayers for Phosphorus Doping of Silicon for Field Effect Devices

Moore’s law continues to drive the semiconductor industry to create smaller transistors and improve device performance. Smaller transistors require shallower junctions, especially for the non-planar geometries such as FinFETs and nanowires which are becoming more common. Conventional doping techniques such as ion implantation and spin-on diffusants have difficulty producing shallow junctions, especially for conformal doping of non-planar structures. Molecular monolayer doping (MLD) is presented as an alternative doping method with the capability to produce ultra-shallow junctions with low sheet resistances for planar and non-planar structures. MLD relies on the formation of a self-assembled monolayer of a dopant-containing compound which is annealed to diffuse dopants into the substrate, forming an ultra-shallow junction with a high surface concentration. This work fabricates and characterizes field effect devices using MLD to dope the source and drain regions.
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Hybrid dielectrics composed of Al2O3 and phosphonic acid self-assembled monolayers for performance improvement in low voltage organic field effect transistors

Hybrid dielectrics composed of Al2O3 and phosphonic acid self-assembled monolayers for performance improvement in low voltage organic field effect transistors

is limited by the thermally activated hopping process between the molecules in the disordered regions [11, 12]. To improve the device performance, the disordered region of the semiconductor should be suppressed, and additional interface treatments are required for optimal charge transport. For example, the molecular parameters of organic semiconductors were modified by controlling their regioregularity, molecular weight, side chain length, doping level and end-group. Inter- face engineering has been introduced to improve the molecular ordering, orientation, assembly, packing and film morphology of organic semiconductors [13]. Self- assembled monolayers (SAMs) are good candidates for effective surface treatment due to their high-packing density, being only a few nm thick and allowing inter- face control with end-functional groups [14]. Among various SAMs with different binding groups, such as carboxyl groups, thiols and silanes, phosphonic acid self-assembled monolayers (PA-SAMs) have attracted attention due to readily assembling on activated metal oxides because their reaction is not limited by the con- tents of surface hydroxyl groups and supplies their own hydroxyl moieties [15]. They also have the advan- tages of stability and prevention of homocondensation between phosphonic acid molecules compared with other binding groups, resulting in the highly ordered, dense and robust monolayers of phosphonic acid mol- ecules on metal oxide surfaces.
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Investigating self assembled monolayers and understanding small molecule/polymer blend thin films in organic field effect transistors

Investigating self assembled monolayers and understanding small molecule/polymer blend thin films in organic field effect transistors

whereas 4-FTP annealed devices, shown in Fig.4.11(d), appears more disordered with an increase in R.M.S roughness to 8.4 nm. The formation of needle–like topography of TIPS-pentacene thin-films have been identified as main cause of hampered charge-transport across the channel region. [20,21] This would be expected of such small grains to severely limit the device performance due to the irregular nucleation of the OSC layer. With this considered, we see excellent subthreshold swing with increased mobility after annealing of the 4-FTP electrode, as well as very low threshold voltage, which indicates a reduced influence from trap-sites at grain boundaries. The shape of the mobility curve for 4-FTP annealed devices may be explained by morphological effects. A rougher semiconductor surface close to the conducting channel can lead to increased gate voltage dependence with charge- carrier mobility. [22] Additionally, smaller grains forming closer to the electrode edge may help to increase uniformity and packing at this interface leading to better charge-injection and extraction from the edges of the contacts. Heightened surface roughness of the underlying substrate, particularly the electrode surface, can cause hindrance of charge-injection/extraction, as the occurrence of voids or non- uniformity in the subsequently deposited organic semiconductor can lead to surface scattering at the dielectric/semiconductor interface. The charge transport within the channel region of the device typically occurs in the first few monolayers of the semiconductor, closest to the dielectric/semiconductor interface, therefore the surface state of the underlying layer prior to completion of this interface has a large impact on charge-carrier mobility. [23,24]
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Inhibition Effect of 3D Nanostructures on the Corrosion Resistance of 1-Dodecanethiol Self-Assembled Monolayers on Copper in Nacl Solution

Inhibition Effect of 3D Nanostructures on the Corrosion Resistance of 1-Dodecanethiol Self-Assembled Monolayers on Copper in Nacl Solution

Reportedly, the protective properties of SAMs are closely related to thickness and chain length. Laibinis et al. [8] firstly reported that thicker SAMs retarded the oxidation of copper more obviously than thinner SAMs, and an increase in SAM thickness by about 6 Å led to a corresponding decrease in the rate of oxidation by around 60%. Furthermore, Itoh et al. [14] demonstrated that further chemical modification of an 11-mercapto-1-undecanol SAMs with alkyltrichlorosilanes improved the protective capability of monolayers against corrosion in aqueous and atmospheric environments. The anodic process of corrosion was inhibited by network structures owing to two-dimensional polymerization with lateral siloxane linkage between molecules absorbed on copper.
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Use of Self-Assembled Monolayers and Light to Tailor Adhesion on Surfaces for Nanomanufacturing Applications

Use of Self-Assembled Monolayers and Light to Tailor Adhesion on Surfaces for Nanomanufacturing Applications

• Using thiol SAMs to pattern polymers, biomaterials, and conjugated oligomersA. • Comparison of thermal stability of thiol and silane monolayers.[r]

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Self assembled monolayers of oligophenylenecarboxylic acids on silver formed at the liquid solid interface

Self-assembled monolayers of oligophenylenecarboxylic acids on silver formed at the liquid-solid interface

For the monocarboxylic acid species, C 1s signals are present corresponding to the aromatic carbons and the carboxylate moiety. No signal is detected in the range of the free carboxylic acid, thus, contrasting the dicarboxylic acids which show peaks of both the carboxylate and free carboxylic acid moieties. In accordance with the dense packing seen in the STM images, we conclude that the molecules in all monolayers are bound to the silver through a carboxylate-metal bond and adopt an upright geometry. Hence, in the case of the monocarboxylic acids, the outer surface of the SAM is formed by an aromatic ring and whereas in the case of the dicarboxylic acids it is COOH.
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X-ray Photoelectron Spectroscopy for Determining Interface Dipoles of Self-Assembled Monolayers

X-ray Photoelectron Spectroscopy for Determining Interface Dipoles of Self-Assembled Monolayers

In the present contribution it is shown that X-ray photoelectron spectroscopy is a suitable tool for determining interface dipoles in densely-packed self-assembled monolayers. This is shown via simulations on a number of biphenyl-based monolayers bonded to a Au(111)-substrate by a broad range of different docking groups. The varying interface dipoles in these systems result in shifts of the core-level binding energies by more than one eV, concomitantly shifting also the associated XP spectra. For SAMs not bearing polar tail groups the electrostatically triggered core-level shifts directly correlate with SAM-induced work-function changes. This correlation is broken, when work functions are further modified by polar tail-group substituents. Nevertheless, even in these cases the XP spectra are a direct measure for the interface dipoles. The situation changes, when the dipole density at the interface is reduced. Then core-level binding energies are still determined by the local electrostatic
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Self Assembled Monolayers on Pd Substrates and Kubas based hydrogen storage materials

Self Assembled Monolayers on Pd Substrates and Kubas based hydrogen storage materials

Besides the exploitation of adsorbates conformations to generate controlled interfacial properties of SAMs, the morphology of substrates on which a SAM forms also contributes to manipulate the interfacial/surface properties of these materials [1] - [4]. By changing the experimental methods, compositions and conditions to form metal thin films, various types of substrate’s surface can be composed with different roughness, grain sizes and defects [5] - [6]. For exam- ple, as deposited (As-dep) normally by e-beam deposition, the grains size of thin palladium films formed on silicon wafer are 15-30 nm in diameter; while employing ”template stripping (TS) methods [7] (Figure 2.1)” after e-beam deposition can create much smaller grains size <1 nm on palladium surface. The smaller grains size of metal thin film is, the more suitable it is to use as substrate for microcontact printing and etching [8] - [9].
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Atomic Structure Optical Properties and Electron Transport in Self-assembled Monolayers on Surfaces

Atomic Structure Optical Properties and Electron Transport in Self-assembled Monolayers on Surfaces

Self-assembled molecular systems with NDR are promising molecular devices due to their utility in fast switching logic and simplicity in integration. Therefore, theoret- ical understanding of their electron transport properties and of the underlying NDR mechanisms is critical for the design of molecular devices. However, in many cases the NDR mechanisms have not been unraveled either from experiments or from theory. The redox effect, i.e., a change of the charge state with bias, has been suggested to explain the NDR for ferrocenyl-alkanethiolate SAM on Au(111) surface [135]. How- ever, resonant tunneling may also play an important role in NDR. Another possibility is some level of bond breaking under current[137], i.e., the structure of the molecule itself or of the molecule-substrate interface changes dramatically when a large bias is applied to the system.
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Functionalized self assembled monolayers on mesoporous silica nanoparticles with high surface coverage

Functionalized self assembled monolayers on mesoporous silica nanoparticles with high surface coverage

nanomaterilas and their use for in sensors and energy storage. DWS received her B.Sc. degree in the School of Materials Science and Engineering from Shanghai Jiao Tong University (China) and is currently doing her Graduate thesis in Prof Zhang's group in Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University. Her research focus includes carbon nanomaterials for application in sensors and energy storage. ZHZ received his PhD degree in the Shanghai Jiao Tong University. He is now an assistant professor at the University of Electronic Science and Technology of China. His research focus includes nanomaterials for application in solar cells and energy storage. We are grateful for the financial support from the National Natural Science Foundation of China (No. 51272155), National High- Tech R & D Program of China (863, No. 2011AA050504), and the Analytical and Testing Center of SJTU. His research focus now includes the preparation of CNT and CNT field emission display. LYL is an assistant professor at Shanghai Jiao Tong University. Her research focus is characterization of nanomaterials. CXC is currently an associated professor at Shanghai Jiaotong University, China. His research interests include preparation of carbon-based nanomaterilas and their use for in sensors and energy storage. YFZ is currently a professor at Shanghai Jiaotong University, China. His research interests include synthesis of gas-sensing nanomaterials and their applications in nanodevice.
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Studies of the self-assembled growth mechanism on nanocrystalline silicon nanodots

Studies of the self-assembled growth mechanism on nanocrystalline silicon nanodots

creased absorption in the red and infrared wavelengths, which make it an important material for use in a-Si solar cells [3]. One of the most important advantages of nanocrystalline silicon, however, is that it has increased stability over a-Si, one of the reasons being because of its lower hydrogen concentration. Although it currently cannot attain the mobility that poly-Si can, it has the advantage over poly-Si that it is easier to fabricate, as it can be deposited using conventional low temperature a-Si deposition techniques, such as PECVD, as opposed to laser annealing or high temperature CVD processes, in the case of poly-Si.
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Self-Assembled Monolayers of Alkanethiol as Inhibitors against Copper Corrosion in Synthetic Acid Rain

Self-Assembled Monolayers of Alkanethiol as Inhibitors against Copper Corrosion in Synthetic Acid Rain

Self-assembled monolayers of 1-octanethiol (OT), 1-dodecanethiol (DT) and 1-octadecanethiol (ODT) on the copper surface show very good corrosion inhibition in simulated acid rain. The adsorption kinetics of selected alkanethiols on copper surface were studied by polarization measurements in consideration of different concentrations (0.01, 0.10 and 0.5 mmol L –1 ) and different alkyl chain length (n = 8, 12 and 18). It was found that the adsorption process follows Langmuir adsorption model, independent of chain length of thiols. Calculated values of Gibbs energy indicated that the adsorption mechanism of OT, DT and ODT on copper is the hybrid type of physical and chemical adsorption. Increasing value of Gibbs energy from ─24 kJ mol ─1 for OT to ─32 kJ mol ─1 for ODT indicate that the chemisorption part in the adsorption mechanism prevails with the increase in chain length of alkanethiols.
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Fabrication of molecular nanopatterns at aluminium oxide surfaces by nanoshaving of self-assembled monolayers of alkylphosphonates

Fabrication of molecular nanopatterns at aluminium oxide surfaces by nanoshaving of self-assembled monolayers of alkylphosphonates

Scanning probe microscopy (SPM) techniques have been widely employed to fabricate nanostructures at metal and semi- conductor surfaces. Not only do local probe techniques offer very high resolution, but they are compatible with a wide range of environments. 1,2 Self-assembled monolayers (SAMs) 3–7 have proved to be ideal resist materials for such fabrication methods, and a combination of SAMs and scanning probe lithography has proved to be a very fruitful means to fabricate molecular nanostructures. A wide variety of methods has been developed that can be grouped loosely into two categories. First, localised chemical modication can be achieved by constructive nano- lithography and near-eld optical methods. In constructive nanolithography, 8,9 an atomic force microscope (AFM) probe at a potential difference relative to the sample is used to initiate localized oxidation, facilitating subsequent functionalisation in a wide variety of ways to yield surface chemical patterns and metal nanostructures. 9–11 In scanning near-eld photolithog- raphy (SNP), 12,13 a near-eld optical probe is used to cause a localized photochemical modication, 12 the initiation of a
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Application of 1 octadecanethiol self assembled monolayers for corrosion protection of leaded brass surface

Application of 1 octadecanethiol self assembled monolayers for corrosion protection of leaded brass surface

To mitigate problems with leaded brass corrosion, great efforts have been put into the investigation and lots of technologies have been used [5-7]. Self-Assembled Monolayers (SAMs) on solid surfaces are nowadays very popular because of the versatile functions they can implement, together with their easy preparation, the stability and reproducibility of the obtained systems. It has been showed that the protective properties of the monolayers are closely related to their thickness [8,9]. Since SAMs of n-alkanethiols were shown to be effective in protecting copper surface from air oxidation [10], they became one of the most investigated corrosion inhibitors for this metal [11-14]. More recently, the ability of alkanethiols SAMs to protect Cu–Zn alloys in accelerated indoor atmospheric corrosion condition has been examined [15,16]. To the best of our knowledge, no report has been published on the protection of leaded brass by alkanethiols SAMs. Hence, this study is a first effort to explore the application of 1- octadecanethiol (ODT) monolayers as corrosion inhibitor of leaded brass substrate in non complexing perchloric acid solution. This precludes the formation of oxide or hydroxide films on the alloy surface and the formation of zinc or copper complexes. Open circuit potentials (E OCP ), Tafel polarization curves and electrochemical impedance
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Permeability of Alkanethiols Self-Assembled Monolayers on Gold Prepared by Neat Thiols and Ethanolic Thiols

Permeability of Alkanethiols Self-Assembled Monolayers on Gold Prepared by Neat Thiols and Ethanolic Thiols

Self-assembled monolayers (SAMs) adsorbed on solid substrate are being intensively studied for their wide application in some research fields, such as wetting, biosensing, adhesion, and corrosion[1,2]. Alkanethiols SAMs adsorbed on gold substrate are usually applied due to the strong covalent interaction between thiols and gold [3,4]. The ions permeability and electron transfer performance through thiols SAMs are concerned by researchers. Defects or collapsed sites possibly exist in thiols SAMs on gold, which might influence the ions permeability and electron transfer performance in SAMs. How to prepare compacted, defect-free, and collapsed site-free thiols SAMs on gold is the key problem.
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Applications of isothioureas in surface chemistry : modification of self assembled monolayers and immobilisation on polymer supports

Applications of isothioureas in surface chemistry : modification of self assembled monolayers and immobilisation on polymer supports

gave a low (entries 1,2 and 4) or unreliable value (entries 6 and 7). When using bicyclohexyl or hexadecane as the deposition solvent (Entries 3 and 5) the ellipsometry value was close to the optimum reported in the literature (ca.1.9 nm) but unfortunately these were isolated results and disappointingly could not be reproduced. As toluene gave the most consistent results, with respect to ellipsometry and contact angle, over the largest sample range (Entry 1), this was taken forward as the optimum conditions for deposition for all of the samples discussed in the following sections. A potential reason for the low thickness value could be due to the lack of complete monolayer formation in the self-assembly process. Alkoxysilanes are not as reactive as the corresponding chlorosilanes and as such may not allow for the complete hydrolysis of the Si-OMe groups. [207- 208]
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Electron beam patterned self assembled monolayers as templates for Cu electrodeposition and lift off

Electron beam patterned self assembled monolayers as templates for Cu electrodeposition and lift off

Self-assembled monolayers (SAMs) of 4'-methylbiphenyl-4-thiol (MBP0) adsorbed on polycrystalline gold substrates served as templates to control electrochemical deposition of Cu structures from acidic solution, and enabled the subsequent lift-off of the metal structures by attachment to epoxy glue. By exploiting the negative-resist behaviour of MBP0, the SAM was patterned by means of electron-beam lithography. For high deposition contrast a two-step procedure was employed involving a nucleation phase around −0.7 V versus Cu 2+ /Cu and a growth phase at around −0.35 V versus Cu 2+ /Cu. Structures with features down to 100 nm were deposited and transferred with high fidelity. By using substrates with different surface morphologies, AFM measurements revealed that the roughness of the substrate is a crucial factor but not the only one determining the roughness of the copper surface that is exposed after lift-off.
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Effect of Surface Pretreatment on Electron Transfer of Methylene Blue Covalently Labeled Double-Stranded DNA Self- Assembled Monolayers on Gold

Effect of Surface Pretreatment on Electron Transfer of Methylene Blue Covalently Labeled Double-Stranded DNA Self- Assembled Monolayers on Gold

Exploration of electron transfer mechanism through double stranded DNA(ds-DNA) is especially significant not only in understanding DNA damage, repair and the origin of cancer but also in designing DNA sensor with perfect performance [1,2]. Electron transfer studies through ds-DNA usually includes two systems: homogeneous system (photosensitiser labeled ds-DNA molecules were dispersed in solution and DNA charge transfer rate was detected mainly by fluorescence methods) and heterogeneous system (redox probes labeled ds-DNA molecules were immobilized on a solid surface and DNA electron transfer rate was detected by electrochemical methods such as cyclic voltammetry and electrochemical impedance spectroscopy) [3]. The heterogeneous system based on thiol and redox probes labeled ds-DNA self-assembled monolayers (SAMs) on gold is widely applied due to its simplicity and conveniency. Two main paths are proposed to transfer electrons: 1) electrons are transferred through the interior of DNA duplex and electron transfer reaction is an adsorption controlled process; 2) electrons are transferred by redox probes diffusing to electrode surface and electron transfer reaction is a diffusion controlled process [3−7]. However, the reports from literatures about DNA electron transfer mechanism are not consistent and even controversial. For example, both diffusion and adsorption controlled reaction processes are reported for electron transfer through ds- DNA SAMs on gold [4−7].
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Effect of bis-(3-triethoxysilylpropyl)-tetrasulfide on Super- Hydrophobicity and Corrosion Resistance of Self-Assembled Monolayers on 6061 Aluminum Alloys

Effect of bis-(3-triethoxysilylpropyl)-tetrasulfide on Super- Hydrophobicity and Corrosion Resistance of Self-Assembled Monolayers on 6061 Aluminum Alloys

concentrations of BTESPT 0.06 mol/L, 0.10 mol/L, 0.14 mol/L and 0.18 mol/L in figure 2. It can be seen the surface had different roughness of concave convex structure. Compared with Figure 2b, the surface roughness of the other three concentrations of SAMs were more inhomogeneous. Form the figure 3, With the increase of self-assembly molecular concentrations, the contact angle of water droplets on the surface of SAMs firstly increases and then decreases. When the concentration was 0.10 mol/L, the contact angle reaches 158±2°, which had super-hydrophobic properties. It was found that the solution of 0.10 mol/L of BTESTP was the most advantageous to form superhydrophobic interface structure. It can be inferred that the formation of a uniform roughness film on the surface was more conducive to the formation of superhydrophobic properties. This may be due to the fact that the uniform and rough surface structure is conducive to the sealing of air droplets into discontinuous cavities and the formation of superhydrophobic effect.
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The interface structure of n alkylthiolate self assembled monolayers on coinage metal surfaces

The interface structure of n alkylthiolate self assembled monolayers on coinage metal surfaces

study of decanethiolate (n=10) on Ag(111) [37] came to a similar conclusion, while most recently our own STM and LEED measurements on the pentylthiolate (n=5) layer also indicated an enlarged, incommensurate, surface unit mesh [38]. As a general rule, establishing whether the overlayer is commensurate or incommensurate by measuring nearest-neighbour interatomic distances in STM, or measuring the exact location of diffracted beams corresponding to the surface layer sub-mesh in a conventional diffraction technique (particularly using a standard LEED optics), can place significant demands on the precision of the measurement. However, the presence or absence of the real-space or reciprocal-space features associated with the larger (77)commensurate ‘super-mesh’ of the substrate and overlayer is a more qualitative characteristic of the commensurate and incommensurate phases, and in the case of the pentylthiolate system, at least, the data show the clear signature in both LEED and STM of incommensuration. An incommensurate ordered structure with a larger lateral periodicity than that of the related commensurate mesh, of course, is a clear indicator of a dominant role of intermolecular interactions, and could be taken to indicate true ‘self-assembly’, although in this case it seems that these intermolecular forces are repulsive. In this context, though, it is interesting to note that NIXSW measurements of overlayers of both octylthiolate [39] and pentylthiolate [38] indicate the small S/Ag interlayer spacings found for methylthiolate, indicating that these phases must involve a similar reconstruction of the outermost Ag layer to that seem for the commensurate methylthiolate phase. In some ways this situation is similar to that of the pseudo-(100) reconstruction of Cu(111) by methylthiolate and octylthiolate; in both cases it seems that the lateral periodicity of the reconstructed layer is influenced by intermolecular repulsion. However, on Ag(111) there is clear evidence that there is some dependence of this spacing on the alkyl chain length, whereas on Cu(111), no such evidence has been reported, although no precise comparison of the Cu-Cu distances in for methyl- and octylthiolate was performed.
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