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1.
Patterns of noble‐metal structures on top of self‐assembled monolayers (SAMs) on Au and SiO2 substrates have been prepared following two approaches. The first approach consists of pulsed laser deposition (PLD) of Pt, Pd, Au, or Cu through nano‐ and microstencils. In the second approach, noble‐metal cluster patterns deposited through nano‐ and microstencils are used as catalysts for selective electroless deposition (ELD) of Cu. Cu structures are grown on SAMs on both Au and SiO2 substrates and are subsequently analyzed using X‐ray photoelectron spectroscopy element mapping, atomic force microscopy, and optical microscopy. The combination of PLD through stencils on SAMs followed by ELD is a new method for the creation of (sub)‐micrometer‐sized metal structures on top of SAMs. This method minimizes the gas‐phase deposition step, which is often responsible for damage to, or electrical shorts through, the SAM.  相似文献   

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3.
The cover illustrates two‐step fabrication of metal micro‐ and nanostructures on self‐assembled monolayers (SAMs) by pulsed laser deposition and electroless deposition. Metal–SAM–metal junctions are a key component of molecular electronic devices. Pt was deposited in a micropattern by pulsed laser deposition through a stencil. XPS maps show how the Pt pattern is developed into a Cu pattern using electroless deposition as reported by Ravoo, Brugger, Reinhoudt, Blank, and co‐workers on p. 1337. The Cu pattern can also be observed by optical microscopy (background). Patterns of noble‐metal structures on top of self‐assembled monolayers (SAMs) on Au and SiO2 substrates have been prepared following two approaches. The first approach consists of pulsed laser deposition (PLD) of Pt, Pd, Au, or Cu through nano‐ and microstencils. In the second approach, noble‐metal cluster patterns deposited through nano‐ and microstencils are used as catalysts for selective electroless deposition (ELD) of Cu. Cu structures are grown on SAMs on both Au and SiO2 substrates and are subsequently analyzed using X‐ray photoelectron spectroscopy element mapping, atomic force microscopy, and optical microscopy. The combination of PLD through stencils on SAMs followed by ELD is a new method for the creation of (sub)‐micrometer‐sized metal structures on top of SAMs. This method minimizes the gas‐phase deposition step, which is often responsible for damage to, or electrical shorts through, the SAM.  相似文献   

4.
A method is presented for predicting and precisely controlling the structure of photonic crystals fabricated using sacrificial‐layer atomic layer deposition. This technique provides a reliable method for fabrication of high‐quality non‐close‐packed inverse shell opals with large static tunability and precise structural control. By using a sacrificial layer during opal infiltration, the inverse‐opal pore size can be increased with sub‐nanometer resolution and without distorting the lattice to allow for a high degree of dielectric backfilling and increased optical tunability. For a 10 % sacrificial layer, static tunability of 80 % is predicted for the inverse opal. To illustrate this technique, SiO2 opal templates were infiltrated using atomic layer deposition of ZnS, Al2O3, and TiO2. Experimentally, a static tunability of over 600 nm, or 58 %, was achieved and is well described by both a geometrical model and a numerical‐simulation algorithm. When extended to materials of higher refractive index, this method will allow the facile fabrication of 3D photonic crystals with optimized photonic bandgaps.  相似文献   

5.
A self‐assembled three phase epitaxial nanocomposite film is grown consisting of ≈3 nm diameter fcc metallic Cu nanorods within square prismatic SrO rocksalt nanopillars in a Sr(Ti,Cu)O3‐δ perovskite matrix. Each phase has an epitaxial relation to the others. The core–shell‐matrix structures are grown on SrTiO3 substrates and can also be integrated onto Si using a thin SrTiO3 buffer. The structure is made by pulsed laser deposition in vacuum from a SrTi0.75Cu0.25O3 target, and formed as a result of the limited solubility of Cu in the perovskite matrix. Wet etching removes the 3 nm diameter Cu nanowires leaving porous SrO pillars. The three‐phase nanocomposite film is used as a substrate for growing a second epitaxial nanocomposite consisting of CoFe2O4 spinel pillars in a BiFeO3 perovskite matrix, producing dramatic effects on the structure and magnetic properties of the CoFe2O4. This three‐phase vertical nanocomposite provides a complement to the well‐known two‐phase nanocomposites, and may offer a combination of properties of three different materials as well as additional avenues for strain‐mediated coupling within a single film.  相似文献   

6.
Self‐assembled monolayers (SAMs) of a conjugated bithiophenic system connected to an alkanethiol chain have been deposited on gold surface. The electroactive bithiophenic system involves a 3,4‐ethylenedioxythiophene (EDOT) unit and a thiophene ring on which an alkanethiol is attached at the internal β‐position via a sulfide linkage. The analysis of the structure of the SAMs by IR spectroscopy, ellipsometry, contact angle measurement and X‐ray photoelectron spectroscopy (XPS) provides consistent results indicating compact monolayers in which the alkyl linkers are arranged in an almost vertical fashion while the bithiophenic‐conjugated systems are essentially parallel to the surface. Cyclic voltammetry shows that application of a few potential scans to SAMs immersed in a medium containing only a supporting electrolyte leads to the typical electropolymerization curves while the CV of the electrooxized monolayer exhibits a reversible cyclic voltammogram characteristic of a stable electroactive extended conjugated system. The characterization of the electropolymerized monolayers by IR spectroscopy, ellipsometry, contact angle measurement, and XPS indicates compact monolayers. The analysis of the current voltage characteristics of the monolayers by conducting AFM before and after electrooxidation shows that the enhancement of the effective conjugation resulting from electropolymerization leads to a significant increase of the transport properties.  相似文献   

7.
Using a representative model system, here electronic and structural properties of aromatic self‐assembled monolayers (SAMs) are described that contain an embedded, dipolar group. As polar unit, pyrimidine is used, with its orientation in the molecular backbone and, consequently, the direction of the embedded dipole moment being varied. The electronic and structural properties of these embedded‐dipole SAMs are thoroughly analyzed using a number of complementary characterization techniques combined with quantum‐mechanical modeling. It is shown that such mid‐chain‐substituted monolayers are highly interesting from both fundamental and application viewpoints, as the dipolar groups are found to induce a potential discontinuity inside the monolayer, electrostatically shifting the core‐level energies in the regions above and below the dipoles relative to one another. These SAMs also allow for tuning the substrate work function in a controlled manner independent of the docking chemistry and, most importantly, without modifying the SAM‐ambient interface.  相似文献   

8.
In order to further improve the efficiency and stability of luminescent electrochemical polymerization (EP) films and devices, electroactive self‐assembled monolayers (SAMs) of carbazolyl alkanethiol are successfully designed and applied to modify Au electrode and covalently graft the deposited EP films. The analysis of the formation and coverage of the SAMs by atomic force microscopy (AFM), cyclic voltammetry (CV), and the theoretical calculation provide consistent results indicating the SAM molecules are densely packed and standing upright (liquid‐like) on the Au surface. In addition, ultraviolet photoelectron spectroscopy (UPS), CV, UV, AFM, and sonication treatment reveal that the close‐packed electroactive SAMs are effective at enhancing the work function of electrode, increasing the deposition rate of EP precursor as well as elevating the cross‐linking efficiency and the adhesive property of subsequent EP films. This is a simple and very efficient method for improving the performance of EP device, which has potential applications in display devices.  相似文献   

9.
We describe the suitability of ultra‐high vacuum scanning tunneling microscopy (UHV‐STM) based nanolithography by using highly ordered monomolecular organic films, called self‐assembled monolayers (SAMs), as ultrathin resists. Organothiol‐type SAMs such as hexadecanethiol (SH–(CH2)15–CH3) and N‐biphenylthiol (SH–(C6H6)2–NO2) monolayers have been prepared by immersion on gold films and Au(111) single crystals. Organosilane‐type SAMs such as octadecyltrichlorosilane (SiCl3–(CH2)17–CH3) monolayers have been prepared on hydroxylated Si(100) surfaces as well as hydroxylated chromium film surfaces. Dense line patterns have been written by UHV‐STM in constant current mode for various tunneling parameters (gap voltage, tunneling current, scan speed, and orientation) and transferred into the underlying substrate by wet etch techniques. The etched structures have been analyzed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Best resolution has been achieved without etch transfer for a 20 nm × 20 nm square written in hexadecanethiol/Au(111) with an edge definition of about 5 nm. Etch transfer of the STM nanopatterns in Au films resulted in 55 nm dense line patterns (15 nm deep) mainly broadened by the isotropic etch characteristic, while 35 nm wide and 30 nm deep dense line patterns written in octadecyltrichlorosilane/Si(100) and anisotropically etched into Si(100) could be achieved.  相似文献   

10.
A 3‐aminopropyltrimethoxysilane‐derived self‐assembled monolayer (NH2SAM) is investigated as a barrier against copper diffusion for application in back‐end‐of‐line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO2 dielectric substrate and the Cu over‐layer. Time‐of‐flight secondary ion mass spectrometry and X‐ray spectroscopy (XPS) analysis reveal that the copper over‐layer closes at 1–2‐nm thickness, comparable with the 1.3‐nm closure of state‐of‐the‐art Ta/TaN Cu diffusion barriers. That the NH2SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy‐filtered transmission electron microscopy supported by XPS. The SAM forms a well‐defined carbon‐rich interface with the Cu over‐layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH2SAM/SiO2 system increases with annealing temperature up to 7.2 J m?2 at 400 °C, comparable to Ta/TaN (7.5 J m?2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH2SAM is a suitable candidate for subnanometer‐scale diffusion barrier application in a selective coating for copper advanced interconnects.  相似文献   

11.
Silicon dioxide (SiO2) films prepared by plasma‐enhanced atomic‐layer deposition were successfully grown at temperatures of 100 to 250 °C, showing self‐limiting characteristics. The growth rate decreases with an increasing deposition temperature. The relative dielectric constants of SiO2 films are ranged from 4.5 to 7.7 with the decrease of growth temperature. A SiO2 film grown at 250 °C exhibits a much lower leakage current than that grown at 100°C due to its high film density and the fact that it contains deeper electron traps.  相似文献   

12.
Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers.  相似文献   

13.
The 193 nm photochemistry of (aminoethylaminomethyl)phenethylsiloxane (PEDA) self‐assembled monolayers (SAMs) under ambient conditions is described. The primary photodegradation pathways at low exposure doses (< 100 mJ cm–2) are benzylic C–N bond cleavage (ca. 68 %), with oxidation of the benzyl C to the aldehyde, and Si–C bond cleavage (ca. 32 %). Amine‐containing photoproducts released from the SAM during exposure remain physisorbed on the surface, where they undergo secondary photolysis leading to their complete degradation and removal after ca. 1200 mJ cm–2. NaCl(aq) post‐exposure rinsing removes the physisorbed materials, showing that degradation of the original PEDA species (leaving Si–OH) is substantially complete after ca. 450 mJ cm–2. Consequently, patterned, rinsed PEDA SAMs function as efficient templates for fabrication of high‐resolution, negative‐tone, electroless metal and DNA features with good selectivity at low dose (i.e., ca. 400 mJ cm–2) via materials grafting to the intact amines remaining in the unirradiated PEDA SAM regions.  相似文献   

14.
In this work heteroepitaxial stabilization with nanoscale control of the magnetic Co2FeO4 phase at 250 °C is reported. Ultrasmooth and pure Co2FeO4 thin films (5–25 nm) with no phase segregation are obtained on perovskite SrTiO3 single crystal (100) and (110) oriented substrates by atomic layer deposition (ALD). High resolution structural and chemical analyses confirm the formation of the Co‐rich spinel metastable phase. The magneto‐crystalline anisotropy of the Co2FeO4 phase is not modified by stress anisotropy because the films are fully relaxed. Additionally, high coervice fields, 15 kOe, and high saturation of magnetization, 3.3 μB per formula unit (at 10 K), are preserved down to 10 nm. Therefore, the properties of the ALD‐Co2FeO4 films offer many possibilities for future applications in sensors, actuators, microelectronics, and spintronics. In addition, these results are promising for the use of ALD compared to the existing thin‐film deposition techniques to stabilize epitaxial multicomponent materials with nanoscale control on a wide variety of substrates for which the processing temperature is a major drawback.  相似文献   

15.
采用等离子体增强原子层沉积(PEALD)技术在斜切的砷化镓(GaAs)衬底上低温沉积了氮化镓(GaN)薄膜,对生长过程、表面机制以及界面特性等进行分析,得到GaN在215~270℃的温度窗口内生长速度(Growth-Per-Cycle, GPC)为0.082 nm/cycle,并从表面反应动力学和热力学方面对GPC的变化进行了分析。研究发现,生长的GaN薄膜为多晶,具有六方纤锌矿结构,且出现(103)结晶取向。在GaN/GaAs界面处观察到约1 nm厚的非晶层,这可能与生长前衬底表面活性位点的限制和前驱体的空间位阻效应有关。值得注意的是,在沉积的GaN薄膜中,所有的N皆与Ga以Ga-N键结合生成GaN,但是存在少部分Ga形成了Ga-O键和Ga-Ga键。这种成键方式,可能与GaN薄膜中存在的缺陷和杂质有关。  相似文献   

16.
Molecular layer deposition (MLD) is a useful technique for fabricating hybrid organic‐inorganic thin films. MLD allows for the growth of ultrathin and conformal films using sequential, self‐limiting reactions. This article focuses on the MLD of hybrid organic‐inorganic films grown using metal precursors and various organic alcohols that yield metal alkoxide films. This family of metal alkoxides can be described as “metalcones”. Many metalcones are possible, such as the “alucones” and “zincones” based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic diols such as ethylene glycol. Alloys of the various metalcones with their parent metal oxide atomic layer deposition (ALD) films can also be fabricated that have an organic‐inorganic composition that can be adjusted by controlling the relative number of ALD and MLD cycles. These metalcone alloys have tunable chemical, optical, mechanical, and electrical properties that may be useful for designing various functional films. The metalcone hybrid organic‐inorganic materials offer a new tool set for engineering thin film properties.  相似文献   

17.
Crack‐free, mesoporous SnO2 films with highly crystalline pore walls are obtained by evaporation‐induced self‐assembly using a novel amphiphilic block‐copolymer template (“KLE” type, poly(ethylene‐co‐butylene)‐block‐poly(ethylene oxide)), which leads to well‐defined arrays of contracted spherical mesopores by suitable heat‐treatment procedures. Because of the improved templating properties of these polymers, a facile heat‐treatment procedure can be applied whilst keeping the mesoscopic order intact up to 600–650 °C. The formation mechanism and the mesostructural evolution are investigated by various state‐of‐the‐art techniques, particularly by a specially constructed 2D small‐angle X‐ray scattering setup. It is found that the main benefit from the polymers is the formation of an ordered mesostructure under the drastic conditions of using molecular Sn precursors (SnCl4), taking advantage of the large segregation strength of these amphiphiles. Furthermore, it is found that the crystallization mechanism is different from other mesostructured metal oxides such as TiO2. In the case of SnO2, a significant degree of crystallization (induced by heat treatment) already starts at quite low temperatures, 250–300 °C. Therefore, this study provides a better understanding of the general parameters governing the preparation of mesoporous metal oxides films with crystalline pore walls.  相似文献   

18.
The controlled adsorption of the iron‐containing cage protein ferritin at the nanoscale using stimuli‐responsive self‐assembled diblock copolymer thin‐film templates is reported. The diblock copolymer used study consists of a cylinder‐forming polystyrene‐block‐polyferrocenylsilane (PS‐b‐PFS), with PFS as the minor block, and shows reversible redox properties. To prevent any spontaneous protein adsorption on either block, the electrolyte pH is selected to leave the ferritin negatively charged, and the protein concentration and solution ionic strength are carefully tuned. Selective adsorption of ferritin on the PFS domains of the self‐assembled thin films is then triggered in situ by applying a positive potential, simultaneously oxidizing the PFS and attracting the ferritin electrostatically.  相似文献   

19.
The electrochemical oxidation process of self‐assembled monolayers formed by n‐octadecyltrichlorosilane (OTS) molecules on silicon wafers has been studied in a droplet of water by means of in situ water contact angle measurements. The application of different bias voltages between the substrate and a counter electrode placed into the droplet resulted in changes of the chemical nature of the monolayer, which yielded a significant alteration of the surfaces properties. Due to the changes of the wetting properties of the monolayer during the electro‐oxidation process a change in the contact angles of the water droplet is concomitantly observed. This allows the in situ monitoring of the electro‐oxidation process for large modified areas of several millimeters in diameter. The chosen approach represents an easy way to screen the major parameters that influence the oxidation process. Afterwards, the oxidized regions are characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) measurements, and atomic force microscopy (AFM) investigations to obtain more information about the electro‐oxidation process. The observations are correlated to experimental results obtained for oxidations performed on a smaller dimension range in the water meniscus of a conductive, biased AFM tip. A good correlation of the results in the different dimension ranges could be found.  相似文献   

20.
Controlling charge doping in organic semiconductors represents one of the key challenges in organic electronics that needs to be solved in order to optimize charge transport in organic devices. Charge transfer or charge separation at the molecule/substrate interface can be used to dope the semiconductor (substrate) surface or the active molecular layers close to the interface, and this process is referred to as surface‐transfer doping. By modifying the Au(111) substrate with self‐assembled monolayers (SAMs) of aromatic thiols with strong electron‐withdrawing trifluoromethyl (CF3) functional groups, significant electron transfer from the active organic layers (copper(II) phthalocyanine; CuPc) to the underlying CF3‐SAM near the interface is clearly observed by synchrotron photoemission spectroscopy. The electron transfer at the CuPc/CF3‐SAM interface leads to an electron accumulation layer in CF3‐SAM and a depletion layer in CuPc, thereby achieving p‐type doping of the CuPc layers close to the interface. In contrast, methyl (CH3)‐terminated SAMs do not display significant electron transfer behavior at the CuPc/CH3‐SAM interface, suggesting that these effects can be generalized to other organic‐SAM interfaces. Angular‐dependent near‐edge X‐ray absorption fine structure (NEXAFS) measurements reveal that CuPc molecules adopt a standing‐up configuration on both SAMs, suggesting that interface charge transfer has a negligible effect on the molecular orientation of CuPc on various SAMs.  相似文献   

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