Preparation and Characterization of SrTiO_3 Thin Film on Functional Organic Self-Assembled Monolayers

SrTiO3 thin film was successfully prepared on the functionalized organic self-assembled monolayers（SAMs） by the Liquid Phase Deposition（LPD） method.The as-prepared samples were characterized by X-ray diffraction（XRD）,atomic force microscope（AFM）,scanning electron microscopy（SEM） and metallographic microscope.Measurement of contact angle showed that the hydrophobe substrate was changed into hydrophile by UV irradiation.AFM photographs of octadecyl-trichloro-silane self-assembled monolayer（OTS-SAM） surface approved that UV irradiation did change the morphology of OTS monolayer and provided evidence for the conversion of hydrophilic characteristic.Photographs of Metallographic Microscope showed that OTS-SAM had an active effect on the deposition of SrTiO3 thin film.XRD and SEM indicated that the thin film was of pure cubic phase SrTiO3 and composed of nanosized grains with a size in the range of 100-500 nm.The formation mechanism of the SrTiO3 film was proposed.

High-Quality FeTe_(1-x)Se_x Monolayer Films on SrTiO_3(001) Substrates Grown by Molecular Beam Epitaxy

We report the growth process of FeTe1-xSex （0 〈 x 〈 1） monolayer films on SrTi03 （STO） substrates through molecular beam epitaxy and discuss the possible ways to improve the film quality. By exploring the parameters of substrate treatment, growth control and post growth annealing, we successfully obtain a series of FeTe1-xSex monolayer films. In the whole growth process, we find the significance of the temperature control through surface roughness monitored by the reflection high-energy electron diffraction and scanning tunneling microscopy. We obtain the best quality of FeSe monolayer films with the STO substrate treated at T = 900 950℃ before growth, the FeSe deposited at T = 310℃ during growth and annealed at T = 380℃ after growth. For FeTe1-xSex （x-1）, both the growth temperature and annealing temperature decrease to T=260℃. According to the angle- resolved photoemission spectroscopy measurements, the superconductivity of the FeTe1-xSex film is robust and insensitive to Se concentration. All the above are instructive for further investigations of the superconductivity in FeTe1-xSex films.

Electron Transport Properties of Two-Dimensional Monolayer Films from Au-P-Au to Au-Si-Au Molecular Junctions

We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.

Stability Behaviour of Monolayer Tetraether Lipids on the Amino-Silanised Silicon Wafer: Comparative Study between Langmuir-Blodgett Monolayers with Self-Assembled Monolayers

This study investigated the stability behaviour of molecular monolayer symmetric chemically modified tetraether lipids caldarchaeol-PO4 on the amino-silanised silicon wafer using Langmuir-Blodgett films, Self Assembling Monolayers (SAMs), ellipsometry, and atomic force microscopy (AFM). The monolayers of caldarchaeol-PO4 were stable on the solid surface amino-silanised silicon wafer. The organizations of molecular monolayers caldarchaeol-PO4 by Langmuir-Blodgett method and SAMs have been analyzed. The surface of pressure in Langmuir-Blodgett processing is carried out monolayers caldarchaeol-PO4 more flat island inhomogeneous. Another method of monolayers caldarchaeol-PO4 by SAMs is showed a large flat domain. Monolayers caldarchaeol-PO4 by Langmuir-Blodgett method seems to be stable and chemically resistant after washing with organic solvent and an additional treatment ultrasonification with various thickness lipids arround 2 nm to 6 nm. Conversely, monolayer caldarchaeol-PO4 by SAMs appears fewer than monolayers caldarchaeol-PO4 by Langmuir-Blodgett method, the thickness of various from 1 nm to 3 nm.

Odd-even effects in the structure and properties of aryl-substituted aliphatic self-assembled monolayers

Self-assembled monolayers(SAMs)represent an important tool in context of nanofabrication and molecular engineering of surfaces and interfaces.The properties of functional SAMs depend not only on the character of the tail groups at the SAM-ambient interface,but are also largely defined by their structure.In its turn,the latter parameter results from a complex interplay of the structural forces and a variety of other factors,including so called odd-even effects,viz.dependence of the SAM structure and properties on the parity of the number(odd or even)of individual building blocks in the backbone of the SAM constituents.The most impressive manifestation of the odd-even effects is the structure of aryl-substituted alkanethiolate SAMs on Au(111)and Ag(111),in which,in spite of the fact that the intermolecular interaction is mostly determined by the aryl part of the monolayers,one observes a pronounced dependence of molecular inclination and,consequently,the packing density of the SAM-forming molecules on the parity of number of methylene units in the alkyl linker.Here we review the properties of the above systems as well as address fundamental reasons behind the odd-even effects,including the existence of a so-called bending potential,which is frequently disregarded in analysis of the structure-building forces.The generality of the odd-even effects in SAMs is additionally supported by the recent data for SAMs on GaAs,scanning tunneling microscopy data for SAMs on Ag(111),and the data for the monolayers with selenolate and carboxyl anchoring groups on Au(111)and Ag(111).The implications of these effects in terms of the control over the packing density and orientation of the tail groups at the SAM-ambient interface,structural perfection,polymorphism,temperature-driven phase transitions,and SAM stability toward such factors as ionizing radiation,exchange reaction,and electrochemical desorption are discussed.These implications place the odd-even effects as an important tool for the design of functional SAMs in context of specific applications.

Novel self-assembled films of La-based phosphonate 3-aminopropyltriethoxysilane

Silane coupling reagent (3-aminopropyltriethoxysilane (APTES)) was prepared on single-crystal silicon substrates to form two-dimensional self-assembled monolayer (SAM). The terminal-NH2 groups in the film were in situ phosphorylated to -PO(OH)2 group to endow the film with good chemisorption ability. Then La-based thin films were deposited on phosphorylated APTES-SAM in order to make good use of the chemisorption ability of -PO(OH)2 groups. The thickness of the film was determined with ellipsometer, while phase transformation and surface morphology, surface energy, phase composition were analyzed by means of atomic force microscope (AFM), contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that the terminal-NH2 groups could be completely transformed into desirable-PO(OH)2 groups after phosphorylation of APTES-SAM. Detailed XPS analysis of the La3+ peaks revealed that lanthanum element existed in the films in different states. As a result, conclusion could be made that lanthanum reacted with -PO(OH)2 groups on the surface of the substrate by chemical bond which would improve the bonding strength between the film and silicon substrate. Since the La-based thin films were well adhered to the silicon substrate, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).

Interfacial Behaviors of Azocalixarene Derivatives at the Air/Water Interface and Photochromism in the Langmuir-Blodgett Films

The interfacial behaviors of the non-typical amphiphilic compound p-methylphenylazocalix[4]arene 1 and p-chlorophenylazocalix[4]arene 2 at the air/water interface and photochromism in the Langmuir-Blodgett films were studied by surface pressure-area isotherm and UV-Vis spectra. The results indicate that they can form stable monolayers at the air / water interface although they have no hydrophobic alkyl chains, and their LB film underwent reversible trans-cis photoisomerization on UV and daylight illumination.

Langmuir-Blodgett Films and Calcium Ion Coordination of Biliverdin and Its Amphiphilic Derivatives

Monolayer formation and LB film fabrication of amphiphilic derivative of biliverdin 1, diododecyl biliverdinamide [B(CONHC12H25)(2), 2] at an air-water interface on pure water subphase and subphase containing calcium ion were investigated and compared with 1. The coordination in ordered molecular films is much different from that in bulk solution. The formation of ligand-calcium complex was confirmed by X-ray photoelectron spectroscopy.

Coordination Interaction between Rare Earth and/or Transition Metal Centers and Thiophene Series Oligomer Derivatives in Ultrathin Langmuir-Blodgett Films

It has been shown by thermodynamic and electro-chemical methods that coordination interactions are involved in the process of incorporation of rare-earth elements and/or Fe into Langmuir monolayers of oligomer with alkyl fragment. A coordination mechanism, which is responsible for self-organization of octahedral Fe(II)-complexes of nano-cyclic ligands obtained from oligomer of thiophene pyrrole series derivatives in compressed Langmuir monolayers has been proposed. It has been established that a coordinational-polymeric hexagonal network of nano-cyclic ligands with metal centers is formed at the phase transition when compressing the Langmuir monolayers of thiophene pyrrole series oligomer with alkyl fragment on surface of subphase with rare-earth (Sm, Er, Ce) and/or Fe ions.

Large Room Temperature Magneto-Resistance in Magnetically Disordered Fe_1.5Ti_0.5O_3-δThin Films

Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.

Cu_(2)O-Au复合结构的制备及其在SERS中的应用

表面等离激元催化反应为表面过程的拓展提供了一条新的途径,但在单一贵金属表面的反应效率往往较低,因此发展符合纳米结构已经成为该领域的研究热点。通过合成八面体的氧化亚铜(Cu_(2)O),并引入高均匀性和高SERS活性的金纳米粒子单层膜(Au MLF),将两者完全结合,构建了Cu_(2)O-Au复合异质结SERS基底。以对硝基苯硫酚(PNTP)为探针,通过表面增强拉曼光谱(SERS)研究了Cu_(2)O-Au表面等离激元驱动的偶联反应。结果表明,Cu_(2)O与Au MLF的复合,其SERS性能及催化活性都得到了较大的提升,为发展高性能的新型复合纳米结构提供了实验基础。

Polymorphism of domains in phase-separated mixed monolayer films investigated by atomic force microscopy

The domain structures of amphophilic molecules at the air-water interface have beenwidely studied by fluorescence and Brewster angle microscopy over the past ten years.However, these studies were mainly focused on the transition from the liquid-expanded(LE) phase to the liquid-condensed (LC) phase in a one-component monolayer. Therewere only a few reports dealing with the direct observation of domain structures in

Influence of laser conditioning on defects of HfO_2 monolayer films

The influence of laser conditioning on defects of HfO2 monolayer films prepared by electron beam evaporation （EBE） is investigated utilizing the spot-size effect of the laser-induced damage.It is found that the laser-induced damage threshold of HfO2 monolayer films can be increased by a factor of 1.3-1.6.It is also found that the defects with low threshold can be removed by laser conditioning and defects with higher threshold may be removed partially.

ADO-phosphonic acid self-assembled monolayer modified dielectrics for organic thin film transistors

This study explores a strategy of using the phosphonic acid derivative （11-（（12-（anthracen-2- yl）dodecyl）oxy）-11-oxoundecyl） phosphonic acid （ADO-phosphonic acid） as self-assembled monolayers （SAMs） on a Si/SiO2 surface to induce the crystallization ofrubrene in vacuum deposited thin film transistors, which showed a field-effect mobility as high as 0.18 cm2/（V.s）. It is found that ADO-phosphonic acid SAMs play a unique role in modulating the morphology ofrubrene to form a crystalline film in the thin-film transistors.

Large-scale area of magnetically anisotropic nanoparticle monolayer films deposited by MAPLE

Magnetically anisotropic nanoparticle monolayer films are of great interest for the development of ap-plications such as high-density data storage,sensors.However,the formation of large-scale magnetically anisotropic monolayer film is a challenging task.Here,we provide a new way to fabricate large-scale area of Fe_(3)O_(4) nanoparticle monolayer films by vacuum deposition technique(matrix-assisted pulsed laser evaporation,MAPLE).During the deposition process,only interactions between nanoparticles influence nanoparticle self-assembly behaviors.A strong magnetic anisotropy,characterized by in-plane and out-of-plane coercivity and saturation field obtained by DCM(dynamic cantilever magnetometry),was obtained both in cubic and spherical Fe_(3)O_(4) nanoparticle monolayer films.The inter-particle dipolar interaction but not crystal anisotropy is responsible for this effective magnetic anisotropy,which has been proved by Monte-Carlo simulations.

Control of polymorphism in solution-processed organic thin film transistors by self-assembled monolayers

Polymorphism of organic semiconductor films is of key importance for the performance of organic thin film transistors(OTFTs).Herein,we demonstrate that the polymorphism of solution-processed organic semiconductors in thin film transistors can be controlled by finely tuning the surface nanostructures of substrates with self-assembled monolayers(SAMs).It is found that the SAMs of 12-cyclohexyldodecylphosphonic acid(CDPA)and 12-phenyldodecylphosphonic acid(Ph DPA)induce different polymorphs in the dip-coated films of 2-dodecyl[1]benzothieno[3,2-b][1]benzothiophene(BTBT-C12).The film of BTBT-C12 on CDPA exhibits field effect mobility as high as 28.1 cm2 V-1 s-1 for holes,which is higher than that of BTBT-C12 on Ph DPA by three times.The high mobility of BTBT-C12 on CDPA is attributable to the highly oriented films of BTBT-C12 with a reduced in-plane lattice and high molecular alignment.

Epitaxial fabrication of AgTe monolayer on Ag(111)and the sequential growth of Te film

Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like structure possess exotic electronic structures.Here,we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111)and annealing.Few intrinsic defects are observed and studied by scanning tunneling microscopy,indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary.Then,the monolayer AgTe can serve as the template for the following growth of Te film.Meanwhile,some Te atoms are observed in the form of chains on the top of the bottom Te film.Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.

Nanopatterning of substrates by self-assembly in supramolecular block copolymer monolayer films

Many technological applications require templates with nanoscale patterns.Block copolymer self-assembly is a method of choice for obtaining a large variety of such patterns,with greatest flexibility achieved when combined with a supramolecular approach.One of the ways to fabricate block copolymer templates is the Langmuir-Blodgett (LB) technique.Here,we briefly summarize recent work with LB films of polystyrene-poly(4-vinyl pyridine) (PS-P4VP) mixed with 3-n-pentade cylphenol (PDP),illustrating the different types of patterns possible and the principles governing them.One interesting pattern that can be easily achieved with this system is the so-called "nanostrand network",which,when used as a template for gold deposition,can produce double striped lines of gold.Here,we show how this pattern can be modified by acetone swelling to give rise to gold monolayer ribbons with internal structure.The results also suggest new insights into the early stages of morphology formation at the air/water interface.

相转移方法制备银纳米粒子单层膜

在油酸钠保护下用NaBH4 还原AgNO3 ,制得了银纳米粒子胶体溶液 .利用相转移剂NaH2 PO4 等 ,使Ag纳米粒子在水 /有机相界面之间形成薄膜 .形成的Ag纳米粒子膜可以转移到玻璃等基质上 ,讨论了其转移机理 ;并用石英晶体微天平 (QCM)定量检测了银纳米粒子的相转移量 .

自组装单分子膜的摩擦学研究进展

综述了自组装单分子膜的摩擦学研究与应用的主要成果 ,着重介绍了自组装单分子膜的结构与其摩擦学性能之间的关系 。