A new patterning method using photocatalytic lithography and selective atomic layer deposition

We report a new patterning method using photocatalytic lithography of alkylsiloxane self-assembled monolayers and selective atomic layer deposition of thin films. The photocatalytic lithography is based on the fact that the decomposition rate of the alkylsiloxane monolayers in contact with TiO2 is much faster than that with SiO2 under UV irradiation in air. The photocatalytic lithography, using a quartz plate coated with patterned TiO2 thin films, was done to prepare patterned monolayers of the alkylsiloxane on Si substrates. A ZrO2 thin film was selectively deposited onto the monolayer-patterned Si substrate by atomic layer deposition.     

Preparation of submicron-structured alkylsiloxane monolayers using prepatterned silicon substrates by laser direct writing

A new constructive method for the preparation of laterally structured alkylsiloxane monolayers is demonstrated. Laser direct writing has been used to create oxide patterns on H-terminated Si(100) samples under ambient conditions. Depending on the laser power and the writing speed, oxide structures with a lateral resolution below 500 nm are prepared routinely. The patterned samples are suitable as temporary templates for the preparation of laterally structured octadecylsiloxane monolayers. Prior to immersion in an octadecyltrichlorosilane solution, however, hydration of the samples in water is essential to facilitate a selective coating of the oxidized areas. After coating, atomic force microscopy reveals the formation of octadecylsiloxane islands exclusively on top of the oxide lines.     

Light stamping lithography: microcontact printing without inks

We report a new patterning method, called light-stamping lithography (LSL), that uses UV-induced adhesion of poly(dimethylsiloxane) (PDMS). LSL is based on the direct transfer of the contact surface of the PDMS stamp to a substrate via a UV (254 nm)-induced surface bonding between the stamp and the substrate. This procedure can be adopted in automated printing machines that generate patterns with a wide range of feature sizes on diverse substrates. To demonstrate its usefulness, the LSL method was applied to prepare several PDMS patterns on a variety of substrates. The PDMS patterns were then used as templates for selective deposition of TiO2 thin film using atomic layer deposition as well as resists for selective wet etching.     

水溶液法制备图案化TiO2薄膜

从硫酸钛Ti(SO4)2的水溶液出发, 采用化学浴沉积和电沉积法来制备图案化TiO2薄膜. 通过硫酸和双氧水来稳定Ti4+, 配制了pH=1.0的硫酸钛溶液和pH=1.6的过氧硫酸钛溶液. 结合微接触印刷术在硅基底上制得自组装膜预图案, 再化学浴沉积TiO2即可得规则图纹. 无机配体对钛溶液的稳定性和TiO2的晶型均有影响, 溶液的酸度关系到所得图案的质量. 过氧硫酸钛溶液同样适用于电沉积, 在导电玻璃基底上旋涂光刻胶后选择性曝光、显影, 通过控制阴极电位可获得高差达200 nm的清晰图案.     

水溶液法制备图案化TiO_2薄膜

从硫酸钛Ti(SO4)2的水溶液出发,采用化学浴沉积和电沉积法来制备图案化TiO2薄膜.通过硫酸和双氧水来稳定Ti4+,配制了pH=1.0的硫酸钛溶液和pH=1.6的过氧硫酸钛溶液.结合微接触印刷术在硅基底上制得自组装膜预图案,再化学浴沉积TiO2即可得规则图纹.无机配体对钛溶液的稳定性和TiO2的晶型均有影响,溶液的酸度关系到所得图案的质量.过氧硫酸钛溶液同样适用于电沉积,在导电玻璃基底上旋涂光刻胶后选择性曝光、显影,通过控制阴极电位可获得高差达200nm的清晰图案.     

Positive and negative TiO2 micropatterns on organic polymer substrates

Ordered titanium dioxide (TiO2) films have received increasing attention because of their great potential in photocatalysis, energy conversion, and electrooptical techniques. Such films are often fabricated as coatings on various substrates such as silicon or a variety of polymers. Liquid-phase deposition (LPD) of TiO2 films is especially promising for organic substrates due to its very mild reaction conditions. In the present paper, LPD is conducted on a wettability-patterned polypropylene surface to fabricate positive and negative TiO2 micropatterns. A thin layer of ammonium persulfate in an aqueous solution was sandwiched between two biaxially oriented polypropylene (BOPP) films, and a photomask was employed to control the irradiation region. Within a short time interval, a high hydrophilicity could be obtained on the irradiation region, and an effective wettability contrast between the irradiated and unirradiated regions could be created to further induce the formation of two types of TiO2 micropatterns. Up until now, most approaches for micropatterning have been based on self-assembled monolayers on surfaces of gold (or other noble metals), silicon, and various polyesters. With the present method, however, there is no longer any limitation in the type of substrate used. Our work demonstrates that an anatase TiO2 film could be selectively deposited on a hydrophilic region, giving rise to a positive pattern with significant bonding strength and good line edge acuity, providing an effective solution toward the microfabrication on various inert polymer substrates. More surprisingly, we find, for the first time, that TiO2 could also be selectively retained on a hydrophobic region to form a negative pattern by simply adjusting the reaction conditions. Further analysis of the mechanism shows that, independent of the deposition conditions, the TiO2 deposition pattern changes gradually, from being initially negative to becoming positive as the deposition time increases. The surface functionality changes (from sulfate to hydroxyl groups) during the deposition, and the resulting difference in the affinity for TiO2 is used to interpret this negative-to-positive pattern change. Such negative patterns refute the conventional opinion that only hydrophilic regions favor the formation of TiO2 films and could be used to fabricate large areas (mm2) of interconnected TiO2 micronetworks. Such networks are difficult to obtain by conventional metallic masks, and the present method is expected to provide new strategies in the fabrication of flexible photomasks and macro/mesoporous TiO2 films. An example is given wherein a patterned photografting of poly(acrylic acid) on the surface of BOPP is achieved by using such a polymer-based photomask. The innovativeness of this method arises from its ability to provide negative patterning, whereas present related approaches have been found only to give positive patterns from an equivalent photomask. Unlike complex photolithography procedures, our irradiation and patterning process does not require the use of positive or negative photoresists, and should thus prove to be a simple, fast, and low-cost method.     

Fabrication of Stable Chiral Polyaniline Nanocomposite‐Based Patterns

Summary: We report an artful method to form a stable pattern of chiral polyaniline nanocomposites (CPANs). It consists of the preparation of a diazoresin (DR)/poly(acrylic acid) (PAA) thin buffer layer on an Si substrate by self‐assembly, followed by the deposition of a multi‐layer film by spin‐assembly, leading to the formation of a (DR/PAA)₂DR/(CPAN/DR)_n film on the substrate. After selective exposure to UV light through a photomask and the development process, a defined pattern is formed.

Scanning electron microscopy image of the patterned (CPAN/DR)₅ thin film on Si wafer.     

用简便方法组装二维模板银纳米阵列

通过制备甲基和羧基混合自组装单层膜, 然后在羧基基团上选择性地生长银制备二维模板银纳米阵列. 利用微接触印刷在金膜上制备模板自组装单层膜, 也就是利用具有二维微米图案的弹力印模把有机巯基化合物转移到金膜上. 改善的银镜反应被用来制备银纳米结构, 银纳米粒子选择性地生长在二维模板有机单分子层的羧基位置. 甲醇作为还原剂具有高的选择性和原子经济性, 一分子甲醇可以还原六个银离子. 利用原子力显微镜和扫描电子显微镜确定了银纳米结构的形貌, 用拉曼光谱研究银纳米结构的光学性质.     

Nonlithographic micro- and nanopatterning of TiO2 using polymer stamped molecular templates

The polymer-on-polymer stamping technique was used to template patterned TiO2 onto polymer thin films. Polystyrene-b-polyvinyl pyridine diblock copolymer (PS-b-PVP) was stamped on a layer-by-layer assembled thin film of poly(allylamine hydrochloride) and poly(acrylic acid). After rinsing the surface with a good solvent for the block copolymer, an adsorbed PS-b-PVP monolayer remained on the polyelectrolyte film, resulting in a pattern of alternating hydrophobic and carboxylic acid containing hydrophilic regions. The surface was used as a template for the selective deposition of TiO2 on the multilayer surface, using an acid-catalyzed hydrolysis of(NH4)2TiF6. Using this novel approach, we have successfully demonstrated the patterning of TiO2 film on a polyelectrolyte multilayer. Finally, nanoscale features consisting of 200 nm lines alternating with a 350 nm period was accomplished. This paper represents the first such attempt to create an all-polymer nonlithographic template for the directed deposition of TiO2 or related metal oxides; this technique, which utilizes the versatile polyelectrolyte multilayer process, enables the construction of complex polymer-inorganic microstructures suitable for electrooptical and photonic applications.     

Micropatterning of Sol-Gel Derived Thin Films Using Hydrophobic-Hydrophilic Patterned Surface

Formation process of convexly shaped oxide micropatterns using hydrophobic-hydrophilic patterned surface has been examined, and this technique was applied to several oxide thin films such as SnO₂, ZrO₂, TiO₂ and Al₂O₃. Hydrophobic-hydrophilic patterned surfaces were prepared on glass substrates by selective UV irradiation through a photomask on double-layered films of a very thin TiO₂ gel film as the underlayer and a hydrolyzed fluoroalkyltrimethoxysilane layer as the top layer. Precursor solutions were then spin-coated on the hydrophobic-hydrophilic patterns, and the coated substrates were dried at room temperature. The micropatterns of oxides were very difficult to be formed on the hydrophobic-hydrophilic patterned surfaces from metal-alkoxides as a precursor solution, but convexly shaped micropatterns were formed on the hydrophilic regions of the pattern when metal chlorides or oxychlorides were used as starting materials. This patterning technique potentially has a wide variety of applications such as fabrication of micro-optical components and finely patterned transparent electrodes.     

TiO2颗粒在羟基表面的沉积行为及图案化

比较了3种具有羟基表面SiO2层的差异:紫外光照SAMs形成的羟基表面,紫外光照射前、照射后的羟基表面;用光照前后表面的差异,结合化学浴沉积技术在单晶硅基底上制得了TiO2微图案薄膜。系统考察了光源、硅片表面性质的变化、溶液等方面对图案生成的影响。实验表明TiO2沉积在未照区,电子和空穴动力学上的差异造成光照区表面正电荷增多,抑制了TiO2的沉积。该方法不需要光刻胶和自组装膜作为辅助模板,具有简单廉价的特点。     

In situ growth of CuS thin films on functionalized self-assembled monolayers using chemical bath deposition

Nano-structured CuS thin films were deposited on the functionalized -NH(2)-terminated self-assembled monolayers (SAMs) surface by chemical bath deposition (CBD). The deposition mechanism of CuS on the -NH(2)-terminated group was systematically investigated using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS), UV-vis absorption. The optical, electrical and photoelectrochemical performance of CuS thin films incorporating with the X-ray diffraction (XRD) analysis confirmed the nanocrystalline nature of CuS with hexagonal crystal structure and also revealed that CuS thin film is a p-type semiconductor with high electrical conductivity (12.3Ω/□). The functionalized SAMs terminal group plays a key role in the deposition of CuS thin films. The growth of CuS on the varying SAMs surface shows different deposition mechanisms. On -NH(2)-terminated surfaces, a combination of ion-by-ion growth and cluster-by-cluster deposition can interpret the observed behavior. On -OH- and -CH(3)-terminated surfaces, the dominant growth mechanism on the surface is cluster-by-cluster deposition in the solution. According to this principle, the patterned CuS microarrays with different feature sizes were successfully deposited on -NH(2)-terminated SAMs regions of -NH(2)/-CH(3) patterned SAMs surface.     

Site selective micro-patterned rutile TiO2 film through a seed layer deposition

Micro-patterned films obtained from micro-contact printing (microCP) method are often challenged by site selectivity limitation. For applications site-selectivity requires improvements. In this paper a site-selective deposition of the rutile TiO2 thin films on patterned SnO2 film, which was formed on the patterned octadecyltrichlorosilane (OTS) SAMs through microCP is described. The depositions proceeded in an environmentally friendly aqueous solution (SnCl4 and peroxotitanium acidic solution) at a lower temperature (80 degrees C). It is shown that the OTS SAMs has a good selectivity deposition for SnO2 particles, which was mainly dominated by the heterogeneous nucleation mechanism. The SnO2 layer had a structure-directing effect for growth of the rutile TiO2, which was usually formed above 600 degrees C. The patterned films were characterized by a variety of techniques, including ellipsometry, optical microscopy, SEM, AFM, XPS, and DLS to determine the thicknesses, topologies, microstructures, chemical compositions of the films, particle sizes and zeta potentials of the titanium particles.     

Selective deposition in multilayer assembly: SAMs as molecular templates

Self-assembled monolayers (SAMs) on surfaces may be used as molecular templates for the selective deposition of polymer multilayer films. SAMs of ω-functionalized alkane thiolates are patterned onto gold surfaces with micron scale features using the microcontact printing method; glass substrates can also be patterned with trichloroalkylsilane SAMs. Patterned polymeric monolayer and multilayer films are adsorbed atop the SAM from dilute polymer solutions using ionic macromolecular self-assembly techniques which have been developed recently. The effects of polymer molecular weight and ionic content, as well as the use of a second SAM in the unpatterned regions to promote selectivity are discussed. Surface roughness, selectivity and other film properties are presented. It is demonstrated that this technique can be used successfully in the patterning of micron scale features with multilayers of low molecular weight upon adsorption from dilute solution.     

Thin films of Ag nanoparticles prepared from the reduction of AgI nanoparticles in self-assembled films

A novel method for the preparation of thin films of Ag nanoparticles is reported. Using mercaptoacetic acid as the stabilizing agent, AgI nanoparticles were prepared in aqueous solution. And based on electrostatic interactions, the thiol-passivated AgI nanoparticles were assembled in a self-assembled film by alternative deposition with a cationic polyelectrolyte. Then the AgI nanoparticles in the composite film were reduced by NaBH(4), which resulted in the formation of a thin film of Ag nanoparticles. UV-visible spectra and X-ray photoelectron spectroscopy data confirmed the transformation from AgI to Ag. Atomic force microscopy (AFM) showed that the formed Ag nanoparticles distributed on the film homogeneously. Surface-enhanced Raman spectroscopy (SERS) measurement indicated that the prepared thin films could be used as effective SERS substrates. The reduction process was also carried out by UV light at selective surface regions, which resulted in the formation of patterned nanoparticle arrays.     

Electron beam-treated organic monolayers as a negative resist for Cu immersion plating on Si

In the present work, we investigate selective immersion plating of Cu on n-type Si(111) surfaces chemically modified with different organic monolayers and subsequently directly patterned by an electron-beam (e-beam). The organic molecules (1-undecylenic acid, 1-decene and 1-octadecene) were covalently attached to a hydrogen-terminated Si surface. The use of such monolayers as masks for electroless copper deposition by immersion plating on Si surfaces was investigated. Clearly, a masking effect can be observed, the efficiency of which depends on the type of molecule. Further, the effect of e-beam irradiation to improve the masking properties of the organic monolayers was studied. For this, the monolayers were locally irradiated using a scanning electron microscope (SEM) equipped with a lithographic tool. The results show that e-beam-modified organic monolayers can be used as a negative tone resist for copper electroless plating. The selectivity of the Cu deposition at e-beam-untreated regions strongly depends on the applied e-beam dose and on the nature of organic molecules. By optimizing the electroless deposition parameters, homogeneous deposition with complete selectivity can be achieved, leading to high lateral resolution of the Cu patterns.Dedicated to Zbigniew Galus on the occasion of his 70th birthday.     

Preparation of silica-on-titania patterns with a wettability contrast

The preparation of patterned inorganic surfaces consisting of silica (SiO2) and titania (TiO2) is described. The approach is based on a combination of standard photolithography and plasma-enhanced chemical vapor deposition. Silicon wafers coated with a titania layer (40 nm) were patterned by use of a positive photoresist and then a thin silica layer (10-40 nm) was plasma-deposited. The photoresist was removed by decomposition at 800 degrees C. The inorganic patterned surfaces possessed excellent high-temperature resistance. Since the silica patches were effectively dehydroxylated during the thermal treatment, the patterns consisted of moderately hydrophobic (silica) and hydrophilic (titania) domains with a significant wettability contrast (40 degrees for water). The surface was further hydrophobized with a self-assembled monolayer of fluoroalkylsilane (FAS) and exposed to UV light. The FAS layer was locally oxidized on the TiO2 patches and the wettability contrast was maximized to 120 degrees (the highest possible value on smooth surfaces).     

Atomic/molecular layer deposited thin-film alloys of Ti-4,4'-oxydianiline hybrid-TiO(2) with tunable properties

By combining atomic layer deposition (ALD) and molecular layer deposition (MLD) thin-film techniques, the latter being a variant of the former in which organic precursors are used, it is possible to deposit thin films containing precisely controlled portions of inorganic and organic constituents. This in turn enables the adjustment of material properties by changing the number of ALD and MLD cycles applied during the deposition. In this work, the properties of such thin-film "alloys" prepared by varying the portions of Ti-4,4'-oxydianiline (Ti-ODA) inorganic-organic hybrid and TiO(2) in the structure were investigated. The films were deposited at 280 °C using TiCl(4) and water as precursors for TiO(2), and TiCl(4) and ODA for the Ti-ODA hybrid. The results demonstrate excellent tunability of the film properties such as degree of crystallinity, roughness, refractive index, and hardness depending on the relative number of TiO(2) and Ti-ODA cycles employed.     

Bioanalysis by Immobilization of Antibodies on Hafnium(IV) Oxide with 3-Aminopropyltriethoxysilane

Self-assembled monolayers of 3-aminopropyltriethoxysilane (APTES) are commonly used to promote adhesion between substrates and organic or metallic materials with applications ranging from advanced composites to biomolecular lab-on-a-chip devices. In this work, the silanization on hafnium oxide (HfO₂) films is reported. The layers of HfO₂ were deposited on Si (001) substrates by atomic layer deposition. The grown HfO₂ films were modified in accordance with three main steps: oxidation, silanization, and cross-linking of the APTES monolayer using glutaraldehyde as cross-linking agent. Microscopic features were characterized by atomic force microscopy. Further, both bovine serum albumin and antibovine serum albumin agents were deposited on the samples to test their potential use as the immunosensor.     

PET表面锐钛矿-板钛矿相TiO2薄膜的制备及表征

利用改进的溶胶-凝胶法在经表面改性的PET(聚对苯二甲酸乙二醇酯)表面制备得到TiO2薄膜. 利用X射线衍射(XRD)、原子力显微镜(AFM)、UV-Vis 透光率曲线、接触角测试仪等测试手段对TiO2样品的性能进行表征.结果表明, PET表面过渡层的引入有效地改善了有机基底与无机薄膜之间的界面相容性, 在其表面形成透明、均一、附着力良好且具有光催化活性的TiO2薄膜.通过控制实验过程, 在低温下成功制备了不同锐钛矿/板钛矿比的TiO2薄膜,同时发现适量板钛矿相的存在能有效提高薄膜的光致亲水性.