MOCVD生长铁电氧化物薄膜MO源研究进展

高性能铁电氧化物薄膜是当今功能材料的研究热点之一.随着新型MO源的不断研究与开发,利用MOCVD技术制备高质量铁电薄膜材料得到了快速的发展.本文在分析金属醇盐和金属β-二酮化合物等MO源的结构与其物性依赖关系基础上,分类综述了近年来在用于MOCVD方法生长铁电氧化物薄膜的新型MO源研究和开发方面的发展动态与趋势,为MOCVD方法制备铁电薄膜材料MO源的选择提供有用的参考与借鉴.     

Study of the Lead Environment in Liquid and As-Dried Precursors of PZ, PT and PZT Thin Films

The environment of lead and zirconium atoms in liquid and as-dried precursors for PbZrO3 (PZ), PbTiO3 (PT) and Pb1.1Zr0.53Ti0.47O3 (PZT) thin film deposition were analyzed by EXAFS. The sols were prepared by 2-methoxyethanol route with lead acetate and lead oxide as lead sources. Pb—O—M (M = Zr and/or Ti, depending on the sol composition) linkages were determined in all sols. The choice of lead source weakly influences the lead environment, and strongly influences that of zirconium in both PZ and PZT sols. By drying lead oxide based sols the Pb–M correlation is moderately reduced in PZ, PT and is strongly reduced in PZT.     

From Precursors to Thin Films - Thermoanalytical Techniques in the Thin Film Technology

Processing thin films for advanced applications, for instance in electronics and optoelectronics, involves several steps starting from precursor synthesis and ending up with the devices. Especially when optimizing the first steps of this chain of processes, thermoanalytical techniques play an important role. The review will focus on the main chemical deposition methods (CVD, ALE, spray pyrolysis, sol-gel) giving selected examples of problem-solving by thermal analysis. The techniques discussed are TG, DTA/DSC, EGA and their combinations. High-temperature X-ray diffraction (HTXRD) is also a powerful tool for in situ studies of thin films. The examples are taken from solar cell, superconductor and flat panel electroluminescent display technologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of the Structure of Precursors on the Crystallization of PbTiO3 Thin Films

PbTiO₃ (PT) thin films and their respective sols derived from three lead sources have been studied in order to elucidate the role of the starting materials in the crystallization of the products. EXAFS analysis of sols revealed similar oligomeric Ti-units in PT precursors derived from lead oxide or lead 2-methoxyethoxide acetate and a significantly different local Ti neighborhood in those derived from lead acetate. Structural details of the perovskite phase in the thin films follow the same pattern of similarity.     

Toward Photopatternable Thin Film Optical Sensors Utilizing Reactive Polyphenylacetylenes

Substituted polyphenylacetylenes featuring reactive pentafluorophenyl (PFP) ester moieties are synthesized. Parts of the reactive PFP groups are then converted with a mono ortho‐nitrobenzyl‐protected diamine in variable ratios. Thin films are prepared from these copolymers and irradiated with UV light (λ = 365 nm), resulting in crosslinking of the irradiated areas and hence enabling a photopatterning. We found that during the photocrosslinking process, the excess of PFP ester moieties is stable and remained intact, enabling a subsequent post‐polymerization modification step with amines. Noteworthy, this subsequent modification with amines results in a dramatically shift in the UV–vis absorption spectra, rendering these patterned conjugated polymer films ideal candidates for optical sensors.     

Liquid Film Deposition of Chalcogenide Thin Films

Thin films of MoS _x were prepared by liquid film deposition of MoS₄ ^2– solutions in 1,2-diaminoethane (en) and 1,2-diaminopropane (pn) and subsequent thermolysis at temperatures up to 800°C under N₂. As the coatings show a high carbon content of up to 30 at.% that influences the morphology and the physical properties, the precursor thermolysis and the solution properties were analysed in detail and correlated to the coating properties. A reduction of the intermediately formed MoS₃ by organic residues at approx. 300°C was made out as the main cause of the carbon contamination during the thermolysis of the precursor salts (enH₂)MoS₄ and (pnH₂)MoS₄, leading to an immobilisation of the organic carbon. In the corresponding solutions cations of the form [RNH₂...H...NH₂R]⁺ could be detected, that result in an incorporation of additional diamine with 3–4 molecules per MoS₄ ^2– ion in the wet films. This cross-linked structure on the one hand reduces the tendency of the precursor salts to crystallise and thus makes it easier to obtain amorphous precursor films, but on the other hand increases the content of organic residues before thermolysis.     

Kinetic Study of the Maillard Reaction in Thin Film Generated by Microdroplets Deposition

The Maillard reaction kinetics in the confined volume of the thin film produced by ESI microdroplet deposition was studied by mass spectrometry. The almost exclusive formation of the Amadori product from the reaction of D-xylose and D-glucose toward L-glycine and L-lysine was demonstrated. The thin film Maillard reaction occurred at a mild synthetic condition under which the same process in solution was not observed. The comparison of the thin film kinetics with that of the reaction performed in solution showed strong thin film rate acceleration factors.     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Atmospheric Pressure Plasma Deposition of Polyfuran

The atmospheric pressure radiofrequency (RF) plasma polymerization of furan was carried out with the objective of synthesizing polyfuran thin film. The structure, compositions and morphology of the plasma deposited polyfuran film were investigated by Fourier transform infrared (FTIR), atomic force microscopy (AFM), ultraviolet‐visible absorption spectroscopy (UV‐vis) and thermogravimetric analysis (TGA). The formation of polyfuran was confirmed using FTIR and UV‐visible analysis. The properties of plasma‐deposited polyfuran were compared with those of chemically synthesized polyfuran. Although the plasma deposited thin film polyfuran shows lower thermal stability than that of chemically synthesized polyfuran. It has better solubility in CHCl₃, also. Thin uniform polyfuran films are obtained in plasma assisted polyfuran deposition, while particles are obtained in chemical polyfuran polymerization.     

水溶液中电化学沉积GaSb相变存储薄膜

利用恒电位共沉积技术和热处理的方法成功制备了GaSb薄膜,探索了添加乙二醇溶剂对薄膜结晶性和形貌的影响. 采用循环伏安法初步研究了共沉积GaSb的机理,并用X-射线衍射技术（XRD）、扫描电子显微技术（SEM）和能谱分析（EDS）表征、观察样品. 研究表明,在沉积过程中,SbO⁺先还原成Sb单质,再诱导Ga³⁺发生共沉积;沉积电位对薄膜的结晶性、微观形貌和成分有显著影响;电解液加入乙二醇更利于在较正电位下直接沉积出GaSb,且有效地提高了薄膜的结晶度,改善了薄膜的微观形貌.     

金属β－二酮化合物用于MOCVD法生长铁电氧化物薄膜

对用于MOCVD法生长铁电氧化物薄膜的金属β－二酮化合物的制备、结构及性质进行了评述，对它们在生长铁电薄膜中的应用现状进行了介绍，并对它们的应用前景作了展望。     

自组装成膜技术制备TiO2薄膜的XPS研究

采用自组装成膜技术制备里TiO2薄膜,应用X射线光电子能谱研究自组装膜及其氧化膜和淀积的TiO2薄膜，结果表明，硅烷偶联剂成功地组装在玻璃基片上，足够长时间的氧化对使端基（-SH）完全氧化为磺酸基，淀积在基片上的TiO2膜牢固性好，平均膜厚在10nm．淀积膜中的钛可能有几种不同的氧化态，不同的酸度影响TiO2的淀积效果     

Encapsulation of Proteins in Bulk and Thin Film Sol-Gel Matrices

This paper considers the nature of the interactions between the sol-gel derived inorganic matrix and a specific biomolecule, cytochrome c. Optical absorption and impedance spectroscopies are used to characterize the influence of synthesis conditions on the protein’s stability and conformation within the silica matrix. In some instances, encapsulation within the sol-gel matrix provides stabilization. For example, protein denaturation is reversible and aggregation is prevented. Moreover, the drying process does not negatively affect the protein; it is possible to regenerate the aged gel state by rehydration. The flexibility of the sol-gel process enables high quality cytochrome c-doped SiO₂ thin films to be prepared. These films possess the characteristic reactivity and chemical function of cytochrome c in solution.     

Precise Control of Metal Oxide Thin Films Deposition in Magnetron Sputtering Plasmas for High Performance Sensing Devices Fabrication

Magnetron sputtering deposition is a widely used technique to deposit thin film precisely at nanoscale level. During the deposition of metal oxide thin films, reactive oxygen gas is introduced into the deposition chamber. Pure metal and metal oxide materials can be used as sputter target, although the simplest way is by using a pure metal target. In such reactive process, the effect of target poisoning significantly influence the deposition process and the growth mechanisms of metal oxide thin films became very complex. In general, external parameters such as discharge power, working pressure, reactive gases ratio and substrate temperature are used to optimize the properties of deposited thin films. Then, ex-situ analyses such as scanning electron microscope and X-ray diffraction analysis are performed to obtain the optimized parameter. Sample depositions and ex-situ analyses consume time to achieve the goal through try and error. In this article, in-situ plasma diagnostics are reviewed focusing on an optical emission spectroscopy to precisely control and investigate the sputter target poisoning effect during the deposition of metal oxide thin films. The emission of atomic lines from several metal and oxygen atoms were used to discuss the deposition mechanisms and their correlation with the deposited thin films was observed. Finally, the deposited metal oxide thin films were proposed and tested for several applications such as gas sensor and frequency selective surface glass.     

Deposition of Diamond-Like Carbon Film in a Closed-Space CH4 RF Plasma

Deposition of diamond-like carbon (DLC) film and mass spectrometry measurements were carried out in a closed-space CH₄ rf (13.56 MHz) plasma (without both gas injection and vacuum pumping during the process). At pressures less than 0.6 Torr, the thickness of the DLC film deposited increased with increasing elapsed deposition time, and reached a maximum value, but after this the film thickness started to decrease, which was considered to be caused predominantly by ion-induced sputter etching. The maximum film thickness appeared at larger elapsed time for higher deposition pressure. The mass concentrations of hydrocarbon ions indicated anomalous behavior at early deposition times, but those of higher hydrocarbon ions are clearly increased at the point where the film thickness started to decrease. These results suggested that the ratio of precursor CH₃al density to the total hydrocarbon ion density (_CH3/_ion in the CH₄a was an important factor for the carbon film formation, and when this ratio reduced to a certain critical value with increasing elapsed deposition time, the deposited film was then re-etched predominately by the secondary higher hydrocarbon ions. At 1.0 Torr where a polymer-like soft carbon film was deposited, such re-etching of the deposited film was not observed.     

Additive-Free Electrophoretic Deposition of Graphene Quantum Dots Thin Films

The electrophoretic deposition (EPD) of graphene-based materials on transparent substrates is highly potential for many applications. Several factors can determine the yield of the EPD process, such as applied voltage, deposition time and particularly the presence of dispersion additives (stabilisers) in the suspension solution. This study presents an additive-free EPD of graphene quantum dot (GQD) thin films on an indium tin oxide (ITO) glass substrate and studies the deposition mechanism with the variation of the applied voltage (10–50 V) and deposition time (5–25 min). It is found that due to the small size (≈3.9 nm) and high content of deprotonated carboxylic groups, the GQDs form a stable dispersion (zeta-potential of about −35 mV) without using additives. The GQD thin films can be deposited onto ITO with optimal surface morphology at 30 V in 5 min (surface roughness of approximately (3.1±1.3) nm). In addition, as-fabricated GQD thin films also possess some interesting physico-optical properties, such as a double-peak photoluminescence at about λ=417 and 439 nm, with approximately 98 % visible transmittance. This low-cost and eco-friendly GQD thin film is a promising material for various applications, for example, transparent conductors, supercapacitors and heat conductive films in smart windows.     

Low-Pressure Chemical Vapor Deposition of Silicon Carbide Thin Films from Organopolysilanes

(Me₃Si)₂SiMe₂, (Me₃Si)₃SiMe and (Me₃Si)₄Si were used as precursors for the deposition of polycrystalline β-SiC thin films on silicon substrates at 1000–1200°C in a low-pressure hot-wall chemical vapor deposition reactor. The thin films were analyzed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy.     

Soluble Powders as Precursors for TiO<Subscript>2</Subscript> Thin Films

Amorphous precursor powders have proven to be highly advantageous for the sol–gel processing of TiO₂ thin films. Oxide yield, density, solubility, and thermal degradation of powders prepared under various conditions were determined; the thermoanalytical data could be assigned to the oxidative decomposition of different organic constituents. Certain powders are suitable for the preparation of alcohol-based sols, whereas also aqueous coating solutions can be prepared from others. Thin films prepared from both systems show excellent adhesion and optical properties when deposited on borosilicate glass substrates.