自组装法制备Au纳米结构衬底及其表面增强荧光效应研究

采用自组装方法,在(APS)分子修饰后的玻璃衬底 表面,制备得 到Au纳米结构衬底。采取激光光谱学方法,研究所制备衬底对沉积其表面的Rhodamine 6G(R h6G) 分子的荧光辐射增强效应。实验发现,利用自组装方法制备的Au纳米结构衬底具有较强的荧 光增 强特性。理论分析表明,制备的Au纳米结构在外光场激发下,所形成的强局部电磁场分布 能够有效提升探针分子的电子跃迁速率,从而实现增强荧光效应。     

红荧烯薄膜在Bi(0001)表面从高阶公度相到非公度相转变

在红荧烯薄膜中发现了一类新的相变:分子从高阶的公度相转变到弱的非公度相.前者表现出"格点位于线上"(point-on-line)关系;后者是一种混合相,包含红荧烯的晶态畴和自组装的畴壁.相比于红荧烯晶体的a-b面,晶态畴中存在着极大的各向异性应变.通过改变衬底的温度,发现在室温下畴壁呈现出"之"字型网状结构;而在高温下...     

美国科学家研制出单分子晶体管

美国朗讯贝尔实验室用一个单一的有机分子制造出了世界上最小的晶体管，针尖般大小的尺寸上可以容纳１０００万个这种晶体管，这种晶体管将会导致更小的芯片诞生。据美国《科学》周刊报道，这种晶体管被称为“纳米晶体管”，大小接近１nm。这种晶体管以碳为基础，包含氢和硫的有机半导体分子为晶体管材料，以金原子层为电极。包括两名中国科学家在内的研究小组，设计了一种“自组装”工艺，设法让分子自己找到接触点并进行“自组装”，而且这种化学“自组装”技术与硅晶体管的制造工艺相比更容易和便宜。这种晶体管是微型化的终极，但在真正…     

C60自组装单分子膜的摩擦行为研究

随着高新技术的发展对润滑提出了更高要求 ,借助分子自组装技术 ,期望把长链化合物或聚合物的一端置入摩擦表面 ,形成一层“分子刷” ,以达到降低摩擦磨损的目的。这一概念在纳米摩擦学中尤其引人注目。即利用化学的方法 ,在诸如ＭＥＭｓ等机件摩擦表面建立起一层高度定向致密的超薄有机膜 ,以减少其摩擦损伤 ,延长使用寿命。可以预计分子自组装技术对纳米摩擦学基础及应用研究将将起到巨大的推动作用。本工作选用含端氨基的氨基酸在银基底形成的自组装膜表面通过氨基与Ｃ6 0反应制备了Ｃ6 0单分子膜 ,研究了Ｃ6 0分子自组装膜的微观摩擦行…     

极性自组装单层膜取向铁电液晶器件

采用极性自组装单层膜和摩擦的方法制备了非对称的液晶盒.在铁电液晶相变的过程中不施加电场,得到了排列均一的铁电液晶器件.实验表明:极性自组装单层膜极性越大器件的对比度越高.经过分析得出该器件液晶分子取向机理为:基板附近的铁电液晶通过偶极和极性自组装膜的作用,使得靠近自组装膜表面处的偶极和靠近摩擦表面的偶极的指向相同,通过分子的相互作用使得体内分子排列方向一致.     

科技简讯

日本TDK公司新近在3in硅(Si)基板上形成均匀的强介电体单晶薄膜获得成功.新方法,通过采用适于强介电体膜形成的新的缓冲层和Si基板前处理方式及使金属和氧反应方法达最佳化,可在3in整个基板面上使均匀的氧化物薄膜外延生长.首先在硅基板上形成达分子级平坦程度的氧化锆单晶薄膜作为绝缘膜缓冲层,然后在其上面形成钙钛矿系介电体单晶薄膜.进而,采用同样的生长方法,使新材料YMnO_3系强介电体生长,使其形成晶格有序的单晶膜.这种YMnO_3系单晶膜形成ZrO_2和晶格有序排列的异质外延结构.通过在此基本结构的表面形成金属电极,可获得MFIS结构.这种结构便成为栅形强介电体存储器的基本靶结构,这种单晶YMnO_3系薄膜,     

信息园

科学家发现新一代半导体材料南京大学、中科院物理所和摩托罗拉中国研究院2 5日在京宣布 ,他们发现铝酸镧 (LAO)和镧铝氧氮(LAON)这两种材料在所有候选的高介电常数材料中具有最好的热稳定性 ,能很经济地集成到传统的半导体工艺过程中 ,有希望在 6 5纳米以下工艺中替代二氧化硅 ,用作半导体晶体管的栅介质层 ,或者用作半导体电容的介电材料 ,有望代替传统的二氧化硅 ,从而在下一代的半导体元器件制造中扮演重要角色。据报道 ,自半导体工业开始 4 0多年来 ,二氧化硅一直被用作晶体管中的栅介质和电容介质。随着半导体集成电路加工工艺的不…     

有机酸修饰ITO对OLED器件性能的影响

分别采用二氯苯氧乙酸和溴乙酸对ITO表面进行修饰,研究其对OLED器件(ITO/PVK/ FIrPic:SimCP/TPBi/LiF/Al)性能的影响.结果显示,相较于未修饰的器件,采用二氯苯氧乙酸修饰后的器件最大亮度由673.4 cd/m2提升至1 875.2 cd/m2,同时器件的启亮电压由6.2V降至5.3V.研究发现,有机酸处理能够改变ITO的表面能和功函数,一方面改变ITO和后续膜层的接触性能,影响后续膜层的成膜;另一方面也可以有效减少ITO与有机层间的势垒,提升载流子注入.这种用有机酸修饰ITO阳极的方法工艺简单,能有效降低空穴注入势垒,优化ITO和有机层的接触性能,对器件性能的提升起到一定的促进作用.     

微接触印刷法制备图形化自组装膜

复微接触印刷技术成功地制备了由不同末端官能团组成的图形化自组装膜。详细讨论了“印章”上图案的高度以及作为“印尼”的自组装分子的性质对制备图形化自组装膜的影响,结果表明,选择具有低蒸气压,在金表面非反应铺展的自斥性硫醇分子溶液作“印泥”有利于自组装人在接触区形成。“印章”上图案的凸起应有一定高度,否则“图形”难以形成。     

基于自组装工艺的ZnO纳米线网络晶体管

本文提出了一种,制备均匀高密度ZnO纳米线网络的简单高效的自组装方法。在此方法中,ZnO纳米线经3-氨丙基三乙氧基硅烷修饰后,其表面出现带正电的氨基功能团。经亲水性处理后的SiO2层在水中带负电,从而凭借静电吸引作用,修饰后的ZnO纳米线吸附在SiO2/Si基底,形成纳米线网络。利用此纳米线网络制备得场效应晶体管。纳米线密度为2.8/μm2的晶体管,其电流开关比为2.4×105,跨导为336 nS, 场效应迁移率为27.4 cm2/V?s.     

Simultaneous Modification of Bottom‐Contact Electrode and Dielectric Surfaces for Organic Thin‐Film Transistors Through Single‐Component Spin‐Cast Monolayers

An efficient process is developed by spin‐coating a single‐component, self‐assembled monolayer (SAM) to simultaneously modify the bottom‐contact electrode and dielectric surfaces of organic thin‐film transistors (OTFTs). This effi cient interface modifi cation is achieved using n‐alkyl phosphonic acid based SAMs to prime silver bottom‐contacts and hafnium oxide (HfO₂) dielectrics in low‐voltage OTFTs. Surface characterization using near edge X‐ray absorption fi ne structure (NEXAFS) spectroscopy, X‐ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, atomic force microscopy (AFM), and spectroscopic ellipsometry suggest this process yields structurally well‐defi ned phosphonate SAMs on both metal and oxide surfaces. Rational selection of the alkyl length of the SAM leads to greatly enhanced performance for both n‐channel (C₆₀) and p‐channel (pentacene) based OTFTs. Specifi cally, SAMs of n‐octylphos‐phonic acid (OPA) provide both low‐contact resistance at the bottom‐contact electrodes and excellent interfacial properties for compact semiconductor grain growth with high carrier mobilities. OTFTs based on OPA modifi ed silver electrode/HfO₂ dielectric bottom‐contact structures can be operated using < 3V with low contact resistance (down to 700 Ohm‐cm), low subthreshold swing (as low as 75 mV dec^?1), high on/off current ratios of 107, and charge carrier mobilities as high as 4.6 and 0.8 cm² V^?1 s^?1, for C60 and pentacene, respectively. These results demonstrate that this is a simple and efficient process for improving the performance of bottom‐contact OTFTs.     

Organic Thin‐Film Transistors: Simultaneous Modification of Bottom‐Contact Electrode and Dielectric Surfaces for Organic Thin‐Film Transistors Through Single‐Component Spin‐Cast Monolayers (Adv. Funct. Mater. 8/2011)

An efficient process is developed by spin‐coating a single‐component, self‐assembled monolayer (SAM) to simultaneously modify the bottom‐contact electrode and dielectric surfaces of organic thin‐film transistors (OTFTs). This effi cient interface modifi cation is achieved using n‐alkyl phosphonic acid based SAMs to prime silver bottom‐contacts and hafnium oxide (HfO₂) dielectrics in low‐voltage OTFTs. Surface characterization using near edge X‐ray absorption fi ne structure (NEXAFS) spectroscopy, X‐ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, atomic force microscopy (AFM), and spectroscopic ellipsometry suggest this process yields structurally well‐defi ned phosphonate SAMs on both metal and oxide surfaces. Rational selection of the alkyl length of the SAM leads to greatly enhanced performance for both n‐channel (C₆₀) and p‐channel (pentacene) based OTFTs. Specifi cally, SAMs of n‐octylphos‐phonic acid (OPA) provide both low‐contact resistance at the bottom‐contact electrodes and excellent interfacial properties for compact semiconductor grain growth with high carrier mobilities. OTFTs based on OPA modifi ed silver electrode/HfO₂ dielectric bottom‐contact structures can be operated using < 3V with low contact resistance (down to 700 Ohm‐cm), low subthreshold swing (as low as 75 mV dec^?1), high on/off current ratios of 107, and charge carrier mobilities as high as 4.6 and 0.8 cm² V^?1 s^?1, for C60 and pentacene, respectively. These results demonstrate that this is a simple and efficient process for improving the performance of bottom‐contact OTFTs.     

Direct Patterning of Self‐Assembled Monolayers by Stamp Printing Method and Applications in High Performance Organic Field‐Effect Transistors and Complementary Inverters

Self‐assembled monolayer (SAM) is usually applied to tune the interface between dielectric and active layer of organic field‐effect transistors (OFETs) and other organic electronics, a time‐saving, direct patterning approach of depositing well‐ordered SAMs is highly desired. Here, a new direct patterning method of SAMs by stamp printing or roller printing with special designed stamps is introduced. The chemical structures of the paraffin hydrocarbon molecules and the tail groups of SAMs have allowed to use their attractive van der Waals force for the direct patterning of SAMs. Different SAMs including alkyl and fluoroalkyl silanes or phosphonic acids are used to stamp onto different dielectric surfaces and are characterized by water contact angle, atomic force microscopy, X‐ray diffraction, and attenuated total reflectance Fourier transform infrared. The p‐type dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (DNTT) and n‐type F₁₆CuPc OFETs show competitive mobility as high as 3 and 0.018 cm² V^?1 s^?1, respectively. This stamp printing method also allows to deposit different SAMs on certain regions of same substrate, and the complementary inverter consists of both p‐type and n‐type transistors whose threshold voltages are tuned by stamp printing SAMs and shows a gain higher than 100. The proposed stamp or roller printing method can significantly reduce the deposition time and compatible with the roll‐to‐roll fabrication.     

Growth of rubrene crystalline thin films using thermal annealing on DPPC LB monolayer

High crystalline thin films of 5,6,11,12-tetraphenylnaphthacene (rubrene) can be obtained after in situ thermal post annealing using SiO₂ gate dielectric modified with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer obtained via Langmuir–Blodgett transfer. Such formed rubrene crystalline films are interconnected and highly ordered with defined molecular orientation. Organic thin film transistors (OTFTs) with high performance are reproducibly demonstrated with the mobility of 0.98 cm²/V s, the threshold voltage of −8 V and the on–off current ratio of higher than 10⁷. The results indicate that our approach is a promising one for preparing high quality rubrene crystalline films.     

Transparent organic thin-film transistors based on high quality polycrystalline rubrene film as active layers

Transparent organic thin-film transistors (OTFTs) with high performance are demonstrated by using high quality polycrystalline 5,6,11,12-Tetraphenylnaphthacene (rubrene) as an active layer, which is prepared by weak epitaxy growth (WEG) method. Benefiting from epitaxial relationship is formed between the inducing layer and the rubrene films, highly oriented and continuous organic polycrystalline thin films with large grains were obtained, which enhances the carrier transport in the film plane. The mobility of devices reaches 1.3 cm²/Vs, the threshold voltage is lower than ?0.9 V and the on–off current ratio (I_on/I_off) is higher than 10⁶ after the photolithography process. Moreover, the array consisting of the transparent thin-film transistors displays a high optical transparency more than 65% in visible light regions. The high-performance transparent OTFTs promote the practical applications for large-area and flexible active-matrix organic light-emitting diodes (AMOLEDs) display.     

Rubrene thin-film transistors with crystalline channels achieved on optimally modified dielectric surface

We report on the fabrication of rubrene thin-film transistors (TFTs) with surface-modified dielectrics adopting several kinds of self-assembled-monolayer (SAM) on SiO₂/p⁺?Si substrate. With the dielectric of lower surface energy, the crystalline rubrene growth or amorphous-to-crystalline transformation kinetics is faster during in-situ vacuum post-annealing, which was performed after rubrene vacuum deposition. In the present study, hexamethyldisilazane (HMDS) was finally determined to be the most effective SAM interlayer for polycrystalline rubrene channel formation. Our rubrene TFT with HMDS-coated SiO₂ dielectric showed quite a high field mobility of ～10^?2 cm²/V s and a high on/off current ratio of ～10⁵ under 40 V.     

Valence band structure of rubrene single crystals in contact with an organic gate dielectric

Organic field effect transistors (OFETs) using crystalline organic semiconductors are of great interest because of their well-defined structural and electronic properties to study the intrinsic charge carrier transport mechanisms in π-conjugated molecular solids, as well as to unravel their potential to be applied as a novel type of electronic device. In the present study, the valence band structure of the channel region of an OFET is proposed based on photoemission results of a well-defined interface between a dielectric molecular monolayer and single crystals of 5,6,11,12-tetraphenyltetracene (rubrene) which is known to exhibit the highest field effect mobility of all organic semiconductors at room temperature. Commensurate growth of clusters of tetratetracontane (TTC; n-C₄₄H₉₀) on the rubrene single crystal surface and their morphological transformation into a uniform overlayer were observed by atomic force microscopy. Photoelectron spectroscopy measurements at various electron take-off angles were then conducted to derive the valance band width of the rubrene single crystal covered by the TTC overlayers. The valence band width at this hetero-interface was found to be equivalent to that of the pristine rubrene, which suggests an unchanged ‘band effective mass ?²(d²E/dk_||²)’ of accumulated holes even at the vicinity of hydrocarbon-based gate dielectrics.     

High performance organic thin film transistors using chemically modified bottom contacts and dielectric surfaces

A compatible process of orthogonal self-assembled monolayers (SAMs) is applied to intentionally modify the bottom contacts and gate dielectric surfaces of organic thin film transistors (OTFTs). This efficient interface modification is first achieved by 4-fluorothiophenol (4-FTP) SAM to chemically treat the silver source–drain (S/D) contacts while the silicon oxide (SiO₂) dielectric interface is further primed by either hexamethyldisilazane (HMDS) or octyltrichlorosilane (OTS-C8). Results show that the field effect mobilities of the bottom-gate bottom-contact PTDPPTFT4 transistors were significantly improved to 0.91 cm² V⁻¹ s⁻¹.     

Effect of hydroxyl density on condensation behaviors of self-assembled monolayers and performance of pentacene-base organic thin-film transistors

A series of self-assembled monolayers (SAMs), comprising octadecyltrichlorosilane (ODTS), dodecyltrichlorosilane (DDTS), and hexamethyldisilazane (HMDS), were prepared to examine the effects of phase states and condensation behaviors of SAMs on the morphologies and performance of pentacene-based organic field-effect transistors (OFETs) by means of Fourier Transform Infrared (FT-IR) spectrometer, atomic force microscope (AFM), X-ray diffraction (XRD), and semiconductor parameter analyzer. Experimental results reveal that the treatment of SiO₂ substrates with O₂ plasma (denoted as O₂-SiO₂) and the preparation temperature of SAMs dramatically influence the morphologies of SAMs and the performance of corresponding pentacene-based (no purification) OFETs. When the SAMs were prepared at 30 °C, the OFET based on ODTS-treated O₂-SiO₂ substrate had the highest hole mobility, reaching as large as 1.15 cm² V^?1 s^?1, and an on/off current ratio in excess of 10⁵; these values are both much larger than those of a device based on ODTS-modified SiO₂ substrates without O₂ plasma treatment and O₂-SiO₂ substrates modified by ODTS SAMs prepared at other temperatures. OFETs based on O₂-SiO₂ substrates that were modified by DDTS and HMDS SAMs prepared at 4 °C performed best.     

High-speed organic single-crystal transistors gated with short-channel air gaps: Efficient hole and electron injection in organic semiconductor crystals

Short-channel, high-mobility organic filed-effect transistors (OFETs) are developed based on single crystals gated with short-channel air gaps. The high hole mobility of 10 cm²/Vs for rubrene, and high electron mobility of 4 cm²/Vs for PDIF-CN₂ crystals are demonstrated even with a short channel length of 6 μm. Such performance is due to low contact resistance in these devices estimated to be as low as ～0.5 kΩ cm at gate voltage of ?4 V for rubrene. With the benefit of the short channel length of 4.5 μm in a new device architecture with less parasitic capacitance, the cutoff frequency of the rubrene air–gap device was estimated to be as high as 25 MHz for drain voltage of ?15 V, which is the fastest reported for p-type OFETs, operating in ambient conditions.