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1、 3附件 3：作者姓名：作者姓名：汤庆鑫 论文题目论文题目：酞菁单晶微纳材料与微纳光电器件的研究 作者简介作者简介：汤庆鑫，男，1977 年 11 月出生，2004 年 9 月师从于中国科学院化学研究所胡文平教授，于 2007 年 7 月获博士学位。中中 文文 摘摘 要要 有机半导体材料具有质轻、价廉、柔性、制备工艺简单、种类繁多、性能各异以及分子构形和材料性能可人为设计等优点而受到人们的重视，被用于场效应晶体管、发光二极管和太阳能电池等分子电子学领域的研究中，取得了一系列研究进展。其中，有机场效应晶体管是有机半导体应用的一个重要方面，能够被用于高稳定性、低能耗的数字互补对称电路，而且其具有的
2、柔性特征使之可以被用作下一代柔性显示和照明设备等的驱动电路，具有广阔的应用前景。传统的有机场效应晶体管多采用有机薄膜作为半导体层传输电荷，但是有机薄膜中存在大量晶界和无序缺陷，这些缺陷在电荷传输时很容易束缚和散射电荷，降低器件性能。有机单晶中分子高度有序排列，不存在晶界和无序缺陷，能够有效提高器件的性能，是获得高性能光电器件的最佳选择之一，同时还能够反映材料本征性质，近年来受到人们的广泛关注。然而，有机晶体通常难于长大，多数以微纳晶的形式存在，因此，如果能直接在微纳晶的基础上构筑器件，开展研究，不仅能克服有机单晶难于长大的缺点，实现对材料的高效表征，同时也必将促进有机晶体和微纳光电子器件的融合
3、，推动纳米分子电子学的发展。酞菁（Pcs）类材料是目前最稳定的有机半导体之一，不仅具有良好的化学和热稳定性，同时具有很好的光电性能，在有机光电材料的研究中一直备受关注。本论文以酞菁材料为代表，开展了有机单晶微纳材料与微纳光电子器件的研究。主要内容如下：1.发展了一种普遍适用于有机微纳单晶制备的方法，成功获得了酞菁铜（CuPc）和氟代酞菁铜（F16CuPc）的单晶微/纳米带。采用温区变化相对剧烈、梯度可良好控制的两段控温管式电阻炉对CuPc和F16CuPc进行物理气相输运生长，成功获得了宽几十纳米到几微米，长几十微米的一维单晶微纳米带。这种方法具有良好的普适性，能够将其他多种有机半导体材料制备成
4、单晶微纳结构。使用高精度手动机械探针台实现了对CuPc微纳单晶带的操作，将单晶带精确移动到目标衬底上，使带与衬底表面良好贴和，为下一步电极沉积做好准备。利用开发的多次移动金丝掩模法，实现了无损真空镀膜蒸镀电极，成功制备了低阈值电压(-3 V)、高迁移率(0.2 cm2/Vs)的有机单晶微纳器件。2.机械移动有机单晶的过程中容易损伤晶体表面，降低器件性能，如果能在绝缘层表面原位生长有机单晶就能够有效克服这一问题。在先前物理气相输运生长有机半导体微纳结构的基础上，在沉积衬底上预先制备晶核，诱导CuPc纳米带的生长，获得了沿衬底表面平贴生长的单根CuPc纳米带和构成交叉、平行等多种构形的CuPc纳米
5、带。结合多次移动金丝掩模板法，直接将原位贴和于衬底表面的纳米带制备成器件，获得的器件具有更低的阈值电压(6104,which is in a class with the highest mobility for air-stable n-type OFETs.The performances of the transistors were highly 9reproducible.The excellent stability and electrical characteristics of F16CuPc transistors showed strong potential for f
6、uture application in organic electronics.4.Phototransistors have much higher sensitivity and lower noise than photodiodes and take the advantages to combine the light detection and signal magnification properties together to realize the greater functionality in a single device.It is an important ele
7、ment for the subject of optoelectronic integration.Since the first idea of phototransistor proposed by William Shockley in 1951,inorganic phototransistors have been developed fast and used in a variety of applications.However,few literatures have addressed the phototransistors of organic semiconduct
8、ors,especially of organic single crystals.Based on the previously fabricated F16CuPc single-crystalline submicro/nanoribbon transistors with asymmetrical electrodes,the photoresponse characteristics of F16CuPc devices were investigated.i)High quality photo switchers of F16CuPc single crystals were o
9、btained,which were capable to switch reversible and fast.ii)Single crystal field-effect phototransistors of F16CuPc individual submicro/nanoribbon exhibited strong photo dependence,i.e.,the light can act as an independent variable to control the output current of the single crystalline transistors.i
10、ii)The maximum on/off ratio of the phototransistor was at 4.5104(at gate voltage VG=-6.0 V),which was probably due to the gate applied bias providing an efficient way for the dissociation of the photo generated excitons,and which was beneficial for the formation of the conducting channel of the phot
11、otransistors.iv)The high light sensitivity,large on/off ratio of the phototransistors suggested their potential applications in optoisolators,optical switches,retro sensors and circuits etc.,which opened a new way to realize the light detection and signal magnification in a single organic device,ind
12、icating a future for low cost,ultrahigh density organic photoelectric integration.5.As we know,one main challenge for the fabrication of organic single crystalline OFETs is electrical contact.The conventional method for electrode fabrication is metal deposition on the single crystal or/and on the di
13、electric by evaporation or sputtering.On one hand,due to the fragility of the organic materials,high-temperature and high-energy metal atoms will damage the crystalline surface seriously and degrade the device performance.On the other hand,in the process of the metal deposition,the metal atoms easil
14、y fill the pinholes in the dielectric causing the high current leakages.This may conceal the properties of the organic materials,even may cause to fail in measuring the electrical properties of organic.i)One novel device fabrication method without thermal evaporation process for air-dielectric OFETs
15、 was developed to overcome the challenge.The FETs was composed of the Si wafer,the spin-coated polymethyl methacrylate(PMMA)supporting layer,the F16CuPc ribbon,and the 10stamped Au layers.The facile processability of the polymer PMMA and high rigidity of the Si material made it easy to create a free
16、-space gap by manipulating a mechanical probe to scratch the polymer layer coated onto a Si substrate.The Si substrate could directly serve as the gate electrode.The high tenacity and good tractility of the Au made it feasible to stamp the thin Au layers onto the submicro/nanoribbon as source/drain
17、electrodes.It should be addressed that the air-gap technique presented an all-dry manufacturing process except the spin coating of the PMMA layer.It not only avoided the use of toxic or environmentally harmful solvents,but also effectively avoided the wrinkles of the Au layer and the degradation of
18、the device performance.In addition,this technique eliminated the solid dielectric material,which simplified the process of device fabrication and provided a way to characterize organic semiconductors more effectively.ii)Based on this method,F16CuPc submicror/nanoribbon devices were fabricated,which
19、showed electron mobility as high as 0.35 cm2/Vs,and the on/off ratio were 3105.iii)The changing-temperature electrical properties of F16CuPc submicror/nanoribbon devices were measured in vaccum.With the increasing temperature,the mobility,initially rapidly increases(220-240 K),and then increases slo
20、wly(240-315 K).This shows that the transport in the vacuum dielectric F16CuPc ribbon device is thermally activated.iv)The transfer curves of F16CuPc air-dielectric devices by the continuously forward and reverse scan and multi-measured results hardly showed any hysteresis.The electrical characterist
21、ics of the devices measured in air were completely identical with those measured in vacuum.The multi-measured results also remained consistent in air and in vacuum.The characteristics of the device could be promptly restored to its original state once the illumination was terminated.The high electro
22、n mobility,excellent stability and high reproducibility showed the decreased defect density in air/vacuum dielectric devices than in SiO2 dielectric devices.6.Ambipolar OFETs have attracted considerable interest for realizing complementary-like organic integrated circuits,which operate with low powe
23、r dissipation,wide noise margins and great operational stability.However,until recently,there have been few reports on achieving ambipolar OFET operation.A main challenge is the efficient injection of both charge carriers.For most organic semiconductors,the ionization potential(the highest occupied
24、molecular orbital level,i.e.,HOMO level)has the same order of magnitude as the work functions of the usually used metal electrodes(for example,Au 5.2 eV).As a result,the barrier for hole injection is small,but the barrier for electron injection is large so that the device can not exhibit n-type oper
25、ation.By using narrow bandgap semiconductors,low-work-function metals,or asymmetric electrodes can reduce the injection barriers.However,the number of the narrow-bandgap organic semiconductors is very limited.There are still few metals 11which work functions match with the electron affinity(the lowe
26、st unoccupied molecular orbital level,i.e.,LUMO level)of organic semiconductors.Further,these metals are generally unstable(for example,Ca and Mg).The deposition of the asymmetric electrodes is relatively complex.Therefore,it is difficult for researchers to find really effective methods to resolve t
27、his problem.Another challenge for the realization of the ambipolar transport is the trapping of one or both carriers.For example,electrons are likely to be trapped by impurities,moisture,oxygen or hydroxyl groups of dielectric.As a result,the electron mobilities are generally much smaller than the h
28、ole mobilities in ambipolar devices.These trapping effects can be weakened or prevented by using high pure materials,processing in an inert atmosphere,and using hydroxyl-free dielectric.However,the rigorous operation environment enhances the difficulty of organic device physics research and applicat
29、ions.Therefore,air-stable ambipolar OFETs are an important issue in organic electronics.Finally,high charge mobility is required in all organic transistors in order to build electronic circuits with high-frequency operation.However,due to the above-mentioned difficulties for effective injection and
30、transport of both carriers in ambipolar OFETs,most devices show low hole and electron mobilities in 10-4 to 10-3 cm2V-1s-1 range,which are even lower than those values in the corresponding unipolar OFETs.As a result,low mobility is still a limitation for ambipolar OFETs.i)Evoking by the advantages o
31、f the good stability and high mobilities of CuPc and F16CuPc,and the great advantages of air dielectric for the investigation of organic semiconductors,series of ambipolar transistors were fabricated by using air-gap dielectric technique based on single crystalline submicrometer ribbons of CuPc and
32、F16CuPc.ii)The ambipolar devices showed excellent air-stable characteristics with electron and hole mobilities as high as 0.17 and 0.1 cm2/Vs,respectively.iii)The symmetrical ambipolar characteristics,the high electron and hole mobilities,and the excellent air stability indicate the potential applic
33、ations of the ambipolar devices in organic integrated circuits.7.Some fundamental and novel properties of CuPc and F16CuPc sub-micro/nanomaterials and devices have been studied,These studies are important for researchers to understand the structural,mechanical,and optoelectronic properties of Pcs.i)
34、To apply these organic micro/nanoribbons on flexible electronic devices,it is important to understand their mechanical properties,the corresponding response to external force,the effect of the mechanical properties on the growth,and their relation with electrical properties.We took CuPc and F16CuPc
35、micro/nanoribbons as the example,to show their flexibility and resistance to fracture by directly manipulate the single micro/nanoribbon with the tip of one mechanical probe under the observation of optical microscope and SEM.ii)The effects of mechanical bending on electrical properties of single mi
36、cro/nanoribbons were experimental studied by straight and 12curving micro/nanoribbon devices fabricated on the low-cost flexible substrates with electrode adherence technique.iii)Mechanical assembly of high performance organic field-effect transistors and circuits on soft substrates was performed by using organic single crystalline nanoribbon as semiconductor,polymer layer as gate insulator and transparent-conductive-nanoribbon as source and drain electrodes,respectively.Key words:Phthalocyanines;single crystal;submicro/nanoribbons;field-effect transistors