Trichlorosilanes As Anchoring Groups for Phenylenethiophene Molecular

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FULL PAPER 1 Con- eld effect The mol- [ 18,19 ] [ 12 ] wileyonlinelibrary.com www.afm-journal.de The breakthrough uence on the device [ 14,16 ] Dolores Caras- ectance – Fourier transform ectance – Fourier 1 µm, due to high contact resist- >

Early attempts to fabricate SAMFETs attempts to fabricate SAMFETs Early lms were characterized by atomic force -conjugated cores. chemical sensors where direct access to chemical sensors where layer by analytes the charge transport will have a strong infl properties. resulted in poor performance at channel lengths ance and poor long range order of the π was achieved when Smits et al. reported a was achieved when Smits et al. reported SAMFET molecule consisting of a monochlorosilane anchoring group separated could be obtained eld effect characteristics [ 8–11,17,25,26 ] Further, the introduction of the phenylene units the introduction of the phenylene Further, [ 19–21 ] Herein, we report a novel p-type SAMFET molecule we report Herein, jugated mesogens based on a phenylene-bithiophene core due (PTTP) are promising semiconductors employed in OFETs to the simple synthesis and favorable liquid crystalline phase behavior. ecule showed long range order when deposited onto a silicon ecule showed long range order when deposited dioxide surface and fi to 40 µm. SAMFETs over large areas for channel lengths up acid anchoring have now been reported using phosphonic oxide and alternative groups to covalently attach to aluminum transistors over long aromatic cores to create p- and n-type channel lengths. infrared (VATR-FTIR) spectroscopy. spectroscopy. infrared (VATR-FTIR) anchored through a trichlorosilane to give working fi anchored through a trichlorosilane to give lengths (100 µm). transistors for devices with long channel accelerated deposition The use of a trichlorosilane allows an areas with minimal of a continuous monolayer over large post processing. The fi (XPS) and photoelectron spectroscopy microscopy (AFM), X-ray variable angle attenuated total refl 2. Results and Discussion 2.1. Molecular Design Considerations of the SAM molecule The choice of the semiconducting core is crucial to the realization of high-performance SAMFETs It has with a dense and ordered semiconducting monolayer. been recognized that conjugated mesogens can be self-organ- ized into large area monodomains without defects caused by grain boundaries by processing in the mesophase. lowers the HOMO level leading to improved device stability in ambient, humid conditions relative to that of the analogous from a quinquethiophene core by an alkyl spacer. spacer. from a quinquethiophene core by an alkyl

lms, covalently lms, [ 8–14,16 ] eld of

, currents of up to 15 µA 1 − [ 1–16 ] s 1 − V 2 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2014 WILEY-VCH Verlag © lms from the bottom lms from the bottom cm 2 − 10 × eld effect transistors (SAMFETs) eld effect transistors (SAMFETs) eld effect transistors (SAMFETs) are reported transistors (SAMFETs) eld effect ) with device yields close to unity over large areas ) with device yields close to unity over 6 eld effect transistors (OFETs). eld effect transistors (OFETs). , 2014

, Leszek A. Majewski , and Michael L. * Turner

-conjugated semiconducting core that is coupled to a π

Self assembled monolayer fi DOI: 10.1002/adfm.201401392 Dr. A. V. S. Parry, Dr. K. Lu, Dr. D. J. Tate, D. J. Tate, K. Lu, Dr. Dr. S. Parry, A. V. Dr. D. Caras-Qintero, Dr. B. Urasinska-Wojcik, Dr. Prof. M. L. Turner School of Chemistry University of Manchester Manchester M13 9PL , UK E-mail: [email protected] L. A. Majewski Dr. School of Electronics and Electronic Engineering University of Manchester Manchester M13 9PL , UK The principal building blocks of these devices are molecules The principal building blocks of these with a have been demonstrated consisting of a single molecular layer have been demonstrated consisting of a self assembled from solution. of organic semiconductor, for channel lengths up to 100 µm. DOI: 10.1002/adfm.201401392 Adv. Funct. Mater. Funct. Adv. up. SAMs have been extensively used to modify the surface of up. SAMs have been extensively used to have recently shown dielectric layers and metal electrodes but or semicon- great promise as single molecular layer dielectrics ductors in organic fi 1. Introduction (SAMs) are dense molecular layers Self assembled monolayers from solution. They deposited at an interface spontaneously electronics for have become a critical technology in organic the deposition of functional nanoscale fi using a phenylene-thiophene containing semiconducting mesogen attached containing semiconducting mesogen using a phenylene-thiophene anchoring group. Monolayer fi through a trichlorosilane in less than 10 h from solution, attached to silicon dioxide substrates, form Devices trichlorosilane anchor. thanks to the accelerated reaction of the exhibit mobilities as high as 1.7 Self assembled monolayer fi Self assembled monolayer Adam V. S. , Parry Kexin Lu , Daniel J. , Tate Barbara , Urasinska-Wojcik Thiophene Molecular Monolayer Field Effect Transistors Transistors Field Effect Monolayer Molecular Thiophene Trichlorosilanes as Anchoring Groups for Phenylene- Groups as Anchoring Trichlorosilanes Quintero surface anchoring group capable of covalently binding to a sur- monolayer between face. These molecules create a self-limiting source and drain contacts that functions as a two dimensional comparable in thickness to the charge charge transport layer, accumulation layer in a device. Thanks to this two dimensional show great potential in the fi transport layer SAMFETs (on/off current ratio of 10 www.MaterialsViews.com FULL PAPER 2 wileyonlinelibrary.com ible dodecane(C 4 et al.(33ppmPt,80eqsilane,90 sion underoptimumconditionsdeterminedbyPonomarenko compounds tion of smoothly toyieldcompound ment with Scheme1. 0.5 mgmL of compound glove boxandplacedinasealedvesselcontainingsolution in UV-Ozone. Thesubstratesweretransferredintoanitrogen in acetone,propan-2-olandmethanolfollowedbyactivation the silicondioxidesubstrateswererinsedandsonicated tric respectively. To enhancetheanchoringofsilanesto mally grownoxidewereusedasthegateelectrodeanddielec- Highly doped(n++) siliconsubstrateswith300nmofther- Devices and SAMs of Fabrication 2.3. homeotropically alignedfi (I-SmA-G), mesogen,allowedmeltprocessingof inaPTTP oligothiophenes. Thesequenceofliquidcrystallinephases www.afm-journal.de interaction betweenadjacentmolecules. dehydrohalogenation upontreatmentwith 1,12-dibromododecane toafford In brief, Compounds Synthesis 2.2. the trichlorosilaneanchoringgroup. polarizers (seeSupporting Information). indicated byatypicalfantexturewhenviewedbetweencrossed ited anarrowsmecticmesophasebetween214 olayer, n-hexyl(C chosen asthesemiconductingcoreformolecularmon- material andimpurities,followed bydryingunderastreamof solvent andsonicatedfor30 minutes toremovephysisorbed tion forbetween1hand7days, transferredtoavialofclean PTFE syringefi coupling between ii ) ) waspreparedaccordingtotheprocedureofHu etal. t BuOK/THF, 95%; 6 withdimethylchlorosilaneortrichlorosilaneafforded Synthetic schemeforsynthesisofSAMFETmaterials,compounds 1 waslithiatedwith n − -BuLi andtributyltinchlorideafforded 1 7a 7a (3m and lter. Thesubstrateswereincubatedinthissolu- 7a and 12 or 6 ) chainastheend-cappinggroupandafl 3 ) spacerlinkedthesemiconductingcoreto M iii and 7b 7b ) 1. ) thathadbeenfi 7b respectivelyinnearquantitativeconver- werepreparedasdepictedin n inchloroformataconcentrationof -Buli/THF 2.Bu 5 lms andstrongintermolecular withPd(PPh n 6 -BuLi, followedbyworkupwith inexcellentyield.Hydrosilyla- 2 , whichinturnunderwent ° C). ltered througha0.2 3 SnCl, 84%; [ 23]

3 [ 19] ) Compound 4 inDMFproceeded Hence,was PTTP © t BO. Compound BuOK. 2014WILEY-VCHVerlag GmbH&Co. KGaA, Weinheim ° C and218 iv 5 ) Pd(PPh ) . Stillecross Scheme [ 22] 6 exhib- Treat- 3 π ) ex- μ 4 ° –

/DMF/ m 1 C π .

derivative ( tion of The growthandmorphologyoftheSAMsformedbydeposi- Microscopy Force Atomic 2.4.1. Analysis Monolayer 2.4. areas (4cm effect transistorswerefabricatedinlessthan10hoverlarge a shadowmasktonominalthicknessof50nm. by theevaporationofgoldsourceanddrainelectrodesthrough 120 nitrogen. Thesubstrateswereannealedonahotplatefor2hat reported quinquethiophenederivative. monolayers fromthiscompound,incontrasttothepreviously silicon dioxidesurfaceanditwasnotpossibletoformcomplete copy. Themonochlorosilanederivative( methyl groupsbondedtosilicon, free monochlorosilane(identifi that alargeportionofthesolution wasstillintheformof of aliquotstakenduringthe depositionprocessconfi between thesourceanddrain electrodes.NMRspectroscopy properties duetolimitedpercolation pathsforchargecarriers fi polar silicondioxideinhibitsthegrowthoffullmonolayer action betweentheconjugatedsemiconductingcoreand the solutionreachesequilibriumwithsubstrate.Theinter- tion betweenthesurfaceandchlorosilaneissoslowthat removed bysonication.Itappearsthatthecondensationreac- tion ofsomelargerislandsandaggregatesthatcouldnotbe the coverageincreasestoapproximately35%withforma- stand inamoreuprightposition.Afterimmersionfor3days larger heightprofi the substratesurface.Thepresenceoflargerislands,with a 7a height, whichisslightlylowerthanthepredictedheightof line scanshowsthattheislandsareapproximately3nmin (<100 nm)andcoverapproximately25%ofthesurface.A (Figure S14,Supporting Information) theislandsaresmall observed evenafterseveraldaysinsolution.After1day slow growthrateandincompletemonolayerformationwas lms. Attempts tofabricateOFETdevicesledinsulating Δ 7a , 85%; (3.5nm),suggestingthatthemoleculesaretiltedtoward The monochlorosilane( and ° C toremoveresidualsolvent.Transistors werecompleted 7b 7a v ) Karstedt’sCatalyst/SiX . Reagents: and 7b 2 ) forlongchannellengths(upto100µm). ) wasmorereactiveandworkingmonolayerfi 7b le (4.5nm)suggeststhatthesemolecules wereinvestigatedbyatomicforcemicros- i ) 1. n -BuLi,/THF, 2.1,12-dibromododecane,71%; 7a ) showedaverylowreactivityat 2 ClH/toluene/ ed bythepresenceoftwo δ

= 0.41ppm)conﬁ DOI: 10.1002/adfm.201401392 [ 12] www.MaterialsViews.com Thetrichlorosilane Δ , 100%. Adv. Funct. 7a ) exhibiteda

Mater. rming rmed

2014 eld , FULL PAPER 3 ,ip)) 3 and 1 shows − , SAMs 2 absorp-

2 (CH )) absorp- 7b a 3 ν To investi- ( 3 (CH lms deposited Figure [ 1,24 ] s ν wileyonlinelibrary.com www.afm-journal.de ( 3 rm the presence of cant portion of the and Fermi resonance and Fermi contained no chlorine 3 7b lms of compound lm with those assigned for lm (Supporting Information lm (Supporting were obscured by the other 3 ) fi lm. In contrast fi lms are consistent with a highly 7b and the in-plane CH 1 − 0.053, the measured value from XPS )) are observed at 2851.6 cm )) are 2 = (CH a ν rmation of surface coverage by the semicon- . The out-of-plane CH . The out-of-plane The SAMFET fi 1 ), is 2/38 compares the peak positions of the CH stretches − 2 1

[ 24 ]

respectively, the symmetric CH respectively, 7b 1 − (CH s ν Table and a total of 1024 scans were averaged. 1 − (monochlorosilane), which formed incomplete monolayers, lm has crosslinked. lm has crosslinked. observed for the SAMFET ( were deposited on the native oxide of bare silicon substrates infra red spectros- and investigated by variable angle ATR Spectra were recorded at a resolution of copy (VATR-FTIR). 2 cm at 2964.7 cm tions ( crystalline and liquid alkanes and a crystalline octadecyl- trichlorosilane (OTS) monolayer fi S20). Figure peaks. deposited on to silicon dioxide substrates (see Supporting Infor- (see Supporting deposited on to silicon dioxide substrates mation for further details). All spectra confi The calculated sulphur to carbon ratio for carbon and sulphur. compound of 0.051 is confi compound derived from Films ducting molecular monolayer. 7a spectra, indicating showed the presence of chlorine in the XPS unreacted species within the fi gate the degree of crystallinity of fi tion appears at 2879.7 cm splitting of the symmetric CH the C-H stretching region of the IR spectrum. The peaks are assigned as follows, symmetric and asymmetric CH 2919.2 cm crystalline molecular monolayer demonstrating the potential of this molecule for large area deposition of well-ordered monolayers. from the trichlorosilane derivative has completely and it can be postulated that the monolayer reacted with the surface and that a signifi fi ectance – FTIR Refl Angle, Attenuated Total Variable 2.4.3. the alkyl chains The position of C-H stretching frequencies for information about of a SAM observed in the IR spectrum gives the degree of crystallinity within a monolayer.

growing on silicon dioxide substrates after a) 1, b) 3, and c) 9 h in solution, dioxide substrates after a) 1, b) 3, and c) growing on silicon ) 7b 7a 7b rming Fitting [ 28 ] In SAMFET , reducing the [ 29 ] 7b 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2014 WILEY-VCH Verlag on silicon dioxide, © (monochlorosilane) 7b over 7a lm stability and poten- 7a have a surface roughness of have a surface roughness 7b

) (see Supporting Information for ) (see Supporting 1 − lm, improving ﬁ shows the growth of shows 1

, (trichlorosilane) and ve times greater than that of the monochloro- grows in the form of small islands (<100 nm) 2014 In order to gain some insight into our system In order to

7b 7b rst order, Langmuir kinetics model was used to Langmuir kinetics model rst order, Figure [ 27 ] tting the molecular packing and overall device per- ), is fi 1 Atomic force microscopy topography images of compound Atomic force microscopy topography images − (100 µm), confi lms, even at large channel lengths It has been seen that monochlorosilanes have different self The increased reactivity of the trichlorosilane derivative ( The increased reactivity of the Complete monolayers of Complete monolayers 2 nm. Working devices were successfully fabricated from devices were 2 nm. Working the model to the coverage measured from the AFM images the model to the coverage measured from compound showed that the rate constant for the trichlorosilane (0.23 s silane derivative (0.04 s a simple, fi systems. estimate the rate constants for the two X-ray photon electron spectroscopy was performed on both X-ray compounds 2.4.2. X-Ray Photon Electron Spectroscopy devices the improved molecular packing of these SAMs should translate to higher device performance. assembly kinetics than the corresponding di- and tri-chloro assembly kinetics than the corresponding derivatives. DOI: 10.1002/adfm.201401392 Adv. Funct. Mater. Funct. Adv. that the lack of full coverage was not due to consumption of that the lack of full coverage was not due Figure 1. nm. with corresponding line scans, scale bar is 400 in solution. by self-condensation was aided by the higher solubility of amount of solution aggregation possible during monolayer amount of solution aggregation possible formation. these fi details of the calculation). ≈ tially benefi formance. Previous work has shown that trichlorosilane SAMs generally lead to higher grafting densities and smaller tilt angles than mono- or di-chlorosilane derivatives, the long range order of the molecular monolayer. The choice of the long range order of the molecular monolayer. trichlorosilane anchoring group allows for a crosslinking of the molecules within the fi after 1 hour the surface coverage is already greater than 60%, after 1 hour the surface coverage is already and complete cov- after 3 hours the coverage increases to 90% the monochlorosilane, erage is observed after 9 hours. As with compound that are distributed homogeneously across the surface and that are distributed homogeneously across monolayers with ultimately lead to the formation of crystalline little or no grain boundaries. www.MaterialsViews.com FULL PAPER 4 from compound Figure3. Table 1. wileyonlinelibrary.com a) liquid andcrystallinepeaksasdescribedinthetext. chains withinthemonolayer(Table 1 ). oxide substrates.Peakpositionsconfirm thecrystallinenatureofalkyl Figure2. www.afm-journal.de ν ν ν ν ν ν Mode Stretching s s a a s a Taken fromtheliterature; (CH (CH (CH (CH (CH (CH 3 3 3 3 3 2 ,FR) ) ) ,op) ,ip) ) VATR-FTIR C-HstretchesoftheSAMFET( a) Saturation(blackline)andlinear(greytransfercharacteristics, andb)outputhysteresischaracteristicsof VATR-FTIR spectraofcompound Crystalline [cm 9625 964– 2956.4 2957 2956 8125 8082851.6 2919.2 2850.8 2918.3 2855 2924 2851 2918 7b 961– 2879.7 2936.1 2878.7 – – – – 9572964.7 2965.7 – – − . Channellengthof90μmandchannelwidth 2000μm. 1 ] a) [ 24]

b) Se uprig Information Supporting See Liquid [cm − 1 a) ]

Spin Cast OTS [cm 7b onbaresilicon/native − 1 © ]

2014WILEY-VCHVerlag GmbH&Co. KGaA, Weinheim b) 7b

) referencedto SAMFET [cm − 1 ] mobility ofthetransistorwasfoundtobe1.6 2000 µm)arepresentedin monolayer coverage(channellengthof90µm,channelwidth Typical transferandoutputcharacteristicsforadevicewithfull Characterization Transistor 2.5. tics passingthroughtheorigin. contacts isconfi fabrication procedure.Goodelectricalchargeinjectionfromthe 36 devicestested),confi (20–100 µm)andadeviceyieldof100%wasobtained(out Functioning deviceswereobservedforallchannellengths shorter channellengths.For longchannellengths( of theincreasedcontributionfromcontactresistanceatthese length. Below50 both parametersshowthesamedependenceonchannel mobility isslightlyhigherthanthesaturationbut devices fabricatedonthesamesubstrate.Ingenerallinear channel length(20–100µm)arepresentedin channel lengthsgreaterthan40µm(totalof24devices). linear mobility. Theaveragesaretakenoveralldeviceswith and arepresentedin swing andhysteresis,remainconstantforallchannellengths ratio ofgreaterthan10 and 1.7 FETs wasaresultofincompletecoverage. with channellengthseeninearlierattemptsatcreatingSAM- jssen etal.,whoreportedthattheexponentialdecayofmobility incomplete coverage.Similar behaviorwasreportedbyMathi- minimal conductionbarriersarisingfromgrainboundariesor charge transportthroughadenselypackedmonolayerwith lengths greaterthan40µmisconfi channel lengthof100 the mobilityplateausandstayssameuptomaximum The dependenceofthesaturationandlinearmobilityon Other extractedparameters,thresholdvoltage,subthreshold × 10 − 2 cm rmed bythelinearityinoutputcharacteris- 2 μ V m themobilityreducesasaconsequence − 1 rmingthelargeareaapplicabilityof μ Table s m. Theconsistentmobilityatchannel 6 − andanonsetvoltageclosetozero. 1 respectively, withanon/offcurrent Figure

2 alongwiththesaturationand

3 . Thesaturationandlinear rmation oflong-range DOI: 10.1002/adfm.201401392 [ 30] www.MaterialsViews.com

transistors fabricated Adv. Funct. × 10 Figure − 2 cm

Mater. >

2 40 4 V

o 9 for −

1 μ 2014 s m) − 1 ,

FULL PAPER 5

. Transfer 1 −

(230–400 mesh) H} NMR spectra H} NMR 1 C to facilitate the wileyonlinelibrary.com 254 ° www.afm-journal.de C{ 13 : XPS measurements were : XPS H and H and 1 , linear regime , saturation regime : Unless stated otherwise, all : AFM images were recorded on : AFM images were recorded C for 2 h. ° < > 1 V respectively. Parameter extraction was 1 V respectively. : Transistors were tested in a top were tested in : Transistors − DS G th , : Solutions were prepared in an inert prepared in an inert : Solutions were : Monolayers were prepared on bare silicon , 2 ) for a total of 1024 scans. 1 60 V and − − () ( CV V V V V with a resonant frequency of approximately 50–80 kHz. A with a resonant 1 CV V V V V V − C) and are uncorrected. μ ° μ L L 512 pixels. Cantilevers had a spring constant of approximately had a spring 512 pixels. Cantilevers 2 W W × . Both the background and the sample spectra were recorded at a . Both the background and the sample spectra =− − =− − ° Transistor Characterization Transistor Synthesis—General Considerations Monolayer Preparation Microscopy (AFM) Atomic Force X-Ray Photoelectron Spectroscopy (XPS) Infrared Transform ectance-Fourier Refl Angle Attenuated Total Variable X-ray source (1486.69 eV). Detailed spectra of individual peaks were X-ray source (1486.69 eV). Detailed spectra of individual peaks α DS lin iDS G th sat DS i DS G G th th I I characteristics were recorded in the saturation and linear regimes with characteristics were recorded in the saturation drain voltages of eld effect transistor equations: performed using the standard fi silica or Aldrich neutral alumina and HPLC grade solvents. Distillation was carried out using standard Kugelrohr equipment with an oil cation by recrystallization refers to the process of diffusion pump. Purifi repeated recrystallization to a constant melting point. Melting points degrees heating stage, quoted in were recorded on a Linkam LTSE350 ( Celsius contact, bottom gate geometry. Thermally grown silicon dioxide (IDB Thermally grown silicon dioxide contact, bottom gate geometry. was used as the gate dielectric with a thickness of Technologies) 11.4 nFcm approximately 300 nm and a capacitance of An Agilent B1500a equipped with 3 SMUs was used in conjunction with a probe station. All transistors were tested in air at ambient temperature and pressure. reagents and solvents were obtained from commercial suppliers and cation. Anhydrous THF was pre-dried over used without further purifi sodium wire prior to continuous distillation over sodium-benzophenone under an atmosphere of argon. Other anhydrous solvents were used as supplied (water content < 0.05%). 4. Experimental Section microscopy, atomic force lm characterization, information on fi Further measurements can IR and electrical spectroscopy, X-ray photoelectron the Supporting Information. be found in concentration with the chosen solvent. The atmosphere to the desired to approximately 40 solutions were then heated They were then left to stand until reaching solvation of all of the material. a 0.2 μm ltered through they were then fi room temperature where substrates. into a sealed container with the freshly cleaned lter syringe fi to time the substrates were transferred After the desired immersion solvent, removed from the inert atmosphere sealed jars containing fresh 30 min. The clean substrates were and sonicated for approximately dried on a hotplate at 120 nally fi a resolution of tapping mode at in Peak Force a Bruker Multimode 8 512 0.350 Nm modulation frequency of 2 kHz was used. aluminum performed using a Kratos Axis Nova with a monochromated K eV with a power of 225 W. taken at energy of 20 eV with a step size of 0.1 The spectra were analyzed using CasaXPS. Spectroscopy (VATR-FTIR) of the IR radiation. A substrates as this enhances the attenuation accessory and with a Harrick Seagull ATR 70 equipped Bruker Vertex The a MCT detector. a germanium crystal is used in conjunction with by applying a torque of sample is brought into contact with the crystal of the source was 7.4 in.lbs to the sample mount. The angle of incidence 65 resolution of 2 cm were recorded on a Bruker 400 MHz or 500 MHz spectrometer. The were recorded on a Bruker 400 MHz or 500 MHz spectrometer. progress of reactions was monitored by TLC on pre-coated silica or alumina plates visualized by ultraviolet light or staining with vanillin or potassium permanganate in the absence of a chromophore. Column chromatography employed Merck Kieselgel (60 Å) F

1 ± [V] Hys ] eld effect 1 − 0.3 3 . Large-area, ± 1 SS − 0.70 2.6 is the saturation s [V dec 1 sat − μ 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2014 WILEY-VCH Verlag V 3 0.84 2 © ±

m. Errors correspond to th

μ 20 [V] V − cm 2 18.2 − − ) in the saturation (circles) and ) in the saturation (circles) and

L 2 10 − ] ×

1 is the threshold voltage, SS is the 2 − 10 −

th s ×

V 1 − 10 lin ×

μ V 0.1 lms have great promise for sensing 2 ± [cm rming the promising choice of this rming the 1.61 2 − ] 1.7 1 ) vs channel length ( 2 − , 10 − µ s ×

1 − 10 sat 2014 × V

0.1 2 ± 1.6 is the linear mobility, is the linear mobility, [cm lms. These thin ﬁ lin 1.39 μ Mobility ( lms offer stability against delamination in the presence Parameters extracted from transfer curves.

Best Average DOI: 10.1002/adfm.201401392 Adv. Funct. Mater. Funct. Adv. 3. Conclusion summarize, a novel self assembled monolayer fi To demonstrating an transistor (SAMFET) has been produced, average saturation mobility of 1.5 of solvents. of solvents. high yield monolayer devices have been fabricated, in less than high yield monolayer devices have been fabricated, utilizing a trichlorosi- 10 hours on a silicon dioxide surface by devices showed high lane anchoring group. These monolayer the highest reported mobilities, on the order of magnitude of to date, confi SAMFETs semiconducting core. The good performance demonstrates the high coverage and good connectivity within long-range order, the SAM fi applications as the ultrathin monolayer thickness could lead to improved sensitivity to analytes in these devices over the com- the covalently bound mon- parable bulk devices. Furthermore, olayer fi Table 2. Table linear (squares) regime for devices fabricated on one substrate. Increase linear (squares) regime for devices fabricated on contact resistance at in mobility is due to a decreased contribution from longer channel lengths (Supporting Information). subthreshold swing, and Hys is the hysteresis. The averages are taken over all devices with channel lengths above 40 mobility, mobility, the standard deviation over 4 devices. Figure 4. www.MaterialsViews.com FULL PAPER 6 wileyonlinelibrary.com 28.2; IR(ATR): 119.2, 35.4,34.1,32.8,31.3,29.6,29.52,29.50,29.44,29.41,29.2,28.8, HRMS (EI+)m/z[M] Anal. calcdforC afford thetitlecompoundasayellow/greenoil(15.86g,84%). was purifi ed overBrockmanngradeIIaluminaelutingwithhexaneto brine (2 Anal. calcdforC 28.9; IR(ATR): 130.2, 119.2,114.1,35.4,33.8,31.3,29.6,29.5,29.47,29.44,29.2,29.1, colorless oil. with hexane(Rf in vacuo.Theresiduewaspurifi ed bycolumnchromatography, eluting H 6.99,Br39.87. (12.20 g,71%)(bp180 (MgSO washed successivelywithwater(2 water (2 residue wasdissolvedinhexane(250mL),washedsuccessivelywith 100 mL).Thecombinedorganicfi ltrate were concentrated invacuo.The to removeinorganicsaltsandthefi ltrand waswashedwithhexane(2 3 hours.Thereactionwasallowedtocoolroomtemperature,fi ltered THF (100mL),werestirredatrefl (2.78 g,24.74mmol)and was quenchedwithsat.NH allowed towarmroomtemperatureandstirredovernight.Thereaction completion ofthetransfer, themixturewasstirredat THF (250mL)cooledto 1,12-dibromododecane (34.77g,105.97mmol)dissolvedinanhydrous via cannularapidlytoasecondfl whereby afi ne whiteprecipitateformed.Thewastransferred completion oftheaddition,stirringat THF (150mL)cooledto 1,4-dibromobenzene (10.0g,42.39mmol)dissolvedinanhydrous 42.39 mmol)wasaddeddropwisetoafl Tetrakis(triphenylphosphine)palladium(0) (162.5mg,0.14mmol,2 29.0, 28.96,27.3,22.6,14.1,13.7,10.9. 136.5, 136.1,131.6,128.9,125.5, 124.7, 124.3,123.2,35.7,31.7,31.4, 7.06 (d, HRMS (EI+)m/z[M] mp 37 www.afm-journal.de 1.25 (m14H); 2H), 1.91–1.83(m,1.611.541.451.351.31 (d, 3.76 Hz,1H),7.09(d, washed successivelywithsat.NaHCO the inorganicsalts.Thefi ltrate wasdilutedwithhexane(300mL), single portion.Afterstirringfor1hthereactionwasfi ltered toremove overnight andpotassiumfl 20 min.Thereactionwasallowedtoequilibrateroomtemperature tributyltin chloride(9.14mL,33.69mmol)wasaddeddropwiseover (400 MHz,CDCl 8.32, Br24.73. fi rst isolated(bp110 purifi ed byshortpathdistillation.Excess1,12-dibromododecanewas 1.28 (m,14H); (t, 7.28 Hz,12H); 1.53 (m,8H),1.41–1.2812H), 1.16–1.12(m,6H),0.93(t,J 1H), 7.20(d, drop wiseover30min.Afterstirringforanadditionalhourat butyllithium (12.82mL,32.16mmol,2.5Minhexanes)wasadded anhydrous THF(250mL).Thereactionwascooledto dried fl 1-Bromo-4-(dodec-11-en-1-yl)benzene 5-(4-Dodec-11-en-1-yl)phenyl)-5 1-Bromo-4-(12-bromododecyl)benzene 5-(Tri-n-butylstannyl)-5-(4-n-hexylphenyl)-2,2’-bithiophene J J

= = 7.56Hz,2H),2.08–2.03(m,1.621.571.41 8.40Hz,2H),3.43,(t, ° ask underargon,wascharged 4 C. ) andconcentratedinvacuotoaffordacrudeoil,whichwas × J ×

100mL),dried(MgSO4)andconcentratedinvacuo.Thecrude = 100mL),brine(2 1 8.32Hz,2H),5.87–5.80(m,1H),5.034.942.57 H NMR(400MHz,CDCl 1 J H NMR(400MHz,CDCl

13 13 13 = ν ≈ ν C{ 18 3 8.20Hz,2H),7.20(d, C{ C{ 18 max 0.60)toaffordthetitlecompound(3.79g,95%)asa , max H H 1 δ 1 1 H} NMR(100MHz,CDCl H} NMR(100MHz,CDCl 27 H} NMR(100MHz, CDCl ): 7.52(d, (cm (cm 28 ° + Br: C66.87,H8.42,Br24.71;found:67.02, + C, 5 J Br ° calcdforC calcdforC

C, 5 = 2 3.36Hz,1H),2.63(t, − : C53.48,H6.98,Br39.53;found:53.68, − 2 1 − 1 uoride (1.4g,24.10mmol)wasaddedina × − (5.0g,12.37mmol),dissolvedinanhydrous ) 3077,2918,2849,1642,1498,1458,1076; ) 3077,2918,2849,1458,1203,1076,997; 78 × × 10 78 4 10 100mL),dried(MgSO Cl (20mL),dilutedwithEt ° − J J ° C underandargonatmosphere.Upon − 6

C underanargonatmosphere.Upon ’ 6 mbar)followedbythetitlecompound = = ux under anatmosphereofargonfor -(4-hexylphenyl)-2,2 mbar),whichcrystallisedonstanding, 8.20Hz,2H),7.32(d, 6.88Hz,2H),2.57(t, × 18 18 100mL),brine(2 3 H , H 3 − (3 ame driedﬂ δ 28

( 27 78 2 ): 7.39(d, 3 Br ) , ( Br, 322.1291;found322.1287. 3 ame driedﬂ × : n-Butyllithium(2.5 3 J δ 2 (10.0g,30.62mmol)and

° 100mL),water(3 ) , 402.0552;found402.0557. ): 7.40(d, = C wascontinuedfor30min, : Potassium 3.76Hz,1H)7.15(d, 3 3 3 , , , J

δ δ δ = © ): 141.8,131.2,130.2, J ): 141.9,139.3,131.2, ): 142.9,142.8,136.6, 7.80Hz,2H),1.68–

− 2014WILEY-VCHVerlag GmbH&Co. KGaA, Weinheim = 78 4 ask chargedwith ’ 8.40Hz,2H),7.07 ) andconcentrated -bithiophene ask chargedwith J °

× = C for60minand 100mL),dried 8.32Hz,2H),

( 5) 2 O (500mL), J J tert −

M 30 :To aﬂ = = × , 16.95mL, 7.56Hz, 3.36Hz, 100mL), -butoxide 1 H NMR H − °

C and 30 ame ( 6) ° J

C, × = = :

for afurtherhourandbroughtto80 degassed anhydrousDMF(80mL).Thereactionmixturewas charged with dodecyl)silane (m, 4H),1.37–1.1922H),0.90(t, temperature (7 transferred toahighvacuumturbopumpanddriedthoroughlyatroom with stirringundervacuum.Thenitrogenpurgedglasswarewas overnight. Thereactionwasallowedtocoolandevaporateddryness 75.3 mmol,80eq).Theglasswarewassealedandbroughtto90 Karstedt’s catalyst(92μL,33ppmPt)andchlorodimethylsilane(8.34mL, charged with glassware wastransferredtoanitrogenglovebox.The dodecyl)dimethylsilane 80.10, H8.84,S11.26. glovebox forstorageandhandling. powder. Theevacuatedfl 568.3195. Anal.calcdforC δ Facility. XPS Service(NEXUS)atNewcastle University, anEPSRCMid-Range X-ray photoelectronspectrawere obtainedattheNationalEPSRC for theirhelpfuldiscussionsconcerning thehydrosilylationofalkenes. also wishtothankDr. S.A. PonomarenkoandProf.D.M.deLeeuw NowNano PhDstudentshipforAVSP andforgrantEP/C523857/1. They The authorswishtothanktheEPSRCforfi nancial supportfora Acknowledgements from theauthor. Supporting InformationisavailablefromtheWileyOnlineLibraryor Information Supporting 1 yield abrightyellowprecipitate.mp218ºC; title compound(3.41g,85%),whichwasrecrystallizedfromtolueneto eluting withDCM.Thefi ltrate wasconcentratedinvacuotoaffordthe was dryloadedontosilicaandfi ltered throughasilica/Celite plug methanol (250mL).Theresultantprecipitatewasfi lteredandthefi ltrand reaction, itwasallowedtocoolroomtemperatureandpouredon mol%) wasaddedunderafaststreamofargontofl 10 vacuum turbopumpanddriedthoroughlyatroomtemperature(7 under vacuum.Thenitrogenpurgedglasswarewastransferredtohigh reaction wasallowedtocoolandevaporateddrynesswithstirring 80 eq).Theglasswarewassealedandbroughtto90 catalyst (92μL,33ppmPt)andtrichlorosilane(7.58mL,75.3mmol, with was transferredtoanitrogenglovebox.Theglasswarecharged (m, 6H),7.15(d, once againpassedintoanitrogengloveboxforstorageandhandling. bright yellowpowder(quantitativeconversion).Theevacuatedfl IR (ATR): 31.7, 31.40,31.37,29.59,29.57,29.5,29.3,29.2,28.98,28.95,22.6,14.1; 142.6, 139.3,136.3,131.5,129.0,125.5,124.3,123.3,114.1,35.7,33.8, 1076, 997;HRMS(EI+)m/z[M] (d, 0.92 (t, 4H), 2.09–2.03(m,2H),1.681.611.391.2924H), 2H), 5.89–5.80(m,1H),5.034.932.64(t, (t, (t, H NMR(500MHz,CDCl ): 7.54(d, − J Trichloro(12-(4-(5 Chloro(12-(4-(5-(5-(4-hexylphenyl)thiophen-2-yl)thiophen-2-yl)phenyl) J 8 J

mbar)for2hourstoaffordthetitlecompoundasabright yellow = = = 6 6.85Hz). 7.70Hz,4H),1.66–1.55(m,1.421.2622H),0.90 8.20Hz,4H),7.21–7.17(m,6H),7.15(d, (500mg,0.939mmol),anhydroustoluene(55.5mL),Karstedt’s J

= ν 6.76Hz,3H); max J

= 6 ( 7b) (4.07g,7.03mmol)and 8.12Hz,4H),7.21–7.16(m,6H),(d, (cm (500mg,0.939mmol),anhydroustoluene(55.5mL), × 10 J

: Undervacuum,assembled,ﬂ = − 3.75Hz,2H),2.63(t, − 1 ) 3077,2918,2849,1642,1498,1458,1314,1124, 8

’ mbar)for2htoaffordthetitlecompoundasa -(4-hexylphenyl)-[2,2 ( 7a) ask wasonceagainpassedintoanitrogen 3 : Undervacuum,assembled,ﬂ 38 13 , H C{ δ ): 7.53(d, 48 1 H} NMR(100MHz,CDCl S + 2 calcdforC : C80.22,H8.50,S11.27;found: 1 ° H NMR(500MHz,CDCl C for16h.Uponcompletionofthe 3 J

(2.5g,7.73mmol)dissolvedin = J 6.85Hz,3H),0.41(s,6H).

J =

1 8.15Hz,4H),7.21–7.17 = ’ DOI: 10.1002/adfm.201401392 H NMR (400MHz,CDCl -bithiophen]-5-yl)phenyl) 7.75Hz,4H),1.66–1.58 38 www.MaterialsViews.com H ame driedglassware J 48

Adv. Funct. = S 3.75Hz,2H),2.65 2 , 568.3192;found ° C overnight.The ame driedﬂ J

J 3 ae dried ame

, = Mater. = 3 7.68Hz, δ 3.80Hz, , ): 143.3, ask was δ ): 7.52

2014 ask ° C 3 × , ,

FULL PAPER 7

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