Mixed alkyl/fluoroalkyl phosphonic acid self‐assembled monolayers have been prepared as ultra‐thin dielectrics in low‐voltage organic thin‐film transistors and complementary circuits. Mixed monolayers enable continuous threshold‐voltage tuning simply by adjusting the molecular mixing ratio Continuous threshold‐voltage control makes it possible to place the switching voltage of the circuits at precisely half the supply voltage, producing the maximum noise margin.

(Meth)acrylated methyl oleates substituted with a hydroxy or bromo group were synthesized starting from oleic acid. The latter belongs to materials derived from renewable resources. These new hydroxy or bromo substituted methacrylated methyl oleates possess a higher reactivity compared to lauryl methacrylate in photoinitiated polymerization using Ivocerin® as photoinitiator. Hydroxy acrylated methyl oleate is more efficient in photopolymerization compared to bromo acrylated methyl oleate and lauryl acrylate in the presence of both nitrogen and air.Furthermore, the (meth)acrylated methyl oleates are interesting in applications for coatings because the design of the monomers opens a certain oxygen barrier function.

Grundlagenuntersuchungen zum Mechanismus kurzlebiger Zustände führen in der Photochemie zum Verständnis der Wirkprinzipien. Von diesen Erkenntnissen profitieren die industriellen Anwendungen.

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For many applications of organic thin-film transistors (TFTs), high-capacitance gate dielectrics that can be processed at low temperature are of interest. Several approaches exist, including vapor-deposited metal oxides [1], ultra-thin polymers [2], self-assembled nanodielectrics [3], and thin hybrid dielectrics based on alkyl phosphonic acid self-assembled monolayers (SAMs) on plasma-oxidized aluminum gates [4]. None of these approaches, however, provides deterministic and continuous control of the threshold voltage. A few reports of low-voltage ( 5 V) organic complementary circuits with symmetric switching threshold and large noise margins exist [5-9], but the TFTs were not air-stable and had to be operated in an inert gas, which is not practical for real applications. Here we show how the threshold voltage of air-stable, low-voltage organic TFTs and the switching threshold and noise margin of air-stable, low-voltage, low-power organic complementary circuits can be reproducibly tuned over a wide range by using a mixed alkyl/fluoroalkyl phosphonic acid self-assembled monolayer (SAM) as a high-capacitance gate dielectric.The TFTs and circuits were prepared on glass substrates. 40 nm thick aluminum gates were deposited by evaporation through a shadow mask, followed by an oxygen plasma to create a 3.6 nm thick aluminum oxide layer. The substrate was then immersed in a mix of octadecylphosphonic acid (C 18 H 37 PO(OH) 2 ; purchased from PCI Synthesis, Newburyport, MA) and pentadecylfluoro-octadecylphosphonic acid (C 7 F 15 C 11 H 22 PO(OH) 2 ; synthesized by Matthias Schlörholz) in 2-propanol, allowing a 2.1 nm thick mixed monolayer to self-assemble on the oxidized Al gate electrodes. The total thickness of the AlO x /SAM gate dielectric is 5.7 nm, and it has a capacitance of 700 nF/cm 2 . For the semiconductors, a 30 nm thick layer of pentacene or hexadecafluorocopperphthalocyanine (F 16 CuPc) was deposited in vacuum through shadow masks. TFTs, inverters, and ring oscillators were completed by evaporating Au source and drain contacts through another shadow mask (see Fig. 1). All measurements were performed in ambient air.Compared with alkyl SAMs, the electronegative substituents in fluoroalkyl SAMs systematically reduce the electron density in the carrier channel, causing the threshold voltage to shift towards more positive values [10]. Unlike neat SAMs, mixed SAMs allow continuous tuning of the TFT threshold voltage (Fig. 2), which in turn allows us to place the inverter switching threshold at precisely half the supply voltage and reproducibly maximize the noise margins (Fig. 3). In the case of inverters using pentacene p-channel and F 16 CuPc n-channel TFTs, the optimum SAM is a mix of 50% alkyl phosphonic acid and 50% fluoroalkyl phosphonic acid, providing large hole and electron mobilities (0.7 cm 2 /Vs for pentacene, 0.025 cm 2 /Vs for F 16 CuPc), symmetric switching threshold (at ½V DD ), and almost ideal noise margins: NM L = 0.86 V (86% of ½V DD ) and NM H = 0.80 V (80% of ½V DD ) for a supply voltage of 2 ...