Influence of The Dielectric on The Growth and Performance of Pentacene Thin Film Transistors

Abstract

The electronic transport and the device properties of pentacene thin film transistors are reported, showing the influence of the dielectric on the structural and transport properties. The structure and morphology of pentacene films on organic and inorganic dielectrics were compared by x-ray diffraction measurements and atomic force microscopy. For the investigated dielectrics we observed a clear correlation between the morphology and the structural properties of the highly polycrystalline films. In the case of inorganic dielectrics the roughness of the dielectric has a distinct influence on the morphology and the structural properties, whereas the films on organic dielectrics bonding between pentacene and the dielectric may have an influence on the growth mechanism. We find that careful control of the deposition conditions give films with similar transport properties on organic and inorganic dielectrics. To study the electronic properties we have realized inverted staggered transistors. The TFTs exhibit mobilities of ~0.4 cm 2 /Vs and on/off ratios of 10 8 on organic and inorganic dielectrics. The influence of the dielectric on the device mobility, threshold voltage and sub-threshold voltage slope are discussed.

Low‐k Insulators as the Choice of Dielectrics in Organic Field‐Effect Transistors

“…Extended states will ªseeº the average polarization field due to a number of interface dipoles. Dipolar localization is probably not an issue with single crystals of pentacene and may be less important in ªband-likeº polycrystalline pentacene, [10] although some published data leads us to believe that it could still be partly operating in the latter. [7,25] A possible experiment to separate morphology effects from energetic disorder in such devices would be to use substrates with and without SAMs for semiconductor deposition, but fabricate the gate on top with a low-k insulator.…”

Polymer Gate Dielectrics and Conducting-Polymer Contactsfor High-Performance Organic Thin-Film Transistors

“…The photo-initiated reaction of gaseous hydrazine is known a) to alter the refractive index of aromatic polymers such as poly(styrene) and poly(2-vinylnaphthalene), [15] and b) to reductively bleach conjugated materials. [16] The latter feature is exploited here.…”

“…[3] To our knowledge, the largest carrier mobility reported for organic TFTs with polymer gate dielectric layer and with source and drain contacts deposited through a shadow mask is 0.7 cm 2 V ±1 s ±1 . [15,16] Lithographically patterned polymer gate dielectric TFTs have been reported with carrier mobility as large as 0.1 cm 2 V ±1 s ±1 . [9] The present work focuses on the substitution of inorganic vacuum-deposited gate dielectric materials with spin-coated poly-4-vinylphenol (PVP), and on the substitution of inorganic metals with the conducting polymer polyethylenedioxythiophene, doped with polystyrene sulfonic acid (PEDOT:PSS; Baytron P formulation).…”

“…[2,12,13,15] PVP was mixed with the additive poly(melamine-co-formaldehyde) methylated in propylene glycol monomethyl ether acetate (PGMEA). The solution was deposited by spin coating, followed by a 1 min hotplate bake at 100 C and a 5 min hotplate cure at 200 C. During the 200 C cure step, the poly-(melamine-co-formaldehyde) additive caused the PVP to cross-link, making the film robust against exposure to acetone, PGMEA, and photoresist developer.…”

Pentacene thin film transistors on large area compatible gate dielectrics

“…Pentacene thin film transistors can be fabricated on various low cost substrates. The hole mobility of pentacene thin films is close to the intrinsic transport limit of bulk single crystals, and TFTs with mobility of P 1 cm 2 /V s have been fabricated by several groups [1][2][3][4]. The mobility is therefore comparable with amorphous silicon thin film transistors (TFTs) and hence pentacene TFTs might be considered for large area active matrix based displays and sensor arrays.…”