Low-temperature solution-processed alumina dielectric films for low-voltage organic thin film transistors

Abstract

We studied low-temperature alumina (AlO x ) gate dielectrics by a simple spin-coating of home-made aluminum acetate hydroxide precursor (Al(OH)(C 2 H 3 O 2 ) 2 ) for low-voltage organic thin-film transistors (OTFTs). To improve the inorganic/organic interface, a thin PS polymer was introduced as interface modifier layer. Low leakage current of 7 9 10 -6 A/cm 2 and high dielectric constant of 5.8 were achieved for AlO x dielectrics at the low temperature of 200°C. The OTFT with 200°C annealed AlO x dielectrics can operate at the low voltage of 5 V. Moreover, the OTFT with 200°C annealed AlO x film realized a high charge carrier mobility of 0.46 cm 2 /Vs and high on/off ratio of 1.04 9 10 4 , comparable to the mobility of 0.51 cm 2 /Vs and on/off ratio of 2.53 9 10 4 for OTFT with 400°C annealed AlO x film. Our results suggested that simple low-temperature annealing can offer high-performance dielectric films for OTFTs, providing a promising approach for low-power organic electronics at a low cost.

Frequency dispersion analysis of thin dielectric MOS capacitor in a five-element model

“…In figure 6(a), ε r is constant 9.2 for frequency f < 100 kHz. This value is a little smaller the reported results [22][23][24][25] (discuss later). The ε r decrease from 9.2 to ~7.9 (corresponding to C decrease) for frequency 100 kHz-1.6 MHz is attributed to dielectric polarization mechanism by equation ( 4).…”

“…the large variation of ε r from ~1 to 200 is obviously not due to intrinsic dielectric constant dispersion, because the ε r of IL is considered as ~3.9 (SiO 2 ) [22][23][24][25]. Large ε r ~ 200 (large ~200 nF for C IL ) at LF f < 30 kHz is attributed to two reasons: (1) large trap polarization capacitance due to high density traps, and (2) decreased effective capacitor spacing because trapping and de-trapping of large number of electrons in IL.…”