Effect of Silicon Dioxide Surface on Bias Stress Effect for Organic Field-Effect Transistors

Abstract

We have investigated the effect of the surface roughness and surface wettability of silicon dioxide (SiO 2 ) on the threshold voltage shift caused by gate bias stressing in organic field-effect transistors (OFETs). We observed that the threshold voltage shift was extremely sensitive to changes in the small roughness of the SiO 2 surface; the shift increased with roughness. On the other hand, the threshold voltage shift was not significantly affected by the wettability of the SiO 2 surface. The large shift in OFETs with rough SiO 2 insulators can be attributed to lattice distortion in pentacene layers deposited on rough SiO 2 surfaces. We observed that long-time application of gate bias stress caused not only a threshold voltage shift but also a mobility decrease.

Bias Stress in Organic Thin-Film Transistors Towards Low-Cost Flexible Gas Sensors

“…At lower VGS bias, these results are even comparable to amorphous silicon (a-Si: t = 2×10 6 s and b = 0.39) [61]. A change in ID due to gate bias stress on OTFTs based on SiO2 dielectric has been previously related to deep traps with very long release time constant [62]. Some of these traps originate from dangling bonds (-O -) and hydroxyl groups at the interface.…”

“…In this work, however, most of these bonds were passivated by the OTS treatment. Impurities such as ambient oxygen and adsorbed water on the SiO2 surface can also capture holes in the channel layer [62]. In addition, water and oxygen molecules diffusion is enhanced in polycrystalline structures, as in the PBTTT-C14 polymer thin-film, due to spacing defects and disconnections in grain boundaries [63].…”

Time variation of source‐drain current for organic field‐effect transistors with dipoles of insulator surface

“…Therefore, the characteristics of OFETs are strongly influenced by the characteristics of the insulator surface [9][10][11]. From this point of view, we have examined the time variation of the source-drain current of OFETs when the chemical species of the insulator surface can change the conformational structure.…”

Projeto, caracterização e avaliação de transistores de filmes finos orgânicos para uso em narizes eletrônicos.

“…Em valores baixos de VGS, estes resultados são comparáveis com silício amorfo (a-Si: τ = 2×10 6 s e β = 0,39) [175]. As mudanças na ID devido ao estresse de polarização na porta de OTFTs com SiO2 como dielétrico foram anteriormente relacionadas a armadilhas profundas (deep trap) com constantes de tempo de relaxamento muito longas [176]. Algumas destas armadilhas são originadas por ligações incompletas e grupos hidroxilos na interface.…”

“…Neste caso, muitas destas ligações foram passivadas com tratamento de octadeciltriclorosilano (OTS -Octadecyltrichlorosilane). Impurezas como oxigênio e vapor de água absorvidas pelo SiO2 podem capturar as lacunas no canal [176]. Além disso, há uma maior difusão de moléculas de água e oxigênio em estruturas policristalinas, como no filme fino de PBTTT-C14, devido ao espaçamento dos defeitos e desconexões nos limites dos grãos [101].…”