Picture of smart phone in human hand

World leading smartphone and mobile technology research at Strathclyde...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by Strathclyde researchers from the Department of Computer & Information Sciences involved in researching exciting new applications for mobile and smartphone technology. But the transformative application of mobile technologies is also the focus of research within disciplines as diverse as Electronic & Electrical Engineering, Marketing, Human Resource Management and Biomedical Enginering, among others.

Explore Strathclyde's Open Access research on smartphone technology now...

Effect of substrate temperature on vapor-phase self-assembly of n-octylphosphonic acid monolayer for low-voltage organic thin-film transistors

Gupta, Swati and Sutta, Pavol and Lamprou, Dimitrios and Gleskova, Helena (2013) Effect of substrate temperature on vapor-phase self-assembly of n-octylphosphonic acid monolayer for low-voltage organic thin-film transistors. Organic Electronics, 14 (10). 2468–2475. ISSN 1566-1199

[img]
Preview
PDF (Gupta-etal-OE-2013-Effect-of-substrate-temperature-on-vapor-phase-self-assembly-of-n-octylphosphonic-acid)
Gupta_etal_OE_2013_Effect_of_substrate_temperature_on_vapor_phase_self_assembly_of_n_octylphosphonic_acid.pdf - Accepted Author Manuscript
License: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 logo

Download (681kB) | Preview

Abstract

N-octylphosphonic acid (C8PA) monolayer was self-assembled on aluminium oxide (AlOx) from vapour in vacuum, while the substrate temperature was varied between 25 and 150°C. The capacitance, water contact angle measurement, Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) confirmed the presence of C8PA on AlOx for all growth temperatures. However, the structural and electrical properties of such monolayers depend on their growth temperature. The minimum surface roughness of 0.36 nm, the maximum water contact angle of 113.5°±1.4°, the lowest leakage current density of ~ 10-7 A/cm2 at 3 V, and the capacitance of 0.43 µF/cm2 were obtained for AlOx/C8PA bi-layers with C8PA deposited at 25°C. The elevated temperature led to increased surface roughness, decreased water contact angle, increased leakage current, inferior molecular ordering, and lower molecular coverage; while the effect on the chemisorption of the phosphonate was minimal. Methyl and methylene FTIR vibrations associated with C8PA aliphatic tails exhibited similar centre-peak wavenumbers to those observed for C8PA monolayers assembled from solutions, presenting a viable ‘dry’ alternative to the existing solution process. The substrate temperature applied during C8PA self-assembly also affected the parameters of pentacene thin-film transistors with AlOx/C8PA gate dielectrics. The increase in the growth temperature from 25 to 150°C decreased the field-effect mobility from 0.060 to 0.026 cm2/Vs and increased the threshold voltage from -1.19 to -1.38 V, while maintaining the off-current at or below 10-12 A and the subthreshold slope near 90 mV/decade.