Deposition of low sheet resistance indium tin oxide directly onto functional small molecules
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Abstract© 2014 Elsevier B.V. All rights reserved. We outline a methodology for depositing tin-doped indium oxide (ITO) directly onto semiconducting organic small molecule films for use as a transparent conducting oxide top-electrode. ITO films were grown using pulsed laser deposition onto copper(II)phthalocyanine (CuPc):buckminsterfullerene (C60) coated substrates. The ITO was deposited at a substrate temperature of 150 °C over a wide range of background oxygen pressures (Pd) (0.67-10 Pa). Deposition at 0.67 ≤ Pd ≤ 4.7 Pa led to delamination of the organic films owing to damage induced by the high energy ablated particles, at intermediate 4.7 ≤ Pd < 6.7 Pa pressures macroscopic cracking is observed in the ITO. Increasing Pd further, ≥ 6.7 Pa, supports the deposition of continuous, polycrystalline and highly transparent ITO films without damage to the CuPc:C60. The free carrier concentration of ITO is strongly influenced by Pd; hence growth at > 6.7 Pa induces a significant decrease in conductivity; with a minimum sheet resistance (Rs) of 145 /□ achieved for 300 nm thick ITO films. To reduce the Rs a multi-pressure deposition was implemented, resulting in the formation of polycrystalline, highly transparent ITO with an Rs of - 20/□ whilst maintaining the inherent functionality and integrity of the small molecule substrate.
CitationFranklin JB, Fleet LR, Burgess CH, McLachlan MA (2014) Deposition of low sheet resistance indium tin oxide directly onto functional small molecules. Thin Solid Films 570: 129–133. Available: http://dx.doi.org/10.1016/j.tsf.2014.09.043.
SponsorsThe authors gratefully acknowledge the EPSRC (EP/J016039/1) and KAUST (KAUST-Imperial College Academic Excellence Alliance) for research support, and thank Dr. Sandrine Heutz (Imperial College London) for access to the OMBD facilities.
JournalThin Solid Films