Mechanistic Study of Surface Contamination of Dielectric Oxides Using Isotope Labeling

Raghu, P.; Yim, C. T.; Iqbal, Asad; Shadman, Farhang; Shero, Eric; Verghese, Mohith

doi:10.1021/ie0305972

Cited by 3 publications

(1 citation statement)

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“…Herein, the difference in Δ d corresponds to different functional groups on the substrate surface. For cleaning 1 substrate, the dehydration between the surface OH group and 2-propanol occurred during ultrasonication in 2-propanol, thus decreasing the number of surface OH groups with increasing number of 2-propyl groups. , The 2-propyl groups on the substrate surface may have a high affinity with three 2-propyl groups in TIPS pentacene molecules, resulting in higher orientation of the molecules in the organic thin film (Figure B). These positive interactions were directly observed at lower contact angles (Δ d < 0).…”

Section: Resultsmentioning

confidence: 99%

Direct Observation of the Interaction between the Substrate Surface and Organic Molecules for the Formation of Highly Oriented Organic Thin Films

Okuda,

Yoshida

2024

J. Phys. Chem. C

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The orientation of organic molecules is a key factor in improving the electrical performance of organic thin films. The interaction between the substrate surface and organic molecules dissolved in the solvent influences the orientation of the thin film during wet deposition. This study proposes a novel and simple evaluation criterion using the contact angle to directly and quantitatively observe the aforementioned interaction. SiO 2 substrates were treated using four common cleaning methods: organic solvent cleaning, piranha cleaning, UV/O 3 cleaning, and UV/O 3 with organic solvent cleaning. The aforementioned interaction was assessed by varying the contact angle of toluene in the presence and absence of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene). The orientation of TIPS pentacene thin films formed on various SiO 2 substrates by spin coating was investigated by using out-of-plane and in-plane X-ray diffraction. The field-effect mobility of top-contact organic thin-film transistors (OTFTs) fabricated using these thin films was evaluated. Independent of the surface states of the prepared SiO 2 substrates, TIPS pentacene thin films exhibited a horizontal orientation, as perpendicular alignment was notably influenced by the surface states. The strong affinity between the substrate surfaces and organic molecules favored the formation of perpendicular oriented thin films, whereas repulsive interactions led to nonoriented perpendicular thin films. This affinity can be gauged by the difference in the contact angle between the solvent with and without organic molecules, contributing to the development of highly oriented organic thin films. Furthermore, the affinity between the substrate surface and organic semiconductor molecules enhanced the orientation of thin films and the performance of OTFTs.

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Section: Resultsmentioning

confidence: 99%