Surface treatment and characterization of ITO thin films using atmospheric pressure plasma for organic light emitting diodes

Jung, Mi-Hee; Choi, Ho‐Suk

doi:10.1016/j.jcis.2007.02.011

Cited by 40 publications

(28 citation statements)

References 32 publications

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“…This was because oxygen ions were produced in larger quantities in the Ar/O 2 APP and O 2 LPP than in the Ar APP. 19 The XPS results also show changes in the surface concentration of O and Sn after the plasma treatment. The O concentration means that the plasma treatments incorporate more oxygen onto the surface.…”

Section: Resultsmentioning

confidence: 93%

“…AFM images of plasma-treated ITO surfaces were presented in another manuscript. 19 The morphology of Ar/O 2 APP-treated ITO is similar to that of untreated ITO, while a significant change in surface morphology occurred for O 2 LPP-treated ITO. Figure 5 shows the I-V characteristics of devices built on ITO surfaces treated in different plasma systems.…”

Section: Aging Time ͑Min͒mentioning

confidence: 81%

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Surface Treatment of Indium Tin Oxide Using Radio Frequency Atmospheric and Low Pressure Plasma for OLEDs

Jung

Choi

2008

J. Electrochem. Soc.

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We investigated the effect of atmospheric-pressure plasma ͑APP͒ and low-pressure plasma ͑LPP͒ treatments on the performance of organic light emitting diodes ͑OLEDs͒ with an indium tin oxide ͑ITO͒ layer. The Owens-Wendt and Lifshitz-van der Waals acid-base methods revealed that the increase of surface energy was mainly attributed to polar component ͑␥ s p ͒ and Lewis base ͑␥ s − ͒ interactions, respectively, independent of either APP or LPP treatments. Unlike APP treatment, LPP treatment more plentifully produced reactive oxygen species in the plasma. Therefore, the LPP-treated ITO surfaces slowly proceeded with reorientation compared to APP-treated ITO. The carbon content in untreated ITO was approximately 0.045%, while those of Ar APP-, Ar/O 2 APP-, and O 2 LPP-treated ITO were 0.014, 0.011, and 0.010%, respectively, mostly containing incorporated reactive oxygen. The O 2 LPP-treated surface showed more uniform roughness than Ar or Ar/O 2 APP-treated surfaces. The highest work-function ͑⌽͒ value ͑4.58 eV͒ was obtained from O 2 LPP-treated ITO, intermediate values ͑4.47-4.48 eV͒ from Ar and Ar/O 2 APP-treated ITOs, and the smallest value from untreated ITO ͑4.46 eV͒. Thus, OLED fabricated on the surface of O 2 LPP-treated ITO substrate exhibited superior performance among all plasma-treated samples.Indium tin oxide ͑ITO, ϳ9 to 10 mol % tin oxide in indium oxide͒ is a highly degenerate n-type semiconductor with a wide bandgap ͑3.5-4.5 eV͒. ITO films have excellent electrical and optical properties due to their easy availability ͑fabrication of liquidcrystal industry͒, good optical transparency ͑Ͼ90% at 550 nm͒, good conductivity due to oxygen vacancies in In 2 O 3 and doped impurities, i.e., Sn, low electrical resistivity, and the ease with which it can be patterned. Therefore, ITO has been widely used in organic light emitting diodes ͑OLEDs͒. [1][2][3][4][5][6] Recently, OLEDs have received much attention through their potential use in full-color display because of many merits like low driving voltage ͑3-15 V͒, high brightness ͑Ͼ1000 cd/m 2 ͒, high response time, wide view angle, slim and light, and simple process. OLED devices are usually made up of ITO anode/organic layer/ metal cathode contact. Because the organic film is in direct contact with the ITO, there exists an interfacial barrier formed between the organic layer and ITO. The barrier influences the injection of holes from ITO to the organic layer and results in lower emission efficiency due to abnormal behaviors such as shorting, unstable current-voltage ͑I-V͒ characteristics, and damage on the surface of the top cathode contact after continuous operation of the device in the OLED built on bare, cleaned ITO substrates. Because the increase in work function of ITO decreases the barrier height 7 through modifying the surface properties of ITO, many researchers have attempted various methods, including chemical processes ͑aquage-ria, degreasing, and RCA protocol͒ 8 and physical treatments using oxygen, 9-14 argon plasma, 15,16 and UV ozone treatment, 17,1...

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Section: Resultsmentioning

confidence: 93%

Section: Aging Time ͑Min͒mentioning

confidence: 81%

Surface Treatment of Indium Tin Oxide Using Radio Frequency Atmospheric and Low Pressure Plasma for OLEDs

Jung

Choi

2008

J. Electrochem. Soc.

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“…Common surface treatments include halogenation, [16][17][18][19][20] plasma reactions, [21][22][23][24][25][26][27] UV-ozone [28][29][30] and controlled air exposure. [31][32][33][34][35][36] Buffer layers include vapor-deposited small molecules, [37][38][39] spincast polymers, [40][41][42][43][44][45][46] inorganic salts, 12,47-52 covalently bound selfassembled monolayers [53][54][55][56][57][58] and thin metal oxide layers.…”

Section: Introduction To Organic Electronicsmentioning

confidence: 99%

Thin-film metal oxides in organic semiconductor devices: their electronic structures, work functions and interfaces

2013

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Thin-film metal oxides are among the key materials used in organic semiconductor devices. As there are no intrinsic charge carriers in a typical organic semiconductor, all charges in the device must be injected from electrode/organic interfaces, whose energetic structure consequentially dictates the performance of devices. The energy barrier at the interface depends critically on the work function of the electrode. For this reason, various types of thin-film metal oxides can be used as a buffer layer to modify the electrode work function. This paper provides a review on recent progress in metal oxide/organic interface energetics, oxide valence structure and work function, as well as the impact of defects and interfacial reactions on oxide work functions. This review provides a rational guide to process engineers in selecting the best suitable electrode/oxide structures for a targeted applications.

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“…In addition, the parallel-plate type discharge, although representing the simplest geometrical configuration, has the potential for applications that require large-area uniformity. In atmospheric-pressure applications, rare gases, such as helium and argon, have generally been used [10,11], dramatically increasing operating costs. Thus, efficient use of cheaper gases, such as nitrogen or air, has become an important issue in practical applications.…”

Section: Introductionmentioning

confidence: 99%

Effects of Oxygen Addition and Treating Distance on Surface Cleaning of ITO Glass by a Non-Equilibrium Nitrogen Atmospheric-Pressure Plasma Jet

Chiang

Liao

Lin

et al. 2010

Plasma Chem Plasma Process

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Effects of oxygen addition and treating distance on cleaning organic contaminants on stationary and non-stationary (1-9 cm/s) ITO glass surfaces by a parallel-plate nitrogen-based dielectric barrier discharge (DBD) are investigated experimentally; the DBD is driven by a 60 kHz bipolar quasi-pulsed power source. The results show that two regimes of favorable operating condition for improving the hydrophilic property of the surface (reducing the contact angle from 84°to 25-30°) are found. The measured spatial distribution of NO-c UV emission, O 3 concentration and OES spectra are shown to strongly correlate with the measured hydrophilic property. At the near jet downstream locations (z \ 10 mm), the metastable N 2 ðA 3 P þ u Þ and photo-induced dissociation of ozone play dominant roles in cleaning the ITO glass surface; while at the far jet downstream locations (z [ 10 mm), where the ratio of oxygen to nitrogen is lower, only the long-lived metastable N 2 ðA 3 P þ u Þ plays a major role in cleaning the ITO glass surface.

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Surface treatment and characterization of ITO thin films using atmospheric pressure plasma for organic light emitting diodes

Cited by 40 publications

References 32 publications

Surface Treatment of Indium Tin Oxide Using Radio Frequency Atmospheric and Low Pressure Plasma for OLEDs

Surface Treatment of Indium Tin Oxide Using Radio Frequency Atmospheric and Low Pressure Plasma for OLEDs

Thin-film metal oxides in organic semiconductor devices: their electronic structures, work functions and interfaces

Effects of Oxygen Addition and Treating Distance on Surface Cleaning of ITO Glass by a Non-Equilibrium Nitrogen Atmospheric-Pressure Plasma Jet

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