The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Positive ion emission

We report the low temperature (T<70 ºC) fabrication of ZnO thin films (~140 nm) with Hall mobility of up to 17.3 cm 2 V-1 s-1 making them suitable for thin film transistor (TFT) applications. The films were deposited by rf magnetron sputtering at T<70 ºC and subsequently laser processed in ambient temperature in order to modify the Hall mobility and carrier concentration. Medium-to-low energy laser radiation densities and a high number of pulses were used to avoid damaging the films. Laser annealing of the films after aging in the lab under 25%-35% relative humidity and at an average illuminance of 120 lux resulted in an overall higher mobility and relatively low carrier concentration in comparison to the non-aged films that were laser processed immediately after deposition. A maximum overall measured Hall mobility of 17.3 cm 2 V-1 s-1 at a carrier density of 2.3×10 18 cm-3 was measured from a 1 GΩ as deposited and aged film after the laser treatment. We suggest that the aging of non-processed films reduces structural defects mainly at grain boundaries by air species chemisorption, with concomitant increase in thermal conductivity so that laser processing can have an enhancing effect. Such a processing combination can act synergistically and produce suitable active layers for TFT applications with low temperature processing requirements.

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“…During a single laser pulse the temperature change at the top surface layer follows equation ( 2) [57].…”

Section: Discussionmentioning

confidence: 99%

Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

Tsakonas¹,

Кузнецов²,

Cranton³

et al. 2017

J. Phys. D: Appl. Phys.

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The interaction of 193 nm excimer laser radiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

Khan

Langford

Dickinson

et al. 2013

Journal of Applied Physics

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We report mass-resolved time-of-flight measurements of neutral particles from the (101¯0) surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

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The interaction of 193-nm excimer laser radiation with single-crystal zinc oxide: The generation of atomic Zn line emission at laser fluences below breakdown

Khan

Langford

Dickinson

et al. 2013

Journal of Applied Physics

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The production of gas phase atomic and ionic line spectra accompanying the high laser fluence irradiation of solid surfaces is well known and is most often due to the production and interaction of high densities of atoms, ions, and electrons generated from laser-induced breakdown. The resulting plasma expands and moves rapidly away from the irradiated spot and is accompanied by intense emission of light. This type of “plume” is well studied and is frequently exploited in the technique of chemical analysis known as laser induced breakdown spectroscopy. Here, we describe a similar but weaker emission of light generated in vacuum by the laser irradiation of single crystal ZnO at fluences well below breakdown; this emission consists entirely of optical line emission from excited atomic Zn. We compare the properties of the resulting laser-generated gas-phase light emission (above and below breakdown) and describe a mechanism for the production of the low-fluence optical emission resulting from a fortuitous choice of material and laser wavelength.

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The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Positive ion emission

Cited by 7 publications

References 36 publications

Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

The interaction of 193 nm excimer laser radiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

The interaction of 193-nm excimer laser radiation with single-crystal zinc oxide: The generation of atomic Zn line emission at laser fluences below breakdown

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