Browsing by Subject "Self-limiting growth"

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Open Access
Low - temperature self - limiting growth of III - nitride thin films by plasma - enhanced atomic layer deposition
(American Scientific Publishers, 2012) Bıyıklı, Necmi; Ozgit, C.; Donmez, I.
We report on the low-temperature self-limiting growth and characterization of III-Nitride thin films. AlN and GaN films were deposited by plasma-enhanced atomic layer deposition (PEALD) on various substrates using trimethylaluminum (TMA), trimethylgallium (TMG) and triethylgallium (TEG) as group-III, and ammonia (NH3) as nitrogen precursor materials. Self-limiting growth behavior, which is the major characteristic of an ALD process, was achieved for both nitride films at temperatures below 200 °C. AlN deposition rate saturated around 0.86 Å/cycle for TMA and NH3 doses starting from 0.05 and 40 s, respectively, whereas GaN growth rate saturated at a lower value of 0.56 Å/cycle and 0.48 Å/cycle for TMG and TEG doses 0.015 s and 1 s, respectively. The saturation dose for NH3 was measured as 90 s and 120 s, for TMG and TEG experiments, respectively. Within the self-limiting growth temperature range (ALD window), film thicknesses increased linearly with the number of deposition cycles. At higher temperatures (≥225 °C and ≥350 °C for AlN and GaN respectively), deposition rate became temperature-dependent, with increasing growth rates. Chemical composition and bonding states of the films deposited within the self-limiting growth regime were investigated by X-ray photoelectron spectroscopy (XPS). GaN films exhibited high oxygen concentrations regardless of the precursors choice, either TMG or TEG, whereas low-oxygen incorporation in AlN films was confirmed by high resolution Al 2p and N 1s spectra of AlN films. AlN films were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction (GIXRD). GaN films showed amorphous-like XRD signature, confirming the highly defective layers. High-resolution transmission electron microscopy (HR-TEM) images of the AlN thin films revealed a microstructure consisting of several-nanometer sized crystallites, whereas GaN films exhibited sub-nm small crystallites dispersed in an amorphous matrix.
Open Access
Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition
(2012) Ozgit, C.; Donmez I.; Alevli, M.; Bıyıklı, Necmi
We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH 3). At 185 °C, deposition rate saturated for TMA and NH 3 doses starting from 0.05 and 40 s, respectively. Saturative surface reactions between TMA and NH 3 resulted in a constant growth rate of ∼ 0.86 Å/cycle from 100 to 200 °C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (≤ 225 °C) deposition rate increased with temperature. Chemical composition and bonding states of the films deposited at 185 °C were investigated by X-ray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 °C were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at ∼ 5.8 eV and an optical transmittance of > 95% in the visible region of the spectrum. © 2011 Elsevier B.V. All rights reserved.
Open Access
Structural properties of AIN films deposited by plasma-enhanced atomic layer deposition at different growth temperatures
(Wiley, 2012) Alevli, M.; Ozgit, C.; Donmez, I.; Bıyıklı, Necmi
Crystalline aluminum nitride (AlN) films have been prepared by plasma-enhanced atomic layer deposition (PEALD) within the temperature range from 100 to 500 °C. A self-limiting, constant growth rate per cycle temperature window (100-200 °C) was established which is the major characteristic of an ALD process. At higher temperatures (>225 °C), deposition rate increased with temperature. Chemical composition, crystallinity, surface morphology, mass density, and spectral refractive index were studied for AlN films. X-ray photoelectron spectroscopy (XPS) analyses indicated that besides main Al-N bond, the films contained Al-O-N, Al-O complexes, and Al-Al metallic aluminum bonds as well. Crystalline hexagonal AlN films were obtained at remarkably low growth temperatures. The mass density increased from 2.65 to 2.96 g/cm 3 and refractive index of the films increased from 1.88 to 2.08 at 533 nm for film growth temperatures of 100 and 500 °C, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.