Browsing by Author "Huang, Jheng-Ming"

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Annealing effect on the optical response and interdiffusion of n-ZnO/p-Si, (111) heterojunction grown by atomic layer deposition
(2010-11-01)
Ku, Ching-Shun
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Huang, Jheng-Ming
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Cheng, Ching-Yuan
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Lin, Chih-Ming
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Lee, Hsin-Yi
Optical and structural properties of n-ZnO films grown on a p-Si (111) substrate by atomic layer deposition were observed using in situ synchrotron x-ray diffraction during annealing. The photoluminescence showed a complicated photon response with increasing annealing temperature. In situ x-ray diffraction indicated the growth of grains for an annealing temperature from 500 to 800 degrees C with the orientation altering from polycrystalline to preferential (200). Measurements with a time-of-flight secondary-ion mass spectrometer indicated that the outgassing of hydrogen atoms and ZnO/Si interdiffusion behavior were correlated with the intensity and position of emissions in photoluminescence spectra. (c) 2010 American Institute of Physics. [doi:10.1063/1.3511284]
Enhanced electrical properties and field emission characteristics of AZO/ZnO-nanowire core-shell structures
(2016-06-14)
Huang, Jheng-Ming
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Tsai, Shang-You
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Ku, Ching-Shun
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Lin, Chih-Ming
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Chen, San-Yuan
The electrical properties and field-emission characteristics of ZnO nanowires (ZnO-NWs) fabricated using a vapor-liquid-solid method were systematically investigated. In particular, we explored the effects of Al-doped ZnO (AZO) films (thickness 4-100 nm) deposited on ZnO-NWs using an atomic layer deposition (ALD) method on the optoelectronic properties. The results show that the sheet resistance of net-like ZnO-NW structures can be significantly improved, specifically to become similar to 1/1000 of the sheet resistance of the as-grown ZnO-NWs, attaining less than 10 Omega Sq(-1). The emission current density measured at the maximum field was roughly quadrupled relative to that of the as-grown ZnO-NWs. The data of the enhanced field-emission characteristics show that, with the ALD system, the AZO films of small resistance are readily coated on a structure with a high aspect ratio and the coating radius is controlled relative to the turn-on voltage and current density. The ultrathin AZO film from a one-monolayer coating process also significantly improved emission properties through modification of the effective work function at the AZO/ZnO-NW surface.
Epitaxial Growth of m-Plane ZnO Thin Films on (10(1)over-bar0) Sapphire Substrate by Atomic Layer Deposition with Interrupted Flow
(2010-04-01)
Ku, Ching-Shun
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Lee, Hsin-Yi
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Huang, Jheng-Ming
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Lin, Chih-Ming
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材料科學與工程學系
Nonpolar ZnO films were grown epitaxially on (10 (1) over bar0) sapphire substrates at 200 degrees C by atomic layer deposition with interrupted flow. The latter method improved the crystalline quality of ZnO films, transformed the structure from polycrystalline to epitaxial, and enhanced the optical properties of near-band-edge emission. The interfacial structure shows multiple domain phases along sapphire (020) and the disappearance of a minor phase near the surface. As determined by X-ray diffraction, the epitaxial relation between ZnO and sapphire follows [002](ZnO)vertical bar vertical bar[020](sapphire) and [020](ZnO)vertical bar vertical bar[006](sapphire). The photoluminescence intensity increased with increasing crystalline quality and thickness of ZnO films.
Epitaxial growth of ZnO films at extremely low temperature by atomic layer deposition with interrupted flow
(2010-04-15)
Ku, Ching-Shun
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Lee, Hsin-Yi
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Huang, Jheng-Ming
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Lin, Chih-Ming
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材料科學與工程學系
Thin crystalline films of zinc oxide (ZnO) of high quality have been grown epitaxially on a (0 0 0 1) c-plane of a sapphire substrate with atomic layer deposition (ALD) at extra-low temperature. With diethylzinc (DEZn) and deionized water as precursors in combination with interrupted flow, we obtained ZnO thin films with an optimal growth window in a range 25-160 degrees C, so effectively lowering the growth temperature by about 120 degrees C relative to the conventional method involving a continuous-flow. We characterized the microstructure of these films with X-ray reflectivity and high-resolution X-ray diffraction (XRD) measurements. The XRD results indicate that the stock time might extend the reaction of DEZn and water through an increased duration. This low temperature for growth results in increased crystalline quality and reduced the non-radiative recombination process to enhance the optical properties of ZnO films. (c) 2009 Elsevier B.V. All rights reserved.
Fabrication of epitaxial ZnO films by atomic-layer deposition with interrupted flow
(2009-12-31)
Ku, Ching-Shun
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Huang, Jheng-Ming
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Lin, Chih-Ming
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Lee, Hsin-Yi
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材料科學與工程學系
We formed epitaxial ZnO thin films on a (0001) c-plane sapphire substrate through deposition of atomic layers (ALD) at 25-160 degrees C using diethylzinc (DEZn) and deionized water as precursors in combination with interrupted flow. High-resolution X-ray diffraction measurements were employed to characterize the microstructure of these films. With interrupted flow, we obtained ZnO thin films with an optimal growth window in a range of 40-160 degrees C, effectively decreasing the growth temperature by about 120 degrees C relative to a conventional method involving continuous flow. X-ray reflectivity measurements showed that the rate of growth increased also between 20 degrees C and 120 degrees C. The XRD results indicate that the stock time might extend the reaction of DEZn and water through an increased duration. All results show that a low temperature for growth improves the crystalline quality and is consistent with thermodynamically blocked self-compensation. (C) 2009 Elsevier B.V. All rights reserved.
Growth of high-quality epitaxial ZnO films on (10-10) sapphire by atomic layer deposition with flow-rate interruption method
(2013-09-01)
Huang, Jheng-Ming
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Ku, Ching-Shun
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Lee, Hsin-Yi
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Lin, Chih-Ming
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Chen, San-Yuan
A novel process in an atomic layer deposition system with "flow-rate interruption" (FRI) was developed to obtain epitaxial ZnO films of high quality. The m-plane ZnO thin films were grown on m-plane sapphire substrates by atomic layer deposition with FRI or a conventional continuous-flow method at the temperature in the range of 25-260 degrees C; 200 degrees C appeared optimal. Measurements of X-ray reflectivity indicated that the thickness of ZnO films with FRI is almost twice than that grown with the continuous-flow method. The structural, optical and electrical properties were investigated with X-ray diffraction (XRD), photoluminescence and Hall measurements. The diffraction results indicated that the interrupted flow might extend the reaction of diethylzinc and water through an increased duration to improve the crystallographic quality of the films. According to the results from XRD at high resolution, to substantiate the epitaxial relation between the thin film and the substrate, an off-normal azimuthal scan along ZnO (201) demonstrated two-fold symmetry that indicated the ZnO films to be in epitaxial growth on sapphire. The photoluminescence results showed a strongly enhanced near-band-edge emission of an FRI sample, and the donor-bond exciton appearing in films also indicated superior crystalline qualities. The Hall mobility of the FRI method was up to 64.7 cm(2) V-1 s(-1). The FRI method evidently improved the structural, optical and electrical properties of the ZnO films with small consumption of precursors. (C) 2012 Elsevier B.V. All rights reserved.
High mobility transparent conductive Al-doped ZnO thin films by atomic layer deposition
(2017-12-15)
Lin, Man-Ling
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Huang, Jheng-Ming
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Ku, Ching-Shun
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Lin, Chih-Ming
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Lee, Hsin-Yi
The effects of growth temperature on the microstructure, transport and optoelectronic properties of a series of Al-doped ZnO (AZO) films with thickness of similar to 30 nm deposited on polished silicon-(100) and glass substrates by the atomic layer deposition (ALD) were investigated. By adopting an in-situ doping growth scheme the critical length effect associated with adjacent Al2O3 layers commonly encountered in previous ALD growth schemes was avoided and effective Al-doping was achieved with the growth temperature ranging from 100 degrees C to 300 degrees C. Experimental results showed that, in general, increasing the growth temperature would result in much improved film crystallinity and carrier mobility, with the average transmittance in the visible wavelength range being exceeding 95% in all cases. In particular, for AZO films grown at 300 degrees C, an unprecedented mobility of 136 cm(2)V(-1)s(-1) was obtained, comparing to the typical values of 50-60 cm(2)V(-1)s(-1) reported previously. The resistivity of these 300 degrees C films (rho approximate to 6 x 10(-4) Omega-cm), nevertheless, is slightly higher than that of some highly-doped ZnO (rho approximate to 2 -4 x 10(-4) Omega-cm) prepared by sputtering methods. The secondary ion mass spectroscopy (SIMS) analyses revealed that hydrogen incorporation is the key in reducing the charge trap density and, hence, resulting in much enhanced carrier mobility. The present results promise a keen competitiveness of AZO with the indium tin oxide (ITO) film for thin-film-transistor (TFT) as well as in photovoltaic device applications. (C) 2017 Elsevier B.V. All rights reserved.
In situ Al-doped ZnO films by atomic layer deposition with an interrupted flow
(2015-09-01)
Huang, Jheng-Ming
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Ku, Ching-Shun
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Lin, Chih-Ming
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Chen, San-Yuan
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Lee, Hsin-Yi
In situ aluminum-doped ZnO (AZO) films were grown on glass substrates by atomic layer deposition (AID) with an interrupted flow at temperatures in range 200-280 degrees C; the optimal temperature, 260 degrees C, depended on the electrical properties. To assess the effect of the ratio of pulses of diethylzinc (DEZn) and trimethylaluminium (TMA) on the structural, optical and electrical properties, we grew AZO films with various pulse ratios of DEZn:TMA in a range from 3:1 to 10:1 at 260 degrees C. These properties and the content of Al were investigated with X-ray diffraction, X-ray reflectivity (XRR), a high-resolution transmission electron microscope (HRTEM), a secondary-ion mass spectrometer (SIMS), transmission spectra, Hall measurements and X-ray photoelectron spectra (XPS). The electrical resistivity was least, 5.7 x 10(-4) Omega cm, for ALD-AZO films with pulse ratio 6:1; the carrier mobility was 8.80 cm(2) V-1 s(-1) and optical transmittance up to 94%. The epitaxial AZO films grown in situ also on m-plane sapphire exhibited the two-fold symmetry of ZnO (110) in the orthorhombic crystal system. All results show that a novel in situ doping method with an interrupted flow controls the Al content of AZO films more easily, and is more usefully applicable for a structure with a large aspect ratio for an advanced photoelectric device. (C) 2015 Elsevier B.V. All rights reserved.
Optoelectronic Properties of Density-Controlled ZnO Nanopillar Arrays
(2012-04-12)
Chang, Yuan-Ming
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Huang, Jheng-Ming
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Lin, Chih-Ming
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Lee, Hsin-Yi
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Chen, San-Yuan
An effective method of controlling the density of ZnO nanopillars (ZnO-NPs) by using the self-assembled silver nanoislands as the growth catalyst is demonstrated. We were able to vary the density of the ZnO-NPs to within the range of similar to 10-30 mu m(-2) by properly manipulating the size distribution of the silver nanoislands partially covering the Si substrates. Continuous silver film can also be used as the catalyst to facilitate the growth of ZnO islands and pillars on Si substrates, albeit with much less control of the resultant density and morphological appearances. The field emission measurements indicate that the performance of field emission for ZnO-NPs can be. improved markedly by reducing the density of the ZnO-NPs. The turn-on field of the low-density ZnO-NPs was as low as 2.39 V/mu m with a corresponding current density of 10 mu A/cm(2) and a field enhancement factor (beta value) of similar to 3500. The enhancement of field emission characteristics is attributed to the much reduced field screen effect by properly controlled density of the ZnO-NPs.