Research

14 pages, 634 KiB

Open AccessArticle

Crystallographic Characterisation of Ultra-Thin, or Amorphous Transparent Conducting Oxides—The Case for Raman Spectroscopy

by David Caffrey, Ainur Zhussupbekova, Rajani K. Vijayaraghavan, Ardak Ainabayev, Aitkazy Kaisha, Gulnar Sugurbekova, Igor V. Shvets and Karsten Fleischer

Materials 2020, 13(2), 267; https://doi.org/10.3390/ma13020267 - 07 Jan 2020

Cited by 9 | Viewed by 3486

Abstract

The electronic and optical properties of transparent conducting oxides (TCOs) are closely linked to their crystallographic structure on a macroscopic (grain sizes) and microscopic (bond structure) level. With the increasing drive towards using reduced film thicknesses in devices and growing interest in amorphous [...] Read more.

The electronic and optical properties of transparent conducting oxides (TCOs) are closely linked to their crystallographic structure on a macroscopic (grain sizes) and microscopic (bond structure) level. With the increasing drive towards using reduced film thicknesses in devices and growing interest in amorphous TCOs such as n-type InGaZnO

_{4}

(IGZO), ZnSnO

_{3}

(ZTO), p-type Cu

_{x}

CrO

_{2}

, or ZnRh

_{2}

O

_{4}

, the task of gaining in-depth knowledge on their crystal structure by conventional X-ray diffraction-based measurements are becoming increasingly difficult. We demonstrate the use of a focal shift based background subtraction technique for Raman spectroscopy specifically developed for the case of transparent thin films on amorphous substrates. Using this technique we demonstrate, for a variety of TCOs CuO, a-ZTO, ZnO:Al), how changes in local vibrational modes reflect changes in the composition of the TCO and consequently their electronic properties. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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10 pages, 2408 KiB

Open AccessArticle

Influence Mechanism of Cu Layer Thickness on Photoelectric Properties of IWO/Cu/IWO Films

by Fengbo Han, Wenyuan Zhao, Ran Bi, Feng Tian, Yadan Li, Chuantao Zheng and Yiding Wang

Materials 2020, 13(1), 113; https://doi.org/10.3390/ma13010113 - 25 Dec 2019

Cited by 6 | Viewed by 2135

Abstract

Transparent conductive IWO/Cu/IWO (W-doped In₂O₃) films were deposited on quartz substrates by magnetron sputtering of IWO and Cu in the Ar atmosphere. The X-ray diffraction (XRD) patterns identified the cubic iron–manganese ore crystal structure of the IWO layers. The [...] Read more.

Transparent conductive IWO/Cu/IWO (W-doped In₂O₃) films were deposited on quartz substrates by magnetron sputtering of IWO and Cu in the Ar atmosphere. The X-ray diffraction (XRD) patterns identified the cubic iron–manganese ore crystal structure of the IWO layers. The influence of the thickness of the intermediate ultra-thin Cu layers on the optical and electrical properties of the multilayer films was analyzed. As the Cu layer thickness increases from 4 to 10 nm, the multilayer resistivity gradually decreases to 4.5 × 10⁻⁴ Ω·cm, and the optical transmittance in the mid-infrared range increases first and then decreases with a maximum of 72%, which serves as an excellent candidate for the mid-infrared transparent electrode. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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16 pages, 2708 KiB

Open AccessArticle

Electrical Properties of Low-Temperature Processed Sn-Doped In₂O₃ Thin Films: The Role of Microstructure and Oxygen Content and the Potential of Defect Modulation Doping

by Getnet Kacha Deyu, Jonas Hunka, Hervé Roussel, Joachim Brötz, Daniel Bellet and Andreas Klein

Materials 2019, 12(14), 2232; https://doi.org/10.3390/ma12142232 - 11 Jul 2019

Cited by 9 | Viewed by 3368

Abstract

Low-temperature-processed ITO thin films offer the potential of overcoming the doping limit by suppressing the equilibrium of compensating oxygen interstitial defects. To elucidate this potential, electrical properties of Sn-doped In

_{2}

O

_{3}

(ITO) thin films are studied in dependence on film thickness. [...] Read more.

Low-temperature-processed ITO thin films offer the potential of overcoming the doping limit by suppressing the equilibrium of compensating oxygen interstitial defects. To elucidate this potential, electrical properties of Sn-doped In

_{2}

O

_{3}

(ITO) thin films are studied in dependence on film thickness. In-operando conductivity and Hall effect measurements during annealing of room-temperature-deposited films, together with different film thickness in different environments, allow to discriminate between the effects of crystallization, grain growth, donor activation and oxygen diffusion on carrier concentrations and mobilities. At

200^{\circ} C

, a control of carrier concentration by oxygen incorporation or extraction is only dominant for very thin films. The electrical properties of thicker films deposited at room temperature are mostly affected by the grain size. The remaining diffusivity of compensating oxygen defects at

200^{\circ} C

is sufficient to screen the high Fermi level induced by deposition of Al

_{2}

O

_{3}

using atomic layer deposition (ALD), which disables the use of defect modulation doping at this temperature. The results indicate that achieving higher carrier concentrations in ITO thin films requires a control of the oxygen pressure during deposition in combination with seed layers to enhance crystallinity or the use of near room temperature ALD. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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30 pages, 4515 KiB

Open AccessArticle

Enhanced Sol–Gel Route to Obtain a Highly Transparent and Conductive Aluminum-Doped Zinc Oxide Thin Film

by Mohammad Hossein Nateq and Riccardo Ceccato

Materials 2019, 12(11), 1744; https://doi.org/10.3390/ma12111744 - 29 May 2019

Cited by 26 | Viewed by 3924

Abstract

The electrical and optical properties of sol–gel derived aluminum-doped zinc oxide thin films containing 2 at.% Al were investigated considering the modifying effects of (1) increasing the sol H₂O content and (2) a thermal treatment procedure with a high-temperature approach followed [...] Read more.

The electrical and optical properties of sol–gel derived aluminum-doped zinc oxide thin films containing 2 at.% Al were investigated considering the modifying effects of (1) increasing the sol H₂O content and (2) a thermal treatment procedure with a high-temperature approach followed by an additional heat-treatment step under a reducing atmosphere. According to the results obtained via the TG-DTA analysis, FT-IR spectroscopy, X-ray diffraction technique, and four-point probe resistivity measurements, it is argued that in the modified sample, the sol hydrolysis, decomposition of the deposited gel, and crystallization of grains result in grains of larger crystallite size in the range of 20 to 30 nm and a stronger c-axis preferred orientation with slightly less microstrain. The obtained morphology and grain-boundary characteristics result in improved conductivity considering the resistivity value below 6 mΩ·cm. A detailed investigation of the samples’ optical properties, in terms of analyzing their absorption and dispersion behaviors through UV-Vis-NIR spectroscopy, support our reasoning for the increase of the mobility, and to a lesser extent the concentration of charge carriers, while causing only a slight degradation of optical transmittance down to nearly 80%. Hence, an enhanced performance as a transparent conducting film is claimed for the modified sample by comparing the figure-of-merit values. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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11 pages, 4810 KiB

Open AccessArticle

Fabrication of Nanopillar Crystalline ITO Thin Films with High Transmittance and IR Reflectance by RF Magnetron Sputtering

by Ling Dong, Guisheng Zhu, Huarui Xu, Xupeng Jiang, Xiuyun Zhang, Yunyun Zhao, Dongliang Yan, Le Yuan and Aibing Yu

Materials 2019, 12(6), 958; https://doi.org/10.3390/ma12060958 - 22 Mar 2019

Cited by 16 | Viewed by 4244

Abstract

Nanopillar crystalline indium tin oxide (ITO) thin films were deposited on soda-lime glass substrates by radio frequency (RF) magnetron sputtering under the power levels of 100 W, 150 W, 200 W and 250 W. The preparation process of thin films is divided into [...] Read more.

Nanopillar crystalline indium tin oxide (ITO) thin films were deposited on soda-lime glass substrates by radio frequency (RF) magnetron sputtering under the power levels of 100 W, 150 W, 200 W and 250 W. The preparation process of thin films is divided into two steps, firstly, sputtering a very thin and granular crystalline film at the bottom, and then sputtering a nanopillar crystalline film above the bottom film. The structure, morphology, optical and electrical properties of the nanopillar crystalline ITO thin films were investigated. From X-ray diffraction (XRD) analysis, the nanopillar crystalline thin films shows (400) preferred orientation. Due to the effect of the bottom granular grains, the crystallinity of the nanopillar crystals on the upper layer was greatly improved. The nanopillar crystalline ITO thin films exhibited excellent electrical properties, enhanced visible light transmittance and a highly infrared reflectivity in the mid-infrared region. It is noted that the thin film deposited at 200 W showed the best combination of optical and electrical performance, with resistivity of 1.44 × 10⁻⁴ Ω cm, average transmittance of 88.49% (with a film thickness of 1031 nm) and IR reflectivity reaching 89.18%. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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13 pages, 3478 KiB

Open AccessArticle

Tailoring Electro/Optical Properties of Transparent Boron-Doped Carbon Nanowalls Grown on Quartz

by Mattia Pierpaoli, Mateusz Ficek, Michał Rycewicz, Mirosław Sawczak, Jakub Karczewski, Maria Letizia Ruello and Robert Bogdanowicz

Materials 2019, 12(3), 547; https://doi.org/10.3390/ma12030547 - 12 Feb 2019

Cited by 16 | Viewed by 4158

Abstract

Carbon nanowalls (CNWs) have attracted much attention for numerous applications in electrical devices because of their peculiar structural characteristics. However, it is possible to set synthesis parameters to vary the electrical and optical properties of such CNWs. In this paper, we demonstrate the [...] Read more.

Carbon nanowalls (CNWs) have attracted much attention for numerous applications in electrical devices because of their peculiar structural characteristics. However, it is possible to set synthesis parameters to vary the electrical and optical properties of such CNWs. In this paper, we demonstrate the direct growth of highly transparent boron-doped nanowalls (B-CNWs) on optical grade fused quartz. The effect of growth temperature and boron doping on the behavior of boron-doped carbon nanowalls grown on quartz was studied in particular. Temperature and boron inclusion doping level allow for direct tuning of CNW morphology. It is possible to operate with both parameters to obtain a transparent and conductive film; however, boron doping is a preferred factor to maintain the transparency in the visible region, while a higher growth temperature is more effective to improve conductance. Light transmittance and electrical conductivity are mainly influenced by growth temperature and then by boron doping. Tailoring B-CNWs has important implications for potential applications of such electrically conductive transparent electrodes designed for energy conversion and storage devices. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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10 pages, 2238 KiB

Open AccessArticle

Nanostructure and Optical Property Investigations of SrTiO₃ Films Deposited by Magnetron Sputtering

by Da Xu, Yafei Yuan, Huanfeng Zhu, Ling Cheng, Chunmin Liu, Jing Su, Xintong Zhang, Hao Zhang, Xia Zhang and Jing Li

Materials 2019, 12(1), 138; https://doi.org/10.3390/ma12010138 - 03 Jan 2019

Cited by 10 | Viewed by 3211

Abstract

Strontium titanate thin films were deposited on a silicon substrate by radio-frequency magnetron sputtering. The structural and optical properties of these films were characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and spectroscopic ellipsometry, respectively. After annealing at 600–800 °C, [...] Read more.

Strontium titanate thin films were deposited on a silicon substrate by radio-frequency magnetron sputtering. The structural and optical properties of these films were characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and spectroscopic ellipsometry, respectively. After annealing at 600–800 °C, the as-deposited films changed from amorphous to polycrystalline. It was found that an amorphous interfacial layer appeared between the SrTiO₃ layer and Si substrate in each as-deposited film, which grew thicker after annealing. The optical parameters of the SrTiO₃ film samples were acquired from ellipsometry spectra by fitting with a Lorentz oscillator model. Moreover, we found that the band gap energy of the samples diminished after thermal treatment. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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13 pages, 3240 KiB

Open AccessArticle

A Comparative Study of E-Beam Deposited Gate Dielectrics on Channel Width-Dependent Performance and Reliability of a-IGZO Thin-Film Transistors

by Gwomei Wu, Anup K. Sahoo, Dave W. Chen and J. W. Chang

Materials 2018, 11(12), 2502; https://doi.org/10.3390/ma11122502 - 09 Dec 2018

Cited by 3 | Viewed by 3157

Abstract

A comparative study on the effects of e-beam deposited gate dielectrics for amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) has been carried out using SiO₂, Si₃N₄, and Ta₂O₅ dielectric materials. [...] Read more.

A comparative study on the effects of e-beam deposited gate dielectrics for amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) has been carried out using SiO₂, Si₃N₄, and Ta₂O₅ dielectric materials. The channel width dependent device electrical performances were investigated using three different sizes of 500 μm, 1000 μm, and 1500 μm. The reliability characteristics were revealed by the threshold voltage variation and drain current variation under positive bias stress. The e-beam deposited high-k dielectric Ta₂O₅ exhibited the highest stability at the stress voltage of 3 V for 1000 s due to its high capacitance density at 34.1 nF/cm². The threshold voltage variation along the channel width decreased from SiO₂, then Si₃N₄, to Ta₂O₅, because of the increased insulating property and density of capacitance. The SiO₂-based a-IGZO TFT achieved a high field effect mobility of 27.9 cm²/V·s and on–off current ratio > 10⁷ at the lower channel width of 500 μm. The gate leakage current also decreased with increasing the channel width/length ratio. In addition, the SiO₂ gate dielectric-based a-IGZO TFT could be a faster device, whereas the Ta₂O₅ gate dielectric would be a good candidate for a higher reliability component with adequate surface treatment. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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11 pages, 8417 KiB

Open AccessArticle

Indium-Zinc-Tin-Oxide Film Prepared by Reactive Magnetron Sputtering for Electrochromic Applications

by Ke-Ding Li, Po-Wen Chen, Kao-Shuo Chang, Sheng-Chuan Hsu and Der-Jun Jan

Materials 2018, 11(11), 2221; https://doi.org/10.3390/ma11112221 - 08 Nov 2018

Cited by 11 | Viewed by 3676

Abstract

This paper reports on the fabrication of indium-zinc-tin-oxide (IZTO) transparent conductive film deposited by direct current (DC) reactive magnetron sputtering. The electrical, structural, and optical properties of IZTO film were investigated by Hall measurement, X-ray diffraction (XRD), and optical transmission spectroscopy with various [...] Read more.

This paper reports on the fabrication of indium-zinc-tin-oxide (IZTO) transparent conductive film deposited by direct current (DC) reactive magnetron sputtering. The electrical, structural, and optical properties of IZTO film were investigated by Hall measurement, X-ray diffraction (XRD), and optical transmission spectroscopy with various sputtering powers. The IZTO film prepared used power at 100 W showed the lowest resistivity of 5.2 × 10⁻⁴ Ω cm. To accomplish rapid switching and high optical modulation, we have fabricated an electrochromic device (ECD) consisting of an working electrode (WO₃ electrode film deposited on IZTO/ITO/glass) and a counter-electrode (Pt mesh) in 0.2 M LiClO₄/PC liquid solution. The device demonstrated an optical contrast of 44% and switching times of 4.6 s and 8.1 s for the coloring and bleaching state, respectively, at the wavelength of 550 nm. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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12 pages, 4162 KiB

Open AccessArticle

Tunable Coupled-Resonator-Induced Transparency in a Photonic Crystal System Based on a Multilayer-Insulator Graphene Stack

by Hanqing Liu, Jianfeng Tan, Peiguo Liu, Li-an Bian and Song Zha

Materials 2018, 11(10), 2042; https://doi.org/10.3390/ma11102042 - 19 Oct 2018

Cited by 2 | Viewed by 3530

Abstract

We achieve the effective modulation of coupled-resonator-induced transparency (CRIT) in a photonic crystal system which consists of photonic crystal waveguide (PCW), defect cavities, and a multilayer graphene-insulator stack (MGIS). Simulation results show that the wavelength of transparency window can be effectively tuned through [...] Read more.

We achieve the effective modulation of coupled-resonator-induced transparency (CRIT) in a photonic crystal system which consists of photonic crystal waveguide (PCW), defect cavities, and a multilayer graphene-insulator stack (MGIS). Simulation results show that the wavelength of transparency window can be effectively tuned through varying the chemical potential of graphene in MGIS. The peak value of the CRIT effect is closely related to the structural parameters of our proposed system. Tunable Multipeak CRIT is also realized in the four-resonator-coupled photonic crystal system by modulating the chemical potentials of MGISs in different cavity units. This system paves a novel way toward multichannel-selective filters, optical sensors, and nonlinear devices. Full article

(This article belongs to the Special Issue Transparent Conductive Films and Their Applications)

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