MDPI - Publisher of Open Access Journals

12 pages, 3172 KiB

Open AccessArticle

Effect of Rapid Thermal Annealing on the Characteristics of Micro Zn-Doped Ga₂O₃ Films by Using Mixed Atomic Layer Deposition

by Jiajia Tao, Xishun Jiang, Aijie Fan, Xianyu Hu, Ping Wang, Zuoru Dong and Yingjie Wu

Nanomaterials 2025, 15(7), 499; https://doi.org/10.3390/nano15070499 - 26 Mar 2025

Viewed by 498

Abstract

In this work, micro Zn-doped Ga₂O₃ films (GZO) were deposited by one-step mixed atomic layer deposition (ALD) followed by post-thermal engineering. The effects of Zn doping and post-annealing temperature on both structure characteristics and electric properties were investigated in detail. [...] Read more.

In this work, micro Zn-doped Ga₂O₃ films (GZO) were deposited by one-step mixed atomic layer deposition (ALD) followed by post-thermal engineering. The effects of Zn doping and post-annealing temperature on both structure characteristics and electric properties were investigated in detail. The combination of plasma-enhanced ALD of Ga₂O₃ and thermal ALD of ZnO can realize the fast growth rate (0.62 nm/supercyc.), high density (4.9 g/cm³), and smooth interface (average R_q = 0.51 nm) of Zn-doped Ga₂O₃ film. In addition, the thermal engineering of the GZO was achieved by setting the annealing temperature to 400, 600, 800, and 1000 °C, respectively. The GZO film annealed at 800 °C exhibits a typical crystalline structure (Ga₂O₃: β phase, ZnO: hexagonal wurtzite), a lower roughness (average R_q = 2.7 nm), and a higher average breakdown field (16.47 MV/cm). Notably, compared with the pure GZO film, the breakdown field annealed at 800 °C increases by 180%. The O_V content in the GZO after annealing at 800 °C is as low as 34.8%, resulting in a remarkable enhancement of electrical properties. These research findings offer a new perspective on the high-quality ALD-doped materials and application of GZO in high-power electronics and high-sensitive devices. Full article

(This article belongs to the Topic Preparation and Application of Polymer Nanocomposites)

► Show Figures

Figure 1

20 pages, 5668 KiB

Open AccessArticle

Study of the Influence of Thermal Annealing of Ga-Doped ZnO Thin Films on NO₂ Sensing at ppb Level

by Benjamin Paret, Richard Monflier, Philippe Menini, Thierry Camps, Yohann Thimont, Antoine Barnabé and Lionel Presmanes

Chemosensors 2025, 13(1), 1; https://doi.org/10.3390/chemosensors13010001 - 24 Dec 2024

Cited by 1 | Viewed by 1278

Abstract

In this paper, the sensitivity to sub-ppm NO₂ concentration of 50 nm thick Ga-doped ZnO (GZO) films grown by RF magnetron sputtering is studied. The films were annealed under dry air for 4 h at either 500 °C, 600 °C, or 700 [...] Read more.

In this paper, the sensitivity to sub-ppm NO₂ concentration of 50 nm thick Ga-doped ZnO (GZO) films grown by RF magnetron sputtering is studied. The films were annealed under dry air for 4 h at either 500 °C, 600 °C, or 700 °C. The increase in the annealing temperature leads to an improvement of the crystallinity while no significant evolution of the surface grain size is observed. The electrical resistance of the thin films was measured at 250 °C under neutral argon atmosphere, humid air reference atmosphere, and reference atmosphere polluted by 100 ppb of NO₂. An increase in sensitivity to NO₂ is noted for samples annealed at 600 °C, leading to a response R_NO2/R_air of ~10 for 100 ppb of NO₂. Finally, photoluminescence spectra are compared with their electrical resistance at 250 °C under the various atmospheres to understand this phenomenon. It is proposed that the origin of the NO₂ maximum sensitivity for films annealed at 600 °C is the consequence of a specific annihilation of point defects resulting in an increase in the relative concentration of oxygen vacancies, which improves selectivity toward NO₂. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors)

► Show Figures

Figure 1

13 pages, 3516 KiB

Open AccessArticle

Analysis of Hazy Ga- and Zr-Co-Doped Zinc Oxide Films Prepared with Atmospheric Pressure Plasma Jet Systems

by Yu-Tang Luo, Zhehan Zhou, Cheng-Yang Wu, Li-Ching Chiu and Jia-Yang Juang

Nanomaterials 2023, 13(19), 2691; https://doi.org/10.3390/nano13192691 - 1 Oct 2023

Cited by 3 | Viewed by 1742

Abstract

Co-doped ZnO thin films have attracted much attention in the field of transparent conductive oxides (TCOs) in solar cells, displays, and other transparent electronics. Unlike conventional single-doped ZnO, co-doped ZnO utilizes two different dopant elements, offering enhanced electrical properties and more controllable optical [...] Read more.

Co-doped ZnO thin films have attracted much attention in the field of transparent conductive oxides (TCOs) in solar cells, displays, and other transparent electronics. Unlike conventional single-doped ZnO, co-doped ZnO utilizes two different dopant elements, offering enhanced electrical properties and more controllable optical properties, including transmittance and haze; however, most previous studies focused on the electrical properties, with less attention paid to obtaining high haze using co-doping. Here, we prepare high-haze Ga- and Zr-co-doped ZnO (GZO:Zr or ZGZO) using atmospheric pressure plasma jet (APPJ) systems. We conduct a detailed analysis to examine the interplay between Zr concentrations and film properties. UV-Vis spectroscopy shows a remarkable haze factor increase of 7.19% to 34.8% (+384%) for the films prepared with 2 at% Zr and 8 at% Ga precursor concentrations. EDS analysis reveals Zr accumulation on larger and smaller particles, while SIMS links particle abundance to impurity uptake and altered electrical properties. XPS identifies Zr mainly as ZrO₂ because of lattice stress from Zr doping, forming clusters at lattice boundaries and corroborating the SEM findings. Our work presents a new way to fabricate Ga- and Zr-co-doped ZnO for applications that require low electrical resistivity, high visible transparency, and high haze. Full article

(This article belongs to the Special Issue Nanomaterials and Nanofabrication for Solar Cells and Energy Harvesting)

► Show Figures

Graphical abstract

14 pages, 5355 KiB

Open AccessArticle

Effects of Post-Annealing on the Properties of ZnO:Ga Films with High Transparency (94%) and Low Sheet Resistance (29 Ω/square)

by Li-Wen Wang and Sheng-Yuan Chu

Materials 2023, 16(19), 6463; https://doi.org/10.3390/ma16196463 - 28 Sep 2023

Cited by 10 | Viewed by 2324

Abstract

This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films [...] Read more.

This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films with a film thickness of 100 nm showed high transparency (94%), while the sheet resistance of the films was reduced to 29 Ω/square, which was comparable with the performances of commercial indium tin oxide (ITO) samples. Post-annealing under nitrogen and hydrogen forming gas enhanced the films’ conductivity while altering the thin-film composition and crystallinity. Nitrogen gas played a role in improving the crystallinity while maintaining the oxygen vacancy of the proposed films, whereas hydrogen did not dope into the thin film, thus maintaining its transparency. Furthermore, hydrogen lowered the resistance of GZO thin films during the annealing process. Then, the detailed mechanisms were discussed. Hydrogen post-annealing helped in the removal of oxygen, therefore increasing the Ga³⁺ content, which provided extra electrons to lower the resistivity of the films. After the preferable nitrogen/hydrogen forming gas treatment, our proposed films maintained high transparency and low sheet resistance, thus being highly useful for further opto-electronic applications. Full article

(This article belongs to the Special Issue Advances in Thin-Film Deposition via Plasma-Assisted and Pulsed Laser Techniques)

► Show Figures

Figure 1

12 pages, 7536 KiB

Open AccessArticle

Gallium-Modified Zinc Oxide Thin Films Prepared by Chemical Solution Deposition

by Izabela Stojanoska, Brigita Kmet, Hana Uršič and Danjela Kuscer

Crystals 2023, 13(7), 1030; https://doi.org/10.3390/cryst13071030 - 28 Jun 2023

Cited by 2 | Viewed by 1611

Abstract

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine [...] Read more.

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine confirmed the decomposition of the organic components upon heating and the formation of ZnO at 450 °C. The thin films fired at 600 °C in oxygen and air, and the films annealed at 400 °C in Ar/H_2, were polycrystalline, 140 nm thick, and exhibited a homogeneous microstructure with 50 nm grains and a smooth surface, as shown by X-ray powder diffraction and scanning electron and atomic force microscopy. The sheet resistance R_s measured using the 4-probe technique showed a change in R_s within 80 days for all samples. The R_s of the GZO thin films annealed in oxygen and air with values of MΩ/sq decreased over time. R_s values of 150 kΩ/sq were obtained for GZO thin films annealed in Ar/H₂, but the R_s increased over time. We suggest that the degradation of R_s is related to the adsorption of water on GZO and that the responses depend on the nature of the defects in the GZO lattice. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

► Show Figures

Figure 1

9 pages, 1638 KiB

Open AccessArticle

Enhanced Thermoelectric Performance of ZnO-Based Thin Films via Interface Engineering

by Zhifang Zhou, Yunpeng Zheng, Yueyang Yang, Wenyu Zhang, Mingchu Zou, Ce-Wen Nan and Yuan-Hua Lin

Crystals 2022, 12(10), 1351; https://doi.org/10.3390/cryst12101351 - 24 Sep 2022

Cited by 11 | Viewed by 2911

Abstract

Zinc oxide (ZnO) is a potential thermoelectric material with good chemical and thermal stability as well as an excellent Seebeck coefficient. However, the extremely low carrier concentration brings poor electrical transport properties. Although Gallium (Ga) doping could increase the carrier concentration of ZnO [...] Read more.

Zinc oxide (ZnO) is a potential thermoelectric material with good chemical and thermal stability as well as an excellent Seebeck coefficient. However, the extremely low carrier concentration brings poor electrical transport properties. Although Gallium (Ga) doping could increase the carrier concentration of ZnO film, its thermoelectric performance is still limited due to the deteriorated Seebeck coefficient and enhanced thermal conductivity. Interface engineering is an effective strategy to decouple electron-phonon interaction for thermoelectric materials. Thus, in this work, GZO (Ga-doped ZnO)/NAZO (Ni, Al co-doped ZnO) multilayer films were designed to further improve the thermoelectric properties of GZO films. It was found that GZO/NAZO multilayer films possessed better electrical conductivity, which was attributed to the increased carrier concentration and Hall mobility. Meanwhile, benefiting from the energy filtering that occurred at GZO/NAZO interfaces, the density of states effective mass increased, resulting in comparable Seebeck coefficient values. Ultimately, an enhanced power factor value of 313 μW m⁻¹ K⁻² was achieved in the GZO/NAZO multilayer film, which is almost 46% larger than that of GZO film. This work provides a paradigm to optimize the thermoelectric performance of oxide films and other thermoelectric systems by multilayer structure design with coherent interfaces. Full article

(This article belongs to the Special Issue Advances in Thermoelectric Thin Films)

► Show Figures

Figure 1

14 pages, 5382 KiB

Open AccessArticle

Using Modified-Intake Plasma-Enhanced Metal–Organic Chemical Vapor Deposition System to Grow Gallium Doped Zinc Oxide

by Po-Hsun Lei, Jia-Jan Chen, Ming-Hsiu Song, Yuan-Yu Zhan and Zong-Lin Jiang

Micromachines 2021, 12(12), 1590; https://doi.org/10.3390/mi12121590 - 20 Dec 2021

Cited by 2 | Viewed by 2844

Abstract

We have used a modified-intake plasma-enhanced metal–organic chemical vapor deposition (MIPEMOCVD) system to fabricate gallium-doped zinc oxide (GZO) thin films with varied Ga content. The MIPEMOCVD system contains a modified intake system of a mixed tank and a spraying terminal to deliver the [...] Read more.

We have used a modified-intake plasma-enhanced metal–organic chemical vapor deposition (MIPEMOCVD) system to fabricate gallium-doped zinc oxide (GZO) thin films with varied Ga content. The MIPEMOCVD system contains a modified intake system of a mixed tank and a spraying terminal to deliver the metal–organic (MO) precursors and a radio-frequency (RF) system parallel to the substrate normal, which can achieve a uniform distribution of organic precursors in the reaction chamber and reduce the bombardment damage. We examined the substitute and interstitial mechanisms of Ga atoms in zinc oxide (ZnO) matrix in MIPEMOCVD-grown GZO thin films through crystalline analyses and Hall measurements. The optimal Ga content of MIPEMOCVD-grown GZO thin film is 3.01 at%, which shows the highest conductivity and transmittance. Finally, the optimal MIPEMOCVD-grown GZO thin film was applied to n-ZnO/p-GaN LED as a window layer. As compared with the indium–tin–oxide (ITO) window layer, the n-ZnO/p-GaN LED with the MIPEMOCVD-grown GZO window layer of the rougher surface and higher transmittance at near UV range exhibits an enhanced light output power owing to the improved light extraction efficiency (LEE). Full article

► Show Figures

Figure 1

11 pages, 1670 KiB

Open AccessArticle

Ga-Doped ZnO Coating—A Suitable Tool for Tuning the Electrode Properties in the Solar Cells with CdS/ZnS Core-Shell Quantum Dots

by Mariya Aleksandrova, Tatyana Ivanova, Velichka Strijkova, Tsvetozar Tsanev, Ajaya Kumar Singh, Jai Singh and Kostadinka Gesheva

Crystals 2021, 11(2), 137; https://doi.org/10.3390/cryst11020137 - 29 Jan 2021

Cited by 9 | Viewed by 2606

Abstract

Two layer system from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO, GZO) were studied for transparency in the visible electromagnetic range, reflectivity in the near infrared range, conductivity and valent band for a solar cells with quantum dots. The [...] Read more.

Two layer system from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO, GZO) were studied for transparency in the visible electromagnetic range, reflectivity in the near infrared range, conductivity and valent band for a solar cells with quantum dots. The bi-layer coatings produced at optimized oxygen partial pressure, films thickness and surface roughness exhibit improved optical properties without worsening the electrical parameters, even if additional oxygen introduction during the reactive sputtering of the GZO. With an average optical transmittance of 91.3% in the visible range, average reflection and resistivity lower than 0.4 × 10⁻² Ω.cm, these coatings are suitable for top electrode in the solar cells. The obtained results reveal that multilayered stacks of transparent ITO/Ga-doped ZnO coatings possess relatively low surface roughness (7–9 nm) and appropriate refractive index. The additional oxidation of GZO films induces modification of the film thickness and respectively of their optical performances. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Graphical abstract

11 pages, 1490 KiB

Open AccessArticle

Low-Temperature Fabrication of High-Performance and Stable GZO/Ag/GZO Multilayer Structures for Transparent Electrode Applications

by Akmedov K. Akhmedov, Aslan Kh. Abduev, Vladimir M. Kanevsky, Arsen E. Muslimov and Abil Sh. Asvarov

Coatings 2020, 10(3), 269; https://doi.org/10.3390/coatings10030269 - 13 Mar 2020

Cited by 15 | Viewed by 3841

Abstract

Presently, research and development of indium-free stable highly transparent conductive (TC) materials is of paramount importance for the blooming world of information display systems and solar energy conversion. Development of devices based on flexible organic substrates further narrows the choice of possible TC [...] Read more.

Presently, research and development of indium-free stable highly transparent conductive (TC) materials is of paramount importance for the blooming world of information display systems and solar energy conversion. Development of devices based on flexible organic substrates further narrows the choice of possible TC materials due to the need for lower deposition and process temperatures. In our work, the structural, electrical, and optical performances of Ga-doped ZnO/Ag/Ga-doped ZnO (GZO/Ag/GZO) multilayered structures deposited on glass substrates by direct current (DC) magnetron sputtering in a pure Ar medium without any purposeful substrate heating have been investigated. The highest figure of merit achieved was 5.15 × 10⁻² Ω⁻¹ for the symmetric GZO/Ag/GZO multilayer, featuring GZO and Ag thicknesses of 40 and 10 nm, respectively, while the average optical transmittance was over 81% in the visible range of wavelengths and the resistivity was 2.2 × 10⁻⁵ Ω·cm. Additionally, the good durability of the performances of the multilayer structures was demonstrated by their testing in the context of long-term storage (over 500 days) in standard environmental conditions. Full article

(This article belongs to the Special Issue Optical Thin Films and Structures: Design and Advanced Applications)

► Show Figures

Figure 1

11 pages, 2395 KiB

Open AccessArticle

Influences of Ga Doping on Crystal Structure and Polarimetric Pattern of SHG in ZnO Nanofilms

by Hua Long, Ammar Ayesh Habeeb, Dickson Mwenda Kinyua, Kai Wang, Bing Wang and Peixiang Lu

Nanomaterials 2019, 9(6), 905; https://doi.org/10.3390/nano9060905 - 21 Jun 2019

Cited by 8 | Viewed by 4438

Abstract

The second-harmonic generation (SHG) in gallium doped ZnO (GZO) nanofilms was studied. The Ga doping in GZO nanofilms influenced the crystal structure of the films, which affected SHG characteristics of the nanofilms. In our experiments, a strong SHG response was obtained in GZO [...] Read more.

The second-harmonic generation (SHG) in gallium doped ZnO (GZO) nanofilms was studied. The Ga doping in GZO nanofilms influenced the crystal structure of the films, which affected SHG characteristics of the nanofilms. In our experiments, a strong SHG response was obtained in GZO nanofilms, which was excited by 790 nm femtosecond laser. It was observed that the Ga doping concentrations affected, not only the intensity, but also the polarimetric pattern of SHG in GZO nanofilms. For 5.0% doped GZO films, the SHG intensity increased about 70%. The intensity ratio of SHG between the incident light polarization angle of 90° and 0°changed with the Ga doping concentrations. It showed the most significant increase for 7.3% doped GZO films, with an increased ratio of c/a crystal constants. This result was attributed to the differences of the ratios of d₃₃/d₃₁ (the second-order nonlinear susceptibility components) induced by the crystal distortion. The results are helpful to investigate nanofilms doping levels and crystal distortion by SHG microscopy, which is a non-destructive and sensitive method. Full article

(This article belongs to the Special Issue Synthesis and Modification of Nanostructured Thin Films)

► Show Figures

Graphical abstract

12 pages, 10641 KiB

Open AccessArticle

Comparative Studies on Ultraviolet-Light-Derived Photoresponse Properties of ZnO, AZO, and GZO Transparent Semiconductor Thin Films

by Chien-Yie Tsay and Wei-Tse Hsu

Materials 2017, 10(12), 1379; https://doi.org/10.3390/ma10121379 - 1 Dec 2017

Cited by 77 | Viewed by 6125

Abstract

ZnO, Al-doped ZnO (AZO), and Ga-doped ZnO (GZO) semiconductor thin films were deposited on glass substrates via a sol-gel spin-coating process for application in a photoconductive ultraviolet (UV) detector. The doping concentrations of Al and Ga were 1.0 at % in the precursor [...] Read more.

ZnO, Al-doped ZnO (AZO), and Ga-doped ZnO (GZO) semiconductor thin films were deposited on glass substrates via a sol-gel spin-coating process for application in a photoconductive ultraviolet (UV) detector. The doping concentrations of Al and Ga were 1.0 at % in the precursor solutions. In this study, the microstructural features and the optical and electrical properties of sol-gel-derived ZnO, AZO, and GZO thin films were compared, and the performance of ZnO-based UV photodetectors under ultraviolet A (UVA) light were measured. Experimental results confirmed the synthesis of single-phase nanocrystalline ZnO-based thin films and the successful substitution of Al and Ga into Zn sites in ZnO crystals. The results also demonstrated that the optical transmittance and electrical properties of ZnO thin films could be improved by Al and Ga doping. UV photodetectors based on ZnO-based thin films, having a metal-semiconductor-metal (MSM) configuration, were fabricated with Al inter-digitated electrodes. All photodetectors showed an ohmic nature between semiconductor and electrode contacts and exhibited a sharp increase in photocurrent under illumination with UVA light. We found that the MSM UV photodetector based on the GZO semiconductor thin film exhibited the best UV response (I_UVA/I_dark) of 73.3 and the highest photocurrent responsivity of 46.2 A/W under UVA light (power density ~0.825 mW/cm²) at 5 V bias. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Figure 1

4 pages, 265 KiB

Open AccessProceeding Paper

Near Infrared Plasmonic Gas Sensing with Doped Metal Oxide Nanocrystals

by Marco Sturaro, Enrico Della Gaspera, Carlo Cantalini, Massimo Guglielmi and Alessandro Martucci

Proceedings 2017, 1(4), 319; https://doi.org/10.3390/proceedings1040319 - 5 Sep 2017

Cited by 4 | Viewed by 2260

Abstract

In this paper, we demonstrate the application of ZnO doped with gallium (GZO), aluminum (AZO) and germanium (GeZO) nanocrystals as novel plasmonic and chemiresistive sensors for the detection of hazardous gases including hydrogen (H₂) and nitrogen dioxide (NO₂). GZO, [...] Read more.

In this paper, we demonstrate the application of ZnO doped with gallium (GZO), aluminum (AZO) and germanium (GeZO) nanocrystals as novel plasmonic and chemiresistive sensors for the detection of hazardous gases including hydrogen (H₂) and nitrogen dioxide (NO₂). GZO, AZO and GeZO nanocrystals are obtained by non-aqueous colloidal heat-up synthesis with high transparency in the visible range and strong localized surface plasmon resonance (LSPR) in the near IR range, tunable with dopant concentration (up to 20% mol nominal). Thanks to the strong sensitivity of the LSPR to chemical and electrical changes occurring at the surface of the nanocrystals, such optical features can be used to detect the presence of toxic gases. By monitoring the changes in the dopant-induced plasmon resonance in the near infrared, we demonstrate that GZO, AZO and GeZO thin films prepared depositing an assembly of highly doped ZnO colloids are able to optically detect both oxidizing and reducing gases at mild (<100 °C) operating temperatures. Combined optical and electrical measurements show that the dopants within ZnO nanocrystals enhance the gas sensing response compared to undoped ZnO. Full article

(This article belongs to the Proceedings of Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017)

► Show Figures

Figure 1

9 pages, 2910 KiB

Open AccessArticle

Optoelectronic Properties and the Electrical Stability of Ga-Doped ZnO Thin Films Prepared via Radio Frequency Sputtering

by Shien-Uang Jen, Hui Sun, Hai-Pang Chiang, Sheng-Chi Chen, Jian-Yu Chen and Xin Wang

Materials 2016, 9(12), 987; https://doi.org/10.3390/ma9120987 - 6 Dec 2016

Cited by 16 | Viewed by 5479

Abstract

In this work, Ga-doped ZnO (GZO) thin films were deposited via radio frequency sputtering at room temperature. The influence of the Ga content on the film’s optoelectronic properties as well as the film’s electrical stability were investigated. The results showed that the film’s [...] Read more.

In this work, Ga-doped ZnO (GZO) thin films were deposited via radio frequency sputtering at room temperature. The influence of the Ga content on the film’s optoelectronic properties as well as the film’s electrical stability were investigated. The results showed that the film’s crystallinity degraded with increasing Ga content. The film’s conductivity was first enhanced due to the replacement of Zn²⁺ by Ga³⁺ before decreasing due to the separation of neutralized gallium atoms from the ZnO lattice. When the Ga content increased to 15.52 at %, the film’s conductivity improved again. Furthermore, all films presented an average transmittance exceeding 80% in the visible region. Regarding the film’s electrical stability, GZO thermally treated below 200 °C exhibited no significant deterioration in electrical properties, but such treatment over 200 °C greatly reduced the film’s conductivity. In normal atmospheric conditions, the conductivity of GZO films remained very stable at ambient temperature for more than 240 days. Full article

(This article belongs to the Special Issue Advances in Transparent Conducting Materials)

► Show Figures

Graphical abstract

13 pages, 4198 KiB

Open AccessArticle

Investigation of the Structural, Electrical, and Optical Properties of the Nano-Scale GZO Thin Films on Glass and Flexible Polyimide Substrates

by Fang-Hsing Wang, Kun-Neng Chen, Chao-Ming Hsu, Min-Chu Liu and Cheng-Fu Yang

Nanomaterials 2016, 6(5), 88; https://doi.org/10.3390/nano6050088 - 10 May 2016

Cited by 38 | Viewed by 7880

Abstract

In this study, Ga₂O₃-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition [...] Read more.

In this study, Ga₂O₃-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition rate, all the GZO thin films with a nano-scale thickness of about 150 ± 10 nm were controlled by the deposition time. X-ray diffraction patterns indicated that the GZO thin films were not amorphous and all exhibited the (002) peak, and field emission scanning electron microscopy showed that only nano-scale particles were observed. The dependences of the structural, electrical, and optical properties of the GZO thin films on different deposition temperatures and substrates were investigated. X-ray photoemission spectroscopy (XPS) was used to measure the elemental composition at the chemical and electronic states of the GZO thin films deposited on different substrates, which could be used to clarify the mechanism of difference in electrical properties of the GZO thin films. In this study, the XPS binding energy spectra of Ga2p_3/2 and Ga2p_1/2 peaks, Zn2p_3/2 and Zn2p_1/2 peaks, the Ga3d peak, and O₁_s peaks for GZO thin films on glass and PI substrates were well compared. Full article

(This article belongs to the Special Issue Nanomaterials for Flexible and Stretchable Devices: Synthesis, Processes, and Applications)

► Show Figures

Figure 1

6 pages, 1371 KiB

Open AccessArticle

Synthesis of Ga-Doped ZnO Nanorods by Hydrothermal Method and Their Application to Ultraviolet Photodetector

by Sheng-Joue Young, Chia-Lin Chiou, Yi-Hsing Liu and Liang-Wen Ji

Inventions 2016, 1(1), 3; https://doi.org/10.3390/inventions1010003 - 16 Feb 2016

Cited by 19 | Viewed by 7717

Abstract

In this study, high-density single crystalline Ga-doped ZnO (GZO) nanorods were grown on glass substrate by the hydrothermal method. The structural and optoelectronic properties of Ga-doped ZnO nanorods were studied. The microstructure of the GZO was studied by scanning electrical microscope (SEM). The [...] Read more.

In this study, high-density single crystalline Ga-doped ZnO (GZO) nanorods were grown on glass substrate by the hydrothermal method. The structural and optoelectronic properties of Ga-doped ZnO nanorods were studied. The microstructure of the GZO was studied by scanning electrical microscope (SEM). The structural characteristics of the GZO were measured by X-ray diffraction (XRD). It was found that the peaks related to the wurtzite structure ZnO (100), (002), and (101) diffraction peaks. The (002) peak indicates that the nanorods were preferentially oriented in the c-axis direction. The existence of Ga was examined by energy diffraction spectra (EDS), indicating the Ga atom entered into the ZnO lattice. The optical properties of the GZO were measured by photoluminescence spectra. It was found that all GZO nanorod arrays showed two different emissions, including UV (ultraviolet) and green emissions. GZO nanorod metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PD) were also fabricated. The photo-current and dark-current constant ratio of the fabricated PD was approximately 15.2 when biased at 1 V. Full article

(This article belongs to the Special Issue Innovation and Inventions of Electro-Optical Materials and Devices and their Application)

► Show Figures

Graphical abstract

Search Results (16)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (16)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI