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1.
Characterization of non-stoichiometric Ga2O3-x thin films grown by radio-frequency powder sputtering
Su Yeon Cha Dongwoo Kim Hojoon Lim Bongjin Simon Mun Do Young Noh Hyon Chol Kang 《Ceramics International》2021,47(3):3238-3243
We report the synthesis and characterization of non-stoichiometric Ga2O3-x thin films deposited on sapphire (0001) substrates by radio-frequency powder sputtering. The chemical and electronic states of the non-stoichiometric Ga2O3-x thin films were investigated. By sputtering in an Ar atmosphere, the as-grown thin films become non-stoichiometric Ga2O2.7, due to the difference in sputtering yield between Ga and O species of the Ga2O3 target. The electronic states of the thin films consist of ~85% Ga3+ and ~15% Ga1+, corresponding to Ga2O3 and Ga2O, respectively. The films have the electrical characteristics of a semiconductor, with electrical conductivity of approximately 5.0 × 10-4 S cm-1 and a carrier concentration of 4.5 × 1014 cm-3 at 300 K. 相似文献
2.
Soheil Mobtakeri Yunus Akaltun Ali Özer Merhan Kılıç Ebru Şenadım Tüzemen Emre Gür 《Ceramics International》2021,47(2):1721-1727
In this study, gallium oxide (Ga2O3) thin films were deposited on sapphire and n-Si substrates using Ga2O3 target by radio frequency magnetron sputtering (RFMS) at substrate temperature of 300 °C at variable RF power and deposition pressure. The effects of deposition pressure and growth power on crystalline structure, morphology, transmittance, refractive index and band gap energy were investigated in detail. X-ray diffraction results showed that amorphous phase was observed in all the as-deposited thin films except for the thin films grown at low growth pressure. All the films showed conversion to poly-crystal β-Ga2O3 phase after annealing process. When the deposition pressure increased from 7.5 mTorr to 12.20 mTorr, change in the 2D growth mode to 3D columnar growth mode was observed from the SEM images. Annealing clearly showed formation of larger grains for all the thin films. Lower transmission values were observed as the growth pressure increases. Annealing caused to obtain similar transmittance values for the thin films grown at different pressures. It was found that a red shift observed in the absorption edges and the energy band gap values decrease with increasing growth pressure. For as-deposited and annealing films, increasing sputtering power resulted in the increase refractive index. 相似文献
3.
《Ceramics International》2021,47(21):29748-29757
This study systematically investigated the structural, optical, and morphological evolution of Gallium oxide (Ga2O3) films deposited at different substrate temperatures on Al2O3(0001) using pulsed laser deposition (PLD). The thickness of the Ga2O3 films was standardized in order to eliminate its effect on the film properties. The effect of substrate temperature from room temperature to 600 °C on the film's transmittance, crystalline structure, chemical composition and surface morphology, was explored. The plasma species generated during the deposition of the PLD process were monitored and analyzed employing in situ optical emission spectroscopy. The deposition rate of the films decreased with increasing substrate temperature. X-ray photoelectron spectroscopy was used to detect both Ga3+ and Ga + oxidation states in all prepared films, which indicated substoichiometric Ga2O3 films deficient in oxygen. The percentage of non-lattice oxygen decreased with increasing substrate temperature. At optimal condition, mono-crystaline β-Ga2O3 was produced with a high visible and near-infrared transmittance, large grain size and smooth surface, which is suitable for the application in high-performance power electric devices and photoelectronic devices. 相似文献
4.
《Ceramics International》2016,42(11):12783-12788
(AlGa)2O3 thin films were deposited on (0001) sapphire substrates by pulsed laser deposition at different substrate temperatures. The influence of substrate temperature on surface morphology, optical properties, and crystal quality has been systematically investigated by atomic force microscope, transmission spectra, X-ray diffraction, and Raman spectroscopy. The results reveal that all the (AlGa)2O3 films have smooth surface and high transmittance. The (AlGa)2O3 film with the good crystal quality can be obtained at a substrate temperature of 400 °C. Our results provide an experimental basis for realizing the Ga2O3-based quantum well. 相似文献
5.
Ming‐Chuan Chang Chieh‐Szu Huang Yi‐Da Ho Cheng‐Liang Huang 《Journal of the American Ceramic Society》2018,101(2):674-682
To reduce power consumption of transparent oxide‐semiconductor thin film transistors, a gate dielectric material with high dielectric constant and low leakage current density is favorable. According to previous study, the bulk TiNb2O7 with outstanding dielectric properties may have an interest in its thin‐film form. The optical, chemical states and surface morphology of sol‐gel derived TiNb2O7 (TNO) thin films are investigated the effect of postannealing temperature lower than 500°C, which is crucial to the glass transition temperature. All films possess a transmittance near 80% in the visible region. The existence of non‐lattice oxygen in the TNO film is proposed. The peak area ratio of non‐lattice oxygen plays an important role in the control of leakage current density of MIM capacitors. Also, the capacitance density and dissipation factor were affected by the indium tin oxide (ITO) sheet resistance at high frequencies. The sample after postannealing at 300°C and electrode‐annealing at 150°C possesses a high dielectric constant (>30 at 1 MHz) and a low leakage current density (<1 × 10?6 A/cm2 at 1 V), which makes it a very promising gate dielectric material for transparent oxide‐semiconductor thin film transistors. 相似文献
6.
《Ceramics International》2023,49(7):10634-10644
This work explored the properties of RF magnetron sputtered Sn-doped Ga2O3 films grown on sapphire substrates at different oxygen flow ratios from 0.0 to 2.5%. The in situ optical emission spectroscopy was conducted to monitor the plasma radicals generated during the films’ deposition. All the films deposited at room temperature show amorphous structures with some nanoparticles. The deposition rate decreased monotonically with increasing oxygen flow ratio. The proposed conductive mechanism of the films can be mainly attributed to the changes in the ratio of substitutional Sn (Sn4+ valance state) atoms replacing lattice Ga sites (Ga3+ valance state) and the SnO2 phase in the films. Metal–semiconductor–metal solar-blind photodetectors were developed and analyzed to illustrate the effect of oxygen flow ratio. A high performance photodetector with a low dark current of 1.14 pA, high on/off ratio of 812 and short rise/decay time of 0.05 s/0.12 s was realized at an optimization growth condition. The elaboration of the conductive mechanism and effect of oxygen flow ratio on the performance of Sn-doped Ga2O3 films and their photodetectors is crucial for the preparation of high-quality Sn-doped Ga2O3 films and its application in optoelectronic devices. 相似文献
7.
《Journal of the European Ceramic Society》2014,34(15):3715-3722
The properties of sputtering targets have recently been found to affect the performances of sputtered films and the sputtering process. To develop high-quality GZO ceramic targets, the influences of Ga2O3 content and sintering temperature on the sintering behavior, microstructure, and electrical properties of GZO ceramic targets were studied.The results showed that the increase in Ga2O3 content from 3 wt% (GZO-3Ga) and 5 wt% (GZO-5Ga) not only inhibited the densification but retarded grain growth. During sintering, ZnGa2O4 phase formed before 800 °C, and Zn9Ga2O12 phase was found after sintering at 1000 °C. Moreover, after sintering at 1200 °C, the number of Zn9Ga2O12 precipitates increased at the expense of ZnGa2O4 and ZnGa2O4 disappearing completely. The relative density, grain size, and resistivity of GZO-3Ga sintered at 1400 °C in air were 99.3%, 3.3 μm, and 2.8 × 10−3 Ω cm, respectively. These properties of GZO ceramics are comparable to properties reported in the literature for AZO sintered in air. 相似文献
8.
Tantalum (Ta) and titanium (Ti) metal targets were direct current (DC) magnetron sputtered in the oxygen environment by varying its relative areas to deposit (Ta2O5)1-x- (TiO2)x (TTOx) thin films, with x = 0, 0.03, 0.06, and 0.08, onto the boron-doped p-silicon (1 0 0) and optically polished quartz substrates, at room temperature; and were annealed at 500, 600, 700, and 800 °C, for 1.5 h. The thin films annealed at and above 600 °C show the Ta2O5 structure. The leakage current density and capacitance-voltage (C–V) characteristics were measured for TTOx, x ≤ 0.08, assisted Ag/TTOx/p-Si metal– oxide– semiconductor (MOS) structures. The leakage current density was found minimum, for the films annealed at 800 °C, for all the prepared TTOx films, x ≤ 0.08. The minimum leakage current density 1.6 × 10?8 A/cm2, at 3.5 × 105 V/cm electric field, was observed for x = 0.03, annealed at 800 °C, among the prepared compositions. The prepared TTO0.03 films, annealed at 700 °C show maximum dielectric constant 39, at 1 MHz. The optical parameters, viz., refractive index (n), extinction coefficient (k), and optical band gap (Eg) of the films, with x = 0.03, prepared on quartz substrates, were determined from their optical transmittance plots. The values of n and k of the crystalline films were observed increasing from 2.123 to 2.143, and 0.099 to 0.130, respectively, at 550 nm wavelength; and Eg decreasing from 3.95 to 3.89 eV with the increasing annealing temperature, from 600 to 800 °C. Ohmic emission, in the lower electric field; Schottky and space-charge- limited current conduction mechanisms, in the intermediate to higher electric fields, were generally envisaged from the current-voltage characteristics in the prepared Ag/TTO0.03/p-Si structures. 相似文献
9.
《Ceramics International》2022,48(10):13524-13530
Thin film sensors are employed to monitor the health of hot-section components of aeroengine intelligence (for instance, blades), and electrical insulating layers are needed between the metal components and thin film sensors. For this purpose, the electrical insulation characteristics of an yttria-stabilized zirconia (YSZ)/Al2O3 multilayer insulating structure were investigated. First, YSZ thin films were deposited by DC reactive sputtering at various substrate temperatures, and the microstructural features were investigated by scanning electron microscopy and X-ray diffraction. The results indicate that the micromorphology of the YSZ thin film gradually became denser with increasing substrate temperature, and no new phases appeared. The compact and uniform topography of the YSZ thin film improved the insulation properties of the multilayer insulating structure and enhanced the adhesion of the thin film sensors. In addition, the electrical insulation properties of the YSZ/Al2O3 multilayer insulating structure were evaluated via insulation resistance tests from 25 to 800 °C, in which the YSZ thin film was deposited at 550 °C. The results show that the insulation resistance of the multilayer structure increased by an order of magnitude compared with that of the conventional Al2O3 insulating layer, reaching 135 kΩ (5.1 × 10?6 S/m) at 800 °C. Notably, the insulation resistance was still greater than 75 kΩ after annealing at 800 °C for 5 h. Finally, the shunt effect of the YSZ/Al2O3 multilayer insulating structure was estimated using a PdCr thin film strain gauge. The relative resistance error was 0.24%, which demonstrates that the YSZ/Al2O3 multilayer insulating structure is suitable for thin film sensors. 相似文献
10.
《Ceramics International》2016,42(15):16867-16871
Anew sol-gel route has been applied to synthetize dense Al2O3thin films from aluminum isopropoxide (Al(OPri)3)as raw precursor material. The results show that, in the solution, acetylacetone (AcAc) and aluminum form a complex compound which effectively suppresses the growth of colloidal particles and makes the sol very stable. Al2O3thin films fabricated by spin-coating method and calcined at 500 °C for 3 h possess an amorphous structure and exhibit a highly homogeneous surface texture without evidence of holes or cracks throughout the film. Moreover, the prepared films display a low leakage current and a high transmittance. This new sol-gel route appears to be a highly promising method to synthetize dense Al2O3 thin films from Al(OPri)3, and could provide a wide range of optical and electric applications. 相似文献
11.
《Journal of the European Ceramic Society》2017,37(10):3411-3415
A Ce-doped (Gd2Y)(Ga3Al2)O12 ceramic with good performance was fabricated by sintering in an oxygen atmosphere and hot isostatic pressing. The microstructure as well as the optical and scintillation characteristics of the ceramic was investigated. The ceramic exhibited a high transmittance of 78% in the range of 500–800 nm. The radioluminescence intensity of the ceramic reached up to 30 times that of a bismuth germinate single crystal, and the light yield within 750 ns shaping time was approximately 25800 photons/MeV under 137Cs γ-ray irradiation. 相似文献
12.
《Ceramics International》2021,47(20):28859-28865
Highly transparent polycrystalline Tm2O3 ceramics were successfully fabricated by vacuum sintering at temperatures from 1650 to 1850 °C for 8 h using commercial Tm2O3 and ZrO2 (1 at%) powders as starting materials. It is the first time that ZrO2 was reported as a sintering additive to prepare Tm2O3 transparent ceramics. The effects of sintering temperature on the optical transmittance and microstructure of Tm2O3 transparent ceramics were studied. The desired Tm2O3 ceramics with relative density of 99.8% and an average grain size of approximately 9.7 μm were obtained at 1800 °C and the in-line transmittance reached 75% at 880 nm and fluctuated around 80% from 2100 to 2400 nm, respectively. This study demonstrated that Tm2O3 transparent ceramics with higher in-line transmittance and smaller grain size could be prepared by using ZrO2 as sintering additive at a relatively lower vacuum sintering temperature compared to those already reported in open literatures. 相似文献
13.
《Journal of the European Ceramic Society》2006,26(10-11):2151-2154
BaTi5O11 thin films were grown on the poly-Si/SiO2/Si substrate using rf magnetron sputtering. The BaO-TiO2 thin film deposited on the poly-Si substrate had an amorphous phase even though the growth temperature was high at 550 °C. The amorphous film was crystallized into the BaTi5O11 phase when the film was post annealed above 800 °C. The post annealing temperature is one of the most important factors for the formation of the crystalline BaTi5O11 thin film. The homogeneous BaTi5O11 thin film was obtained when the film was grown at 550 °C and rapid thermal annealed (RTA) at 900 °C for 3 min. The dielectric constant (ɛr) of the BaTi5O11 film measured at 100 kHz was about 35 and the dissipation factors of all the films were smaller than 4.0%. The dielectric properties of the BaTi5O11 thin film were also measured at microwave frequencies. For the BaTi5O11 thin film grown at 550 °C and RTA at 900 °C for 3 min, the ɛr of 34–30 and dielectric loss of 0.025 ± 0.005 were obtained at 1–6 GHz. 相似文献
14.
Lirong Liang Hong Zhou Guangheng Wu Zhong Mo Dinghua Bao 《Ceramics International》2013,39(2):1335-1340
We report on an effective combination of good dielectric properties with bright red emission in Y3+/Eu3+-codoped ZrO2 thin films. The thin films were deposited on fused silica and Pt/TiO2/SiO2/Si substrates using a chemical solution deposition method. The crystal structure, surface morphology, electrical and optical properties of the thin films were investigated in terms of annealing temperature, and Y3+/Eu3+ doping content. The 5%Eu2O3–3%Y2O3–92%ZrO2 thin film with 400 nm thickness annealed at 700 °C exhibits optimal photoluminescent properties and excellent electrical properties. Under excitation by 396 nm light, the thin film on fused silica substrate shows bright red emission bands centered at 593 nm and 609 nm, which can be attributed to the transitions of Eu3+ ions. Dielectric constant and dissipation factor of the thin films at 1 kHz are 30 and 0.01, respectively, and the capacitance density is about 65.5 nf/cm2 when the bias electric field is less than 500 kV/cm. The thin films also exhibit a low leakage current density and a high optical transmittance with a large band gap. 相似文献
15.
《Ceramics International》2022,48(9):12112-12117
Gallium oxide (Ga2O3) is a promising candidate for next-generation solar-blind photodetectors (PDs) because of its large bandgap of 4.9 eV. Its single-crystal nanorod structure improves its photoelectric performance, which promotes carrier transformation and separation. However, Ga2O3 nanorods fabricated by the hydrothermal method have many oxygen vacancies, which largely enhance the dark current and reduce the on/off ratio of PDs, restricting application of such devices. Therefore, in this paper, dual strategies are applied to reduce the dark current of a metal–semiconductor–metal-structured Ga2O3 nanorod PD fabricated by the hydrothermal method. Through these dual strategies, which include annealing treatment and the application of a polymethyl methacrylate (PMMA) coating, the dark current of the PD is reduced from 1.34 × 10?7 to 2.04 × 10?9 A at 1 V, resulting in the on/off ratio of the PD reaching as high as 3.24 × 104. Besides, the responsivity and detectivity of the device reach 1.73 A/W and 2.53 × 1012 Jones respectively, which represents better performance than those of other reported Ga2O3 nanorod array PDs. Results have shown that the new strategy adopted can greatly improve the performance of Ga2O3-based ultraviolet photodetectors. 相似文献
16.
《Ceramics International》2017,43(17):14732-14741
A study was carried out to compare element chemical states and grain orientation growth between two ITO targets, which were respectively sintered at 1560 °C (target A#) and 1600 °C (target B#). The lower sintering temperature can be beneficial to increase mass content ratio of In2O3 to SnO2, reduce the production of Sn2+ ions and the component of O-In as well as increase oxygen holes, and can also promote grain orientation growth of In2O3 and In4Sn3O12 phase. Three groups of ITO films were deposited at 230 °C using these targets to investigate the effects of sputtering parameters on the photoelectric properties of ITO films. Under different sputtering pressures, the sheet resistance for target A# has higher sensitivity to low O2 flow, while target B# displays higher sensitivity to high O2 flow. In the case of sputtering pressure of 0.5 Pa, ITO films for target A# displays the highest visible transmittance. In addition, annealing process could decrease the sheet resistance and improve the transmittance of ITO films because of its effect on the crystallinity and surface morphology of ITO films. 相似文献
17.
We propose a transparent conductive oxide electrode scheme of gallium oxide nanoparticle mixed with a single-walled carbon nanotube (Ga2O3 NP/SWNT) layer for deep ultraviolet light-emitting diodes using spin and dipping methods. We investigated the electrical, optical and morphological properties of the Ga2O3 NP/SWNT layers by increasing the thickness of SWNTs via multiple dipping processes. Compared with the undoped Ga2O3 films (current level 9.9 × 10-9 A @ 1 V, transmittance 68% @ 280 nm), the current level flowing in the Ga2O3 NP/SWNT increased by approximately 4 × 105 times and the transmittance improved by 9% after 15 times dip-coating (current level 4 × 10-4 A at 1 V; transmittance 77.0% at 280 nm). These improvements result from both native high transparency of Ga2O3 NPs and high conductivity and effective current spreading of SWNTs. 相似文献
18.
Prashant Thapliyal Alok S. Kandari Vijendra Lingwal N.S. Panwar G. Mohan Rao 《Ceramics International》2021,47(9):12066-12071
(Ta2O5)1-x- (TiO2)x (TTOx) thin films, with x = 0, 0.03, 0.06, 0.08, and 0.11, were deposited using magnetron direct current (DC) sputtering method onto the P/boron-silicon (1 0 0) substrates by varying areas of Tantalum and Titanium metallic targets, in oxygen environment at ambient temperature. The as-deposited thin films were annealed at temperatures ranging from 500 to 800 °C. Generally, the formation of the Ta2O5 structure was observed from the X-ray diffraction measurements of the annealed films. The capacitance of prepared metal– oxide– semiconductor (MOS) structures of Ag/TTOx/p-Si was measured at 1 MHz. The dielectric constant of the deposited films was observed altering with varying composition and annealing temperature, showing the highest value 71, at 1 MHz, for the TTOx films, x = 0.06, annealed at 700 °C. With increasing annealing temperature, from 700 to 800 °C, the leakage current density was observed, generally decreasing, from 10?5 to 10?8 A cm?2, for the prepared compositions. Among the prepared compositions, films with x = 0.06, annealed at 800 °C, having the observed value of dielectric constant 48, at 1 MHz; and the leakage current density 2.7 × 10?8 A cm?2, at the electric field of 3.5 × 105 V cm?1, show preferred potential as a dielectric for high-density silicon memory devices. 相似文献
19.
《Journal of the European Ceramic Society》1999,19(6-7):753-758
Al2O3-TiO2 thin films were prepared by a sol–gel processing. Sols were prepared having different TiO2/Al2O3 molar ratios, i.e., 9:1, 8:2, and 6:4, without and with the addition of 10 at% of K ions. The films were prepared by dipping the substrates (silicon wafers, alkali-free glass or alumina with comb-type Au electrodes) in the sols. The films were fired in air for 1 h at 300, 500, 650 and 800°C. The films were amorphous, at any composition, up to the firing temperature of 500°C. Crystallization of the films was inhibited by larger contents of Al2O3 and K. The humidity-sensitive electrical properties of the thin films were studied using d.c. and a.c. measurements. The addition of K dramatically improved the relative humidity response of the films. 相似文献
20.
Housei Akazawa 《Ceramics International》2021,47(3):3292-3298
Undoped and Er3+-doped Bi2O3 thin films were sputter-deposited on Si(100) substrates. Sufficiently oxidized Bi2O3 films with refractive indices between 2.17?2.23 were obtained at a wavelength of 633 nm; these values are comparable to those of bulk Bi2O3 crystals. While the film composition was stable for deposition temperatures between room temperature (RT) and 450 °C, the refractive index steeply decreased above 450 °C and reached 1.4 at 600 °C. The lowering of the optical transmittance spectra indicated aggregation of metallic Bi and darkening of the film. All films exhibited X-ray diffraction patterns of α-Bi2O3. The direct and indirect bandgap energies derived from the Tauc plots were 3.4–3.7 eV and 1.9–2.5 eV, respectively, depending on the O2 flow rate and deposition temperature. Upon excitation of Er3+-doped Bi2O3 films at 532 nm, Er3+ emissions peaking at 1537 and 1541 nm appeared, and the photoluminescence spectra included fine structures reflecting crystal-field splitting. Resonant excitation of Er3+ 4f levels and indirect excitation via the defect levels of Bi2O3 followed by energy transfer to Er3+ contributed to the emission. The films deposited at RT with Er concentrations of 2 at.% had the emission intensity of Er3+, but concentration quenching strongly suppressed the Er3+ emission because the doped Er3+ ions stayed inside the Bi2O3 crystals. At deposition temperatures above 400 °C, the concentration quenching was mitigated possibly because out-diffusion of Er3+ ions reduced the effective number of Er3+ ions in the Bi2O3 crystalline domains. 相似文献