Ga Doping Concentrations Research Articles

Gallium-Doped Hydroxyapatite: Shape Transformation and Osteogenesis Activity.

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells.

Hydrothermal growth and ultraviolet sensing performance of well-aligned Ga-doped ZnO nanowire arrays

Herein, gallium (Ga)-doped zinc oxide (ZnO) nanowire arrays (GZNWAs) with different Ga doping concentrations (Ga/Zn = 0–4 atom%) were grown on the interdigital patterned fluoro-doped tin oxide glass substrates by a hydrothermal technique, their crystalline structure, morphology and ultraviolet (UV) sensing performance were focused on investigating. The results showed that all the as-grown samples were hexagonal wurtzite structure of ZnO. When the Ga doping concentration was below 4%, well-aligned GZNWAs were achieved. Furthermore, five UV photodetectors (PDs) were prepared using the GZNWAs as photoactive layers, all the devices were found to be excellent responses towards 365 nm light. Among these devices, the GZNWAs UV PD (1% Ga) maintained the optimal performance, its responsivity, sensitivity, detectivity, external quantum efficiency, response time and decay time were 72.8 A/W at 5 V, 747.8 at 0 V, 5.5 × 1012 Jones, 2.5 × 104%, 10.6 s and 45.6 s, respectively.

Tuning the photoinduced charge transfer from CdTe quantum dots to ZnO nanofilms through Ga doping

Tuning the charge transfer rate between quantum dots (QDs) and metal oxide (MO) is important for improving the performances of QDs-MO devices. And tailoring the energy band of MO is one way to tune the charge transfer rate. In this work, we enhance the charge transfer rate between CdTe QDs and ZnO through tailoring the optical band gap of ZnO nanofilms by Ga-doping. The Ga doping influenced the photo luminescence (PL) performance of CdTe QDs/ZnO hybrid structures. The results of time-resolved fluorescence spectra revealed that the charge transfer rate from CdTe QDs to ZnO nanofilms could be tuned by varying the Ga doping concentrations in ZnO. And, transfer rate were increased by up to ~4.1 times through Ga doping. In addition, the structure showed electron transfer efficiency improvements to the tune of ~25.3%. We attribute the improvement to efficient electron transfer via band-band transfer and the defects pathways induced by Ga-doping. The experimental results will be useful for improving the efficiency of optical devices using QDs/ZnO hybrid structure.

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

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.

Hydrothermal synthesis of Ga-doped In2O3 nanostructure and its structural, optical and photocatalytic properties

In this work, pure and Ga-doped In2O3 nanostructures have been synthesized by facile template-free hydrothermal method. The structural, morphological and optical properties are characterized by using XRD, FT-IR, HR-SEM and TEM, EDS, XPS, UV-DRS, and PL techniques. X-ray diffraction analysis indicates a pure cubic phase while crystallite size decreases with Ga doping. HR-SEM and TEM observations reveal irregular-shaped and spindle-like nanostructures with enhanced crystallinity and reduction in particle size with Ga doping. XPS spectra reveal the oxidation state of Ga is +3. The energy band gap estimated by UV–vis DRS spectroscopy is found to increase slightly from 3.40 to 3.45eV with Ga doping. Photoluminescence spectra display violet, blue and green emission peaks are observed during Ga doping concentrations. Photodegradation of Methylene blue dye under ultra violet light radiation is found to double with Ga doping; i.e. 48% for Ga- In2O3 compared to 22% for pure In2O3.

Effect of Gallium Doping on the Characteristic Properties of Polycrystalline Cadmium Telluride Thin Film

Ga-doped CdTe polycrystalline thin films were successfully electrodeposited on glass/fluorine doped tin oxide substrates from aqueous electrolytes containing cadmium nitrate (Cd(NO3)2·4H2O) and tellurium oxide (TeO2). The effects of different Ga-doping concentrations on the CdTe:Ga coupled with different post-growth treatments were studied by analysing the structural, optical, morphological and electronic properties of the deposited layers using x-ray diffraction (XRD), ultraviolet–visible spectrophotometry, scanning electron microscopy, photoelectrochemical cell measurement and direct-current conductivity test respectively. XRD results show diminishing (111)C CdTe peak above 20 ppm Ga-doping and the appearance of (301)M GaTe diffraction above 50 ppm Ga-doping indicating the formation of two phases; CdTe and GaTe. Although, reductions in the absorption edge slopes were observed above 20 ppm Ga-doping for the as-deposited CdTe:Ga layer, no obvious influence on the energy gap of CdTe films with Ga-doping were detected. Morphologically, reductions in grain size were observed at 50 ppm Ga-doping and above with high pinhole density within the layer. For the as-deposited CdTe:Ga layers, conduction type change from n- to p- were observed at 50 ppm, while the n-type conductivity were retained after post-growth treatment. Highest conductivity was observed at 20 ppm Ga-doping of CdTe. These results are systematically reported in this paper.

Wavelength-Tunable Electroluminescent Light Sources from Individual Ga-Doped ZnO Microwires.

Electrically driven wavelength-tunable light emission from biased individual Ga-doped ZnO microwires (ZnO:Ga MWs) is demonstrated. Single crystalline ZnO:Ga MWs with different Ga-doping concentrations have been synthesized using a one-step chemical vapor deposition method. Strong electrically driven light emission from individual ZnO:Ga MW based devices is realized with tunable colors, and the emission region is localized toward the center of the wires. Increasing Ga-doping concentration in the MWs can lead to the redshift of electroluminescent emissions in the visible range. Interestingly, owing to the lack of rectification characteristics, relevant electrical measurement results show that the alternating current-driven light emission functions excellently on the ZnO:Ga MWs. Consequently, individual ZnO:Ga MWs, which can be analogous to incandescent sources, offer unique possibilities for future electroluminescence light sources. This typical multicolor emitter can be used to rival and complement other conventional semiconductor devices in displays and lighting.

Structural, optical, and electrical properties of low-concentration Ga-doped CdO thin films by pulsed laser deposition

CdO thin films with low Ga doping concentrations were deposited on low-cost glass substrates by pulsed laser deposition. The influence of Ga doping concentration on structural, electrical, and optical properties of CdO thin films was studied. The Ga-doped CdO thin films show decreasing plasma wavelength and resistivity when increasing doping concentration, and the widening optical gap varies from 2.49 to 2.85 eV with the Ga doping concentration increasing from 0.2 to 1.2 at% due to Moss–Burstein effect. When Ga doping concentration in CdO thin films was controlled at low level from 0.6 to 1.0 at%, the films achieved both high conductivity (~10−4 Ω·cm) and high transmittance up to the infrared region (>1600 nm), which demonstrates good potential as an ideal transparent conductor of full-spectrum photovoltaic devices.

Low resistive gallium doped nanocrystalline zinc oxide for gas sensor application via sol–gel process

This paper reports the effect of low concentration of Ga doping on the performance of ZnO thin-film based gas sensors. The ZnO films were synthesized on the alkali-free glass substrates by employing a sol–gel process. Different concentrations of Ga were added to the sol–gel mixture for systematic comparison of doping effect. The effect of Ga doping on the microstructure, optical properties, surface morphology, electrical conductivity and gas sensing characteristics was investigated comparing undoped and Ga-doped ZnO thin films. The results revealed that the grain size decreased after the doping of Ga in ZnO. The optical transmittance and bandgap of ZnO films were not affected by the doping of Ga. The Ga doping resulted in a significant increase in electrical conductivity of ZnO thin films. The gas sensing behavior was studied under different concentrations of H2 exposure in the air at an operating temperature of 130°C. The results indicated that the sensing response for H2 was enhanced after the doping of a trace amount of Ga. It was found that 0.3at.% was the optimum Ga doping concentration for ZnO sensors in the low Ga doping concentrations, which exhibited both high response and short response time. The selectivity of 0.3at.% Ga-doped ZnO sensor was investigated for important industrial gas mixtures. It was found that the Ga-doped ZnO sensors exhibited a better detection capability of H2 than NH3 and CH4.

Effect of Ga doping concentrations, substrate temperatures and working pressures on the electrical and optical properties of ZnO thin films

We fabricated Ga-doped ZnO (GZO) thin films on glass substrate by RF magnetron sputtering method with different conditions of Ga2O3 concentration, substrate temperature and working pressure. Next we investigated the electrical, optical and structural properties of the GZO thin films. At a substrate temperature of 300 °C, a working pressure of 1 mTorr, and a Ga2O3 concentration of 3 wt%, the GZO thin films showed the lowest resistivity of 3.16 × 10−4 Ω cm, a carrier concentration of 7.64 × 1020 cm−3 and a Hall mobility of 25.8 cm2/Vs. Moreover, the GZO thin films exhibited the highest (002) orientation under the same conditions and the full width at half maximum of X-ray peak was 0.34°. All GZO thin films showed the optical transmittance of more than 80 % in the visible range regardless of working conditions. The Burstein–Moss effect was observed by the change of doping concentration of Ga2O3. The GZO thin films were fabricated to have the good electrical and optical properties through optimizing doping concentration of Ga2O3, substrate temperature, working pressure. Therefore, we confirmed the possibility of application of GZO thin film as transparent conductive oxide used in flat panel display and solar cell.

Investigation of thermal resistance and power consumption in Ga-doped indium oxide (In2O3) nanowire phase change random access memory

The resistance stability and thermal resistance of phase change memory devices using ∼40 nm diameter Ga-doped In2O3 nanowires (Ga:In2O3 NW) with different Ga-doping concentrations have been investigated. The estimated resistance stability (R(t)/R0 ratio) improves with higher Ga concentration and is dependent on annealing temperature. The extracted thermal resistance (Rth) increases with higher Ga-concentration and thus the power consumption can be reduced by ∼90% for the 11.5% Ga:In2O3 NW, compared to the 2.1% Ga:In2O3 NW. The excellent characteristics of Ga-doped In2O3 nanowire devices offer an avenue to develop low power and reliable phase change random access memory applications.

Investigation of aluminum and gallium co-doped ZnO powders and their effects on the properties of targets

Aluminum and gallium co-doped ZnO (AGZ) powders were synthesized by the chemical co-precipitation method with the same Al doping concentration (3at%) and different Ga doping concentrations (0–0.5at%). The microstructure, lattice distortion and surface morphology of AGZ powders were investigated because the properties of targets were related to corresponding powders. Both AZO and AGZ targets were prepared by molding and atmospheric pressure sintering. The microstructure, morphologies, electrical properties and densification of sintered targets were also studied. The measured results showed that the grain sizes of AGZ powders are smaller than AZO powder, the former has a larger specific area, and the distribution of AGZ particles are more homogeneous, which are good for preparation of a high-density target. Besides, the extent of ZnO lattice distortion exhibits a downward trend with the increase of the Ga doping concentration. The AGZ target with appropriate concentration of Ga (0.3at%) has the lowest resistivity of 2.518×10−3Ωcm and the highest relative density of 99.2%. In general, the moderate Al–Ga co-doping proportion leads to finer grain size, lower resistivity, higher Hall mobility and higher sintered density.

Effect of Ga Doping Concentration on Electrical and Optical Properties of Nano-ZnO:Ga Transparent Conductive Films

Transparent conductive nano ZnO thin films with different Ga doping concentrations (1, 3, 5, 7 at.%) were prepared on glass substrate by RF magnetron sputtering. The influence of Ga doping concentration on the structural, electrical and optical properties of ZnO:Ga films was investigated by XRD, SEM, Hall measurement and optical-transmission spectroscopy. It shows that the nano ZnO:Ga films are dense and flat, and have polycrystalline structure with preferential (002) and weak (101) orientation. The grain sizes, carrier concentration and Hall mobility changes non-linearly with the increase of Ga-content. The lowest resistivity of 1.44×10−3 Ωcm appears at 3 at.% Ga doping concentration. The average transmittance of the films is about 80∼90% in the visible range. The optical band gap obtained for these films is larger than for pure ZnO (∼3.37 eV).