Ga Doping Research Articles

High Detectivity and Fast Response UV Detector Using Ga Doped SnO₂ Nanowire Arrays

Ga doped SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Nanowires (Ga: SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs) based UV photodetector (PD) were fabricated over Si substrate using glancing angle deposition technique. Among various doping concentrations, the 5% Ga: SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs device exhibited the least dark current (2.67 nA) with high barrier height and highest rectification ratio (~54.6) at −1 V. Samples with Ga doping concentration higher than 5%, induced extra defect level limiting their device performance. Moreover, the 5% Ga: SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs PD exhibited responsivity and specific detectivity of 16.48 A/W and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.33\times 10^{13}$ </tex-math></inline-formula> Jones respectively (at 300 nm) and a low noise equivalent power of 53 fW. Furthermore, this device showed fast photoresponse with a rise and fall time of 2 ms and 1.5 ms respectively after doping. Therefore, this letter demonstrates a well-controlled Ga: SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs based high performance, low-cost UV-PD.

Enhanced photocatalytic activity of chemically deposited ZnO nanowires using doping and annealing strategies for water remediation

Water pollution represents one of the most challenging ecological threats humankind faces nowadays, resulting in the fast growing development of the heterogeneous photocatalysis using ZnO nanowires. A typical approach to improve the photocatalytic activity consists in achieving their extrinsic doping with group-III elements, but the reasons accounting for the resulting, modified photocatalytic processes are multifactorial and still under debate. In this work, we investigate the effect of the Al and Ga doping of ZnO nanowires grown by chemical bath deposition and of the thermal annealing under oxygen atmosphere on their photocatalytic activity and establish the dependence of the photocatalytic processes on their structural morphology, dimensions, dopant-induced defects, surface properties, and optical absorption and emission. We reveal that the photocatalytic processes strongly depend on the nature of dopants and are systematically enhanced after thermal annealing. The photocatalytic activity of annealed, Al-doped ZnO nanowires is found to be more efficient, through the direct action of holes besides the efficient action of radicals in the degradation process of organic dyes. These findings show the significance of decoupling the intricate contributions to the photocatalytic activity of ZnO nanowires when the extrinsic doping is used and of thoroughly selecting the nature of dopants.

Tunable exchange bias in La1.5Sr0.5CoMnO6 double perovskite doped with nonmagnetic Ga ions

The crystal structure, electronic structure, and magnetic behaviors of nonmagnetic Ga ions doped double perovskite La1.5Sr0.5CoMnO6 single phase crystals have been investigated. Different from the traditional magnetic dilution effect of nonmagnetic doping, Ga doping in La1.5Sr0.5CoMnO6 enhances the ferromagnetic (FM) exchange interaction of Co3+-O-Mn3+. Moreover, both conventional and spontaneous exchange bias (EB) effects can be tuned by modulating the Ga doping content, which is accompanied by the variation of the Co3+/4+ and Mn3+/4+ and the effective magnetic moment. The EB field and magnetization can be improved by nonmagnetic Ga3+ doping with content lower than 0.2. The evolution of conventional and spontaneous EB effects in La1.5Sr0.5Co1-xGaxMnO6 can be understood in terms of the unidirectional interface anisotropic coupling between FM/anti-FM, and/or FM/spin glass, which is affected by antisite disorder, spin glass, and the uncompensated coupling between Co and Mn.

Modification of defects in SnO2 nanowire arrays by gallium doping for enhanced photodetection

Glancing angle deposition technique was used to grow as-deposited SnO2 and also Gallium doped SnO2 (Ga: SnO2) Nanowire (NW) arrays over Si substrate. The relative amount of Ga dopants was varied from 5% to 20% and tested for various structural and optical characteristics. A blue shift in bandgap and enhanced photo absorption was observed for Ga: SnO2 NWs as compared to the as-deposited SnO2 NWs. Photoluminescence study indicates the suppression of emission due to modification in defects after Ga doping with the least emission in case of 5% Ga: SnO2 NWs which was also supported by the X-ray photoelectron spectroscopy results. Photodetectors (PD) were fabricated using all samples and among them the based-on Au/5% Ga: SnO2 NW/Si device exhibited the lowest dark current (~2.67 nA) along with a maximum photoresponse of ~27. Furthermore, a superior transient response with a rise time and fall time of 1.3 ms and 2 ms respectively was observed for 5% Ga: SnO2 NWs PDs. Thus, large e-h pair generation and reduced defect states in case of 5% Ga: SnO2 NWs sample signifies that gallium doping level of 5% in SnO2 is the optimum concentration for enhanced optoelectronic applications.

High power factor in epitaxial Mg2Sn thin films via Ga doping

In this work, we present the influence of Ga doping in Mg2Sn thin epitaxial films on sapphire (0001) substrates. Our results suggest that epitaxial nature is essential for achieving high mobility. Furthermore, we found that Ga incorporation influences the carrier concentration and acts as a phonon-scattering center. The optimal power factor and figure of merit values obtained were 1.49 × 10−3 W·m−1·K−1 and 0.08 at 300 K for Mg2Sn0.97Ga0.03. The values are in the same range as the bulk material of Mg-based II–IV semiconductors, suggesting that the combination of doping and epitaxial nature in thin films can be a promising route for miniaturization of thermoelectric devices based on Mg-based materials.

Theoretical Insight Into Diamond Doping and Its Possible Effect on Diamond Tool Wear During Cutting of Steel

Natural diamond tools experience wear during cutting of steel. As reported in our previous work, Ga doping of diamond has an effect on suppressing graphitization of diamond which is a major route of wear. We investigate interstitial and substitutional dopants of different valence and different ionic radii (Ga, B, and He) to achieve a deeper understanding of inhibiting graphitization. In this study, ab initio calculations are used to explore the effects of three dopants that might affect the diamond wear. We consider mechanical effects via possible solution strengthening and electronic effects via dopant-induced modifications of the electronic structure. We find that the bulk modulus difference between pristine and doped diamond is clearly related to strain energies. Furthermore, boron doping makes the resulting graphite with stable sp2 hybridization more perfect than diamond, but Ga-doped diamond needs 2.49 eV to form the two graphene-like layers than only one layer, which would result in the suppressed graphitization and reduced chemical wear of the diamond tool.

ZIF-8 metal-organic framework conjugated to pristine and doped B12N12 nanoclusters as a new hybrid nanomaterial for detection of amphetamine

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were fulfilled to scrutinize the adsorption behavior of amphetamine (AMP) drug molecule on the pristine, aluminum, gallium, carbon, silicon, and germanium-doped ZIF-8/B12N12 nanoclusters. The adsorption analysis demonstrates that CB11N12/ZIF-8 has the strongest interaction with the nitrogen atom of AMP via binding energy of −194.58 kcal.mol−1 in the gas phase. DFT calculations in the various solvents reveal an enhancement in the AMP drug adsorption on the nanocluster with the increasing polarity of the solvent. The results of the electronic and reactivity properties of the considered drug-nanocluster complexes confirm that the energy gap of the nanoclusters reduces after the adsorption of the AMP drug, which could be used as a detectable electrochemical signal. The TD-DFT calculations illustrate that Al, Ga, C, Si, and Ge dopant increases the λmax of B12N12/ZIF-8 nanocluster (red-shift), whereas the electronic spectra of the drug-nanocluster complexes exhibits a blue-shift toward lower wavelengths. Finally, based on different analyses, the proposed XB11N12/ZIF-8 nanoclusters could be promising candidates for sensing and removal of the AMP drug.

Effects of Ga on Mechanical Properties and Microstructure of Cu–Sn–Ti Filler

To solve a series of problems of Cu–Sn–Ti fillers, Ga is added to the fillers to promote its mechanical properties and microstructure. The metallographic structure of Cu–Sn–Ti–xGa filler metals is detected by optical microscope. Energy dispersive spectroscopy (EDS) areal, X‐ray diffraction (XRD), and differential thermal analysis (DSC) are used to analyze the morphology and microstructure of the fillers. The results show that doped Ga can significantly decrease the melting point and increase mechanical properties of the fillers. The shear strength of the filler metals with 1% Ga content is 160% higher than without Ga. In addition, it is also observed that a small amount of Ga refine the CuSnTi filler metals matrix structure. The diffusion of elements in the filler metals is detected. Compared with Sn solid solution, Ga tends to form a solid solution with Cu. When the Ga content is 2 wt%, the shear strength of the filler metal decreases due to the appearance of coarse crystals at the bottom of the dimple. Through the study of the reaction layer between diamond and filler metal, it is found that Ga can increase the thickness of the interface reaction layer.

Effect of oxygen vacancies on the dielectricity of Ga doped equimolar BiMnO3–BaTiO3 characterized by XPS analysis

Double oxide perovskites are fabricated by modifying the one by the other oxide through the ionic substitution process. However, the dielectric performance of typical such compounds is poor in general. It is because of oxygen vacancies concentration (VO··) increases due to the ionic substitution, which affects the conduction of charge carriers. In this work, Ga, which is known to be an element with high oxygen affinity, was chosen to dope the equimolar BiMnO3–BaTiO3 ceramic to decrease VO·· during the mechanochemical synthesis. Consequently, the dielectric loss (at 200 °C with 1 kHz frequency) of BiMn(1-0.2)Ga0.2O3–BaTiO3 ceramic has been observed to decreased from 1.68 to 0.98 as compared to pristine specimen. Also, the resistivity was found to be increased from 1.0225 × 1010 to 5.6452 × 1012. The x-ray diffraction (XRD) scan showed the formation of single-phase perovskite with pseudo-cubic structure and a Ga doping associated lattice distortion. X-ray photoelectron spectroscopy (XPS) analysis explored the charge neutrality reaction of the doped ceramic and the interference effect of Ga in the Mn3+ to Mn2+ transition in this ceramic. The results are discussed in the context of the role of Ga to improve the dielectric behaviour and thus be suitable for storage device applications.

Ga doped Ni3S2 ultrathin nanosheet arrays supported on Ti3C2-MXene/Ni foam: An efficient and stable 3D electrocatalyst for oxygen evolution reaction

Exploring cost-efficient electrocatalysts for oxygen evolution reaction (OER) is still a huge challenge in the electrochemical energy conversion technology. In this work, Gallium (Ga)-doped Ni3S2 nanosheet arrays grown on Ti3C2-MXene/nickel foam (Ga–Ni3S2/Ti3C2/NF) have been synthesized by a successive hydrothermal and sulfidization process. The Ga doping modulates the electronic structure of Ni3S2, so tuning the adsorption energies of oxygen intermediate (∗OOH). The Ga–Ni3S2/Ti3C2/NF delivers outstanding catalytic activities toward OER with an overpotential of 340 mV at 100 mA cm−2, and exhibits superior electrochemical durability. The excellent OER performance of Ga–Ni3S2/Ti3C2/NF can be ascribed to the 3D sheet arrays morphology and optimized electronic structure. Density functional theory (DFT) calculations also demonstrate that electronic disturbance attributed to Ga doping effectively improves the activity of Ni sites, leading to stronger binding strength of ∗OOH intermediate at Ni sites nearby Ga. This study provides insights into the fabrication of advanced electrocatalysts for application.

Doping Concentration Influenced Pyro‐Phototronic Effect in Self‐Powered Photodetector Based on Ga‐Incorporated ZnO Microwire/p+‐GaN Heterojunction

AbstractPyro‐phototronic effect, a coupling of pyroelectric and photovoltaic effect, provides an effective method to improve the performance of self‐powered photodetectors (PDs). Developing high‐performance PDs, the influence of pyroelectric effect on photoelectric characteristics and coupling mechanism deserves further study. Herein, a self‐powered PD made of Ga‐incorporated ZnO microwire (ZnO:Ga MW) and p+‐GaN layer is fabricated, and the performance influenced by pyro‐phototronic effect is investigated systematically. Through varying Ga concentration in ZnO:Ga MWs, the pyroelectric current gradually dominates the photocurrent of PDs under ultraviolet illumination; while the photovoltaic current deteriorates rapidly. The enhanced pyroelectric responsivity can compensate the decreased photovoltaic responsivity, maintaining their high total responsivities (&gt;5 mA W−1) under self‐biased conditions. Furthermore, the decay time of pyroelectric current, representing the duration of pyroelectric effect, decreases markedly from 0.313 to 0.044 s by increasing Ga concentration. Associated with theoretical analysis, incorporating Ga dopant can not only increase the rate of photogenerated temperature variation, but also narrow depletion layer at ZnO:Ga/GaN heterojunction. Besides, the temperature variation can lead to a significant reduction of decay time. These findings give a deeper insight into the influence of pyroelectric effect on photoresponse and its coupling mechanism, providing a scheme to develop high‐performance self‐powered PDs.

Multi-wavelength emission through self-induced defects in GaZnO microrods

Multi-wavelength emission in wide bandgap semiconductors is commonly achieved through ternary alloying or quantum size effects. However, multi-wavelength emission within a single microstructure is highly challenging using these approaches. Here, we demonstrate that the luminescence wavelength within individual GaZnO microrods can be tailored via defect engineering. Fast chemical vapor growth of oxygen-rich ZnO microrods with Ga2O3 as an additive in the ZnO vapour leads to formation of a tapered morphology with graded distribution of Ga dopants, while the Ga incorporation does not significantly alter their crystal structure. With increasing Ga content from 1 to 6 at% from tip to base, the GaZnO microrods increase in diameter towards the substrate in accordance with the birth-and-spread mechanism. The local near-band-edge emission within single ZnO microrods, analyzed by nanoscale cathodoluminescence spectroscopy, exhibits a red shift of ~0.6 eV with increasing Ga content and exhibits signature characteristics of an excitonic emission. Density Functional Theory calculations reveal that the variation in the emission wavelength arises from bandgap narrowing due to the merging of the electronic states of Ga defect complexes with ZnO energy bands. The experimental and theoretical results demonstrate (i) the utility of using the self-regulation of defect compensation effects for band gap engineering and (ii) the possibility of multi-wavelength light sources within individual microrods.

Enhancement of performance of Ga incorporated ZnO UV photodetectors prepared by simplified two step chemical solution process

The present study establishes the UV photodetector capability of Zinc Oxide (ZnO) and Gallium incorporated ZnO (GZO) thin films prepared by a simplified two-step chemical bath deposition technique. The prepared UV detectors were characterized by tools such as XRD, SEM, UV, PL and Photoresponse to investigate their properties. The structural study revealed the enhancement of film crystallinity with respect to Ga doping level. The optical studies confirm the higher absorption at UV range for 3% Ga doped ZnO film. From PL study, the green emission observed at 522 nm is associated with the defects from oxygen vacancies (Vo+). Once the UV light is irradiated on the GZO film surface, electrons and holes are generated as the illumination energy is larger than the ZnO bandgap energy, known as above-band energy illumination. The photo-generated holes then neutralize the chemisorbed ions causing the release of electrons in the conduction band of ZnO, this could increase the photocurrent. In this study, the calculated photo-detectivity (D*), responsivity (R) and external quantum efficiency (EQE) of the prepared UV detectors are 1.24 ×1010 jones, 0.38 AW-1, and 125.10% respectively for 3% Ga doped ZnO film. These parameters are noticeable and this study proves that GZO films in fact work as good sensitive UV detectors.

Thermoelectric behaviors of ZnO mesoporous thin films affected by strain induced from the different dopants radii (Al, Ga, and In)

This study considered effects from thermoelectric property changes due to mesoporous thin film ZnO lattice deformation through doping with various group III elements. The distorted hexagonal wurtzite structure occurred in the ZnO thin film due to ion size differences between Zn and other doping elements. These strains cause distortion, resulting in reduced mobility because they inhibit grain growth and reduce crystallinity. Al doping induced the largest strain since it represented the largest ionic radius difference from Zn, whereas strain differences between Ga and In doped ZnO were almost negligible. In is larger than Zn, whereas Al and Ga dopants have a smaller atomic radius. Thus, carrier concentration for the smaller ion was 18%–26% higher than for the larger ion, and electroconductivity and carrier concentration increased 2–3.5- and 5–10-fold, respectively, with increasing dopant concentration, regardless of the doping element. Ga was the best candidate among the group III elements for doping a ZnO thin film, achieving the highest power factor of 8.01 at 323 K. We verified that thermoelectric properties could be improved by controlling dopant concentration, being influenced from inducing crystal lattice deformation through ion radius differences between the dopant and Zn.

Enhanced output performance of ZnO thin film triboelectric nanogenerators by leveraging surface limited ga doping and insulting bulk

Although triboelectric nanogenerator (TENG) has been developed as a new green energy source, the dominant charge transfer mechanism regarding surface chemistry has not been fully uncovered yet, especially in semiconductor materials. Semiconductor materials are technically important not only capable of tuning total carrier concentrations available for charge transfer in TENG, but corresponding optoelectronic properties for applications into tribo-tronics. However, doping renders one serious drawback as tribo-charges tend to leak and cannot be held in place for energy output. In order to prevent carriers from leaking while maintain the characteristics of tunable carrier concentrations in semiconductors, a two-layer structure of Ga-doped ZnO/undoped-ZnO is proposed by a two-step growth methodology. A ZnO thin film was first grown by magnetron sputter followed by Ga doping restricted to a shallow surface region by thermal diffusion treatment in the second step. The results support that surface work function difference between two materials in electrification under the well preservation of tribo-charges retention governs the charge transfer capability responsible for output performance of TENGs, where the output voltage and current of the ZnO film doped with 0.93 at% Ga can be drastically enhanced by 16 and 13 times, respectively. However, β-Ga2O3 forms on the surface when Ga concentration is higher than 0.93 at%. Nevertheless, the even larger work function of β-Ga2O3 than Ga-doped ZnO does not lead to larger output performance, implying that work function difference is not the prime factor but carrier concentration in the conduction band needs to be considered for the performance of TENGs. This work demonstrated a viable method to modify the work function of ZnO only confined to the surface through doping without disturbing the bulk, optimizing the device structure for TENGs based on semiconductor.

Synthesis, Characterization, and Ionic Conductivity Studies of Simultaneously Substituted K- and Ga-Doped BaZrO3.

Ceramic fuel cells possess tremendous advantages over PMFCs due to their fuel flexibility and requirement of low-purity hydrogen. Despite high conversion efficiency, the high cost of ultra high-purity hydrogen required for the operation limits the application of PMFCs. Although ceramic fuel cells operate at elevated temperature, high performance coupled with multifuel flexibility makes ceramic fuel cells a superior option as a static power source to generate electricity compared to thermal coal-fired power plants. BaZr1–xYxO3–x/2 based protonic conductors get a high degree of interest due to their superior structural stability, but their poor conductivity at higher temperature limits the performance of ceramic fuel cells. To overcome the low ionic conductivity issues of BaZrO3 based materials at elevated temperature, the simultaneous doping of smaller Ga on the Zr site and K on the Ba site was employed here to create higher concentration of oxide-ion vacancies for the realization of superior conductivities. The simultaneous substitution of K and Ga created the oxygen vacancy-type point defects resulting in higher ionic conductivity ∼10–2 S/cm above 650 °C. The conductivity represented here for the Ba0.8K0.2Zr0.8Ga0.2O2.8 sample is superior or equivalent to the conductivity obtained for yttria-stabilized zirconia, a well-known ceramic oxide-ion electrolyte.

Ga-doped Pd/CeO[formula omitted] model catalysts for CO oxidation reactivity: A density functional theory study

Ceria-supported Pd single-atom catalysts (SACs) are important catalysts to catalyze the CO oxidation, often used in three-way catalysts to treat automobile exhaust gases. This paper uses density functional theory (DFT) calculations and transition state theory to systematically study the effect of Ga atom doping on the performance of the Pd/CeO2 SACs system. Noticeably, the results of DFT calculations reveal that the stability of Pd single atoms supported on the surface of CeO2(111) was significantly augmented by doping Ga. An oxygen vacancy generated easily near the Ga and Pd site will act as a crucial role for activating the adsorbed oxygen molecule. Most importantly, the climbing image nudged elastic band (CINEB) calculations show that the doping of Ga remarkably reduces the highest energy barrier during the CO oxidation reaction, meaning that the catalytic performance of the CO oxidation reaction is promoted effectively. This work provides a new perspective for SACs modification.

Effect of Ga Dopants on Oxidation Behaviour of YCu Compounds

Effect of Ga Dopants on Oxidation Behaviour of YCu Compounds

Investigation of structural, morphological, and optoelectronic properties of Ga-doped TiO2 nanoparticles for electron transport layer in solar cell applications: An experimental and theoretical study

In the current work, the sol-gel synthesis method was used to synthesize both undoped and gallium (1%-Ga) doped TiO2 nanoparticles. The as-deposited materials were calcined at 400–500 °C with a temperature variation rate of 5 °C per minute. The crystallographic properties of the semiconductor materials were determined from X-ray diffraction (XRD) which showed the formation of anatase TiO2. The average crystallite sizes, determined from the widths of the XRD reflections, were 11 and 4 nm for undoped and Ga-doped TiO2, respectively. The materials were further studied by density functional theory with meta-generalized gradient approximation exchange–correlation functional. Supercell systems consisting of 24 and 48 atoms were created to form 12.5% and 6.25% Ga dopant substitution, respectively. These structures were optimized to obtain the ground state properties. Transmission electron microscopy showed polycrystalline, spherical powders, with grain sizes comparable to those found using XRD. The surface morphology of the doped TiO2 obtained from scanning electron microscopy showed an improved surface structure compared to pristine TiO2. Moreover, the electronic states of the materials were investigated using X-ray photoelectron spectroscopy. Energy dispersive X-ray spectroscopy verified the elemental composition of titanium, oxygen, and Ga present in the nanoparticles. The surface chemical bonds were analyzed by Fourier-transform infrared spectroscopy. Ultraviolet diffused reflectance spectra analysis was used to examine their optical properties. The experimentally obtained bandgaps of pristine and 1% Ga-doped TiO2 nanoparticles were 2.9 and 3.09 eV, respectively. The optical properties were further analyzed by computing the band structures and density of states using density functional theory. Similar to the experimental results, these electronic structures showed an increase in bandgap after 6.25% Ga incorporation. However, with 12.5% doping, there was a decrement in the bandgap. The analysis showed that, with an appropriate amount of substitution, Ga-doped TiO2 semiconductor material can be used in the electron transport layer and many other fields of photoelectric cells.

Defects assisted photosensing and dye degradation of Ni/Ga co-doped ZnO: A theory added experimental investigation

Ni or Ga doping is well studied in literature. However, a Ga/Ni co-doped ZnO brings in complex competing mechanisms of electron mobility and electron localization. A sol-gel prepared solid solution of Ga/Ni co-doped ZnO with hexagonal wurtzite structure (P63mc space group) is studied in detail to correlate the electronic properties to the structure of the materials. Lattice strain studies correlated to these changes in the electronic properties. The drastic reduction in native defects was detailed using the photoluminescence study of Ni/Ga co-doped ZnO. Lattice and phonon studies were used to explain the lattice strain in the ZnO lattice. The % Sensitivity of UV (290 nm), blue (450 nm), green (540 nm) and red (640 nm) wavelengths were tested and correlated with the defects. Additionally, the photo-catalytic dye degradation of toxic methylene blue was investigated and explained with changes in carrier concentration and mobility. The reason behind the conductive parameters was examined theoretically and a possible reason was found in terms of changes in electron localization due to increasing Ni/Ga concentration.