In2O3 Nanowires Research Articles

Enhanced performance of In2O3 nanowire field effect transistors with controllable surface functionalization of Ag nanoparticles

Indium oxide (In2O3) nanowire field effect transistors (FETs) have great potential in electronic and sensor applications owing to their suitable band width and high electron mobility. However, the In2O3 nanowire FETs reported previously were operated in a depletion-mode, not suitable to the integrated circuits result of the high-power consumption. Therefore, tuning the electrical properties of In2O3 nanowire FETs into enhancement-mode is critical for the successful application in the fields of high-performance electronics, optoelectronics and detectors. In the work, a simple but effective strategy was carried out by preparing Ag nanoparticle functionalized In2O3 NWs to regulate the threshold voltage (Vth) of In2O3 NW FETs, successfully achieving enhanced-mode devices. The threshold voltage can be regulated from −6.9 V to +7 V by controlling Ag density via deposition time. In addition, the devices exhibited high performance: huge Ion/Ioff ratio > 108, large maximum saturation current ≈ 800 mA and excellent carrier mobility ≈ 129 cm2 Vċs−1. The enhanced performance is attributed to the surface passivation by Ag nanoparticles to reduce the density of traps and the charge transfer between traps and the nanowires to regulate the Vth. The result indicates the application of metal nanoparticles significantly improve oxide NW for low-power FETs.

Investigation of Indium Oxide Nanowire Transform to Indium Zinc Oxide (IZO) Via Solid State Reactions

Transition metal oxide nanowires have attracted considerable attention due to their physical characteristics, chemical characteristics, and versatile applications. Among them, indium oxide (In203) nanowires demonstrate promising structure and electrical properties. Simultaneously, it used to be the reactants to synthesize indium zinc oxide (IZO) by solid-state reaction. The applicability would be highly related to the microstructure and synthesis process. Hence, study of conversion kinetics of IZO is essential. However, only few studies have mentioned the formation process of IZO and the solid-state diffusion mechanism. In this work, we successfully observed the transformation of novel IZO nanowire from interesting diffusion behavior between single-crystalline In2O3 nanowires and zinc oxide (ZnO). High resolution transmission electron microscope (HRTEM), fast Fourier transform (FFT) diffraction patterns and energy-dispersive spectrometer (EDS) were used for structural and compositional analysis. Based on the HRTEM images and the corresponding FFTs, the triclinic IZO was defined. Meanwhile, The in-situ TEM and EDS analysis provide the formation behavior and elemental distribution to elucidate the diffusion mechanism. This work exhibited the IZO nanowires with a unique structure and interesting formation behavior. Moreover, the study provides the improvement of controllability of conversion microstructure for further device applications. Figure 1

Investigation of Indium Oxide Nanowire Transform to Indium Zinc Oxide (IZO) Via Solid State Reactions

Transition metal oxide nanowires have attracted considerable attention due to their physical characteristics, chemical characteristics, and versatile applications. Among them, indium oxide (In203) nanowires demonstrate promising structure and electrical properties. Simultaneously, it used to be the reactants to synthesize indium zinc oxide (IZO) by solid-state reaction. The applicability would be highly related to the microstructure and synthesis process. Hence, study of conversion kinetics of IZO is essential. However, only few studies have mentioned the formation process of IZO and the solid-state diffusion mechanism. In this work, we successfully observed the transformation of novel IZO nanowire from interesting diffusion behavior between single-crystalline In2O3 nanowires and zinc oxide (ZnO). High resolution transmission electron microscope (HRTEM), fast Fourier transform (FFT) diffraction patterns and energy-dispersive spectrometer (EDS) were used for structural and compositional analysis. Based on the HRTEM images and the corresponding FFTs, the triclinic IZO was defined. Meanwhile, the in-situ TEM and EDS analysis provide the formation behavior and elemental distribution to elucidate the diffusion mechanism. This work exhibited the IZO nanowires with a unique structure and interesting formation behavior. Moreover, the study provides the improvement of controllability of conversion microstructure for further device applications.

Dual-gate crystalline oxide-nanowire field-effect transistors utilizing ion-gel gate dielectric

Dual-gate structure field-effect transistors (DG FETs) can provide various advantages such as high output current, enhanced mobility, and tunability of threshold voltage (VTH) by adversely controlling the two channels formed at both top and bottom gate dielectric interfaces. Here, we present high-mobility DG structure FETs using crystalline Ga-doped In2O3 (IGO) nanowires (NWs) as channel and high-k ion-gel as a top gate dielectric layer. To enhance the electrical properties of IGO NW FETs such as field-effect mobility, on/off ratio, VTH, and subthreshold slope, optimization of electrospinning, Ga doping in In2O3 NWs, and thermal annealing was carried out. The optimized IGO NW FETs with a single SiO2 gate dielectric exhibited field-effect mobility of ~6.0 cm2/(V·s), on/off ratio of >107, subthreshold slope of 0.73 V/decade, and VTH of ~0 V. Also, the IGO NW FETs showed excellent operation stabilities under positive-gate-bias and negative-bias-illumination stress conditions. Furthermore, by using a high-k ion-gel film as the second gate dielectric layer, DG IGO NW FETs with field-effect mobility up to ~35.1 cm2/(V·s) were realized which is comparably higher than those of single-gated IGO NW FETs (6.0–6.5 cm2/(V·s)).

Ag Nanoparticles Sheltered In2O3 Nanowire as a Capacitive MOS Memory Device

A capacitive memory effect has been reported for Ag nanoparticles (NPs) sheltered In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanowires (NWs) devices. To compare the performance with that of bare In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NWs, two devices (viz. In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW/Ag NPs and In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW) were fabricated on n-Si substrate inside the electron beam (e-beam) evaporator using the double-step glancing angle deposition (GLAD) technique. The field emission scanning electron microscopy (FESEM) shows the formation of In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NWs and Ag NPs. The high-resolution transmission electron microscopy (HRTEM) shows the formation of uneven NWs and selected area electron diffraction (SAED) analysis confirmed the amorphous nature of the NWs. An averagely ~7.5 and ~9.3 fold enhanced absorption was observed in the UV region and visible region for In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW/Ag NPs. The modulation in current density of ~4.5 fold at +10 V and ~5.7 fold at -10 V were observed for the fabricated In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW/Ag NPs MOS device. At 2 MHz frequency response, the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW/Ag NPs device depicted a low interface trap density (Dit) of ~0.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The maximum memory window of 5.61 V at ±8 V was extracted for the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW/Ag NPs device from the large C-V hysteresis curve, thus establishing a strong presence of memory window in the device.

Flexible and transparent sensors for ultra-low NO2 detection at room temperature under visible light illumination

Flexible and transparent sensors based on parallelly aligned In2O3 nanowires can detect ppb-level NO2 at room temperature under visible light (even under an iPhone screen). The sensing performances are maintained after bending and stability tests.

Sr-Doped Cubic In2O3/Rhombohedral In2O3 Homojunction Nanowires for Highly Sensitive and Selective Breath Ethanol Sensing: Experiment and DFT Simulation Studies.

In recent years, it is urgent and challenging to fabricate highly sensitive and selective gas sensors for breath analyses. In this work, Sr-doped cubic In2O3/rhombohedral In2O3 homojunction nanowires (NWs) are synthesized by one-step electrospun technology. The Sr doping alters the cubic phase of pure In2O3 into the rhombohedral phase, which is verified by the high-resolution transmittance electron microscopy, X-ray diffraction, and Raman spectroscopy, and is attributable to the low cohesive energy as calculated by the density functional theory (DFT). As a proof-of-concept of fatty liver biomarker sensing, ethanol sensors are fabricated using the electrospun In2O3 NWs. The results show that 8 wt % Sr-doped In2O3 shows the highest ethanol sensing performance with a high response of 21-1 ppm, a high selectivity over other interfering gases such as methanol, acetone, formaldehyde, toluene, xylene, and benzene, a high stability measured in 6 weeks, and also a high resistance to high humidity of 80%. The outstanding ethanol sensing performance is attributable to the enhanced ethanol adsorption by Sr doping as calculated by DFT, the stable rhombohedral phase and the preferred (104) facet exposure, and the formed homojunctions favoring the electron transfer. All these results show the effective structural modification of In2O3 by Sr doping, and also the great potency of the homojunction Sr-doped In2O3 NWs for highly sensitive, selective, and stable breath ethanol sensing.

Oxidation of polycrystalline indium nanowires induced by electron bombardment: An in situ TEM study

Thin (d < 10 nm) polycrystalline indium nanowires were prepared by pulsed laser ablation in superfluid helium and studied by means of transmission electron microscope (TEM). Nanowires showed disordered fcc structure unlike bulk indium that has tetragonal structure. Oxidation of indium nanowires induced by probing electron beam and yielding single-crystalline In2O3 nanowires was observed by TEM in situ. The oxidation reaction was found to proceed in a mode frontal propagation along the wire axis.

Synthesis and Characterization of Ga2O3 and In2O3 Nanowires

In this work, the thermal synthesis and characterization of gallium oxide and indium oxide nanowires using vapour-liquid-solid mechanism at atmospheric pressure were described. Au nanoislands formed by the solid-state dewetting process of various thickness metal layer were applied as growth catalyst of nanowires while high-purity metal reactants (In, Ga) were applied as AIII precursors. The catalytic layer thickness influence on the morphology of investigated nanostructures was studied. Material composition and structural properties were used for crystallographic quality of AIII-oxide nanowires examination.

Epitaxially Oriented Sn:In2O3 Nanowires Grown by the Vapor–Liquid–Solid Mechanism on m-, r-, a-Al2O3 as Scaffolds for Nanostructured Solar Cells

We have grown highly directional, epitaxial Sn:In2O3 nanowires via the vapor–liquid–solid mechanism on m-, r- and a-Al2O3 between 800 and 900 °C at 1 mbar. The Sn:In2O3 nanowires have the cubic bixbyite crystal structure and are tapered with lengths of up to 80 μm, but they are inclined at ϕ ≈ 60° along one direction on m-Al2O3 while those on r-Al2O3 are inclined at ϕ ≈ 45° and oriented along two mutually orthogonal directions. In contrast, vertical Sn:In2O3 nanowires were obtained on a-Al2O3. We obtain excellent uniformity and reproducible growth of Sn:In2O3 nanowires up to 15 mm × 15 mm on m- and r-Al2O3, which is important for the fabrication of nanowire solar cells. All of the Sn:In2O3 nanowires had a resistivity of 10–4 Ω cm and carrier densities on the order of 1021 cm–3, in which case the charge distribution has a maximum at the surface of the Sn:In2O3 nanowires as a result of the occupancy of sub-bands residing well below the Fermi level, as shown via the self-consistent solution of the Poisson–Schrödinger equations in the effective mass approximation. We also show that the Sn:In2O3 nanowires are capable of light emission and exhibited room-temperature photoluminescence at 3.1 eV as a result of band-to-band radiative transitions but also at 2.25 eV as a result of donor-like states residing energetically in the upper half of the energy band gap. We discuss the advantages of using ordered networks of Sn:In2O3 nanowires in solar cell devices and issues pertaining to their fabrication.

Enhancement-mode field-effect transistors based on Ti-doped In2O3 nanowires fabricated by electrospinning

Recently, indium oxide (In2O3) semiconducting nanowires (NWs) have been extensively explored as building blocks for numerous electronic applications. However, most of the field-effect transistors (FETs) based on In2O3 NWs were operated in depletion mode (D-mode), which exhibits negative threshold voltage (VTH) and non-zero current with zero bias. Besides, these devices based on In2O3 NWs still suffer from high leakage current and low on-off current ratios (Ion/off). In this report, high-performance enhancement-mode (E-mode) FETs based on Ti doped In2O3 NWs were successfully integrated. It was found that the device performance could be effectively modulated by adjusting the doping concentration of Ti. The FETs based on In2O3 NWs with Ti doping concentration of 3 mol% exhibited a saturation current of 4.69 × 10−4 A, a subthreshold swing (SS) of 1.54 V/decade, an on/off current ratio of ~1.5 × 108, and a field-effect mobility of 2.53 cm2 V−1 s−1. When high-κ ZrOx dielectrics were successfully integrated into the FETs, the mobility and SS of the designed device were improved to 12.67 cm2 V−1 s−1 and 150 mV/decade, respectively. The inverters based on InTiO NWs/ZrOx FETs were constructed and showed a gain of ~9.5. All of these results demonstrate that Ti-doped In2O3 NWs are promising candidates for large-scale, high-performance and low-power electronic devices.

Synthesis of coaxial TiO2/In2O3 nanowire assembly using glancing angle deposition for wettability application

Coaxial TiO2/In2O3 nanowire (NW) assembly, TiO2 NW and In2O3 NW were synthesized incorporating glancing angle deposition technique inside electron beam evaporator and their structural and optical properties were analyzed. The field emission scanning electron microscopy and transmission electron microscopy confirmed the growth of TiO2/In2O3 NW. X-ray diffraction confirmed the polycrystalline nature of the deposited TiO2/In2O3 NW structure. The surface roughness was 2.12 nm, 6 nm and 6.35 nm for TiO2 NW, In2O3 NW and TiO2/In2O3 NW, respectively using atomic force microscope. The TiO2/In2O3 NW, bare TiO2 NW and In2O3 NW showed water contact angle (CA) of 129°, 68° and 123°, respectively. On exposure to UV light illumination, the surface CA of coaxial TiO2/In2O3 NW, TiO2 NW and In2O3 NW changed to nearly 10°, 30° and 71°, respectively in 1 h. TiO2/In2O3 NW, TiO2 NW and In2O3 NW CAs changed with wettability transition rate of 1.2 × 10−3 degree−1 min−1, 3.2 × 10−4 degree−1 min−1 and 9.2 × 10−5 degree−1 min−1, respectively. There is improvement in photo-induced wettability switching properties of coaxial TiO2/In2O3 NW compared to TiO2 NW and In2O3 NW. This improvement is due to the interfacial surface morphology modification between TiO2 and In2O3 and efficient interaction of separated photogenerated charge carriers with water molecules to adsorb on the surface. On account of these, the change in wettability of heterostructure surface on interaction with UV light can give prospective applications in smart films as antifogging and self-cleaning surfaces.

Controlled growth and characterization of In2O3 nanowires by chemical vapor deposition

The high-crystalline indium oxide (In2O3) nanowires were deposited by chemical vapor deposition (CVD) method on Si (111) substrates using C and In2O3 powders as the raw materials. The morphology, microstructures and the valences analysis of In2O3 nanowires were characterized by XRD, SEM, EDS, XPS and TEM techniques. The length and density of In2O3 nanowires can be effectively controlled by adjusting the experimental parameters. The optimal growth condition is obtained, namely the Au catalyst thickness of 12 nm, growth temperature of 1050 °C and Ar flow rate of 200 sccm. The cubic bixbyite structure as pure In2O3 (space group I a3¯) as well as large amounts of oxygen vacancies can be observed in the deposited In2O3 nanowires. The photoluminescence (PL) spectrum shows an ultraviolet emission peak located at 390.6 nm and two luminescence peaks located at 423.6 nm and 436.5 nm, which can be attributed to the near-band-edge emission and the presence of oxygen vacancy defects in the In2O3 nanowires, respectively.

Hierarchical Aerographite 3D flexible networks hybridized by InP micro/nanostructures for strain sensor applications

In the present work, we report on development of three-dimensional flexible architectures consisting of an extremely porous three-dimensional Aerographite (AG) backbone decorated by InP micro/nanocrystallites grown by a single step hydride vapor phase epitaxy process. The systematic investigation of the hybrid materials by scanning electron microscopy demonstrates a rather uniform spatial distribution of InP crystallites without agglomeration on the surface of Aerographite microtubular structures. X-ray diffraction, transmission electron microscopy and Raman scattering analysis demonstrate that InP crystallites grown on bare Aerographite are of zincblende structure, while a preliminary functionalization of the Aerographite backbone with Au nanodots promotes the formation of crystalline In2O3 nanowires as well as gold-indium oxide core-shell nanostructures. The electromechanical properties of the hybrid AG-InP composite material are shown to be better than those of previously reported bare AG and AG-GaN networks. Robustness, elastic behavior and excellent translation of the mechanical deformation to variations in electrical conductivity highlight the prospects of AG-InP applications in tactile/strain sensors and other device structures related to flexible electronics.

In2O3 Nanowire Field-Effect Transistors with Sub-60 mV/dec Subthreshold Swing Stemming from Negative Capacitance and Their Logic Applications.

Heat dissipation is a key issue for scaling metal-oxide-semiconductor field-effect transistors (MOSFETs). The Boltzmann distribution of electrons imposes a physical limit on the subthreshold swing (SS), which impedes both the reduction of the switching energy and the further increase of the device density. The negative capacitance effect is proposed to rescue MOSFETs from this phenomenon called "Boltzmann tyranny". Herein, we report In2O3 nanowire (NW) transistors with SS values in the sub-60 mV/dec region, which utilize the ferroelectric P(VDF-TrFE) as the dielectric layer. An ultralow SS down to ∼10 mV/dec is observed and spans over 5 orders of magnitude in the drain current. Meanwhile, a high on/off ratio of more than 108 and a transconductance ( gm) of 2.3 μS are obtained simultaneously at Vd = 0.1 V. The results can be understood by the "voltage amplification" effect induced from the negative capacitance effect. Moreover, the steep slope FET-based inverters indicate a high voltage gain of 41.6. In addition to the NOR and NAND gates, the Schmitt trigger inverters containing only one steep slope FET are demonstrated. This work demonstrates an avenue for low-power circuit design with a steep SS.

Highly sensitive and selective formaldehyde gas sensor based on CdO–In2O3 beaded porous nanotubes at low temperature

Pure In2O3 nanowires (PINW) and CdO–In2O3 composited beaded porous nanotubes (CIBPNT) were successfully prepared by conventional electrospinning method and followed by calcination. The peculiar surface morphological images of as-synthesized nanomaterials were observed via scanning electron microscope (SEM) and transmission electron microscopy (TEM) from which we could observe a series of irregular holes distributed on the surface of beaded nanotubes. The inner structure of the samples was investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results reveal that the element composition of the samples are in conformity with the CdO–In2O3 materials. In addition, the average crystallite size of CIBPNT (17.5 nm) can be estimated from XRD which accords with the TEM images, and XPS analysis supports the oxygen vacancy principle by proving the oxygen vacancies concentration of CIBPNT is more than in PINW. The formaldehyde sensing performances of the samples were evaluated at different temperatures. The result shows that the sensor based on CIBPNT exhibits a excellent response (72–50 ppm formaldehyde) at a low operation temperature of 132 °C, and the value is eight times that of the response of PINW (9 to 50 ppm formaldehyde).The sensor based on CIBPNT could detect 0.1 ppm formaldehyde with a response of 2. In addition, good selectivity and a short response and recovery time (6 s, 12 s) are exhibited. The enhancement of gas sensitivity is attributed to not only the unique beaded shape of hollow and porous 1D nanostructures, but also the high catalytic activity of the CdO additive.

Novel Au-embedded In2O3 nanowire: Synthesis and growth mechanism

In this study, we report novel Au-embedded In2O3 nanowire with octahedral-shaped base by chemical vapor deposition method. The interesting finding is that the catalytic Au is discontinuously distributed along the axial direction in the form of nanodots, which is verified by energy dispersive X-ray spectroscopy and high-resolution transmission electron microscopy analysis. NH3 is found playing the key effect on the formation of Au-embedded In2O3. The nucleation and formation processes of novel Au-embedded In2O3 NWs are co-catalyzed by ammonia and Au. In the presence of ammonia, In-Au alloy efficiently catalyzed the continuous growth of In2O3 and the Au is detached and remained within the nanowire due to the effect of NH3.

Photoconduction mechanism of ultra-long indium oxide nanowires

Photoelectrical mechanism of single Indium Oxide nanowires have been investigated using current-voltage characteristics measurements varying with temperature. The fabricated In2O3 nanowires show high photosensitivity up to 140 at room temperature. It is shown that the photosensitivity of In2O3 nanowires decreases by increasing the temperature due to shorter carrier life time, higher dark conductance and lower electron mobility at higher temperatures. The significantly enhanced photoconduction of single-In2O3 nanowires observed under UV illumination is attributed mainly to the transition from defect levels, which are introduced by the oxygen vacancies that are mostly present on the surface of the nanowires.

Towards high-mobility In2xGa2–2xO3 nanowire field-effect transistors

Recently, owing to the excellent electrical and optical properties, n-type In2O3 nanowires (NWs) have attracted tremendous attention for application in memory devices, solar cells, and ultra-violet photodetectors. However, the relatively low electron mobility of In2O3 NWs grown by chemical vapor deposition (CVD) has limited their further utilization. In this study, utilizing in-situ Ga alloying, highly crystalline, uniform, and thin In2xGa2−2xO3 NWs with diameters down to 30 nm were successfully prepared via ambient-pressure CVD. Introducing an optimal amount of Ga (10 at.%) into the In2O3 lattice was found to effectively enhance the crystal quality and reduce the number of oxygen vacancies in the NWs. A further increase in the Ga concentration adversely induced the formation of a resistive β-Ga2O3 phase, thereby deteriorating the electrical properties of the NWs. Importantly, when configured into global back-gated NW field-effect transistors, the optimized In1.8Ga0.2O3 NWs exhibit significantly enhanced electron mobility reaching up to 750 cm2·V–1·s–1 as compared with that of the pure In2O3 NW, which can be attributed to the reduction in the number of oxygen vacancies and ionized impurity scattering centers. Highly ordered NW parallel arrayed devices were also fabricated to demonstrate the versatility and potency of these NWs for next-generation, large-scale, and high-performance nanoelectronics, sensors, etc.

Formation of Fe-doped In2O3 nanowires and influence evolution of Fe ions on its photoluminescence property

In2O3 and Fe-doped In2O3 nanowires (NWs) were prepared on a Si substrate by using the CVD method. Structure analysis showed that the preparation of Fe-doped In2O3 NWs formed the body-centered cubic structure, which is nearly consistent with that of the In2O3. Importantly, the characteristic peak at (222) and (400) of Fe-doped In2O3 shifted to high angle, owing to the ionic radii of Fe3+ ions (0.79 Å) is much smaller than that of In3+ ions (0.94 Å). Morphology showed that the nanowires, with diameters of 100–150 nm and lengths of tens to hundreds of micrometers, grew along the [100] direction with spacing distance at 0.506 nm. Fluorescence test results showed that the spectral peak of Fe-doped In2O3 nanowires shifted to 419 and 438 nm, 3 nm blue-shifted compared with that of In2O3 NWs in 416 and 435 nm. Thanks to the assessment of the first-principle calculations by using density functional theory, the crystal structures of In2O3 and Fe-doped In2O3 NWs have been designed. It can be found that the doped Fe3+ ions introduced the distortion of the crystal lattice and produced more oxygen vacancies in the crystal lattice, the total volume and valence charge is obviously decreasing from 128.46 to 105.51 and 88 to 78, respectively. Further research found that the doped Fe atoms lead to a smaller band gap, from 1.7 eV to around 0.7 eV, resulting in the blue shift of the PL spectrum. The distortion of the crystal lattice should be responsible for the decrease of the band gap of the In2O3 semiconductor. Thus, the formation of Fe-doped In2O3 NWs is facile and the assessment using first-principle calculations can offer a much deeper understanding of the influence of Fe ions on its photoluminescence property.