Hole Carrier Concentration Research Articles

Investigations of structural, optical and transport property of Sb-doped SnO2 compounds for optoelectronics application

Recently extensive research into the potential uses of oxide materials doped with non-magnetic elements in optoelectronic and spintronic devices has been carried out. In this work, the structural, optical and transport property of the Sn1−xSbxO2 (x = 0–0.10) compounds were studied by using X-ray diffraction (XRD), Raman spectroscopy, UV–vis photo-spectrometer and Hall-effect measurements. For preparation of the samples, the solid-state reaction technique was utilized. Based on the measurement and analysis of the XRD data, it was revealed that these prepared materials were crystallized in a single tetragonal rutile phase of SnO2. Moreover, the XRD data indicated that the solubility limit of Sb was only upto 8 % and thereafter secondary phase of Sb2O3 starts to appear. Using the equation developed by Debye and Scherrer, it was discovered that these samples had an average crystallite size that fell somewhere in the range of 32–36 nm. The microstructural investigation using a scanning electron microscope show a nano meter range sphere-shaped morphology. The rutile phase of SnO2 has been reconfirmed by Raman spectroscopy, and it further shows that there is no lattice disorder upon inclusion of Sb into the SnO2 lattice. An analysis of the optical property by means of a UV–vis Photo-spectrometer indicates that the value of optical band gap reduces as the amount of Sb doping in the material increases. Whereas, the optical transmittance value was found to decrease. The Hall effect measurement indicate the p-type behaviour of these samples and the carrier concentration of holes rises with Sb doping concentration.

Assessing high-energy x-ray and proton irradiation effects on electrical properties of P-GaN and N-GaN thin films

The effects of ionizing and displacement irradiation of high-energy x-ray and 2-MeV proton on GaN thin films were investigated and compared in this study. The electrical properties of both P-GaN and N-GaN, separated from power devices, were gauged for fundamental analysis. It was found that the electrical properties of P-GaN were improved as a consequence of the disruption of the Mg–H bond induced by high-dose x-ray irradiation, as indicated by the Hall and circular transmission line model. Specifically, under a 100-Mrad(Si) x-ray dose, the specific contact resistance ρ c of P-GaN decreased by 30%, and the hole carrier concentration increased significantly. Additionally, the atom displacement damage effect of a 2-MeV proton of 1 × 1013 p/cm2 led to a significant degradation of the electrical properties of P-GaN, while those of N-GaN remained unchanged. P-GaN was found to be more sensitive to irradiation than N-GaN thin film. The effectiveness of x-ray irradiation in enhancing the electrical properties of P-GaN thin films was demonstrated in this study.

Electronic transport properties of GeS single crystals grown by vapor transport from molten GeS source

The electrical properties of GeS single-crystal are determined by the Van der Pauw method as a function of the temperature, thus establishing for the first time the dependence of electrical resistivity on both carrier concentration and mobility. This was possible after the repeated growth of GeS by vapor transport from molten GeS so that high-purity (low concentration of Fe and Na impurities) and high-crystalline (XRC FWHM = 2 min.) GeS single-crystals could be obtained. An extraordinary high electrical conductivity is observed between 180 and 450 K, ranging from 1.1 x10-2 to 3.7 x10-5 Ω−1 cm−1. Acceptors are activated over the whole temperature range, while donor activation takes place above 280 K, partially compensating the hole carrier concentration. In contrast, the mobility is proportional to T−2.4 over the whole temperature range, indicating the predominance of lattice scattering. At room temperature the electrical conductivity is as high as 6.7 × 10-3 Ω−1 cm−1, originating from a hole concentration of 1.7 × 1015 cm−3 and mobility of 25 cm2/Vs.

Contrasting thermoelectric properties in cubic SnSe-NaSbSe2 and SnSe-NaSbTe2: High performance achieved via increasing cation vacancies and charge densities

Cubic SnSe has been recognized as one of the most promising mid-temperature thermoelectric candidates. Herein, the cubic-phase SnSe has been stabilized at room temperature by alloying NaSbSe2 and NaSbTe2, respectively, and the contrasting thermoelectric properties of SnSe-NaSbSe2 and SnSe-NaSbTe2 were systematically investigated. NaSbTe2-alloyed SnSe demonstrates better performance with especially higher electrical properties. According to the DFT calculations, the introduction of NaSbTe2 can bring the lattice parameter of cubic-phase SnSe closer to SnTe, leading to a lower cation vacancy formation energy and producing an ultra-high hole carrier concentration. Meanwhile, Te has a more developed charge density compared with that of Se, providing additional channels for charge transport when bonded to Sn atoms in cubic lattice. Limited by the electrical transport properties, the ZTmax for SnSe-NaSbSe2 only reaches ∼ 0.50 at 773 K, while the ZTmax for SnSe-NaSbTe2 approaches ∼ 0.95. Furthermore, sodium doping was utilized to tune the carrier mobility and carrier concentration of SnSe-NaSbTe2. Resultantly, the PFmax and ZTmax values reach ∼ 11 μW cm−1 K−2 and ∼ 1.20 at 773 K in sodium-doped SnSe-NaSbTe2, 4.4 and 3.0 times higher than those of pure SnSe, respectively. Our study further promotes cubic-phase SnSe thermoelectrics for mid-temperature energy harvesting applications.

The relationship between orbital hybridization and superconductivity of sm-doped YBa2Cu3O7–δ studied by x-ray spectroscopy

Sm-doped YBa2Cu3O7–δ samples were prepared by conventional solid state reaction method in air. The studies of X-ray photoemission spectroscopy and X-ray absorption spectroscopy indicate that the extra electrons fill the holes in CuO2 planes, so that the hole carrier concentration decrease under Sm substitution. The X-ray absorption spectroscopy of Cu L-edge and O K-edge demonstrates that the hybridization strength between Cu 3d and O 2p decreases with increasing content of Sm, but the hybridization strength between Y 4d, Ba 5d, Sm 4f and O 2p increases with the increasing of Sm content, while the superconductivity of the Sm-doped YBa2Cu3O7–δ samples is suppressed, i.e., the superconducting transition temperature of the samples was lowered. Thus, our experimental results suggest a close relationship between the superconductivity and orbital hybridization.

Advancing thermoelectrics by suppressing deep-level defects in Pb-doped AgCrSe2 alloys

AgCrSe2-based compounds have attracted much attention as an environmentally friendly thermoelectric material in recent years due to the intriguing liquid-like properties. However, the ultra-low carrier concentration and the high AgCr deep-level defects limit the overall thermoelectric performance. Here, we successfully introduced Pb into Ag-deficient Ag0.97CrSe2 alloys to tune the carrier concentration across a broad temperature range. The Pb2+ as an acceptor dopant preferentially occupies Cr sites, boosting the hole carrier concentration to 1.77 × 1019 cm−3 at room temperature. Furthermore, the Pb strongly inhibits the creation of intrinsic AgCr defects, weakens the increased thermal excited ionization with the increasing temperature and slowed the rising trend of the carrier concentration. The designed carrier concentration matches the theoretically predicted optimized one over the entire temperature range, leading to a remarkable enhancement in power factor, especially the maximum power factor of ∼ 500 μW⋅m−1⋅K−2 at 750 K is superior to most previous results. Additionally, the abundant point defects promote phonon scattering, thus reducing the lattice thermal conductivity. As a result, the maximum figure of merit zT (∼ 0.51 at 750 K) is achieved in Ag0.97Cr0.995Pb0.005Se2. This work confirms the feasibility of manipulating deep-level defects to achieve temperature-dependent optimal carrier concentration and provides a valuable guidance for other thermoelectric materials.

Vacancy Manipulation Induced Optimal Carrier Concentration, Band Convergence and Low Lattice Thermal Conductivity in Nano‐Crystalline SnTe Yielding Superior Thermoelectric Performance

AbstractSynergetic optimization of electrical and thermal transport properties is achieved for SnTe‐based nano‐crystalline materials. Gd doping is able to suppress the Sn vacancy, which is confirmed by positron annihilation measurements and corresponding theoretical calculations. Hence, the optimal hole carrier concentration is obtained, leading to the improvement of electrical transport performance and simultaneous decrease of electronic thermal conductivity. In addition, the incremental density of states effective mass m* in SnTe is realized by the promotion of the band convergence via Gd doping, which is further confirmed by the band structure calculation. Hence, the enhancement of the Seebeck coefficient is also achieved, leading to a high power factor of 2922 µW m−1 K−2 for Sn0.96Gd0.04Te at 900 K. Meanwhile, substantial suppression of the lattice thermal conductivity is observed in Gd‐doped SnTe, which is originated from enhanced phonon scattering by multiple processes including mass and strain fluctuations due to the Gd doping, scattering of grain boundaries, nano‐pores, and secondary phases induced by Gd doping. With the decreased phonon mean free path and reduced average phonon group velocity, a rather low lattice thermal conductivity is achieved. As a result, the synergetic optimization of the electric and thermal transport properties contributes to a rather high ZT value of ≈1.5 at 900 K, leading to the superior thermoelectric performance of SnTe‐based nanoscale polycrystalline materials.

Ordered phase transformation and Cu doping effects in room-temperature ferromagnetic Sr3YCo4O10.5+δ.

Sr3YCo4O10.5+δ (314-SYCO), with an unusual ordered structure and a high Curie temperature (Tc ≈ 335K), is attracting increasing attention. Herein, to improve the electrical performance of 314-SYCO, Cu-doped Sr3YCo4-x Cu x O10.5+δ (x = 0-0.8) ceramics were prepared using a solid-state reaction method. Systematic research was conducted on both the ordered phase transformation and the effects of Cu doping on the microstructure, electrical transport characteristics, and magnetic properties. For x = 0-0.4, the (103) and (215) planes were observed and combined with Rietveld refinement results for the X-ray diffraction data, confirming the formation of ordered tetragonal Sr3YCo4-x Cu x O10.5+δ . This phase was formed with a mass gain of ∼0.8% and heat released at ∼1,042°C. With increasing Cu content, the concentration of hole carriers also increased, leading to a substantial reduction in electrical resistivity. The electrical resistivity decreased by 92-99% at 300K. The polycrystalline materials have semiconducting behaviour with a three-dimensional Mott variable-range hopping mechanism. For the magnetic properties, a Hopkinson peak was observed at 319K, and the Tc was approximately 321K for x = 0. The magnetisation and Tc decreased with increasing Cu content, and a G-type antiferromagnetic-to-ferromagnetic phase transition occurred due to the spin state change for some Co3+ ions from high/intermediate spin to low/intermediate spin. These results lay the groundwork for refinement of the sintering procedure and doping parameters to enhance the performance of 314-SYCO in the context of current applications such as microwave absorbers and solid oxide fuel cell cathodes.

Electronic properties of van der Waals heterostructures based on F-GaN-H stacking and TMDs single layer

The self-doping effects in atomic layer semiconductor materials have shown great potential for the 2D electronics and optoelectronics devices. In this paper, using the density functional theory (DFT), nonvolatile self-doped p-n junctions are formed in GaN based heterostructures which based on the stacking of the hydro-fluorination buckled GaN monolayer (ML) and bilayer (BL) and transition metal dichalcogenides (TMDs) single layer. The electronic properties demonstrated that the space distribution of carrier, and the band structures of the heterostructures depend on the polarization of GaN. The anisotropic hole and electron carrier concentration (ch and ce) are obtained in the WS2 (MoS2)/ML, BL/WSe2, and WS2 (MoS2)/BL heterostructure systems respectively. Moreover, the nonvolatile self-doped p-n junctions are achieved in type-III TMDs/ML (BL) and (BL) ML/TMDs heterostructures with the ultrahigh hole and electron carrier concentration. The type of band structures and carrier of the TMDs/ML (BL) and (BL) ML/TMDs heterostructure systems have been modulated by the self-doped induced by the polarization of GaN, which provides a new doping strategy for 2D GaN based (or polar) materials and simplifies the device fabrication in electronic and optoelectronic field.

Probing Optoelectronic and Thermoelectric Properties of Lead-Free Perovskite SnTiO3: HSE06 and Boltzmann Transport Calculations

In order to develop a useful material for the optoelectronic sector with a variety of uses in thermoelectric and optical properties at a reasonable price, we researched SnTiO3, a Pb-free and Sn-based perovskite. We used the most recent density functional theory (DFT) methods, such as the gradient approximation (GGA) approach and the screened hybrid functional (HSE06). The calculated electronic structure yields to an indirect band gap of 2.204 eV along with two different K-points such as (X-Γ) using HSE06. The accomplished optical properties have been examined by dispersion, absorption, reflection, optical conductivity, and loss function against photon energy. The thermoelectric properties and electronic fitness function (EFF) were predicted DFT along with the Boltzmann transport theory. The Seebeck coefficient (S) and related thermoelectric properties such as electronic/thermal conductivity and the Hall coefficient were calculated as a function of chemical potential and carrier density (electrons and holes concentration) for room temperature. It was established that the temperature increases the Seebeck coefficient (S) at every hole carrier concentration. SnTiO3 has good EFF at 300, 500, and 800 K as well. The discovered EFF suggests that this material’s thermoelectric performance rises with temperature and can also be improved through doping. These findings demonstrated the potential of SnTiO3 as an n-type or p-type thermoelectric material depending on the doping.

Ni doping and rational annealing boost thermoelectric performance of nanostructured double perovskite Pr1.8Sr0.2CoFeO6

Pr2CoFeO6-based double perovskite exhibits intrinsic low thermal conductivity and high Seebeck coefficient, but its low electrical conductivity induces unsatisfied thermoelectric performance. Here, we employ a synergistic strategy of rational annealing and Ni doping to achieve an improved ZT of ∼0.085 at 573 K in Pr1.8Sr0.2CoFe0.95Ni0.05O6, which is ∼425 % higher than that of pristine Pr2CoFeO6. The annealing process effectively reduces pores in the as-sintered bulk material, leading to an enhanced electrical conductivity without damaging the Seebeck coefficient, and the Ni doping further effectively improves the hole carrier concentration and in turn enhances the electrical conductivity, leading to a peak power factor of ∼113 μW m−1 K−2 at 573 K. Besides, Ni doping induces localized crystal imperfections including point defects, dislocations, and lattice distortions, contributing to an ultra-low thermal conductivity of <0.6 W m−1 K−1. As a result, the as-achieved Pr1.8Sr0.2CoFe0.95Ni0.05O6 has a ZT of ∼0.085 at 573 K, which is highly competitive to reported thermoelectric double perovskites, indicating its potential applications in high-performance thermoelectric devices.

Aliovalent Dilute Doping and Nano-Moiré Fringe Advance the Structural Stability and Thermoelectric Performance in β-Zn4Sb3.

Thermoelectric (TE) generators have come a long way since the first commercial apparatus launched in the 1950s. Since then, the β‐Zn4Sb3 has manifested its potential as a cost‐effective and environmentally friendly TE generator compared with the tellurium‐bearing TE materials. Although the β‐Zn4Sb3 features an intrinsically low thermal conductivity κ, it suffers from a long‐lasting structural instability issue arising from the highly mobile zinc ions. Herein, the dilute Ga dopant gives rise to the aliovalent substitution, lowers the mobile zinc ions, and optimizes the hole carrier concentration n H simultaneously. Meanwhile, the formation of nano‐moiré fringes suggests the modulated distribution of point defect that results from soluble Ga in a β‐Zn4Sb3 lattice, which elicits an ultralow lattice thermal conductivity κ L = 0.2 W m−1 K−1 in a (Zn0.992Ga0.008)4Sb3 alloy. Hence, a fully dense β‐Zn4Sb3 incorporated with the dilute Ga doping reveals superior structural stability with a peak zT > 1.4 at 623 K. In this work, the aliovalent dilute doping coupled with phase diagram engineering optimizes the fluxes of moving electrons and charged ions, which stabilizes the single‐phase β‐Zn4Sb3 while boosting the TE performance at the mid‐temperature region. The synergistic strategies endow the ionic crystals with a thermodynamic route, which opens up a new category for high‐performance and thermal robust TE alloys.

Microwave Synthesis and Enhanced Thermoelectric Performance of p-Type Bi0.90Pb0.10Cu1-xFexSeO Oxyselenides.

BiCuSeO oxyselenide, one of the best oxygen-containing thermoelectric materials, is promising with great potential applications. In this work, we present a high ZT of >1.3 in Bi0.90Pb0.10Cu0.96Fe0.04SeO fabricated via microwave synthesis and subsequent spark plasma sintering (SPS). We added 3-4 atom % Fe to the Pb-doped BiCuSeO to regulate the hole carrier concentration and mobility to 0.8-1.0 × 1020 cm-3 and ∼40 cm2 V-1 S-1, respectively, achieving moderate electrical conductivity, high Seebeck coefficient, and low carrier thermal conductivity simultaneously in a dual-doped sample. Under the synergistic enhancement by stress field, dislocation, and nanophase, the lattice thermal conductivity of Bi0.90Pb0.10Cu0.96Fe0.04SeO is limited to 0.24-0.49 W m-1 K-1 at 300-873 K. The development of efficient preparation methods for high-performance thermoelectric materials is significant to promote the application of thermoelectric conversion technology.

On-State Voltage Drop Analytical Model for 4H-SiC Trench IGBTs

In this paper, a model for the forward voltage drop in a 4H-SiC trench IGBT is developed. The analytical model is based on the 4H-SiC trench MOSFET voltage model and the hole-carrier concentration profile in the N-drift region for a conventional 4H-SiC trench IGBT. Moreover, an on-state voltage drop analytical model is validated using a 2D numerical simulation, and the simulation results demonstrate that there is good agreement between the ATLAS simulation data and analytic solutions.

High-Mobility Metastable Rock-Salt Type (Sn,Ca)Se Thin Film Stabilized by Direct Epitaxial Growth on a YSZ (111) Single-Crystal Substrate.

Metastable cubic (Sn1-xPbx)Se with x ≥ 0.5 is expected to be a high mobility semiconductor due to its Dirac-like electronic state, but it has an excessively high carrier concentration of ∼1019 cm-3 and is not suitable for semiconductor device applications such as thin film transistors and solar cells. Further, thin films of (Sn1-xPbx)Se require a complicated synthesis process because of the high vapor pressure of Pb. We herein report the direct growth of metastable cubic (Sn1-xCax)Se films alloyed with CaSe, which has a wider bandgap and lower vapor pressure than PbSe. The cubic (Sn1-xCax)Se epitaxial films with x = 0.4-0.8 are stabilized on YSZ (111) single crystalline substrates by pulsed laser deposition. (Sn1-xCax)Se has a direct-transition-type bandgap, and the bandgap energy can be varied from 1.4 eV (x = 0.4) to 2.0 eV (x = 0.8) by changing x. These films with x = 0.4-0.6 show p-type conduction with low hole carrier concentrations of ∼1017 cm-3. Hall mobility analysis suggests that the hole transport would be dominated by 180° rotational domain structures, which is specific to (111) oriented epitaxial films. However, it, in turn, clarifies that the in-grain carrier mobility in the (Sn0.6Ca0.4)Se film is as high as 322 cm2/(Vs), which is much higher than those in thermodynamically stable layered SnSe and other Sn-based layered semiconductor films at room temperature. Therefore, the present results prove the potential of high mobility (Sn1-xCax)Se films for semiconductor device applications via a simple thin-film deposition process.

Optical, structural, and electrical properties of sputter-deposited SnOx thin films

This study investigated the effect of deposition parameters on the properties of tin oxide (SnOx) thin films deposited by direct current magnetron sputtering using a Sn metal target. As confirmed by optical bandgap, X-ray photoelectron spectroscopy, high-resolution X-ray diffraction and Hall effect measurements, as-grown samples deposited at 7.5 and 10% oxygen partial pressure (OPP) and post-annealed samples deposited at 5% OPP had a p-type SnO phase, whereas samples fabricated with 7.5 and 10% OPP and annealed at 400°C had a n-type SnO2 phase. Post-annealing at 400°C increases the bandgap and injects more oxygen into the SnOx thin film, further oxidizing the sample. In addition, post-annealing greatly increased the carrier concentration of the SnOx thin film, which increased carrier scattering and, in turn, greatly reduced the mobility of the sample. The SnOx thin film deposited at 7.5% OPP and not heat treated showed the best p-type properties, with a Hall mobility of 5.11 cm2/Vs, a hole carrier concentration of 1.13 × 1015 cm−3, and a resistivity of 1082 Ωcm.

Evolution of Electronic Structure in Pristine and Rb-Reconstructed Surfaces of Kagome Metal RbV3Sb5.

We report on in situ low-temperature (4 K) scanning tunneling microscope measurements of atomic and electronic structures of the cleaved surfaces of an alkali-based kagome metal RbV3Sb5 single crystals. We find that the dominant pristine surface exhibits Rb-1×1 structure, in which a unique unidirectional √3a0 charge order is discovered. As the sample temperature slightly rises, Rb-√3×1 and Rb-√3×√3 reconstructions form due to desorption of surface Rb atoms. Our conductance mapping results demonstrate that Rb desorption not only gives rise to hole doping but also reconstructs the electronic band structures. Surprisingly, we find a ubiquitous gap opening near the Fermi level in tunneling spectra on all the surfaces despite their large differences of hole-carrier concentration, indicating an orbital-selective band reconstruction in RbV3Sb5. The Rb desorption induced electronic reconstructions are further confirmed by our density functional theory calculations.

Ultra-sensitive methanol detection based on S-vacancy-enriched SnS: A combined theoretical and experimental investigation

Theoretical calculations have confirmed that modulation of vacancy defects could enhance the sensing properties of semiconductor gas sensors effectively. In this work, we develop a novel and cost-effective process to prepare S-vacancy-enriched SnS (Vs-SnS) for room temperature methanol sensors and further clarify the enhanced sensing mechanism of Vs-SnS based on first-principles calculation. The Vs-SnS were successful formed via one-step solvothermal process in Sn-rich environment, which could be confirmed by the results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) techniques. Comparative investigations for methanol-sensing properties indicate that the Vs-SnS display an ∼143.9-fold enhancement in gas response at room temperature compared with conventional-SnS (C–SnS). Meanwhile, ultrafast response/recovery and low detection limit are observed for the Vs-SnS sensor (3 s of response time and 7 s of recovery time for 500 ppb methanol). The significant methanol sensing improvement could ascribed to the decrease in effective hole carrier concentration after introducing the S-vacancy as electron donor. The present study demonstrates the considerable effect and potential of vacancy modulation in the field of gas sensor applications, and the Vs-SnS is promising in highly sensitive methanol sensors with low consumption.

Influence of Fe/Ca substitute on fundamental properties of Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy materials

In the present study, the role of Fe/Ca partial replacement in Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy (Bi-2223) superconducting material on the crystallinity, electrical, structural morphology and superconducting properties is studied by way of the electrical resistivity (ρ-T), powder X-ray diffraction (XRD), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) measurements. According to the experimental results, the Fe additives are effectively replaced by the Ca sites in the bulk Bi-2223 superconducting system, verified by evidenced by the ρ-T and EDX results. Further, the SEM images show that the crystallinity quality and surface morphology view undermine considerably with the enhancement in the Fe/Ca partial substitution level in the Bi-2223 system because of nonuniform surface appearance with new induced permeant structural deformations, impurity residues, misorientations of grains and systematic problems in the grain boundary couplings in the superconducting system. Additionally, the disappearance or appearance of some diffraction peaks in the XRD pattern as well as the decrease in the c-axis length and increase a-axis length provides the deviation of the Bi-2223 materials from stabilization in the system because of the degradation in the crystal structure quality. Besides, the dc electrical results represent that the electrical and fundamental superconducting characteristics decrease with the increase of Fe/Ca replacement owing to the increment of inhomogeneities in the oxidation state, structural problems and mobile hole carrier concentration in the bulk Bi-2223 materials.

Effect of Ni and Al doping on structural, optical, and CO2 gas sensing properties of 1D ZnO nanorods produced by hydrothermal method.

In the present study, the one-dimensional ZnO nanorod structures are produced within the different nickel and aluminum molecular weight ratios of 0-7% using the hydrothermal method. It is found that the aluminum (Al) and nickel (Ni) impurities with different ionic radius, chemical valence, and electron configurations of outer shell cause to vary the fundamental characteristic features including the crystallinity quality, crystallite size, surface morphology, nanorod diameter, optical absorbance, energy band gap, resistance, gas response, and gas sensing properties. The structural analyses performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the samples are found to crystallize in the hexagonal wurtzite structure. The presence of optimum nickel and aluminum in the crystal system improves considerably the crystallinity quality and surface morphology. Additionally, the combination of electron dispersive X-ray (EDX) and XRD results declare that the Ni and Al impurities incorporate successfully into the ZnO crystal structure. Moreover, the diameters of nanorod structures in 1D orientation are determined to be 80 nm or below. The hexagonal wurtzite-type ZnO nanorod structure prepared by 5% Ni has more space between the nanorods and thus presents higher response to the CO2 detection. Further, the optical absorbance spectra display that the band gap value is observed to decrease regularly with the increment in the doping level as a result of band shrinkage effect depending on the enhancement of mobile hole carrier concentrations in the crystal structure. In other words, the doping mechanism leads to vary the homogeneities in the interfacial charges, nanorod diameters, ZnO oxide layer composition and thickness. The last test conducted in this study is responsible for the determination of CO2 gas sensing levels. The obtained gas sensing results are further compared with each other and literature findings. It is observed that 5% Ni-doped sample provides more successful results than other samples in the sensing CO2 gas at the different concentrations. All in all, the paper establishing a strong methodology between doping mechanism and change in the fundamental characteristic features of hexagonal wurtzite-type ZnO with the aid of advanced microscopy techniques will become pioneering research to answer key questions in materials sciences and electronic research.