Decrease In Carrier Concentration Research Articles

Na+ doped CuO: A new paradigm electrode material for high performance supercapacitors

This study investigates the influence of sodium doping on the properties of cupric oxide (CuO) thin films synthesized via spray pyrolysis. Comprehensive characterization was conducted using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, Hall effect measurements, and electrochemical studies. All films exhibited p-type conductivity, with an optical band gap variation from 1.53 to 1.73 eV. XRD analysis confirmed the dominance of monoclinic CuO, with minor phases of Cu2O and Cu4O3. EDAX and XPS verified the incorporation of Cu, O, and Na elements. FESEM revealed a densely packed morphology with uniform particle distribution and rough surfaces in the electrically optimized film. The Raman spectra of doped samples showed increased intensity and sharpness, attributed to Na+ ion-induced polarizability enhancement. Hall effect measurements indicated a tenfold decrease in carrier concentration and a more than tenfold increase in mobility upon sodium doping. Films doped with 4 at.% sodium exhibited the lowest resistivity. Additionally, Na doping enhanced the electrochemical performance of CuO. These findings demonstrate that sodium doping significantly enhances the electrical, optical and electrochemical properties of CuO thin films, making them suitable for applications in optoelectronic devices and supercapacitors.

The influence of laser-annealing pulse width on optical transparency and carrier dynamics of ITO thin films

Indium tin oxide (ITO) has important application in photoelectronic and photonic devices, demanding effective approach and appropriate parameters to modulate the ITO properties. The effects of laser annealing at 1064 nm with different pulse width (875 ps, 10 ns, and 300 ns) on optical and nonlinear optical properties of ITO films were investigated. Compared with 875 ps and 10 ns, laser annealing at 300 ns significantly improved the near-infrared transmittance of ITO films. The change arises from the elimination of oxygen vacancies and reduction of tin oxides, resulting in the decrease of carrier concentration. Finite element simulations indicate that laser annealing with pulse width of 875 ps and 10 ns have high instantaneous peak temperatures of 1128.5 K and 783 K, respectively, while the temperature accumulation between pulses is negligible. On the contrary, the laser annealing with a pulse width of 300 nshas lower peak transient temperature of 343 K but high static residence temperature of 973 K. The results reveal that the modification of ITO films depends more on the static average temperature rather than the instantaneous peak temperature. The modulation of carrier dynamics in both amplitude and temporal domain was demonstrated after 300 ns laser annealing, achieving ultrafast transient response approximately 150 fs. This work provides theoretical and experimental basis for us to select suitable laser conditions for directional annealing of ITO film to make it suitable for the applications of broad optical spectrum photovoltaic devices or ultrafast optical exchange for high-speed data processing.

Improved thermoelectric properties by copolymerization of conducting with insulating monomers on carbon nanotubes

In the present work, development of carbon nanotube (CNT)/poly(conducting-co-insulating monomer) structures was proposed to improve the thermoelectric (TE) performance in CNT/polyaniline (PANI) composites. To check the validity of this idea, we prepared multiwalled carbon nanotube (MWNT)/poly(aniline-co-acrylonitrile) composites by in-situ inverted emulsion copolymerization, and applied secondary doping with camphorsulfonic acid in m-cresol medium prior to the investigation of TE properties. The samples were characterized by FT-IR, UV–Vis, 1H NMR, DSC, GPC, CHNS elemental analysis, intrinsic viscosity, SEM, XRD, electrical resistance, Seebeck coefficient, thickness, and Hall measurements. We report that nitrile groups were hydrolyzed during the polymerization reactions to provide a polymer structure exhibiting aniline, acrylamide, acrylic acid, and glutarimide groups. Further, the poly(aniline-co-acrylonitrile) that prepared in the present work were random copolymers. Importantly, we found that 30 % MWNT/70 % poly(90ANI-co-10AN) composite exhibited a 63 % higher power factor (PF) of 5.48 μW/mK2 (σ: 225 S/cm, S: 15.6 μV/K) at 35 °C than that of 30 % MWNT/70 % PANI, which exhibited a PF of about 3.37 μW/mK2 (σ: 238 S/cm, S: 11.9 μV/K). This was ascribed to the decrease of carrier concentration together with the increase of carrier mobility in the 30 % MWNT/70 % poly(90ANI-co-10AN) composite as compared to the 30 % MWNT/70 % PANI.

Electrical transport in epitaxially grown undoped and Si-doped degenerate GaN films

This study investigates the electrical transport properties of undoped and Si-doped, degenerate GaN heteroepitaxial films grown on sapphire by reactive rf sputtering of GaAs (and Si) in Ar-N2 mixture. The room temperature electrical measurements showed that the resistivity of undoped GaN film grown at 100% N2 was ∼2 × 105 Ω cm, which reduced to ∼1 Ω cm in Si-doped film, revealing the effect of Si doping. With decrease of N2 from 100% to 75%, the carrier concentration of Si-doped films increased from ∼7 × 1018 cm−3 to ∼2 × 1019 cm−3, but remained practically unchanged as N2 was decreased to 20%, which is explained by effects due to saturation of Si doping and increase of Ga interstitials as well as compensation by N interstitials and Ga vacancies. Undoped and Si-doped films grown below 20% N2 displayed similar carrier concentrations (∼1020 cm−3), due to dominance of Ga interstitials. Both undoped and Si-doped films were degenerate and displayed increase of mobility with carrier concentration and temperature, which was analyzed by the combined effect of ionized impurity and dislocation scattering, using compensation ratio as fitting parameter. At carrier concentrations ≲1019 cm−3, the mobility was governed by both ionized impurity and dislocation scattering, while at higher carrier concentrations, ionized impurity scattering was found to dominate, limited by compensation due to acceptors. In spite of the degenerate character, the films displayed a small decrease of carrier concentration with temperature, along with a nearly linear decrease of mobility, which are explained by a marginal increase of compensation ratio with decrease of temperature, taking into account the band edge fluctuation effects. These features of electrical transport have not been much explored for heteroepitaxial, n-type degenerate GaN films, possessing high density of dislocations and point defects.

Atomistic origin of high grain boundary resistance in solid electrolyte lanthanum lithium titanate

Lanthanum lithium titanate is one of the promising electrolytes for solid-state lithium-ion batteries due to its high bulk ionic conductivity up to ∼10−3 S/cm. However, the practical application of this material has been bottlenecked by high grain boundary (GB) resistance, while the underlying mechanism is still under debate. Here we report a comprehensive study with direct evidence to reveal the origin of high GB resistance in La2/3–xLi3xTiO3 (LLTO). Atomic-scale observations via advanced scanning transmission electron microscopy show that the GBs are uniformly subject to subsurface segregation of La atoms to compensate for the excess surface charges. The La segregation leads to an abrupt decrease of charge carrier concentration neighboring GBs and hence is supposed to have deleterious effect on GB conductivity. The findings suggest a novel mechanism of space-charge-induced cation segregation, which shed lights on the intrinsic origin of low GB ionic conductivity in LLTO.

Enhanced Thermoelectric Properties in Highly Co-Doped Bi2Se3 by Density-of-State Effective Mass Increase

Bi2Se3 alloys are promising thermoelectric materials for use at near room temperature. In this study, we investigated the thermoelectric transport properties of Co-doped Bi2Se3, Bi2−xCoxSe3 (x=0, 0.03, 0.06, 0.09, and 0.12) polycrystalline alloys. The electrical conductivity of Bi2Se3 increased with Co doping as the electron concentration increased. The power factor increased by 83% (1.17 mW/mK2) with the Co doping compared with 0.64 mW/mK2 for pristine Bi2Se3 at room temperature. The density-of-states effective mass significantly increased to 0.30 m0 (free electron mass) by high Co doping of x =0.12 compared to 0.14 m0 for pristine Bi2Se3. The total thermal conductivity of the Co-doped samples increased owing to the increase in electronic thermal conductivity, despite the systematic decrease in the lattice thermal conductivity caused by Co doping due to additional phonon scattering. Nevertheless, an enhancement in zT was observed for all the Co-doped samples. The maximum zT value of 0.39 in highly Co-doped Bi1.88Co0.12Se3 is observed at 520K, which is 18% higher than that of pristine Bi2Se3. The zT value of the Co-doped sample could be further increased with the decrease in carrier concentration, which could be attained with the decrease in total thermal conductivity owing to the decreased electronic thermal conductivity while maintaining a high power factor originating from the increased effective mass.

Influence of Si content on thermoelectric properties of Mg2(Sn,Si) films by sputtering

Mg2(Sn,Si) films with different Si content were prepared by magnetron sputtering. The phase composition, surface and cross-sectional morphology, chemical composition and element distribution, carrier concentration, carrier mobility, electrical conductivity, Seebeck coefficient and power factor of the deposited Mg–Sn–Si films were studied. The results show that the deposited films are composed of Mg2(Sn,Si) solid solution phase and a small amount of metal Mg phase. The room temperature carrier concentration decreases and mobility increases with increasing Si content in deposited Mg–Sn–Si films, respectively. The room temperature electrical conductivity and Seebeck coefficient decreases and increases with increasing Si content, respectively. The deposited Mg2(Sn,Si) films with moderate Si content possess the maximum power factor value of 2.76 mW m−1 K−2 at 303 °C and its room temperature figure of merit reaches the highest value of 0.44. The thermal conductivity decreases with increasing Si content, indicating that the lattice distortion caused by Si doping can reduce the thermal conductivity of the deposited films.

Elucidating the role of oxygen vacancies on the electrical conductivity of β-Ga2O3 single-crystals

The contribution of oxygen vacancies (VO) to the electrical conductivity of unintentionally doped β-Ga2O3 has been a topic of recent debate. Here, we use a combination of Hall measurements and Raman spectroscopy on as-grown and O2-annealed β-Ga2O3 crystals to investigate the role of VO on electrical conductivity. The annealed samples show a significant decrease in carrier concentration. By comparing the relative Raman shift of individual modes with theoretically calculated contributions of oxygen sites to these modes, we verify the marked reduction of VO in annealed β-Ga2O3 crystals. Furthermore, the IR modes in β-Ga2O3, usually hidden by free carrier absorption, are clearly seen in the annealed sample. The reduction of band tail states as well as free carrier absorption in the annealed samples provides additional evidence for reduced carrier concentration related to VO, making them a key determinant of electrical conductivity in β-Ga2O3.

Temperature dependence of two-dimensional hole gas on hydrogen-terminated diamond surface

The two-dimensional hole gas (2DHG) at hydrogen-terminated diamond (H-diamond) surface has been widely used in the development of diamond-based electronics. However, the carrier transport behaviors of 2DHG are still poorly understood due to the difficulty in controlling surface adsorbates on H-diamond. In this work, the temperature dependence of the electrical properties of 2DHG on H-diamond was investigated through Hall effect measurements before and after thermal annealing. The results revealed that the establishment of 2DHG equilibrium state was closely related to surface adsorbates, and temperature-induced thermal desorption of adsorbates would lead to a decrease in carrier concentration and an enhancement of mobility on H-diamond. Based on this observation, the carrier mobility of 2DHG (at 300 K) was improved from 170 to 340 cm2 V−1 s−1 after thermal annealing to 400 K. Moreover, with thermal desorption of adsorbates, the activation energy of conductance exhibited an increasing tendency, and the carrier concentration became more dependent on temperature, which can be well explained by percolation theory. A dynamic equilibrium process was also proposed to illustrate the influence of surface adsorbate on carrier concentration and mobility of 2DHG, which provides a feasible method to regulate carrier mobility and concentration on H-diamond surface.

Homogeneity- and Stoichiometry-Induced Electrical and Optical Properties of Cu-Se Thin Films by RF Sputtering Power.

P-type Cu-Se thin films were deposited on glass substrates at room temperature using radio frequency magnetron sputtering by a single multi-component CuSe2 target. When using a multi-component target, the impact of the sputtering power on the homogeneity and stoichiometry within the thin films should be investigated in the depth direction to demonstrate a secondary effect on the electrical and optical properties of the thin films. Systematic characterization of the Cu-Se thin films, including the morphology, microstructure, chemical composition, and depth-directional chemical bonding state and defect structure of the thin films, revealed that the sputtering power played an important role in the homogeneity and stoichiometry of the thin films. At very low and very high sputtering power levels, the Cu-Se thin films exhibited more deviations from stoichiometry, while an optimized sputtering power resulted in more homogenous thin films with improved stoichiometry across the entire thin film thickness in the X-ray photoelectron spectroscopy depth profile, despite showing Se deficiency at all depths. A rapid decrease in carrier concentration, indicating a reduction in the net effect of total defects, was obtained at the optimized sputtering power with less deviation from stoichiometry in the Cu-Se thin films and the closest stoichiometric ratio at an intermediate depth.

Healing Donor Defect States in CVD-Grown MoS2 Field-Effect Transistors Using Oxygen Plasma with a Channel-Protecting Barrier.

Molybdenum disulfide (MoS2 ), a metal dichalcogenide, is a promising channel material for highly integrated scalable transistors. However, intrinsic donor defect states, such as sulfur vacancies (Vs ), can degrade the channel properties and lead to undesired n-doping. A method for healing the donor defect states in monolayer MoS2 is proposed using oxygen plasma, with an aluminum oxide (Al2 O3 ) barrier layer that protects the MoS2 channel from damage by plasma treatment. Successful healing of donor defect states in MoS2 by oxygen atoms, even in the presence of an Al2 O3 barrier layer, is confirmed by X-ray photoelectron spectroscopy, photoluminescence, and Raman spectroscopy. Despite the decrease in 2D sheet carrier concentration (Δn2D = -3.82×1012 cm-2 ), the proposed approach increases the on-current and mobility by 18% and 44% under optimal conditions, respectively. Metal-insulator transition occurs at electron concentrations of 5.7×1012 cm-2 and reflects improved channel quality. Finally, the activation energy (Ea ) reduces at all the gate voltages (VG ) owing to a decrease in Vs , which act as a localized state after the oxygen plasma treatment. This study demonstrates the feasibility of plasma-assisted healing of defects in 2D materials and electrical property enhancement and paves the way for the development of next-generation electronic devices.

Influence of DC Magnetron Sputtering Power on Structural, Topography, and Gas Sensor Properties of Nb2O5/Si Thin Films.

This study focuses on synthesizing Niobium pentoxide (Nb2O5) thin films on silicon wafers and quartz substrates using DC reactive magnetron sputtering for NO2 gas sensors. The films undergo annealing in ambient air at 800 °C for 1 hr. Various characterization techniques, including X-ray diffraction (XRD), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), Hall effect measurements, and sensitivity measurements, are employed to evaluate the structural, morphological, electrical, and sensing properties of the Nb2O5 thin films. XRD analysis confirms the polycrystalline nature and hexagonal crystal structure of Nb2O5. The optical band gap values of the Nb2O5 thin films demonstrate a decrease from 4.74 to 3.73 eV as the sputtering power is increased from 25 to 75 W. AFM images illustrate a progressive increase in particle size ranging from (41.86) to (45.56) nm, with varying sputtering power between 25 and 75 W. Additionally, EDS analysis validates the rise in Nb content, increasing from 12.2 at. % to 20.1 at. %, corresponding to the increase in sputtering power. Hall effect measurements show that all films exhibit n-type charge carriers, and increasing sputtering power leads to decreased carrier concentration and enhanced mobility. The gas sensor's sensitivity, response, and recovery time were evaluated at various operating temperatures. The NO2 sensor exhibited an optimal sensitivity of 28.6% at 200 °C when the sputtering power was set to 50 W.

Balanced High Thermoelectric Performance in n-Type and p-Type CuAgSe Realized through Vacancy Manipulation.

As a liquid-like material, CuAgSe has high carrier mobility and ultralow lattice thermal conductivity. It undergoes an n-p conduction-type transition during β- to α-phase transition with increasing temperature. Moreover, optimization of the thermoelectric performance of CuAgSe is rather difficult, owing to the two-carrier conduction in this material. In this work, we reported the free tuning of the conduction type and thermoelectric performance of CuAgSe by manipulating the cation vacancies. Positron annihilation measurements reveal that the increase in CuAg content can effectively suppress the cation vacancies and reduce the hole carrier concentration, resulting in n-type conduction at high temperatures. Doping with Zn at the Cu sublattice in the CuAg-excessive CuAgSe can further decrease the number of vacancies, leading to a significant decrease in hole carrier concentration. Furthermore, the reduction of vacancies leads to weakening of carrier scattering. As a result, carrier mobility is also enhanced, thus improving the thermoelectric performance of n-type CuAgSe. On the other hand, high-performance p-type CuAgSe can be achieved by decreasing the CuAg content to introduce more cation vacancies. Ultimately, both n-type and p-type CuAgSe with superb thermoelectric performance are obtained, with a zTmax of 0.84 in Cu1.01Ag1.02Zn0.01Se (n-type) and 1.05 in (CuAg)0.96Se (p-type) at 600 K and average zT of 0.77 and 0.94 between 470 and 630 K for n-type and p-type, respectively.

Surface-disorder and cationic-site defect-induced ferromagnetism and correlated Raman vibrational modes in Sn0.9 In0.1O2 nanocrystalline thin-films

Exploration of magnetism in otherwise nonmagnetic wide-band oxides through defect-engineering has been become a new challenge to achieve the goal of room-temperature ferromagnetic semiconductor for potential applications in spintronics. In this backdrop, we report surface-disorder and cationic-site defect-induced FM in series of Sn0.9In0.1O2 nanocrystalline thin films prepared using pulsed laser deposition different Argon (Ar) pressure. With the increase of deposition pressure, surface morphology of Sn0.9In0.1O2 nanocrystalline thin-films changes as nanoclusters, nanofibres, nanoflakes and nanowires respectively, crystallite size decreases and surface disorder increases gradually. Raman, X-ray photoelectron and Photoluminescence spectroscopic analysis confirm the formation tin-vacancy (VSn) and associated combinational defects that significantly increase the ferromagnetic signal in In-doped SnO2 thin-films. The substitution of trivalent In3+ in Sn site also cause serious lattice distortion which transform the Raman inactive modes A2g and Eu modes into Raman active modes and thus appeared at 574 cm−1 and 354 cm−1 respectively. The nanowires of Sn0.9In0.1O2 are found to possess highest concentration of VSn defects and therefore it exhibits strongest ferromagnetic moment (MS) ∼ 11.1 emu/cm3 and highest Curie temperature (TC) ∼ 572 K. The gradual decrease in carrier concentration with the increasing deposition pressure suggests stabilization of hole-mediated VSn-induced room temperature FM in series of In-doped SnO2 nanocrystalline thin-films.

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb‐Eu2ZnSb2 Alloys

AbstractAMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M‐site in the planar MX‐layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu1−xZn0.5xSb solid solution. The transition from a fully‐occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn0.5Sb) leads to non‐linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb‐sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK−1 at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn0.5Sb.

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb-Eu2 ZnSb2 Alloys.

AMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M-site in the planar MX-layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu1-x Zn0.5x Sb solid solution. The transition from a fully-occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn0.5 Sb) leads to non-linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb-sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK-1 at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn0.5 Sb.

The effects of Zn doping on the thermoelectric performance of Cu12Sb4S13

In this study, first-principles electronic structure calculations and Boltzmann transport theories were used to understand the thermoelectric behavior of tetrahedrites. Calculations were performed on zinc (Zn)-substituted derivatives with zinc occupying each lattice site in the parent compound Cu12Sb4S13 to study the zinc substitution mechanism and the relation between the zinc substitution site and thermoelectric performance. It was found that the most energetically favorable sites for zinc are the Cu(1) sites, and the next are the Cu(2) sites. Furthermore, the room-temperature Seebeck coefficient of the host was enhanced nearly 255 and seven times by zinc doping at Cu(1) and Cu(2) sites, respectively, owing to the decrease in carrier concentration and the increase in band effective mass, respectively. However, the electrical conductivity showed a marked decrease upon zinc doping at Cu(1) and Cu(2) sites, due to the decrease in carrier contribution and low mobility, respectively. As a result, Cu12Sb4S13 compounds substituted with zinc at Cu(1) sites have a preferable optimizing power factor at room temperature. The optimizing power factor of the host could obtain approximately eight times improvement at room temperature upon zinc substitution at Cu(1) sites.

Impacts of Annealing Temperature and Time on the Thermoelectric Performance of Recycled Carbon Fiber (RCF)/n-Bi2Te3 Heterostructure Thermoelectric Composites

Recycling carbon fibre waste is crucial for sustainability in the composites industry. Herein, we report the fabrication of a heterostructure composite using recycled carbon fiber (RCF) and n-type bismuth telluride (n-Bi2Te3) for thermoelectric applications. In the present study, we have comprehensively investigated the effects of annealing temperature and time on the thermoelectric, structural, charge carrier transport, morphological, and thermal stability properties of annealed RCF/n-Bi2Te3 composites. The optimum annealing temperature and time were at 350 °C and 2 h, respectively, which yielded a maximum power factor of 7.83 μWK−2m−1. Annealing redistributed the bismuth and tellurium atomic percentage, decreased carrier concentration, improved carrier mobility, enhanced the crystallinity and increased the grain size of the bismuth telluride particles, subsequently improving the thermoelectric performance as well as the thermal stability of annealed RCF/n-Bi2Te3 composites. In addition, this study has explored the plausibility of a cross-plane configured Seebeck coefficient measurement utilizing recycled carbon fibre/n-type bismuth telluride heterostructure thermoelectric composite. Energy band diagram analysis indicated favorable heterojunction alignment between RCF and n-Bi2Te3, validating the viability of the thermoelectric composite in a cross-plane configuration. Our study provides a promising route for closing the recycling loop of carbon fiber waste and achieving sustainable thermoelectric materials.

Enhancing the Thermoelectric Performance of GeSb4Te7 Compounds via Alloying Se.

Ge-Sb-Te compounds (GST), the well-known phase-change materials, are considered to be promising thermoelectric (TE) materials due to their decent thermoelectric performance. While Ge2Sb2Te5 and GeSb2Te4 have been extensively studied, the TE performance of GeSb4Te7 has not been well explored. Reducing the excessive carrier concentration is crucial to improving TE performance for GeSb4Te7. In this work, we synthesize a series of Se-alloyed GeSb4Te7 compounds and systematically investigate their structures and transport properties. Raman analysis reveals that Se alloying introduces a new vibrational mode of GeSe2, enhancing the interatomic interaction forces within the layers and leading to the reduction of carrier concentration. Additionally, Se alloying also increases the effective mass and thus improves the Seebeck coefficient of GeSb4Te7. The decrease in carrier concentration reduces the carrier thermal conductivity, depressing the total thermal conductivity. Finally, a maximum zT value of 0.77 and an average zT value of 0.48 (300-750 K) have been obtained in GeSb4Te5.5Se1.5. This work investigates the Raman vibration modes and the TE performance in Se-alloyed GeSb4Te7 sheddinglight on the performance optimization of other GST materials.

Strain induced by temperature evolution of mesoporous ZnO nanopowders and its effect on structural, optical and electrical impedance properties

The structural and optical properties of ZnO nanopowder samples prepared by a novel green hydrothermal method have been studied. The prepared ZnO nanopowder samples were annealed (200, 250, 300, 400, 500 °C) and characterised through XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), BET (Brunauer–Emmett–Teller), FT-IR (Fourier transform infrared spectroscopy), UV–Vis (Ultraviolet–visible) spectroscopy, PL (Photoluminescence) spectroscopy and EIS (Electrochemical Impedance spectroscopy). The XRD Study revealed that the prepared samples were crystalline with ZnO hexagonal wurtzite structures. The crystallite sizes were determined using the Debye–Scherrer and Williamson–Hall methods and found to increase from 20.5037 to 25.9157 nm and 22.3261 to 31.4388 nm respectively with an increase in annealing temperature. The FE-SEM revealed that the prepared ZnO nanopowder samples were of spherical shape which corroborated the XRD results. The BET results showed that the prepared nanopowder samples were mesoporous with the average pore size varying between 15.125 and 25.583 nm and surface area varying between 15.337 and 23.959 m2/g. The presence of functional groups and chemical bonding were confirmed by the FTIR measurements. The energy band gaps were determined using the Kubelka-Munk function applied to UV–Vis spectra and found to be decreasing from 3.243 to 3.160 eV with an increase in annealing temperature. PL results revealed a clear dependence of the emission with annealing temperature which was caused by the decrease of free carrier concentration as the annealing temperature increased. EIS measurements indicated an increase in electrical resistance with an increase in annealing temperature with the sample annealed at 300 °C having the smallest resistance.