A Computational Study on the Variation of Bandgap Due to Native Defects in Non-Stoichiometric NiO and Pd, Pt Doping in Stoichiometric NiO

Itapu, Srikanth; Borra, Vamsi; Mossayebi, Faramarz

doi:10.3390/condmat3040046

Cited by 10 publications

(8 citation statements)

References 46 publications

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“…The obtained values lie well within the previously reported bandgap values (3.6À4.0 eV) for NiO thin films. [32][33][34][35] The higher bandgap of the films grown at 400 and 500 C can be attributed to nonstoichiometry, higher dislocation densities, and extended defect states, [36] as witnessed from previous measurements.…”

Section: Resultssupporting

confidence: 52%

Temperature‐Driven Perturbations in Growth Kinetics, Structural and Optical Properties of NiO Thin Films

Mishra¹,

Barthwal²,

Tak³

et al. 2021

Physica Status Solidi (a)

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Recent years have witnessed a growing demand in the improvement of nanostructured metal oxides with p-type conductivity. Nickel oxide (NiO) is a naturally grown p-type metal-oxide semiconductor pursuing direct wide bandgap (from 3.6 to 4 eV), moderate conductivity, good chemical stability, high transmittance, and excellent optoelectronic properties. [1] It crystallizes in sodium chloride (NaCl)-type face-centered cubic (FCC) structure and exhibits maximum hole conductivity along (111) direction. [1][2][3] Being a transparent p-type semiconducting oxide, NiO offers potential application in the domain of perovskite solar cells (transparent electrodes), visible blind photodetection, solid-state gas sensing and electrochromic displays, etc. [2][3][4][5] Despite its technological importance, the growth of device-grade NiO thin films has remained a challenging task, mainly attributed to its low conductivity. To date, numerous studies on the growth of NiO via various physical and chemical methods including magnetron sputtering, [6,7] plasma-enhanced chemical vapor deposition (PECVD), [8] pulsed laser deposition (PLD), [9] thermal evaporation, [10] spray pyrolysis, [11] sol-gel processing, [12] etc. have been reported so far. However, among the various aforementioned methods, radio-frequency (RF) magnetron sputtering is the most common and a widely used technique for the growth of NiO thin films. [13][14][15][16][17][18] Literature reports that growth parameters play a critical role in governing the properties of NiO films grown by RF magnetron sputtering. [13][14][15][16]19] Modifications in growth parameters may introduce various defects such as structural points defects, dislocations, or perturbation-induced ingap states, [13,15] affecting the structural, optical, and electrical properties of the grown NiO films. Ahmed et al. [16] observed that the growth of NiO is substrate dependent and that the inherent material properties depend strongly on the types of substrate (Si, GaAs, PET, etc). In contrast, Grilli et al. [19] reported that RF power and sputtering gas significantly influence the resistivity (from 10 À2 to 10 À1 Ω-cm) and transmittance of the grown NiO films. A recent study by Turgut et al. [20] said that oxygen partial pressure not only changes the structural and morphological properties, but it also influences the oxidation state of nickel, leading to significant variation in the performance of NiO-based hydrogen sensors. [20] In a recent report, Dhull et al. [21] also demonstrated that substrate temperature can play a significant role in tailoring the morphology of NiO films, leading to perturbation in charge transfer characteristics. However, few other studies were also conducted to explore the influence of growth temperature on structural, optical, morphological, and device applications of NiO thin films, but the extent of study was limited to a lower growth temperature, that is, up to 300 C only. [22][23][24][25] It implies that growth temperature significantly

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Section: Resultssupporting

confidence: 52%

Temperature‐Driven Perturbations in Growth Kinetics, Structural and Optical Properties of NiO Thin Films

Mishra¹,

Barthwal²,

Tak³

et al. 2021

Physica Status Solidi (a)

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“…The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaem.0c02383. Experimental details with supporting references , , , , − ; description and/or additional figures of optical properties, XRD, XPS, XANES, EXAFS, electrochemistry, EIS, and electrochromism; and tables of XPS, EXAFS, EIS, and electrochromic material parameters (PDF) …”

mentioning

confidence: 99%

Structural Evolution in Photodeposited Nickel (oxy)hydroxide Oxygen Evolution Electrocatalysts

Schoen

Randell

Calderon

et al. 2020

ACS Appl. Energy Mater.

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Amorphous metal oxides expand the range of material parameters significantly compared to their crystalline counter parts. However, predictions of the exact nature of the amorphous phase and its effect on material properties are still elusive. Thorough structureproperty investigations of well-known model systems are thus necessary before predictive control of useful material properties is obtained. In this work, we fabricate a series of photodeposited nickel (oxy)hydroxide (NiO x ) thin films and anneal them at temperatures up to 1000 • C. EXAFS, XRD and XPS are used to determine the local structure, allowing us to correlate it to measured electrochemical properties. We find an amorphous Ni(OH) 2 -like local structure for annealing conducted below 250 • C, followed by an amorphous-to-amorphous phase transition to a NiO-like structure by 300 • C, thus supplying evidence for different 1 amorphous polymorphs in this Ni-O system. Above 400 • C a cubic NiO XRD diffraction pattern is detected. Electrochemically, we find a stepwise increase of the onset overpotential at this transition, indicating a change in potential-determining step and possibly OER reaction mechanism. The Tafel slope decreases linearly with annealing temperature, which we attribute to a decrease in (Ni)OOH reaction intermediary coverage, supported by in-operando UV-Vis electrochromism. Furthermore, we find that the (Ni)OOH coordination is increasingly strained with annealing temperature, which manifests in higher electrochromic coloring rates and lower binding energies. We identify this as the root cause of the lowered intermediary coverage. Thus, nano-crystalline NiO should kinetically be a superior catalyst to amorphous Ni(OH) 2 . However, at our benchmarking value of 10 mA cm −2 the amorphous material exhibits lower overpotential, due to a combination of lower onset potential, large chemically active surface area and mass transport limitations under our conditions.

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“…Similarly, ink-jet printed p-type NiO x TFTs annealed at 280 • C in [39] gave the best electrical performance with a field-effect mobility of 0.78 cm 2 /Vs, SS of 1.68 V/dec, on/off current ratio (I on /I off ) of 5.3 × 10 4 with a 50 nm Al 2 O 3 insulator layer. The authors in [40] successfully achieved p-type NiO TFTs with a mobility of 6.0 cm 2 /Vs and on/off current ratio of 10 7 at a temperature of 250 • C. Hence, from our previous works [5][6][7]23,29], we propose a noncontact laser irradiation on sputter-deposited NiO x /SiO 2 -based TFTs as a potential technique to enhance the electrical parameters by tuning the laser fluence and a number of laser pulses. In this work, the relation between the number of laser pulses to the mobility of NiO x , threshold voltage, on/off ratio and subthreshold swing of the NiO x /SiO 2 TFT device is also studied extensively.…”

Section: Introductionmentioning

confidence: 95%

“…Some recent studies used working gas and thermal annealing as viable techniques for interstitial/defect changes. However, the dynamics of interstitials/vacancies created due to laser irradiation are little discussed regarding non-stoichiometric NiO films [23].…”

Section: Introductionmentioning

confidence: 99%

“…In continuation of the previous work in [23], laser irradiation was also employed to study its effects in modifying the intrinsic properties of metallic [24,25], semiconducting [26][27][28][29], superconducting [30], multiferroic [31] and ceramic [32] thin films. In [33], the most frequently used high dielectric material, hafnium oxide (HfO 2 ), was subjected to irradiation by a continuous wave laser with a wavelength of 355 nm to analyze the temporal behavior of absorption annealing.…”

Section: Introductionmentioning

confidence: 99%

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Tuning the Electrical Parameters of p-NiOx-Based Thin Film Transistors (TFTs) by Pulsed Laser Irradiation

Manojreddy¹,

Itapu

Ravali

et al. 2021

Condensed Matter

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We utilized laser irradiation as a potential technique in tuning the electrical performance of NiOx/SiO2 thin film transistors (TFTs). By optimizing the laser fluence and the number of laser pulses, the TFT performance was evaluated in terms of mobility, threshold voltage, on/off current ratio and subthreshold swing, all of which were derived from the transfer and output characteristics. The 500 laser pulses-irradiated NiOx/SiO2 TFT exhibited an enhanced mobility of 3 cm2/V-s from a value of 1.25 cm2/V-s for as-deposited NiOx/SiO2 TFT, subthreshold swing of 0.65 V/decade, on/off current ratio of 6.5 × 104 and threshold voltage of −12.2 V. The concentration of defect gap states as a result of light absorption processes explains the enhanced performance of laser-irradiated NiOx. Additionally, laser irradiation results in complex thermal and photo thermal changes, thus resulting in an enhanced electrical performance of the p-type NiOx/SiO2 TFT structure.

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A Computational Study on the Variation of Bandgap Due to Native Defects in Non-Stoichiometric NiO and Pd, Pt Doping in Stoichiometric NiO

Cited by 10 publications

References 46 publications

Temperature‐Driven Perturbations in Growth Kinetics, Structural and Optical Properties of NiO Thin Films

Temperature‐Driven Perturbations in Growth Kinetics, Structural and Optical Properties of NiO Thin Films

Structural Evolution in Photodeposited Nickel (oxy)hydroxide Oxygen Evolution Electrocatalysts

Tuning the Electrical Parameters of p-NiOx-Based Thin Film Transistors (TFTs) by Pulsed Laser Irradiation

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