Abstract:The solid‐state reaction method was used to prepare tablets of (V2O5)100−x (Al2O3)x with x = 5, 10, 15, 20 wt. %. Thin films of Al2O3‐doped V2O5 were deposited onto glass substrates using an electron‐beam evaporation technique. The influence of doping and annealing temperature on the structural and optical characteristics has been investigated in detail. Optical properties of the films were studied extensively in the wavelength range 200–2500 nm from the measurements of the optical transmittance (T) and optica… Show more
“…(K r J K , K r 1/E B ). This finding suggests that the lower values of K r provide higher values of both α and E B , while the vice is versa for the higher K r , in consistent with the reported elsewhere [ 57 , 58 ]. Fig.…”
Section: Resultssupporting
confidence: 92%
“…Furthermore, the higher valence state of the co-doping (Fe 3+ /Cu 2+/3 ) compared to Zn 2+ led to more deep acceptor levels which trap the electrons from the conduction band and then widening the energy gap. Moreover, it has been expected that (Fe + Cu) clusters may also form individual traces of oxides arising from the band structure and act as prime nonradiative recombination centers (native defects), and consequently a strong potential barrier could be formed [ 55 , 57 , 69 , 70 ]. Consequently, σ 1 and σ L of the Fe/ (Fe + Cu) samples are slightly lower than that of the ZnO, while E B and α are higher.…”
We report here structural morphology and nonlinear behavior of pure and co-doped Zn
0.90-x
Fe
0.1
M
x
O with (M = Cu, Ni and (
x
= 0.00, 0.10) and (0.00 ≤
y
≤ 0.20)) at different sintering temperatures (
T
s
= 850 and 1000 °C). It is found that the co-doping of ZnO by (Fe + Cu) or (Fe + Ni) up to 0.30 does not deform the well-known wurtzite structure of ZnO, as well as pure and 0.1 of Fe-doped ZnO. The SEM micrographs did not show any secondary phases at the boundaries of grains as compared to ZnO, the average grain size is decreased for Fe and (Fe + Cu) samples, while it is increased for (Fe + Ni) samples. The nonlinear coefficient
α
and breakdown field
E
B
are generally increased by 0.1 of Fe addition, but they are shifted to lower values as
T
s
increases for all samples. Furthermore, they are gradually increased/decreased to higher/lower values for (Fe + Cu/Fe + Ni) samples up to 0.30 of co-doping content. The values of
α
and
E
B
are increased from 30.06, 2115.38 V/cm for ZnO at 850 °C to 50.07, 5012 V/cm by (0.1Fe + 0.2Cu) co-doping, and from 23.53, 1956.52 V/cm to 45.58, 4750 V/cm at 1000 °C, while they are, respectively, decreased by (0.1Fe + 0.2Ni) to 13.19, 312 V/cm and 11.85, 172.42 V/cm. Similar behavior was generally obtained for nonlinear conductivity
σ
L
and height of potential barrier φ
B
, whereas the vice is versa for the behavior of leakage current
J
k
and residual voltage
K
r
. Our results are discussed in terms of the comparative participation between the effects of co-doping of (Fe + Cu) and (Fe + Ni) to ZnO for supporting the potential barrier as compared to individual doping by Fe, Cu and Ni. This study perhaps recommended these samples for optoelectronic and ferromagnetic investigation after COVID-19 is over.
“…(K r J K , K r 1/E B ). This finding suggests that the lower values of K r provide higher values of both α and E B , while the vice is versa for the higher K r , in consistent with the reported elsewhere [ 57 , 58 ]. Fig.…”
Section: Resultssupporting
confidence: 92%
“…Furthermore, the higher valence state of the co-doping (Fe 3+ /Cu 2+/3 ) compared to Zn 2+ led to more deep acceptor levels which trap the electrons from the conduction band and then widening the energy gap. Moreover, it has been expected that (Fe + Cu) clusters may also form individual traces of oxides arising from the band structure and act as prime nonradiative recombination centers (native defects), and consequently a strong potential barrier could be formed [ 55 , 57 , 69 , 70 ]. Consequently, σ 1 and σ L of the Fe/ (Fe + Cu) samples are slightly lower than that of the ZnO, while E B and α are higher.…”
We report here structural morphology and nonlinear behavior of pure and co-doped Zn
0.90-x
Fe
0.1
M
x
O with (M = Cu, Ni and (
x
= 0.00, 0.10) and (0.00 ≤
y
≤ 0.20)) at different sintering temperatures (
T
s
= 850 and 1000 °C). It is found that the co-doping of ZnO by (Fe + Cu) or (Fe + Ni) up to 0.30 does not deform the well-known wurtzite structure of ZnO, as well as pure and 0.1 of Fe-doped ZnO. The SEM micrographs did not show any secondary phases at the boundaries of grains as compared to ZnO, the average grain size is decreased for Fe and (Fe + Cu) samples, while it is increased for (Fe + Ni) samples. The nonlinear coefficient
α
and breakdown field
E
B
are generally increased by 0.1 of Fe addition, but they are shifted to lower values as
T
s
increases for all samples. Furthermore, they are gradually increased/decreased to higher/lower values for (Fe + Cu/Fe + Ni) samples up to 0.30 of co-doping content. The values of
α
and
E
B
are increased from 30.06, 2115.38 V/cm for ZnO at 850 °C to 50.07, 5012 V/cm by (0.1Fe + 0.2Cu) co-doping, and from 23.53, 1956.52 V/cm to 45.58, 4750 V/cm at 1000 °C, while they are, respectively, decreased by (0.1Fe + 0.2Ni) to 13.19, 312 V/cm and 11.85, 172.42 V/cm. Similar behavior was generally obtained for nonlinear conductivity
σ
L
and height of potential barrier φ
B
, whereas the vice is versa for the behavior of leakage current
J
k
and residual voltage
K
r
. Our results are discussed in terms of the comparative participation between the effects of co-doping of (Fe + Cu) and (Fe + Ni) to ZnO for supporting the potential barrier as compared to individual doping by Fe, Cu and Ni. This study perhaps recommended these samples for optoelectronic and ferromagnetic investigation after COVID-19 is over.
“…These results indicate that the increase in Ts to 1200 oC decreases non-ohmic characteristics and moves the breakdown fields to lower values. This is due to the decrease in the height of the potential barrier formed at the ZnO grain boundaries, which is usually caused by oxygen vacancies, in accordance with the data published [62,[63][64][65][66]. ZnO varistor's residual voltage ratio Kr is defined as the ratio of the electric field to a given current impulse and the breakdown field EB for a fixed diameter and ZnO thickness as follows; (7.4 mm < D < 21 mm), (0.5 mm <d < 4.5 mm).…”
Section: 2-i-v Characteristicssupporting
confidence: 89%
“…The increase of free carrier concentration up to Ts =1200 o C can be achieved by the decrease of oxygen deficiency or electrons in ZnO. For more clarification, free carrier concentration N is calculated using the average value of m * which has been reported for ZnO (m * =3.82 10 -25 g) [86], and therefore the interatomic distance (R) can be calculated by using the relation; R = (0.86/N (1/3) ) [66,67]. The values of N and R are listed in Table 2, and it is clear that N value is increased by increasing Ts, and the vice is versa for inter-atomic distance R.…”
Section: 4-dielectric Constant and Optical Conductivitymentioning
We report here structural, electrical, photoluminescence (PL), and optical investigations of ZnO nanoparticles. The ZnO samples are initially sintered at various temperatures (T s ) (600-1200 o C) temperatures and their size is reduced twice to nanoscale by using ball friction at 200 rpm rotational speed and 30 minutes duration. It is found that the T s do not influence the well-known peaks associated with the ZnO hexagonal structure, whereas the constants of the lattice and the average crystallite diameters are affected. Although the nonlinear area is observed for all samples in the I-V curves, the breakdown field E B and nonlinear coefficient β are moved to lower values as T s increases, while the residual voltage K r and nonlinear conductivity (σ 2 ) are increased. The empirical relations for K r , E B , and β as a function of T s are; K r = 0.004 T s – 0.487, E B = -1.786T s +2559.5 and β = -0.052 T s +75.19. On the other hand, a maximum UV absorption shift (A max ) is obtained at 412 nm, 400 nm, 384 nm, and 326 nm as the T s increases up to 1200 o C. For each sample, two different energy band gap values are obtained; the first is called the basic bandgap (E gh ) and its value above 3 eV, while the second is called the optical band gap (E gL ), and its value below 2.1 eV. Moreover, the empirical relations of them are E gh = 0.002 T s - 0.24, E gl = -0.0033 T s +5.242 and ∆E = - 0.0015 T s +5.002. Furthermore, the values of (N/m*) and lattice dielectric constant ε L are increased by increasing T s up to 1200 o C, while the vice is versa for the interatomic distance R. The dielectric loss tan δ is almost linear above 4 eV for all samples, and it decreases sharply as the T s increases. The optical and electrical conductivities σ opt and σ ele are decreased as the T s increases up to 1200 o C. Finally, the characteristic of UV band edges against the optimum value of PL intensity for the samples shows 8-continuous peaks. Furthermore, the PL intensity of the peaks is decreased by increasing T s and also by shifting the UV wave number towards the IR region.
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