JIWEN XU
Articles written in Bulletin of Materials Science
Volume 37 Issue 4 June 2014 pp 895-902
Jiwen Xu Zupei Yang Hua Wang Xiaowen Zhang
Aluminum-doped zinc oxide (AZO) target was fabricated using AZO nanopowders synthesized by co-precipitation method and then the AZO films with different thicknesses were deposited on glass by d.c. magnetron sputtering at room temperature. AZO target is nodules free and shows homogeneous microstructure, ultra-high density and low resistivity. ZnAl2O4 phase appears in AZO target and disappears in AZO films. All AZO films show c-axis preferred orientation and hexagonal structure. With increasing film thickness from 153 to 1404 nm, the crystallinity was improved and the angle of (002) peak was close to 34.45°. The increase in grain size and surface roughness is due to the increase in film thickness. The decrease of resistivity is ascribed to the increases of carrier concentration and Hall mobility. The lowest resistivity is 9.6 × 10-4 𝛺.cm. The average transmittance of AZO films exceeds 80%, and a sharp fundamental absorption edge with red-shifting is observed in the visible range. The bandgap decreases from 3.26 to 3.02 eV.
Volume 37 Issue 7 December 2014 pp 1657-1661
Jiwen Xu Zupei Yang Yupei Zhang Xiaowen Zhang Hua Wang
ZnMn2O4 active layer for resistance random access memory (RRAM) was deposited on p+-Si substrate by chemical solution deposition. The bipolar resistive switching behaviours of the Ag/ZnMn2O4/p+-Si capacitor are investigated. The bipolar resistive switching is reproducible and shows high ON/OFF ratio of > 102 and long retention times of > 105 s. The conduction mechanism of the Ag/ZnMn2O4/p+-Si capacitor in the low-resistance state (LRS) is ohmic conduction, whereas that of the device in high-resistance state (HRS) successively undergoes Ohm’s law, trap-filled-limited and Child’s law conduction procedure at room temperature.
Volume 39 Issue 3 June 2016 pp 743-747
HUA WANG XIAYAN ZHAO JIWEN XU XIA ZHAI LING YANG
Lead-free piezoelectric ceramics $(1−x)$[0.95(K$_{0.5}$Na$_{0.5}$)NbO$_3$–0.05LiSbO$_3$]–$x$BiFe$_{0.8}$Co$_{0.2}$O$_{3}$(KNN–LS–$x$BFC) were prepared by a conventional sintering technique. The effect of BFC content on the structure, piezoelectricand electrical properties of KNN–LS ceramics was investigated. The results reveal that the BFC is effective in promoting the sinterability and the electrical properties of the ceramics sintering at low temperature of 1030$^{\circ}$C. Theceramics show a single perovskite structure, in which the tetragonal phase decreases while the orthorhombic phase increases with the increase of $x$. The more the BFC content is, the smaller and homogeneous grains were formed.With the increase of $x$, the $d_{33}$ and the $k_p$ increase to a maximum value and then slightly decrease, but the $Q_m$ increases continuously. As BFC content increases, the Curie temperature $T_c$ and remnant polarization $P_r$ decrease, but the diffusivity of phase transition in KNN–LS ceramics will intensify and the coercive field $E_c$ fluctuate between 1.16 and 1.51 kV mm$^{−1}$. The samples with $x =0.004$ exhibit optimum electrical properties at room temperature ($d_{33} = 268 pC$ N$^{−1}$, $k_p =52$%, $\epsilon_r = 1366$, $\tan \delta =2.11$%, $T_c = 325^{\circ}$C, $P_r = 20.4$ $\mu$C cm$^{−2}$, $E_c =1.16$ kV mm$^{−1}$).
Volume 39 Issue 7 December 2016 pp 1665-1670
SHUAISHUAI YAN HUA WANG JIWEN XU LING YANG WEI QIU QISONG CHEN DONG HAN
Ag/La$_{1−x}$Zn$_x$MnO$_3$/p$^+$-Si devices with different Zn doping contents were fabricated through sol–gel method. The effects of Zn doping concentration on the microstructure of La$_{1−x}$Zn$_x$MnO$_3$ films, as well as on the resistance switching behaviour and endurance characteristics of Ag/La$_{1−x}$Zn$_x$MnO$_3$/p$^{+}$-Si were investigated. After annealing at 600$^{\circ}$C for 1~h, the La$_{1−x}$Zn$_x$MnO$_3$ ($x = 0.1$, 0.2, 0.3, 0.4, 0.5) are amorphous and have bipolar resistance characteristics, with RHRS/RLRS ratios $>$103. However, the endurance characteristics show considerable differences; $x = 0.3$ shows the best endurance characteristics in more than 1000 switching cycles. The conduction mechanism of the Ag/La$_{1−x}$Zn$_x$MnO$_3$/p$^{+}$-Si is the Schottky emission mode at high resistance state. However, the conduction mechanism at low resistance state varies with Zn doping concentration. The dominant mechanism at $x = 0.1$ is filamentary conduction mechanism, whereas that at $x \ge 0.2$ is space-charge-limited current conduction.
Volume 40 Issue 6 October 2017 pp 1159-1163
JIWEN XU WEIDONG ZENG QINGNING LI LING YANG CHANGRONG ZHOU
It is well known that domains and crystal structure control the physical properties of ferroelectrics. The ex-situelectric field-dependent structural study, carried out in unpoled/poled crushed powder and bulk samples for (Li$_{0.5}$Nd$_{0.5}$)$^{2+}$ modified 0.95Bi$_{0.5}$Na$_{0.5}$TiO$_3$−0.05BaTiO$_3$ solid solution, established a correlation between domain configuration andcrystal structure variation. Under applying electric field, the smeared ferroelectric phase structure due to coherence diffractioneffect of nanodomains reappeared due to obsolescent coherence effect associated with the field-induced ordered nanodomains.The macroscopic characterizing techniques of domain configuration such as dielectric constant spectroscopy and X-raydiffraction measurement can provide a basis for understanding the correlation between domains configuration and crystalstructure in ferroelectric ceramics.
Volume 40 Issue 6 October 2017 pp 1285-1289
HUA WANG QISONG CHEN JIWEN XU XIAOWEN ZHANG SHUAISHUAI YAN
Mn$_{0.03}$Zn$_{0.97}$O (MZO)/amorphous La$_{0.7}Zn$_{0.3}$MnO$_3$ (LZMO) heterostructures were deposited on p$^+$-Si substratesthrough sol–gel spin coating. Ag/MZO/LZMO/p$^+$-Si and Ag/LZMO/MZO/p$^+$-Si devices exhibit a bipolar, reversibleand remarkable resistive switching behaviour at room temperature. The ratio of the resistance at high-resistance state (HRS)to that at low-resistance state (LRS) ($R_{\rm HRS}/R_{\rm LRS}$) in the Ag/LZMO/MZO/p$^+$-Si device is approximately five orders of magnitude, and is maintained after over 10$^3$ successive switching cycles or over a period of $2\times 10^6$ s, indicating good endurance property and retention characteristics. Conversely, the ratio in the Ag/MZO/LZMO/p$^+$-Si device began to decrease after 100 successive switching cycles. The LZMO/MZO interface could play an important role in the resistive switching behaviour of the devices. The dominant conduction mechanism of the two devices is charge-trap emission.
Volume 41 Issue 3 June 2018 Article ID 0070
Rectifying resistance-switching behaviour of Ag/SBTO/STMO/p$^+$-Si heterostructure films
WENBO ZHANG HUA WANG JIWEN XU GUOBAO LIU HANG XIE LING YANG
The Sr$_{0.88}$Bi$_{0.12}TiO$_3$/SrTi$_{0.92}$Mg$_{0.08}$O$_3$ (SBTO/STMO) heterostructure films were prepared on p$^+$-Si substratesby sol–gel spin-coating technique, and the films had good crystallinity and uniform grain distribution. The heterostructure films with a structure of Ag/SBTO/STMO/p$^+$-Si exhibited a bipolar, remarkable resistance-switching characteristic, and $R_{\rm HRS}/R_{\rm LRS} \sim 10^4$. More importantly, the heterostructure films showed rectifying characteristic in the low resistance state (LRS), and the rectification ratio can reach 10$^2$ at $\pm$1 V. The dominant resistive-switching conduction mechanism of high resistance state (HRS) was Ohmic behaviour, and the LRS changed to space charge-limited current(SCLC).
Volume 41 Issue 6 December 2018 Article ID 0149
HUA WANG WENBO ZHANG JIWEN XU GUOBAO LIU HANG XIE LING YANG
SrTiO$_3$ and Bi-doped SrTiO$_3$ films were fabricated with different device structures using the sol–gel method for non-volatile memory applications, and their resistance-switching behaviour, endurance and retention characteristics were investigated. SrTiO$_3$ and Sr$_{0.92}$Bi$_{0.08}$TiO$_3$ films grown on Si or Pt have the same phase structure, morphologies and grain size; however, the grain size of the Sr$_{0.92}$Bi$_{0.08}$TiO$_3$ films grown on Si is slightly larger than those of the SrTiO$_3$ films grown on Si and the Sr$_{0.92}$Bi$_{0.08}$TiO$_3$ films grown on Pt. The SrTiO$_3$ or Sr$_{0.92}$Bi$_{0.08}$TiO$_3$ films grown on Si or Pt all exhibitbipolar resistive-switching behaviour and follow the same conductive mechanism; however, the Ag/Sr$_{0.92}$Bi$_{0.08}$TiO$_3$/Si device possesses the highest $R_{\rm HRS}/R_{\rm LRS}$ of 10$^5$ and the best endurance and retention characteristics. The doping of Bi is conducive to enhance the $R_{\rm HRS}/R_{\rm LRS}$ of the SrTiO$_3$ films; meanwhile, the Si substrates help improve the endurance and retention characteristics of the Sr$_{0.92}$Bi$_{0.08}$TiO$_3$ films.
Volume 42 Issue 4 August 2019 Article ID 0163
HUA WANG DONG HAN JIWEN XU LING YANG
Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ ($x = 0.025–0.125$) thin films were synthesized by applying a sol–gel method on fluorine-doped tin oxide substrates. The influence of Ni doping concentration on the structure, leakage current, ferroelectric, magnetic and optical properties of Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ thin films was investigated. Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ thin films are polycrystalline films that present a single perovskite structure without any impurity phase when the Ni doping concentration is below 0.1 and present a Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ phase when the Ni doping concentration is above 0.1. The grain size of the films and their holes gradually decrease with an increase in the Ni doping amount. The saturation magnetization of Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ thin films increases with Ni content.However, appropriate Ni doping concentration can decrease the leakage current and enhance the ferroelectric polarization and optical transmittance of the films. Meanwhile, the absorption edge has a slight red shift. Bi$_{0.85}$Nd$_{0.15}$Fe$_{1−x}$Ni$_x$O$_3$ thin films possess better combination properties at a leakage current density of $4.27 \times 10^{−9}$ A cm$^{−2}$, ferroelectric polarization of 28.58 $\mu$C cm$^{−2}$, saturation magnetization of 2.08 emu cm$^{−3}$ and transmittance of over 85% when the Ni doping concentration, $x$ is 0.05.
Volume 44 All articles Published: 17 April 2021 Article ID 0100
YIXUAN SHEN HANG XIE YABIN SUN JIWEN XU LING YANG XIAOYI PAN CHANGRONG ZHOU HUA WANG
The complex ions (Mn$_{1/3}$Nb$_{2/3}$)$^{4+}$ doped 0.82BNT–0.18BKT (BNKT-xMN) ceramics were prepared by conventional solid-state sintering. The effects of the MN content on the structural and electrical properties of the BNKT-$x$MN ceramics were investigated. The grain size decreases sharply after doping MN. With the increase of the MN content, the phase structure changes from the rhombohedral and tetragonal phase to the tetragonal phase, then to the pseudo-cubic phase. The ferroelectric phase transforms to the relaxor phase. At critical phase (x = 0.03), the maximum positive bipolar strain and unipolar strain are 0.38 and 0.386%, respectively. The corresponding $d^*$$_{33}$ and $d_{33}$ are 767 pm V$^{–1}$ and 158 pC N$^{–1}$, respectively. Meanwhile, the dielectric constant gradually decreases with the increase of the MN content, which flattens the permittivity curves. The large piezoelectric responses are closely associated with the reversible relaxor ferroelectric phase transformation.
Volume 44 All articles Published: 15 May 2021 Article ID 0139
YABING SUN HUA WANG CHANGRONG ZHOU LING YANG JIWEN XU
In this study, Ho$^{3+}$ doped 0.825K$_{0.5}$Na$_{0.5}$NbO$_3$-0.175Sr(Yb$_{0.5}$Nb$_{0.5}$)O$_3$ luminescence transparent ceramics were prepared via the traditional solid-state sintering method. The structure and optical properties of the ceramics before and after polarization were studied at 40 kV cm$^{-1}$ for 0.5 h. With the increase of Ho content, the phase structure of the ceramics changed from a pseudo-cubic phase to the tripartite and the orthorhombic phases, and the light transmittance decreased. The ceramics demonstrated an up-conversion luminescence characteristic under the excitation of a 980 nm laser, and the emission wavelengths were 550 and 670 nm. The best up-conversion luminescence performance was obtained when the Ho content was 0.1%. Moreover, the polarization markedly enhanced the luminescence performance of the 0.825K$_{0.5}$Na$_{0.5}$NbO$_3$-0.175Sr(Yb$_{0.5}$Nb$_{0.5}$)O$_3$-0.1%Ho ceramics due to the increased possibility of energy-level radiative transition of rare-earth Ho$^{3+}$ ions and reduction of the $E$$_g$ value of the ceramic.
Volume 45 All articles Published: 4 January 2022 Article ID 0014
JIANGTING WANG YABING SUN SHAOYANG SHI HUA WANG JIWEN XU LING YANG WEI QIU
The traditional solid-phase reaction method was used to dope the 0.94(k$_{0.5}$Na$_{0.5}$)NbO$_3$–0.06Sr(Zn$_{1/3}$Nb$_{2/3}$)O$_3$ (0.94KNN–0.06SZN) with rare-earth Er$^{3+}$, showing that the transparent ferroelectric ceramics have both up-conversion luminescence. Also the changes in the phase structure, optoelectronic properties of the ceramics after Er$^{3+}$ doping were investigated. The results show that the doping of Er$^{3+}$ has no significant effect on the phase structure, dielectric constant, coercivity field and residual polarization intensity of the ceramics. With the increase of Er$^{3+}$ content, the saturation polarization intensity shows a trend of decreasing and then increasing, and the dielectric constant first decreases and then stabilizes. The large amount of Er$^{3+}$ also greatly reduced the light transmission of the ceramics. In addition, the doping of Er$^{3+}$ gives the ceramics new properties. Under 980 nm laser excitation, the ceramics exhibit luminescent emission bands at 533, 554 nm (green) and 672 nm (red). The luminous intensity of the ceramic first strengthens with the increase of Er$^{3+}$ content and then weakens, and the strongest luminous intensity is obtained when the Er$^{3+}$ content is 1.00% mol. Transparent ferroelectric ceramics with light-emitting functions will have a broad application prospect in the field of photoelectric crossover.
Volume 46, 2023
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Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
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