| 1. |
- Asghar, M., et al.
(författare)
-
Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy
- 2014
-
Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 23:9, s. 097101-
-
Tidskriftsartikel (refereegranskat)abstract
- We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy (MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current-voltage (I-V) measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 +/- 0.03 eV and capture cross-section of 8.57 +/- 10(-18) cm(2). Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy (SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO.
|
|
| 2. |
- Chey, Chan Oeurn, et al.
(författare)
-
Synthesis of Fe-Doped ZnO Nanorods by Rapid Mixing Hydrothermal Method and Its Application for High Performance UV Photodetector
- 2014
-
Ingår i: Journal of Nanomaterials. - : Hindawi Limited. - 1687-4110 .- 1687-4129. ; , s. 524530-
-
Tidskriftsartikel (refereegranskat)abstract
- We have successfully synthesized Fe-doped ZnO nanorods by a new and simple method in which the adopted approach is by using ammonia as a continuous source of OH- for hydrolysis instead of hexamethylenetetramine (HMT). The energy dispersive X-ray (EDX) spectra revealed that the Fe peaks were presented in the grown Fe-doped ZnO nanorods samples and the X-ray photoelectron spectroscopy (XPS) results suggested that Fe3+ is incorporated into the ZnO lattice. Structural characterization indicated that the Fe-doped ZnO nanorods grow along the c-axis with a hexagonal wurtzite structure and have single crystalline nature without any secondary phases or clusters of FeO or Fe3O4 observed in the samples. The Fe-doped ZnO nanorods showed room temperature (300 K) ferromagnetic magnetization versus field (M-H) hysteresis and the magnetization increases from 2.5 mu emu to 9.1 mu emu for Zn0.99Fe0.01O and Zn0.95Fe0.05O, respectively. Moreover, the fabricated Au/Fe-doped ZnO Schottky diode based UV photodetector achieved 2.33 A/W of responsivity and 5 s of time response. Compared to other Au/ZnO nanorods Schottky devices, the presented responsivity is an improvement by a factor of 3.9.
|
|
| 3. |
- Hussain Ibupoto, Zafar, et al.
(författare)
-
Low temperature synthesis of seed mediated CuO bundle of nanowires, their structural characterisation and cholesterol detection
- 2013
-
Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier. - 0928-4931 .- 1873-0191. ; 33:7, s. 3889-3898
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we have successfully synthesised CuO bundle of nanowires using simple, cheap and low temperature hydrothermal growth method. The growth parameters such as precursor concentration and time for duration of growth were optimised. The field emission scanning electron microscopy (FESEM) has demonstrated that the CuO bundles of nanowires are highly dense, uniform and perpendicularly oriented to the substrate. The high resolution transmission electron microscopy (HRTEM) has demonstrated that the CuO nanostructures consist of bundle of nanowires and their growth pattern is along the [010] direction. The X-ray diffraction (XRD) technique described that CuO bundle of nanowires possess the monoclinic crystal phase. The surface and chemical composition analyses were carried out with X-ray photoelectron spectroscopy (XPS) technique and the obtained results suggested the pure crystal state of CuO nanostructures. In addition, the CuO nanowires were used for the cholesterol sensing application by immobilising the cholesterol oxidase through electrostatic attraction. The infrared reflection absorption spectroscopy study has also revealed that CuO nanostructures are consisting of only Cu-O bonding and has also shown the possible interaction of cholesterol oxidase with the sharp edge surface of CuO bundle of nanowires. The proposed cholesterol sensor has demonstrated the wide range of detection of cholesterol with good sensitivity of 33.88 +/- 0.96 mV/decade. Moreover, the CuO bundle of nanowires based sensor electrode has revealed good repeatability, reproducibility, stability, selectivity and a fast response time of less than 10 s. The cholesterol sensor based on the immobilised cholesterol oxidase has good potential applicability for the determination of cholesterol from the human serum and other biological samples.
|
|
| 4. |
- Hussain Ibupoto, Zafar, et al.
(författare)
-
Selective zinc ion detection by functionalised ZnO nanorods with ionophore
- 2011
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 110:10, s. 104702-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, highly dense and well aligned single-crystal zinc oxide nanorods were grown along the c-axis on a gold coated glass substrate using a low temperature aqueous chemical growth approach. The prepared ZnO nanorods were functionalized with plastic membrane coatings containing specific ionophore (12-crown-4) which is highly selective to zinc ions (Zn(+2)). The electrochemical response of the sensor was found to be linear over a relatively wide logarithmic concentration range from 1 mu M to 100mM. The proposed sensor showed a good linearity with a high sensitivity of similar to 35 mV/decade for sensing Zn(+2) ions. A fast response time of less than 5 s with a good selectivity, repeatability, reproducibility, and negligible response to common interferents ions such as calcium (Ca(2+)), magnesium (Mg(2+)), or potassium (K(+)), and iron (Fe(+3)) and copper (Cu(+2)) was also demonstrated. Moreover, the proposed sensor showed good stoichiometric results for potentiometric titration.
|
|
| 5. |
- Hussain Ibupoto, Zafar, et al.
(författare)
-
The synthesis of CuO nanoleaves, structural characterization, and their glucose sensing application
- 2013
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:10
-
Tidskriftsartikel (refereegranskat)abstract
- The present study describes the synthesis of well aligned and highly dense polyethylene glycol template assisted cupric oxide (CuO) nanoleaves on the gold coated glass substrate by hydrothermal growth method. The structural study based investigations of CuO nanoleaves were performed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), infrared reflection-absorption spectroscopy (IRAS), and high resolution transmission electron microscopy (HRTEM). The glucose sensor based on the glucose oxidase immobilized CuO nanoleaves electrode detected the wide range of glucose concentrations with good linearity and exhibited high sensitivity of 61.9+/-2.0 mV/decade. The linear detection range was observed from 1.0 x 10(-5) to 2.0 x 10(-2) M with detection limit of 5.0 x 10(-6) M and a fast response time of less than 5 s was also observed. The glucose sensor electrode possesses good anti-interference ability, stability, repeatability, and reproducibility.
|
|
| 6. |
- Hussain Ibupoto, Zafar, et al.
(författare)
-
Well aligned ZnO nanorods growth on the gold coated glass substrate by aqueous chemical growth method using seed layer of Fe3O4 and Co3O4 nanoparticles
- 2013
-
Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 368, s. 39-46
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, Fe3O4 and Co3O4 nanoparticles were prepared by co-precipitation method and sol-gel method respectively. The synthesised nanoparticles were characterised by X-ray diffraction [XRD] and Raman spectroscopy techniques. The obtained results have shown the nanocrystalline phase of obtained Fe3O4 and Co3O4 nanoparticles. Furthermore, the Fe3O4 and Co3O4 nanoparticles were used as seed layer for the fabrication of well-aligned ZnO nanorods on the gold coated glass substrate by aqueous chemical growth method. Scanning electron microscopy (SEM), high resolution transmission electron microscopy [HRTEM], as well as XRD and energy dispersive X-ray techniques were used for the structural characterisation of synthesised ZnO nanorods. This study has explored highly dense, uniform, well-aligned growth pattern along 0001 direction and good crystal quality of the prepared ZnO nanorods. ZnO nanorods are only composed of Zn and O atoms. Moreover, X-ray photoelectron spectroscopy was used for the chemical analysis of fabricated ZnO nanorods. In addition, the structural characterisation and the chemical composition study and the optical investigation were carried out for the fabricated ZnO nanorods and the photoluminescence [PL] spectrum have shown strong ultraviolet (UV) peak at 381 nm for Fe3O4 nanoparticles seeded ZnO nanorods and the PL spectrum for ZnO nanorods grown with the seed layer of Co3O4 nanoparticles has shown a UV peak at 382 nm. The green emission and orange/red peaks were also observed for ZnO nanorods grown with both the seed layers. This study has indicated the fabrication of well aligned ZnO nanorods using the one inorganic nanomaterial on other inorganic nanomaterial due to their similar chemistry.
|
|
| 7. |
- Khun, K., et al.
(författare)
-
Urea Assisted Synthesis of Flower Like CuO Nanostructures and Their Chemical Sensing Application for the Determination of Cadmium Ions
- 2013
-
Ingår i: Electroanalysis. - : Wiley-VCH Verlag. - 1040-0397 .- 1521-4109. ; 25:6, s. 1425-1432
-
Tidskriftsartikel (refereegranskat)abstract
- The novel nanostructures of CuO with improved morphology are strongly required for the development of devices with enhanced performance. In this study flower like nanostructures of CuO are synthesized by hydrothermal method using urea as tuning material for the morphology of CuO during the growth process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used for the characterization of these nanostructures. The nanostructures are highly dense, uniform and well aligned on the gold coated glass substrate. Moreover, CuO nanostructures exhibited pure phase of CuO. These novel CuO nanostructures were potentially used for the construction of cadmium ion sensor by functionalizing with tetrathia-12-crown-4 a selective cadmium ion ionophore. The proposed cadmium ion sensor has detected the wide range of cadmium ion concentrations from 1.0x10-9-1.0x10-1M with a sensitivity of 29.3 +/- 0.3mV/decade and also a fast response time of less than 10.0s is demonstrated. CuO nanostructures based cadmium ion selective electrode has also shown excellent reproducibility, repeatability, selectivity, and stability. The sensor electrode was also used as indicator electrode for the confirmation of practical utility and the obtained result describes the good behavior of the sensor in the potentiometric titration for the determination of cadmium ions.
|
|
| 8. |
- Kishwar, S, et al.
(författare)
-
Electro-optical and Cathodoluminescence properties of low temperature grown ZnO nanorods/p-GaN white light emitting diodes
- 2010
-
Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : Wiley. - 1862-6300. ; 207:1, s. 67-72
-
Tidskriftsartikel (refereegranskat)abstract
- Vertically aligned ZnO nanorods (NRs) with a diameter in the range of 160-200 nm were grown on p-GaN/sapphire substrates by aqueous chemical growth technique and white light emitting I diodes (LEDs) are fabricated. The properties of this LED were investigated by parameter analyzer, cathodoluminescence (CL), electroluminescence (EL), and photoluminescence (PL). The I-V characteristics of the fabricated ZnO/GaN heterojunction revealed rectifying behavior and the LED emits visible EL when bias is applied. From the CL it was confirmed that both the ZnO NRs and the p-GaN are contributing to the observed peaks. The observed EL measurements showed two emission hands centered at 450 nm and a second broad deep level defect related emission centered at 630 nm and extending from 500 rim and up to over 700 rim. Moreover, the room temperature PL spectrum of the ZnO NRs/p-GaN reveals an extra peak at the green color wavelength centered at 550 nm. Comparison of the PL, CL, and EL data suggest that the blue and near red emissions in the EL spectra are originating from Mg acceptor levels in the p-GaN and from the deep levels defects present in the ZnO NRs, respectively. The mixture of high and low energy colors, i.e., blue, green, and red, has led to the white observed luminescence.
|
|
| 9. |
- Nur, Omer, et al.
(författare)
-
Effect of elevated concentrations of strontium and iron on the structural and dielectric characteristics of Ba(1-x-y)Sr(x)Ti Fe(y)O3 prepared through sol-gel technique
- 2012
-
Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 407:14, s. 2697-2704
-
Tidskriftsartikel (refereegranskat)abstract
- Nano-composite Ba1-xSr(x)TiO3 (BST), where x=0.01-0.50 and doped with different concentrations of iron Ba(1-x-y)Sr(x)TiFe(y)O3 (BSTF), where x=0.01 and y=0.01-0.05 powders were prepared by sol-gel method. The effect of increasing the iron and strontium concentrations substituted in Barium strontium titanate system will be studied. The prepared samples have a tetragonal crystalline phase after sintering for 1 h at 750 degrees C in air. The structural and the morphological features of the systems have been studied using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The dielectric properties of the BST and BSTF systems have been investigated as a function of temperature and frequency. The dielectric measurements are carried out in the frequency range 42 Hz-1 MHz, at a temperature ranging between 25 and 250 degrees C. The results showed a decrease in T-c temperature giving the following values 90 and 85 degrees C for B10ST and B10ST5F prepared powder samples, respectively, implying tetragonal, feroelectric phase at lower temperature into cubic, para-electric phase at temperature higher than T-c.
|
|
| 10. |
|
|
