| 1. |
- Amin, Gul, et al.
(author)
-
Current-transport studies and trap extraction of hydrothermally grown ZnO nanotubes using gold Schottky diode
- 2010
-
In: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : WILEY-V C H VERLAG GMBH, PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY. - 1862-6300. ; 207:3, s. 748-752
-
Journal article (peer-reviewed)abstract
- High-quality zinc oxide (ZnO) nanotubes (NTs) were grown by the hydrothermal technique on n-Si substrate. The room temperature (RT) current-transport mechanisms of Au Schottky diodes fabricated from ZnO NTs and nanorods (NRs) reference samples have been studied and compared. The tunneling mechanisms via deep-level states was found to be the main conduction process at low applied voltage but at the trap-filled limit voltage (V-TFL) all traps were filled and the space-charge-limited current conduction was the dominating current-transport mechanism. The deep-level trap energy and the trap concentration for; the NTs were obtained as similar to 0.27 eV and 2.1 x 10(16) cm(-3), respectively. The same parameters were also extracted for the ZnO NRs The deep-level states observed crossponds to zinc interstitials (Zn-i), which are responsible for the violet emission.
|
|
| 2. |
- Bano, Nargis, et al.
(author)
-
Depth-resolved cathodoluminescence study of zinc oxide nanorods catalytically grown on p-type 4H-SiC
- 2010
-
In: Journal of Luminescence. - : Elsevier Science B.V., Amsterdam.. - 0022-2313 .- 1872-7883. ; 130:6, s. 963-968
-
Journal article (peer-reviewed)abstract
- Optical properties of ZnO nanorods (NRs) grown by vapour-liquid-solid (VLS) technique on 4H-p-SiC substrates were probed by cathodoluminescence (CL) measurements at room temperature and at 5 K complemented with electroluminescence. At room temperature the CL spectra for defect related emission intensity was enhanced with the electron beam penetration depth. We observed a variation in defect related green emission along the nanorod axis. This indicates a relatively poor structural quality near the interface between ZnO NRs and p-SiC substrate. We associate the green emission with oxygen vacancies. Analysis of the low-temperature (5 K) emission spectra in the UV region suggests that the synthesized nanorods contain shallow donors and acceptors.
|
|
| 3. |
- Bano, Nargis, et al.
(author)
-
Study of Au/ZnO nanorods Schottky light-emitting diodes grown by low-temperature aqueous chemical method
- 2010
-
In: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 100:2, s. 467-472
-
Journal article (peer-reviewed)abstract
- High quality vertically aligned ZnO nanorods (NRs) were grown by low-temperature aqueous chemical technique on 4H-n-SiC substrates. Schottky light-emitting diodes (LEDs) were fabricated. The current-voltage (I-V) characteristics of Schottky diodes reveal good rectifying behavior. Optical properties of the ZnO nanorods (NRs) were probed by cathodoluminescence (CL) measurements at room temperature complemented with electroluminescence (EL). The room-temperature CL spectra of the ZnO NRs exhibit near band edge (NBE) emission as well as strong deep level emission (DLE) centered at 690 nm. At room temperature the CL spectra intensity of the DLE was enhanced with the increase of the electron beam penetration depth due to the increase of defect concentration at the interface and due to the conversion of self-absorbed UV emission. We observed a variation in the DLE along the nanorod depth. This indicates a relatively lower structural quality near the interface between ZnO NRs and n-SiC substrate. The room-temperature CL spectra of SiC show very weak emission, which confirms that most of the DLE is originating from the ZnO NRs, and SiC has a minute contribution to the emission.
|
|
| 4. |
- Bano, Nargis, et al.
(author)
-
Study of Radiative Defects Using Current-Voltage Characteristics in ZnO Rods Catalytically Grown on 4H-p-SiC
- 2010
-
In: JOURNAL OF NANOMATERIALS. - : Hindawi. - 1687-4110 .- 1687-4129. ; 2010
-
Journal article (peer-reviewed)abstract
- High-quality ZnO rods were grown by the vapour-liquid-solid (VLS) technique on 4H-p-SiC substrate. The current transport mechanisms of the diodes at room temperature (RT) have been explained in term of the space-charge-limited current model based on the energy band diagram of ZnO rods/4H-p-SiC heterostructure. The tunneling mechanism via deep-level states was found to be the main conduction process at low-applied voltage but at trap-filled limit voltage VTFL all traps are filled and the space-charge-limited current conduction dominated the current transport. From the RT current voltage measurements, the energy of the deep level trap and the trap concentration were obtained as ∼0.24±0.02eV and 4.4×1018cm−3, respectively. The deep level states observed correspond to zinc interstitial (Zni ), responsible for the violet emission.
|
|
| 5. |
- Bano, Nargis, et al.
(author)
-
ZnO-organic hybrid white light emitting diodes grown on flexible plastic using low temperature aqueous chemical method
- 2010
-
In: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 108:4, s. 043103-
-
Journal article (peer-reviewed)abstract
- We demonstrate white light luminescence from ZnO-organic hybrid light emitting diodes grown at 90 degrees C on flexible plastic substrate by aqueous chemical growth. The configuration used for the ZnO-organic hybrid white light emitting diodes (WLEDs) consists of a layer of poly (9, 9-dioctylfluorene) (PFO) on poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate) coated plastic with top ZnO nanorods. Structural, electrical, and optical properties of these WLEDs were measured and analyzed. Room temperature electroluminescence spectrum reveals a broad emission band covering the range from 420 to 750 nm. In order to distinguish the white light components and contribution of the PFO layer we used a Gaussian function to simulate the experimental data. Color coordinates measurement of the WLED reveals that the emitted light has a white impression. The color rendering index and correlated color temperature of the WLED were calculated to be 68 and 5800 K, respectively.
|
|
| 6. |
- Willander, Magnus, et al.
(author)
-
Luminescence from Zinc Oxide Nanostructures and Polymers and their Hybrid Devices
- 2010
-
In: Materials. - Basel, Switzerland : MDPI AG. - 1996-1944. ; 3:4, s. 2643-2667
-
Research review (peer-reviewed)abstract
- Zinc oxide (ZnO) is a strong luminescent material, as are several polymers. These two materials have distinct drawbacks and advantages, and they can be combined to form nanostructures with many important applications, e. g., large-area white lighting. This paper discusses the origin of visible emission centers in ZnO nanorods grown with different approaches. White light emitting diodes (LEDs) were fabricated by combining n-ZnO nanorods and hollow nanotubes with different p-type materials to form heterojunctions. The p-type component of the hybrids includes p-SiC, p-GaN, and polymers. We conclude by analyzing the electroluminescence of the different light emitting diodes we fabricated. The observed optical, electrical, and electro-optical characteristics of these LEDs are discussed with an emphasis on the deep level centers that cause the emission.
|
|
