Hierarchical ZnO Nanostructures: Growth and Optical Properties

2008 ◽  
Vol 8 (12) ◽  
pp. 6355-6360
Author(s):  
Ahmad Umar ◽  
A. Al. Hajry ◽  
S. Al-Heniti ◽  
Y.-B. Hahn
Keyword(s):  
Optical Properties ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Hexagonal Phase ◽  
Hierarchical Structures ◽  
Zinc Powder ◽  
Zno Nanostructures ◽  
Hierarchical Nanostructures ◽  
Uv Emission ◽  
Wurtzite Hexagonal Phase

Growth of hierarchical ZnO nanostructures composed of ZnO nanoneedles have been achieved via simple thermal evaporation process by using metallic zinc powder in the presence of oxygen at low temperature of 460 °C on silicon substrate without the use of any kind of metal catalysts or additives. It is confirmed by detailed structural studies that the as-grown hierarchical nanostructures are single crystalline with a wurtzite hexagonal phase and nanoneedles of these structures are grown along the c-axis in the [0001] direction. The Raman-scattering analysis substantiates a wurtzite hexagonal phase with a good crystal quality for the as-grown products. Room-temperature photoluminescence (PL) exhibits a strong UV emission at 380 nm confirming the excellent optical properties of as-synthesized hierarchical structures. A plausible growth mechanism is also proposed to clearly understand the growth process of the synthesized structures.

Low-Temperature Growth of Flower-Shaped UV-Emitting ZnO Nanostructures on Steel Alloy by Thermal Evaporation

2007 ◽  
Vol 7 (12) ◽  
pp. 4421-4427 ◽  
Author(s):  
Ahmad Umar ◽  
S. H. Kim ◽  
J. H. Kim ◽  
Y. K. Park ◽  
Y. B. Hahn
Keyword(s):  
Thermal Evaporation ◽  
Hexagonal Phase ◽  
Zinc Powder ◽  
Hexagonal Structure ◽  
Structural Defects ◽  
Metal Catalyst ◽  
Steel Alloy ◽  
Zno Nanostructures ◽  
Uv Emission ◽  
Wurtzite Hexagonal Phase

Flower-shaped ZnO nanostructures, containing the triangular-shaped petals (sharpened tips and wider bases) have been achieved by simple thermal evaporation of high purity metallic zinc powder in the presence of oxygen at 440 °C on steel alloy substrate without the use of metal catalyst or additives. Detailed structural studies confirm that the obtained flower-shaped nanostructures are single crystalline and possesses a wurtzite hexagonal structure, grown along the c-axis in the [0001] direction. Raman and room temperature photoluminescence analysis substantiate a wurtzite hexagonal phase with a good crystal quality and a strong UV emission at 378 nm, respectively, indicating few or no structural defects. Additionally, a detailed possible growth mechanism has also been discussed.

EFFECT OF W-DOPING ON MORPHOLOGY, STRUCTURAL AND OPTICAL PROPERTIES OF ZnO NANOSTRUCTURES SYNTHESIZED VIA THERMAL EVAPORATION

2012 ◽  
Vol 26 (27) ◽  
pp. 1250176 ◽  
Author(s):  
HOSEIN ESHGHI ◽  
YASER ARJMAND
Keyword(s):  
Room Temperature ◽  
Thermal Evaporation ◽  
Hexagonal Structure ◽  
Zno Nanostructures ◽  
Structural And Optical Properties ◽  
Thermal Evaporation Method ◽  
Violet Emission ◽  
Pl Spectra ◽  
Uv Emission ◽  
Oxygen Gas

Undoped and W -doped ZnO nanostructures were prepared by heating Zn and WO 3 powders in the presence of oxygen gas without any catalyst, using the thermal evaporation method at 950°C. Samples were characterized by FESEM images, also EDS, XRD and PL spectra. FESEM images showed the formation of nanowires in the undoped sample and porous nanostructures as flat-surface granules with various sizes in the doped samples. XRD spectra of the samples confirmed the formation of wurtzite hexagonal structure with (002) as the preferred orientation, while its intensity has reduced as the doping concentration has increased. Meanwhile, the room temperature PL spectra have indicated this variation is in conjunction with the reduction in the intensity of UV emission and appearance of a violet emission at 420 nm (2.95 eV).

Substrate Dependent Morphologies and Luminescence Properties of ZnO Nanostructures Prepared by Thermal Evaporation

2009 ◽  
Vol 60-61 ◽  
pp. 278-282 ◽  
Author(s):  
Bin Ping Zhuang ◽  
Fa Chun Lai ◽  
Li Mei Lin ◽  
Ming Bao Lin ◽  
Yan Qu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Thermal Evaporation ◽  
Zinc Powder ◽  
Substrate Material ◽  
Zno Nanostructures ◽  
X Ray Diffraction ◽  
Pure Zinc ◽  
X Ray ◽  
Structure Morphology ◽  
Quartz Substrates

High density ZnO nanostructures were fabricated on Au coated Si and quartz substrates through once and the same oxidative evaporation of pure zinc powder. The coated side of the substrate was intentionally positioned in two directions of face and back to the zinc sources. Structure, morphology and optical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, Raman spectra and room temperature photoluminescence measurements. The results showed that the samples on the different substrates with different directions have three different morphologies, including film-, rod- and comb-like nanostructures. Photoluminescence spectra of the samples showed the various bands centered in UV (380-390 nm), blue (470-490 nm), green (500-550 nm) and orange (610-620 nm) region. It demonstrates that the substrate material and the direction of substrate significantly affect the growth of ZnO nanostructures.

Two-Step Growth of Hexagonal-Shaped ZnO Nanowires and Nanorods and Their Properties

2007 ◽  
Vol 7 (12) ◽  
pp. 4522-4528 ◽  
Author(s):  
Ahmad Umar ◽  
S. H. Kim ◽  
J. H. Kim ◽  
Y. B. Hahn
Keyword(s):  
Hexagonal Phase ◽  
Green Emission ◽  
Zinc Powder ◽  
Zno Nanowires ◽  
Thermal Evaporation Method ◽  
Single Crystalline ◽  
Uv Emission ◽  
Nano Structures ◽  
Wurtzite Hexagonal Phase ◽  
Step Growth

Single-crystalline with perfect hexagonal-shaped ZnO nanowires and nanorods, possessing the Zn-terminated (0001) facets bounded with the six-crystallographic equivalent {0110} surfaces, have been grown on Au-coated silicon substrate via thermal evaporation method using the metallic zinc powder in presence of oxygen. The detailed structural analyses reveal that the obtained nano-structures are single-crystalline with the wurtzite hexagonal phase and are preferentially oriented in the c-axis, [0001] direction. Raman spectra exhibit a sharp and strong optical phonon E2 mode at 437 cm−1 further confirms the good crystal quality with wurtzite hexagonal crystal structure for the deposited products. The room-temperature photoluminescence (PL) spectra, for both the structures, showed a sharp and strong UV emission with a suppressed green emission, indicating the good optical properties for the as-grown nanostructures.

Controllable Synthesis of ZnO Nanonails by Vapor-Solid Process: Growth Mechanism and Structural and Optical Properties

2006 ◽  
Vol 957 ◽  
Author(s):  
Ahmad Umar ◽  
Q. Ahsanul Haq ◽  
Sang Hoon Kim ◽  
Yeon Ho Im ◽  
Yoon Bong Hahn
Keyword(s):  
Optical Properties ◽  
Substrate Surface ◽  
Hexagonal Phase ◽  
Zinc Powder ◽  
Metal Catalyst ◽  
Single Crystalline ◽  
Morphological Studies ◽  
Wurtzite Hexagonal Phase ◽  
Photoluminescence Studies ◽  
Source Materials

ABSTRACTSingle-crystalline with good optical properties aligned ZnO nanonails were grown on steel alloy substrate without the use of metal catalyst or additives by the thermal evaporation process using high purity metallic zinc powder and oxygen as source materials for zinc and oxygen, respectively. Detailed morphological studies by FESEM revealed that the obtained nanonails are grown in a high density over the whole substrate surface and are exhibiting perfect hexagonal-shaped caps. The diameters of the nanonails at their tops and bases are ranges from 120∼160nm and 50∼70 nm, respectively. The detailed structural characterizations confirmed that the synthesized nanostructures are single-crystalline and grown along the c-axis direction. Raman scattering and room-temperature photoluminescence studies demonstrated the wurtzite hexagonal phase and good optical properties, respectively for the grown nanonails.

Fabrication of ZnO Nanowall-Based Hydrogen Gas Nanosensor

2013 ◽  
Vol 684 ◽  
pp. 21-25 ◽  
Author(s):  
Tse Pu Chen ◽  
Sheng Po Chang ◽  
Shoou Jinn Chang
Keyword(s):  
Seed Layer ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Hydrogen Gas ◽  
Two Dimensional ◽  
Defect Related Emission ◽  
Room Temperature Photoluminescence ◽  
Hydrogen Sensing ◽  
Uv Emission ◽  
Sensing Characteristics

Two-dimensional ZnO nanowalls were rapidly grown on glass substrate by thermal evaporation at low temperature without any catalysts or the pre-deposition of a ZnO seed layer on the substrate. Most of the ZnO nanowalls grown at 450°C were vertical on substrate and they were about 70-200 nm thick and 2 µm long. The room-temperature photoluminescence (PL) spectra showed a strong intrinsic ultraviolet (UV) emission and a weak defect-related emission. Hydrogen-sensing characteristics of the ZnO nanowalls have been investigated, and that make them become attractive candidates for gas sensor.

ZnO Nanostructures Obtained by Mist-Atomization Method Growth on Different Au-Seeded Substrates Temperature

2015 ◽  
Vol 1109 ◽  
pp. 603-607
Author(s):  
A.N. Afaah ◽  
N.A.M. Asib ◽  
Aadila Aziz ◽  
M. Rusop ◽  
Ruziana Mohamed ◽  
...  
Keyword(s):  
Glass Substrate ◽  
Room Temperature ◽  
Nitrate Solution ◽  
Zinc Nitrate ◽  
Morphological Properties ◽  
Nitrate Hexahydrate ◽  
Zno Nanostructures ◽  
Glass Substrates ◽  
Uv Emission ◽  
Surface Morphologies

Mist-atomization deposition method was applied in order to grow ZnO nanostructures with various surface morphologies. ZnO was deposited from the mixture of zinc nitrate hexahydrate (Zn (NO3)2.6H2O) and stabilizer, hexamethylenetetramine (HMTA, C6H12N4) aqueous solutions onto Au-seeded glass substrate. The mixture was sprayed onto the surface of Au-seeded glass substrate at various growth temperatures of room temperature (RT), 100, 200, and 300 °C. The obtained structures were characterised by room-temperature photoluminescence (PL), field emission scanning electron microscopy (FESEM), and UV-VIS-NIR spectrophotometer. It is found that ZnO growth on 300 °C substrate temperature shows the best absorbance properties and highest UV emission peak with denser distribution amongst all. The optical and morphological properties of sprayed ZnO nanostructures largely depend on the substrates temperature during spraying the zinc nitrate solution and on the Au-seeded glass substrates.

Effect of O2 Flow Rate on the Morphological and Optical Properties of ZnO Nanocrystals

2012 ◽  
Vol 554-556 ◽  
pp. 70-75
Author(s):  
Hui Juan Tian ◽  
Jun Bo Xu ◽  
Ya Jun Tian ◽  
Hao Wen
Keyword(s):  
Optical Properties ◽  
Room Temperature ◽  
Morphological Evolution ◽  
Zno Nanorods ◽  
Dynamics Simulation ◽  
Flow Rates ◽  
Uv Emission ◽  
Zno Nanocrystals ◽  
Vapor Partial Pressure ◽  
Axial Growth

The morphological and optical properties of ZnO nanocrystals prepared by thermal evaporation of Zn powders were studied at both upstream and downstream under different O2flow rates. The morphological evolution was observed by scanning electron microscopy. With O2flow rates changing from 0.25 sccm to 1 sccm, the caps of the ZnO nanonails become bigger and the stems gradually disappear at upstream, and the diameters at the top of ZnO nanorods become thicker and the length become longer at downstream. Room temperature PL study shows that UV emission is relatively enhanced with increasing O2flow rates. Computational fluid dynamics simulation was performed, which indicates that the morphological evolution of the ZnO structures results from the competition between the axial growth and the radial growth based on different O2and Zn vapor partial pressure.

Fabrication and Characterization of In-Doped Zinc Oxide Nanodisks

2007 ◽  
Vol 121-123 ◽  
pp. 127-130
Author(s):  
Juan Liu ◽  
Yue Zhang ◽  
Jun Jie Qi ◽  
Yun Hua Huang ◽  
Xiao Mei Zhang
Keyword(s):  
Room Temperature ◽  
Thermal Evaporation ◽  
Graphite Powder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uv Emission ◽  
Hexagonal Shape ◽  
Catalyst Morphology ◽  
Fabrication And Characterization

In-doped ZnO nanodisks were successfully fabricated by thermal evaporation Zn, In2O3 and graphite powder mixture without catalyst. Morphology, structures and components of ZnO nanodisks were investigated by SEM, HRTEM, EDS and X-Ray diffraction. ZnO nanodisks have perfect hexagonal shape, with 1~3μm size and 40~100 nm in thickness. The nanodisks are single-crystalline ZnO with wurtzite structure and In content of nanodisks reaches 2.2%. The growth along [0001] is suppressed leading to the formation of ZnO nanodisks. Room temperature photoluminescence spectra of the nanodisks shows that the UV emission peak blueshifts and becomes broader after doping.

Fine control over the morphology and photocatalytic activity of 3D ZnO hierarchical nanostructures: capping vs. etching

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 56232-56238 ◽  
Author(s):  
Jawayria Mujtaba ◽  
Hongyu Sun ◽  
Fang Fang ◽  
Mashkoor Ahmad ◽  
Jing Zhu
Keyword(s):  
Photocatalytic Activity ◽  
Citric Acid ◽  
Potassium Hydroxide ◽  
Room Temperature ◽  
Hierarchical Structures ◽  
Capping Agent ◽  
Hierarchical Nanostructures ◽  
Fine Control

ZnO 3D hierarchical structures with different morphologies can be selectively synthesized at room temperature by using potassium hydroxide and citric acid as an etchant and capping agent, respectively.

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